如何在SpringCloud中配置刷新？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
一、环境变化
1.1、关于ContextRefresher
当我们访问/refresh时，会被RefreshEndpoint类所处理。我们来看源代码：
package org.springframework.cloud.endpoint;
import java.util.Arrays;
import java.util.Collection;
import java.util.Set;
import org.springframework.boot.actuate.endpoint.AbstractEndpoint;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.context.refresh.ContextRefresher;
import org.springframework.jmx.export.annotation.ManagedOperation;
import org.springframework.jmx.export.annotation.ManagedResource;
/**
* @author Dave Syer
* @author Venil Noronha
*/
@ConfigurationProperties(prefix = "endpoints.refresh", ignoreUnknownFields = false)
@ManagedResource
public class RefreshEndpoint extends AbstractEndpoint<Collection<String>> {
private ContextRefresher contextRefresher;
public RefreshEndpoint(ContextRefresher contextRefresher) {
super("refresh");
this.contextRefresher = contextRefresher;
}
@ManagedOperation
public String[] refresh() {
Set<String> keys = contextRefresher.refresh();
return keys.toArray(new String[keys.size()]);
}
@Override
public Collection<String> invoke() {
return Arrays.asList(refresh());
}
}通过源代码我们了解到：当访问refresh端点时，实际上执行的是ContextRefresher的refresh方法，那么我们继续追踪源代码，找到其refresh方法：
public synchronized Set<String> refresh() {
Map<String, Object> before = extract(
this.context.getEnvironment().getPropertySources());
addConfigFilesToEnvironment();
Set<String> keys = changes(before,
extract(this.context.getEnvironment().getPropertySources())).keySet();
this.context.publishEvent(new EnvironmentChangeEvent(context, keys));
this.scope.refreshAll();
return keys;
}我们可以看到refresh方法做了如下几件事情：
1）获取刷新之前的所有PropertySource
2) 调用addConfigFilesToEnvironment方法获取最新的配置
3) 调用changes方法更新配置信息
4) 发布EnvironmentChangeEnvent事件
5）调用refreshScope的refreshAll方法刷新范围
我们重点关注一下2，3，4步骤
1.2、addConfigFilesToEnvironment方法
我们先来看看这个方法是怎么实现的：
/* for testing */ ConfigurableApplicationContext addConfigFilesToEnvironment() {
ConfigurableApplicationContext capture = null;
try {
StandardEnvironment environment = copyEnvironment(
this.context.getEnvironment());
SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class)
.bannerMode(Mode.OFF).web(false).environment(environment);
// Just the listeners that affect the environment (e.g. excluding logging
// listener because it has side effects)
builder.application()
.setListeners(Arrays.asList(new BootstrapApplicationListener(),
new ConfigFileApplicationListener()));
capture = builder.run();
if (environment.getPropertySources().contains(REFRESH_ARGS_PROPERTY_SOURCE)) {
environment.getPropertySources().remove(REFRESH_ARGS_PROPERTY_SOURCE);
}
MutablePropertySources target = this.context.getEnvironment()
.getPropertySources();
String targetName = null;
for (PropertySource<?> source : environment.getPropertySources()) {
String name = source.getName();
if (target.contains(name)) {
targetName = name;
}
if (!this.standardSources.contains(name)) {
if (target.contains(name)) {
target.replace(name, source);
}
else {
if (targetName != null) {
target.addAfter(targetName, source);
}
else {
// targetName was null so we are at the start of the list
target.addFirst(source);
targetName = name;
}
}
}
}
}
finally {
ConfigurableApplicationContext closeable = capture;
while (closeable != null) {
try {
closeable.close();
}
catch (Exception e) {
// Ignore;
}
if (closeable.getParent() instanceof ConfigurableApplicationContext) {
closeable = (ConfigurableApplicationContext) closeable.getParent();
}
else {
break;
}
}
}
return capture;
}1) 该方法首先拷贝当前的Environment
2) 通过SpringApplicationBuilder构建了一个简单的SpringBoot启动程序并启动
builder.application().setListeners(Arrays.asList(new BootstrapApplicationListener(), new ConfigFileApplicationListener()));
这里面会添加两个监听器分别为：BootstrapApplicationListener与ConfigFileApplicationListener，通过先前的学习，我们知道BootstrapApplicationListener是引导程序的核心监听器，而ConfigFileApplicationListener也是非常重要的类：
/*
* Copyright 2012-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.boot.context.config;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.springframework.beans.BeansException;
import org.springframework.beans.CachedIntrospectionResults;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.bind.PropertiesConfigurationFactory;
import org.springframework.boot.bind.PropertySourcesPropertyValues;
import org.springframework.boot.bind.RelaxedDataBinder;
import org.springframework.boot.bind.RelaxedPropertyResolver;
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.boot.context.event.ApplicationPreparedEvent;
import org.springframework.boot.env.EnumerableCompositePropertySource;
import org.springframework.boot.env.EnvironmentPostProcessor;
import org.springframework.boot.env.PropertySourcesLoader;
import org.springframework.boot.logging.DeferredLog;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.context.event.SmartApplicationListener;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.EnumerablePropertySource;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.PropertySource;
import org.springframework.core.env.PropertySources;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.util.Assert;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StringUtils;
import org.springframework.validation.BindException;
/**
* {@link EnvironmentPostProcessor} that configures the context environment by loading
* properties from well known file locations. By default properties will be loaded from
* 'application.properties' and/or 'application.yml' files in the following locations:
* <ul>
* <li>classpath:</li>
* <li>file:./</li>
* <li>classpath:config/</li>
* <li>file:./config/:</li>
* </ul>
* <p>
* Alternative search locations and names can be specified using
* {@link #setSearchLocations(String)} and {@link #setSearchNames(String)}.
* <p>
* Additional files will also be loaded based on active profiles. For example if a 'web'
* profile is active 'application-web.properties' and 'application-web.yml' will be
* considered.
* <p>
* The 'spring.config.name' property can be used to specify an alternative name to load
* and the 'spring.config.location' property can be used to specify alternative search
* locations or specific files.
* <p>
* Configuration properties are also bound to the {@link SpringApplication}. This makes it
* possible to set {@link SpringApplication} properties dynamically, like the sources
* ("spring.main.sources" - a CSV list) the flag to indicate a web environment
* ("spring.main.web_environment=true") or the flag to switch off the banner
* ("spring.main.show_banner=false").
*
* @author Dave Syer
* @author Phillip Webb
* @author Stephane Nicoll
* @author Andy Wilkinson
* @author Eddú Meléndez
*/
public class ConfigFileApplicationListener
implements EnvironmentPostProcessor, SmartApplicationListener, Ordered {
private static final String DEFAULT_PROPERTIES = "defaultProperties";
// Note the order is from least to most specific (last one wins)
private static final String DEFAULT_SEARCH_LOCATIONS = "classpath:/,classpath:/config/,file:./,file:./config/";
private static final String DEFAULT_NAMES = "application";
/**
* The "active profiles" property name.
*/
public static final String ACTIVE_PROFILES_PROPERTY = "spring.profiles.active";
/**
* The "includes profiles" property name.
*/
public static final String INCLUDE_PROFILES_PROPERTY = "spring.profiles.include";
/**
* The "config name" property name.
*/
public static final String CONFIG_NAME_PROPERTY = "spring.config.name";
/**
* The "config location" property name.
*/
public static final String CONFIG_LOCATION_PROPERTY = "spring.config.location";
/**
* The default order for the processor.
*/
public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 10;
/**
* Name of the application configuration {@link PropertySource}.
*/
public static final String APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME = "applicationConfigurationProperties";
private final DeferredLog logger = new DeferredLog();
private String searchLocations;
private String names;
private int order = DEFAULT_ORDER;
private final ConversionService conversionService = new DefaultConversionService();
@Override
public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
return ApplicationEnvironmentPreparedEvent.class.isAssignableFrom(eventType)
|| ApplicationPreparedEvent.class.isAssignableFrom(eventType);
}
@Override
public boolean supportsSourceType(Class<?> aClass) {
return true;
}
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent(
(ApplicationEnvironmentPreparedEvent) event);
}
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent(event);
}
}
private void onApplicationEnvironmentPreparedEvent(
ApplicationEnvironmentPreparedEvent event) {
List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();
postProcessors.add(this);
AnnotationAwareOrderComparator.sort(postProcessors);
for (EnvironmentPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessEnvironment(event.getEnvironment(),
event.getSpringApplication());
}
}
List<EnvironmentPostProcessor> loadPostProcessors() {
return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class,
getClass().getClassLoader());
}
@Override
public void postProcessEnvironment(ConfigurableEnvironment environment,
SpringApplication application) {
addPropertySources(environment, application.getResourceLoader());
configureIgnoreBeanInfo(environment);
bindToSpringApplication(environment, application);
}
private void configureIgnoreBeanInfo(ConfigurableEnvironment environment) {
if (System.getProperty(
CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME) == null) {
RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(environment,
"spring.beaninfo.");
Boolean ignore = resolver.getProperty("ignore", Boolean.class, Boolean.TRUE);
System.setProperty(CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME,
ignore.toString());
}
}
private void onApplicationPreparedEvent(ApplicationEvent event) {
this.logger.replayTo(ConfigFileApplicationListener.class);
addPostProcessors(((ApplicationPreparedEvent) event).getApplicationContext());
}
/**
* Add config file property sources to the specified environment.
* @param environment the environment to add source to
* @param resourceLoader the resource loader
* @see #addPostProcessors(ConfigurableApplicationContext)
*/
protected void addPropertySources(ConfigurableEnvironment environment,
ResourceLoader resourceLoader) {
RandomValuePropertySource.addToEnvironment(environment);
new Loader(environment, resourceLoader).load();
}
/**
* Bind the environment to the {@link SpringApplication}.
* @param environment the environment to bind
* @param application the application to bind to
*/
protected void bindToSpringApplication(ConfigurableEnvironment environment,
SpringApplication application) {
PropertiesConfigurationFactory<SpringApplication> binder = new PropertiesConfigurationFactory<SpringApplication>(
application);
binder.setTargetName("spring.main");
binder.setConversionService(this.conversionService);
binder.setPropertySources(environment.getPropertySources());
try {
binder.bindPropertiesToTarget();
}
catch (BindException ex) {
throw new IllegalStateException("Cannot bind to SpringApplication", ex);
}
}
/**
* Add appropriate post-processors to post-configure the property-sources.
* @param context the context to configure
*/
protected void addPostProcessors(ConfigurableApplicationContext context) {
context.addBeanFactoryPostProcessor(
new PropertySourceOrderingPostProcessor(context));
}
public void setOrder(int order) {
this.order = order;
}
@Override
public int getOrder() {
return this.order;
}
/**
* Set the search locations that will be considered as a comma-separated list. Each
* search location should be a directory path (ending in "/") and it will be prefixed
* by the file names constructed from {@link #setSearchNames(String) search names} and
* profiles (if any) plus file extensions supported by the properties loaders.
* Locations are considered in the order specified, with later items taking precedence
* (like a map merge).
* @param locations the search locations
*/
public void setSearchLocations(String locations) {
Assert.hasLength(locations, "Locations must not be empty");
this.searchLocations = locations;
}
/**
* Sets the names of the files that should be loaded (excluding file extension) as a
* comma-separated list.
* @param names the names to load
*/
public void setSearchNames(String names) {
Assert.hasLength(names, "Names must not be empty");
this.names = names;
}
/**
* {@link BeanFactoryPostProcessor} to re-order our property sources below any
* {@code @PropertySource} items added by the {@link ConfigurationClassPostProcessor}.
*/
private class PropertySourceOrderingPostProcessor
implements BeanFactoryPostProcessor, Ordered {
private ConfigurableApplicationContext context;
PropertySourceOrderingPostProcessor(ConfigurableApplicationContext context) {
this.context = context;
}
@Override
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE;
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
throws BeansException {
reorderSources(this.context.getEnvironment());
}
private void reorderSources(ConfigurableEnvironment environment) {
ConfigurationPropertySources
.finishAndRelocate(environment.getPropertySources());
PropertySource<?> defaultProperties = environment.getPropertySources()
.remove(DEFAULT_PROPERTIES);
if (defaultProperties != null) {
environment.getPropertySources().addLast(defaultProperties);
}
}
}
/**
* Loads candidate property sources and configures the active profiles.
*/
private class Loader {
private final Log logger = ConfigFileApplicationListener.this.logger;
private final ConfigurableEnvironment environment;
private final ResourceLoader resourceLoader;
private PropertySourcesLoader propertiesLoader;
private Queue<Profile> profiles;
private List<Profile> processedProfiles;
private boolean activatedProfiles;
Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
this.environment = environment;
this.resourceLoader = resourceLoader == null ? new DefaultResourceLoader()
: resourceLoader;
}
public void load() {
this.propertiesLoader = new PropertySourcesLoader();
this.activatedProfiles = false;
this.profiles = Collections.asLifoQueue(new LinkedList<Profile>());
this.processedProfiles = new LinkedList<Profile>();
// Pre-existing active profiles set via Environment.setActiveProfiles()
// are additional profiles and config files are allowed to add more if
// they want to, so don't call addActiveProfiles() here.
Set<Profile> initialActiveProfiles = initializeActiveProfiles();
this.profiles.addAll(getUnprocessedActiveProfiles(initialActiveProfiles));
if (this.profiles.isEmpty()) {
for (String defaultProfileName : this.environment.getDefaultProfiles()) {
Profile defaultProfile = new Profile(defaultProfileName, true);
if (!this.profiles.contains(defaultProfile)) {
this.profiles.add(defaultProfile);
}
}
}
// The default profile for these purposes is represented as null. We add it
// last so that it is first out of the queue (active profiles will then
// override any settings in the defaults when the list is reversed later).
this.profiles.add(null);
while (!this.profiles.isEmpty()) {
Profile profile = this.profiles.poll();
for (String location : getSearchLocations()) {
if (!location.endsWith("/")) {
// location is a filename already, so don't search for more
// filenames
load(location, null, profile);
}
else {
for (String name : getSearchNames()) {
load(location, name, profile);
}
}
}
this.processedProfiles.add(profile);
}
addConfigurationProperties(this.propertiesLoader.getPropertySources());
}
private Set<Profile> initializeActiveProfiles() {
if (!this.environment.containsProperty(ACTIVE_PROFILES_PROPERTY)
&& !this.environment.containsProperty(INCLUDE_PROFILES_PROPERTY)) {
return Collections.emptySet();
}
// Any pre-existing active profiles set via property sources (e.g. System
// properties) take precedence over those added in config files.
SpringProfiles springProfiles = bindSpringProfiles(
this.environment.getPropertySources());
Set<Profile> activeProfiles = new LinkedHashSet<Profile>(
springProfiles.getActiveProfiles());
activeProfiles.addAll(springProfiles.getIncludeProfiles());
maybeActivateProfiles(activeProfiles);
return activeProfiles;
}
/**
* Return the active profiles that have not been processed yet. If a profile is
* enabled via both {@link #ACTIVE_PROFILES_PROPERTY} and
* {@link ConfigurableEnvironment#addActiveProfile(String)} it needs to be
* filtered so that the {@link #ACTIVE_PROFILES_PROPERTY} value takes precedence.
* <p>
* Concretely, if the "cloud" profile is enabled via the environment, it will take
* less precedence that any profile set via the {@link #ACTIVE_PROFILES_PROPERTY}.
* @param initialActiveProfiles the profiles that have been enabled via
* {@link #ACTIVE_PROFILES_PROPERTY}
* @return the unprocessed active profiles from the environment to enable
*/
private List<Profile> getUnprocessedActiveProfiles(
Set<Profile> initialActiveProfiles) {
List<Profile> unprocessedActiveProfiles = new ArrayList<Profile>();
for (String profileName : this.environment.getActiveProfiles()) {
Profile profile = new Profile(profileName);
if (!initialActiveProfiles.contains(profile)) {
unprocessedActiveProfiles.add(profile);
}
}
// Reverse them so the order is the same as from getProfilesForValue()
// (last one wins when properties are eventually resolved)
Collections.reverse(unprocessedActiveProfiles);
return unprocessedActiveProfiles;
}
private void load(String location, String name, Profile profile) {
String group = "profile=" + (profile == null ? "" : profile);
if (!StringUtils.hasText(name)) {
// Try to load directly from the location
loadIntoGroup(group, location, profile);
}
else {
// Search for a file with the given name
for (String ext : this.propertiesLoader.getAllFileExtensions()) {
if (profile != null) {
// Try the profile-specific file
loadIntoGroup(group, location + name + "-" + profile + "." + ext,
null);
for (Profile processedProfile : this.processedProfiles) {
if (processedProfile != null) {
loadIntoGroup(group, location + name + "-"
+ processedProfile + "." + ext, profile);
}
}
// Sometimes people put "spring.profiles: dev" in
// application-dev.yml (gh-340). Arguably we should try and error
// out on that, but we can be kind and load it anyway.
loadIntoGroup(group, location + name + "-" + profile + "." + ext,
profile);
}
// Also try the profile-specific section (if any) of the normal file
loadIntoGroup(group, location + name + "." + ext, profile);
}
}
}
private PropertySource<?> loadIntoGroup(String identifier, String location,
Profile profile) {
try {
return doLoadIntoGroup(identifier, location, profile);
}
catch (Exception ex) {
throw new IllegalStateException(
"Failed to load property source from location '" + location + "'",
ex);
}
}
private PropertySource<?> doLoadIntoGroup(String identifier, String location,
Profile profile) throws IOException {
Resource resource = this.resourceLoader.getResource(location);
PropertySource<?> propertySource = null;
StringBuilder msg = new StringBuilder();
if (resource != null && resource.exists()) {
String name = "applicationConfig: [" + location + "]";
String group = "applicationConfig: [" + identifier + "]";
propertySource = this.propertiesLoader.load(resource, group, name,
(profile == null ? null : profile.getName()));
if (propertySource != null) {
msg.append("Loaded ");
handleProfileProperties(propertySource);
}
else {
msg.append("Skipped (empty) ");
}
}
else {
msg.append("Skipped ");
}
msg.append("config file ");
msg.append(getResourceDescription(location, resource));
if (profile != null) {
msg.append(" for profile ").append(profile);
}
if (resource == null || !resource.exists()) {
msg.append(" resource not found");
this.logger.trace(msg);
}
else {
this.logger.debug(msg);
}
return propertySource;
}
private String getResourceDescription(String location, Resource resource) {
String resourceDescription = "'" + location + "'";
if (resource != null) {
try {
resourceDescription = String.format("'%s' (%s)",
resource.getURI().toASCIIString(), location);
}
catch (IOException ex) {
// Use the location as the description
}
}
return resourceDescription;
}
private void handleProfileProperties(PropertySource<?> propertySource) {
SpringProfiles springProfiles = bindSpringProfiles(propertySource);
maybeActivateProfiles(springProfiles.getActiveProfiles());
addProfiles(springProfiles.getIncludeProfiles());
}
private SpringProfiles bindSpringProfiles(PropertySource<?> propertySource) {
MutablePropertySources propertySources = new MutablePropertySources();
propertySources.addFirst(propertySource);
return bindSpringProfiles(propertySources);
}
private SpringProfiles bindSpringProfiles(PropertySources propertySources) {
SpringProfiles springProfiles = new SpringProfiles();
RelaxedDataBinder dataBinder = new RelaxedDataBinder(springProfiles,
"spring.profiles");
dataBinder.bind(new PropertySourcesPropertyValues(propertySources, false));
springProfiles.setActive(resolvePlaceholders(springProfiles.getActive()));
springProfiles.setInclude(resolvePlaceholders(springProfiles.getInclude()));
return springProfiles;
}
private List<String> resolvePlaceholders(List<String> values) {
List<String> resolved = new ArrayList<String>();
for (String value : values) {
resolved.add(this.environment.resolvePlaceholders(value));
}
return resolved;
}
private void maybeActivateProfiles(Set<Profile> profiles) {
if (this.activatedProfiles) {
if (!profiles.isEmpty()) {
this.logger.debug("Profiles already activated, '" + profiles
+ "' will not be applied");
}
return;
}
if (!profiles.isEmpty()) {
addProfiles(profiles);
this.logger.debug("Activated profiles "
+ StringUtils.collectionToCommaDelimitedString(profiles));
this.activatedProfiles = true;
removeUnprocessedDefaultProfiles();
}
}
private void removeUnprocessedDefaultProfiles() {
for (Iterator<Profile> iterator = this.profiles.iterator(); iterator
.hasNext();) {
if (iterator.next().isDefaultProfile()) {
iterator.remove();
}
}
}
private void addProfiles(Set<Profile> profiles) {
for (Profile profile : profiles) {
this.profiles.add(profile);
if (!environmentHasActiveProfile(profile.getName())) {
// If it's already accepted we assume the order was set
// intentionally
prependProfile(this.environment, profile);
}
}
}
private boolean environmentHasActiveProfile(String profile) {
for (String activeProfile : this.environment.getActiveProfiles()) {
if (activeProfile.equals(profile)) {
return true;
}
}
return false;
}
private void prependProfile(ConfigurableEnvironment environment,
Profile profile) {
Set<String> profiles = new LinkedHashSet<String>();
environment.getActiveProfiles(); // ensure they are initialized
// But this one should go first (last wins in a property key clash)
profiles.add(profile.getName());
profiles.addAll(Arrays.asList(environment.getActiveProfiles()));
environment.setActiveProfiles(profiles.toArray(new String[profiles.size()]));
}
private Set<String> getSearchLocations() {
Set<String> locations = new LinkedHashSet<String>();
// User-configured settings take precedence, so we do them first
if (this.environment.containsProperty(CONFIG_LOCATION_PROPERTY)) {
for (String path : asResolvedSet(
this.environment.getProperty(CONFIG_LOCATION_PROPERTY), null)) {
if (!path.contains("$")) {
path = StringUtils.cleanPath(path);
if (!ResourceUtils.isUrl(path)) {
path = ResourceUtils.FILE_URL_PREFIX + path;
}
}
locations.add(path);
}
}
locations.addAll(
asResolvedSet(ConfigFileApplicationListener.this.searchLocations,
DEFAULT_SEARCH_LOCATIONS));
return locations;
}
private Set<String> getSearchNames() {
if (this.environment.containsProperty(CONFIG_NAME_PROPERTY)) {
return asResolvedSet(this.environment.getProperty(CONFIG_NAME_PROPERTY),
null);
}
return asResolvedSet(ConfigFileApplicationListener.this.names, DEFAULT_NAMES);
}
private Set<String> asResolvedSet(String value, String fallback) {
List<String> list = Arrays.asList(StringUtils.trimArrayElements(
StringUtils.commaDelimitedListToStringArray(value != null
? this.environment.resolvePlaceholders(value) : fallback)));
Collections.reverse(list);
return new LinkedHashSet<String>(list);
}
private void addConfigurationProperties(MutablePropertySources sources) {
List<PropertySource<?>> reorderedSources = new ArrayList<PropertySource<?>>();
for (PropertySource<?> item : sources) {
reorderedSources.add(item);
}
addConfigurationProperties(
new ConfigurationPropertySources(reorderedSources));
}
private void addConfigurationProperties(
ConfigurationPropertySources configurationSources) {
MutablePropertySources existingSources = this.environment
.getPropertySources();
if (existingSources.contains(DEFAULT_PROPERTIES)) {
existingSources.addBefore(DEFAULT_PROPERTIES, configurationSources);
}
else {
existingSources.addLast(configurationSources);
}
}
}
private static class Profile {
private final String name;
private final boolean defaultProfile;
Profile(String name) {
this(name, false);
}
Profile(String name, boolean defaultProfile) {
Assert.notNull(name, "Name must not be null");
this.name = name;
this.defaultProfile = defaultProfile;
}
public String getName() {
return this.name;
}
public boolean isDefaultProfile() {
return this.defaultProfile;
}
@Override
public String toString() {
return this.name;
}
@Override
public int hashCode() {
return this.name.hashCode();
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj == null || obj.getClass() != getClass()) {
return false;
}
return ((Profile) obj).name.equals(this.name);
}
}
/**
* Holds the configuration {@link PropertySource}s as they are loaded can relocate
* them once configuration classes have been processed.
*/
static class ConfigurationPropertySources
extends EnumerablePropertySource<Collection<PropertySource<?>>> {
private final Collection<PropertySource<?>> sources;
private final String[] names;
ConfigurationPropertySources(Collection<PropertySource<?>> sources) {
super(APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME, sources);
this.sources = sources;
List<String> names = new ArrayList<String>();
for (PropertySource<?> source : sources) {
if (source instanceof EnumerablePropertySource) {
names.addAll(Arrays.asList(
((EnumerablePropertySource<?>) source).getPropertyNames()));
}
}
this.names = names.toArray(new String[names.size()]);
}
@Override
public Object getProperty(String name) {
for (PropertySource<?> propertySource : this.sources) {
Object value = propertySource.getProperty(name);
if (value != null) {
return value;
}
}
return null;
}
public static void finishAndRelocate(MutablePropertySources propertySources) {
String name = APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME;
ConfigurationPropertySources removed = (ConfigurationPropertySources) propertySources
.get(name);
if (removed != null) {
for (PropertySource<?> propertySource : removed.sources) {
if (propertySource instanceof EnumerableCompositePropertySource) {
EnumerableCompositePropertySource composite = (EnumerableCompositePropertySource) propertySource;
for (PropertySource<?> nested : composite.getSource()) {
propertySources.addAfter(name, nested);
name = nested.getName();
}
}
else {
propertySources.addAfter(name, propertySource);
}
}
propertySources.remove(APPLICATION_CONFIGURATION_PROPERTY_SOURCE_NAME);
}
}
@Override
public String[] getPropertyNames() {
return this.names;
}
}
/**
* Holder for {@code spring.profiles} properties.
*/
static final class SpringProfiles {
private List<String> active = new ArrayList<String>();
private List<String> include = new ArrayList<String>();
public List<String> getActive() {
return this.active;
}
public void setActive(List<String> active) {
this.active = active;
}
public List<String> getInclude() {
return this.include;
}
public void setInclude(List<String> include) {
this.include = include;
}
Set<Profile> getActiveProfiles() {
return asProfileSet(this.active);
}
Set<Profile> getIncludeProfiles() {
return asProfileSet(this.include);
}
private Set<Profile> asProfileSet(List<String> profileNames) {
List<Profile> profiles = new ArrayList<Profile>();
for (String profileName : profileNames) {
profiles.add(new Profile(profileName));
}
Collections.reverse(profiles);
return new LinkedHashSet<Profile>(profiles);
}
}
}根据javadoc注释的说明，这个类会从指定的位置加载application.properties或者application.yml并将它们的属性读到Envrionment当中，其中这几个方法大家关注下：
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent(
(ApplicationEnvironmentPreparedEvent) event);
}
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent(event);
}
} 当springboot程序启动时一定会触发该事件监听，如果当前是 ApplicationEnvironmentPreparedEvent事件就会调用 onApplicationEnvironmentPreparedEvent方法，最终该方法会执行：
@Override
public void postProcessEnvironment(ConfigurableEnvironment environment,
SpringApplication application) {
addPropertySources(environment, application.getResourceLoader());
configureIgnoreBeanInfo(environment);
bindToSpringApplication(environment, application);
}其中 bindToSpringApplication方法为：
/**
* Bind the environment to the {@link SpringApplication}.
* @param environment the environment to bind
* @param application the application to bind to
*/
protected void bindToSpringApplication(ConfigurableEnvironment environment,
SpringApplication application) {
PropertiesConfigurationFactory<SpringApplication> binder = new PropertiesConfigurationFactory<SpringApplication>(
application);
binder.setTargetName("spring.main");
binder.setConversionService(this.conversionService);
binder.setPropertySources(environment.getPropertySources());
try {
binder.bindPropertiesToTarget();
}
catch (BindException ex) {
throw new IllegalStateException("Cannot bind to SpringApplication", ex);
}
}很明显该方法是将Environment绑定到对应SpringApplication上，通过这个类就可以获取到我们更改过后的配置了
1.3、changes方法
private Map<String, Object> changes(Map<String, Object> before,
Map<String, Object> after) {
Map<String, Object> result = new HashMap<String, Object>();
for (String key : before.keySet()) {
if (!after.containsKey(key)) {
result.put(key, null);
}
else if (!equal(before.get(key), after.get(key))) {
result.put(key, after.get(key));
}
}
for (String key : after.keySet()) {
if (!before.containsKey(key)) {
result.put(key, after.get(key));
}
}
return result;
}changes方法其实就是处理配置变更信息的，分以下几种情况：
1）如果刷新过后配置文件新增配置就添加到Map里
2) 如果有配置变更就添加变更后的配置
3) 如果删除了原先的配置，就把原先的key对应的值设置为null
至此经过changes方法后，上下文环境已经拥有最新的配置了。
1.4、发布事件
当上述步骤都执行完毕后，紧接着会发布EnvrionmentChangeEvent事件，可是这个事件谁来监听呢？在这里我贴出官网的一段描述：
应用程序将收听EnvironmentChangeEvent，并以几种标准方式进行更改（用户可以以常规方式添加ApplicationListeners附加ApplicationListeners）。当观察到EnvironmentChangeEvent时，它将有一个已更改的键值列表，应用程序将使用以下内容：
1.重新绑定上下文中的任何@ConfigurationProperties bean
2.为logging.level.*中的任何属性设置记录器级别
根据官网描述我们知道将变更一下操作行为@ConfigurationProperties的bean与更改日志level，那么如何做到的呢？结合官网文档我们来关注以下两个类：
ConfigurationPropertiesRebinder:
/*
* Copyright 2013-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.context.properties;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.cloud.context.environment.EnvironmentChangeEvent;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationListener;
import org.springframework.core.env.Environment;
import org.springframework.jmx.export.annotation.ManagedAttribute;
import org.springframework.jmx.export.annotation.ManagedOperation;
import org.springframework.jmx.export.annotation.ManagedResource;
import org.springframework.stereotype.Component;
/**
* Listens for {@link EnvironmentChangeEvent} and rebinds beans that were bound to the
* {@link Environment} using {@link ConfigurationProperties
* <code>@ConfigurationProperties</code>}. When these beans are re-bound and
* re-initialized the changes are available immediately to any component that is using the
* <code>@ConfigurationProperties</code> bean.
*
* @see RefreshScope for a deeper and optionally more focused refresh of bean components
*
* @author Dave Syer
*
*/
@Component
@ManagedResource
public class ConfigurationPropertiesRebinder
implements ApplicationContextAware, ApplicationListener<EnvironmentChangeEvent> {
private ConfigurationPropertiesBeans beans;
private ApplicationContext applicationContext;
private Map<String, Exception> errors = new ConcurrentHashMap<>();
public ConfigurationPropertiesRebinder(ConfigurationPropertiesBeans beans) {
this.beans = beans;
}
@Override
public void setApplicationContext(ApplicationContext applicationContext)
throws BeansException {
this.applicationContext = applicationContext;
}
/**
* A map of bean name to errors when instantiating the bean.
*
* @return the errors accumulated since the latest destroy
*/
public Map<String, Exception> getErrors() {
return this.errors;
}
@ManagedOperation
public void rebind() {
this.errors.clear();
for (String name : this.beans.getBeanNames()) {
rebind(name);
}
}
@ManagedOperation
public boolean rebind(String name) {
if (!this.beans.getBeanNames().contains(name)) {
return false;
}
if (this.applicationContext != null) {
try {
Object bean = this.applicationContext.getBean(name);
if (AopUtils.isAopProxy(bean)) {
bean = getTargetObject(bean);
}
this.applicationContext.getAutowireCapableBeanFactory().destroyBean(bean);
this.applicationContext.getAutowireCapableBeanFactory()
.initializeBean(bean, name);
return true;
}
catch (RuntimeException e) {
this.errors.put(name, e);
throw e;
}
}
return false;
}
@SuppressWarnings("unchecked")
private static <T> T getTargetObject(Object candidate) {
try {
if (AopUtils.isAopProxy(candidate) && (candidate instanceof Advised)) {
return (T) ((Advised) candidate).getTargetSource().getTarget();
}
}
catch (Exception ex) {
throw new IllegalStateException("Failed to unwrap proxied object", ex);
}
return (T) candidate;
}
@ManagedAttribute
public Set<String> getBeanNames() {
return new HashSet<String>(this.beans.getBeanNames());
}
@Override
public void onApplicationEvent(EnvironmentChangeEvent event) {
if (this.applicationContext.equals(event.getSource())
// Backwards compatible
|| event.getKeys().equals(event.getSource())) {
rebind();
}
}
}我们可以看到该类监听了ChangeEnvrionmentEvent事件，它最主要作用是拿到更新的配置以后，重新绑定@ConfigurationProperties标记的类使之能够读取最新的属性
LoggingRebinder:
/*
* Copyright 2013-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.logging;
import java.util.Map;
import java.util.Map.Entry;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.boot.bind.RelaxedPropertyResolver;
import org.springframework.boot.logging.LogLevel;
import org.springframework.boot.logging.LoggingSystem;
import org.springframework.cloud.context.environment.EnvironmentChangeEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.EnvironmentAware;
import org.springframework.core.env.Environment;
/**
* Listener that looks for {@link EnvironmentChangeEvent} and rebinds logger levels if any
* changed.
*
* @author Dave Syer
*
*/
public class LoggingRebinder
implements ApplicationListener<EnvironmentChangeEvent>, EnvironmentAware {
private final Log logger = LogFactory.getLog(getClass());
private Environment environment;
@Override
public void setEnvironment(Environment environment) {
this.environment = environment;
}
@Override
public void onApplicationEvent(EnvironmentChangeEvent event) {
if (this.environment == null) {
return;
}
LoggingSystem system = LoggingSystem.get(LoggingSystem.class.getClassLoader());
setLogLevels(system, this.environment);
}
protected void setLogLevels(LoggingSystem system, Environment environment) {
Map<String, Object> levels = new RelaxedPropertyResolver(environment)
.getSubProperties("logging.level.");
for (Entry<String, Object> entry : levels.entrySet()) {
setLogLevel(system, environment, entry.getKey(), entry.getValue().toString());
}
}
private void setLogLevel(LoggingSystem system, Environment environment, String name,
String level) {
try {
if (name.equalsIgnoreCase("root")) {
name = null;
}
level = environment.resolvePlaceholders(level);
system.setLogLevel(name, LogLevel.valueOf(level.toUpperCase()));
}
catch (RuntimeException ex) {
this.logger.error("Cannot set level: " + level + " for '" + name + "'");
}
}
}该类也是监听了ChangeEnvrionmentEvent事件，用于重新绑定日志级别
二、刷新范围
我们考虑如下场景，当我们变更数据库配置后，通过refresh刷新，虽然能获取到最新的配置，可是我们的DataSource对象早就被初始化好了，换句话说即便配置刷新了我们拿到的依然是配置刷新前的对象。怎么解决这个问题呢？
我们继续看ContextRefresher的refresh方法，最后有一处代码值得我们关注一下this.scope.refreshAll()，此处scope对象是RefreshScope类型，那么这个类有什么作用呢？那么我们先要关注一下@RefreshScope注解。在这里我在贴出官网一段解释：
当配置更改时，标有@RefreshScope的Spring @Bean将得到特殊处理。这解决了状态bean在初始化时只注入配置的问题。例如，如果通过Environment更改数据库URL时DataSource有开放连接，那么我们可能希望这些连接的持有人能够完成他们正在做的工作。然后下一次有人从游泳池借用一个连接，他得到一个新的URL
刷新范围bean是在使用时初始化的懒惰代理（即当调用一个方法时），并且作用域作为初始值的缓存。要强制bean重新初始化下一个方法调用，您只需要使其缓存条目无效。RefreshScope是上下文中的一个bean，它有一个公共方法refreshAll()来清除目标缓存中的范围内的所有bean。还有一个refresh(String)方法可以按名称刷新单个bean。此功能在/refresh端点（通过HTTP或JMX）中公开。
这里我贴出@RefreshScope源码：
/*
* Copyright 2013-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.context.config.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
/**
* Convenience annotation to put a <code>@Bean</code> definition in
* {@link org.springframework.cloud.context.scope.refresh.RefreshScope refresh scope}.
* Beans annotated this way can be refreshed at runtime and any components that are using
* them will get a new instance on the next method call, fully initialized and injected
* with all dependencies.
*
* @author Dave Syer
*
*/
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Scope("refresh")
@Documented
public @interface RefreshScope {
/**
* @see Scope#proxyMode()
*/
ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;
}在这个注解上我们关注一下此处标记了@Scope("refresh")，我们知道Spring的Bean属性有个叫scope的，它定义了bean的作用范围，常见的有singleon,prototype,session等。此处新定义了一个范围叫做refresh，在此我贴出RefreshScope的源代码来分析一下：
/*
* Copyright 2002-2009 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package org.springframework.cloud.context.scope.refresh;
import java.io.Serializable;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.cloud.context.scope.GenericScope;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.core.Ordered;
import org.springframework.jmx.export.annotation.ManagedOperation;
import org.springframework.jmx.export.annotation.ManagedResource;
/**
* <p>
* A Scope implementation that allows for beans to be refreshed dynamically at runtime
* (see {@link #refresh(String)} and {@link #refreshAll()}). If a bean is refreshed then
* the next time the bean is accessed (i.e. a method is executed) a new instance is
* created. All lifecycle methods are applied to the bean instances, so any destruction
* callbacks that were registered in the bean factory are called when it is refreshed, and
* then the initialization callbacks are invoked as normal when the new instance is
* created. A new bean instance is created from the original bean definition, so any
* externalized content (property placeholders or expressions in string literals) is
* re-evaluated when it is created.
* </p>
*
* <p>
* Note that all beans in this scope are <em>only</em> initialized when first accessed, so
* the scope forces lazy initialization semantics. The implementation involves creating a
* proxy for every bean in the scope, so there is a flag
* {@link #setProxyTargetClass(boolean) proxyTargetClass} which controls the proxy
* creation, defaulting to JDK dynamic proxies and therefore only exposing the interfaces
* implemented by a bean. If callers need access to other methods then the flag needs to
* be set (and CGLib present on the classpath). Because this scope automatically proxies
* all its beans, there is no need to add <code><aop:auto-proxy/></code> to any bean
* definitions.
* </p>
*
* <p>
* The scoped proxy approach adopted here has a side benefit that bean instances are
* automatically {@link Serializable}, and can be sent across the wire as long as the
* receiver has an identical application context on the other side. To ensure that the two
* contexts agree that they are identical they have to have the same serialization id. One
* will be generated automatically by default from the bean names, so two contexts with
* the same bean names are by default able to exchange beans by name. If you need to
* override the default id then provide an explicit {@link #setId(String) id} when the
* Scope is declared.
* </p>
*
* @author Dave Syer
*
* @since 3.1
*
*/
@ManagedResource
public class RefreshScope extends GenericScope
implements ApplicationContextAware, Ordered {
private ApplicationContext context;
private BeanDefinitionRegistry registry;
private boolean eager = true;
private int order = Ordered.LOWEST_PRECEDENCE - 100;
/**
* Create a scope instance and give it the default name: "refresh".
*/
public RefreshScope() {
super.setName("refresh");
}
@Override
public int getOrder() {
return this.order;
}
public void setOrder(int order) {
this.order = order;
}
/**
* Flag to determine whether all beans in refresh scope should be instantiated eagerly
* on startup. Default true.
*
* @param eager the flag to set
*/
public void setEager(boolean eager) {
this.eager = eager;
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
throws BeansException {
this.registry = registry;
super.postProcessBeanDefinitionRegistry(registry);
}
@EventListener
public void start(ContextRefreshedEvent event) {
if (event.getApplicationContext() == this.context && this.eager
&& this.registry != null) {
eagerlyInitialize();
}
}
private void eagerlyInitialize() {
for (String name : this.context.getBeanDefinitionNames()) {
BeanDefinition definition = this.registry.getBeanDefinition(name);
if (this.getName().equals(definition.getScope()) && !definition.isLazyInit()) {
Object bean = this.context.getBean(name);
if (bean != null) {
bean.getClass();
}
}
}
}
@ManagedOperation(description = "Dispose of the current instance of bean name provided and force a refresh on next method execution.")
public boolean refresh(String name) {
if (!name.startsWith(SCOPED_TARGET_PREFIX)) {
// User wants to refresh the bean with this name but that isn't the one in the
// cache...
name = SCOPED_TARGET_PREFIX + name;
}
// Ensure lifecycle is finished if bean was disposable
if (super.destroy(name)) {
this.context.publishEvent(new RefreshScopeRefreshedEvent(name));
return true;
}
return false;
}
@ManagedOperation(description = "Dispose of the current instance of all beans in this scope and force a refresh on next method execution.")
public void refreshAll() {
super.destroy();
this.context.publishEvent(new RefreshScopeRefreshedEvent());
}
@Override
public void setApplicationContext(ApplicationContext context) throws BeansException {
this.context = context;
}
}该类继承了GenericScope：
/*
* Copyright 2002-2009 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package org.springframework.cloud.context.scope;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.scope.ScopedObject;
import org.springframework.aop.scope.ScopedProxyFactoryBean;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.Scope;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.ParseException;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;
/**
* <p>
* A generic Scope implementation.
* </p>
*
* @author Dave Syer
*
* @since 3.1
*
*/
public class GenericScope implements Scope, BeanFactoryPostProcessor,
BeanDefinitionRegistryPostProcessor, DisposableBean {
private static final Log logger = LogFactory.getLog(GenericScope.class);
public static final String SCOPED_TARGET_PREFIX = "scopedTarget.";
private BeanLifecycleWrapperCache cache = new BeanLifecycleWrapperCache(
new StandardScopeCache());
private String name = "generic";
private ConfigurableListableBeanFactory beanFactory;
private StandardEvaluationContext evaluationContext;
private String id;
private Map<String, Exception> errors = new ConcurrentHashMap<>();
private ConcurrentMap<String, ReadWriteLock> locks = new ConcurrentHashMap<>();
/**
* Manual override for the serialization id that will be used to identify the bean
* factory. The default is a unique key based on the bean names in the bean factory.
*
* @param id the id to set
*/
public void setId(String id) {
this.id = id;
}
/**
* The name of this scope. Default "generic".
*
* @param name the name value to set
*/
public void setName(String name) {
this.name = name;
}
/**
* The cache implementation to use for bean instances in this scope.
*
* @param cache the cache to use
*/
public void setScopeCache(ScopeCache cache) {
this.cache = new BeanLifecycleWrapperCache(cache);
}
/**
* A map of bean name to errors when instantiating the bean.
*
* @return the errors accumulated since the latest destroy
*/
public Map<String, Exception> getErrors() {
return this.errors;
}
@Override
public void destroy() {
List<Throwable> errors = new ArrayList<Throwable>();
Collection<BeanLifecycleWrapper> wrappers = this.cache.clear();
for (BeanLifecycleWrapper wrapper : wrappers) {
try {
Lock lock = locks.get(wrapper.getName()).writeLock();
lock.lock();
try {
wrapper.destroy();
}
finally {
lock.unlock();
}
}
catch (RuntimeException e) {
errors.add(e);
}
}
if (!errors.isEmpty()) {
throw wrapIfNecessary(errors.get(0));
}
this.errors.clear();
}
/**
* Destroy the named bean (i.e. flush it from the cache by default).
*
* @param name the bean name to flush
* @return true if the bean was already cached, false otherwise
*/
protected boolean destroy(String name) {
BeanLifecycleWrapper wrapper = this.cache.remove(name);
if (wrapper != null) {
Lock lock = locks.get(wrapper.getName()).writeLock();
lock.lock();
try {
wrapper.destroy();
}
finally {
lock.unlock();
}
this.errors.remove(name);
return true;
}
return false;
}
@Override
public Object get(String name, ObjectFactory<?> objectFactory) {
BeanLifecycleWrapper value = this.cache.put(name,
new BeanLifecycleWrapper(name, objectFactory));
locks.putIfAbsent(name, new ReentrantReadWriteLock());
try {
return value.getBean();
}
catch (RuntimeException e) {
this.errors.put(name, e);
throw e;
}
}
@Override
public String getConversationId() {
return this.name;
}
@Override
public void registerDestructionCallback(String name, Runnable callback) {
BeanLifecycleWrapper value = this.cache.get(name);
if (value == null) {
return;
}
value.setDestroyCallback(callback);
}
@Override
public Object remove(String name) {
BeanLifecycleWrapper value = this.cache.remove(name);
if (value == null) {
return null;
}
// Someone might have added another object with the same key, but we
// keep the method contract by removing the
// value we found anyway
return value.getBean();
}
@Override
public Object resolveContextualObject(String key) {
Expression expression = parseExpression(key);
return expression.getValue(this.evaluationContext, this.beanFactory);
}
private Expression parseExpression(String input) {
if (StringUtils.hasText(input)) {
ExpressionParser parser = new SpelExpressionParser();
try {
return parser.parseExpression(input);
}
catch (ParseException e) {
throw new IllegalArgumentException("Cannot parse expression: " + input,
e);
}
}
else {
return null;
}
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
throws BeansException {
this.beanFactory = beanFactory;
beanFactory.registerScope(this.name, this);
setSerializationId(beanFactory);
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
throws BeansException {
for (String name : registry.getBeanDefinitionNames()) {
BeanDefinition definition = registry.getBeanDefinition(name);
if (definition instanceof RootBeanDefinition) {
RootBeanDefinition root = (RootBeanDefinition) definition;
if (root.getDecoratedDefinition() != null && root.hasBeanClass()
&& root.getBeanClass() == ScopedProxyFactoryBean.class) {
if (getName().equals(root.getDecoratedDefinition().getBeanDefinition()
.getScope())) {
root.setBeanClass(LockedScopedProxyFactoryBean.class);
}
}
}
}
}
/**
* If the bean factory is a DefaultListableBeanFactory then it can serialize scoped
* beans and deserialize them in another context (even in another JVM), as long as the
* ids of the bean factories match. This method sets up the serialization id to be
* either the id provided to the scope instance, or if that is null, a hash of all the
* bean names.
*
* @param beanFactory the bean factory to configure
*/
private void setSerializationId(ConfigurableListableBeanFactory beanFactory) {
if (beanFactory instanceof DefaultListableBeanFactory) {
String id = this.id;
if (id == null) {
List<String> list = new ArrayList<>(
Arrays.asList(beanFactory.getBeanDefinitionNames()));
Collections.sort(list);
String names = list.toString();
logger.debug("Generating bean factory id from names: " + names);
id = UUID.nameUUIDFromBytes(names.getBytes()).toString();
}
logger.info("BeanFactory id=" + id);
((DefaultListableBeanFactory) beanFactory).setSerializationId(id);
}
else {
logger.warn(
"BeanFactory was not a DefaultListableBeanFactory, scoped proxy beans "
+ "cannot be serialized.");
}
}
static RuntimeException wrapIfNecessary(Throwable throwable) {
if (throwable instanceof RuntimeException) {
return (RuntimeException) throwable;
}
if (throwable instanceof Error) {
throw (Error) throwable;
}
return new IllegalStateException(throwable);
}
protected String getName() {
return this.name;
}
private static class BeanLifecycleWrapperCache {
private final ScopeCache cache;
public BeanLifecycleWrapperCache(ScopeCache cache) {
this.cache = cache;
}
public BeanLifecycleWrapper remove(String name) {
return (BeanLifecycleWrapper) this.cache.remove(name);
}
public Collection<BeanLifecycleWrapper> clear() {
Collection<Object> values = this.cache.clear();
Collection<BeanLifecycleWrapper> wrappers = new LinkedHashSet<BeanLifecycleWrapper>();
for (Object object : values) {
wrappers.add((BeanLifecycleWrapper) object);
}
return wrappers;
}
public BeanLifecycleWrapper get(String name) {
return (BeanLifecycleWrapper) this.cache.get(name);
}
public BeanLifecycleWrapper put(String name, BeanLifecycleWrapper value) {
return (BeanLifecycleWrapper) this.cache.put(name, value);
}
}
/**
* Wrapper for a bean instance and any destruction callback (DisposableBean etc.) that
* is registered for it. Also decorates the bean to optionally guard it from
* concurrent access (for instance).
*
* @author Dave Syer
*
*/
private static class BeanLifecycleWrapper {
private Object bean;
private Runnable callback;
private final String name;
private final ObjectFactory<?> objectFactory;
public BeanLifecycleWrapper(String name, ObjectFactory<?> objectFactory) {
this.name = name;
this.objectFactory = objectFactory;
}
public String getName() {
return this.name;
}
public void setDestroyCallback(Runnable callback) {
this.callback = callback;
}
public Object getBean() {
if (this.bean == null) {
synchronized (this.name) {
if (this.bean == null) {
this.bean = this.objectFactory.getObject();
}
}
}
return this.bean;
}
public void destroy() {
if (this.callback == null) {
return;
}
synchronized (this.name) {
Runnable callback = this.callback;
if (callback != null) {
callback.run();
}
this.callback = null;
this.bean = null;
}
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((this.name == null) ? 0 : this.name.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
BeanLifecycleWrapper other = (BeanLifecycleWrapper) obj;
if (this.name == null) {
if (other.name != null) {
return false;
}
}
else if (!this.name.equals(other.name)) {
return false;
}
return true;
}
}
@SuppressWarnings("serial")
public class LockedScopedProxyFactoryBean extends ScopedProxyFactoryBean
implements MethodInterceptor {
private String targetBeanName;
@Override
public void setBeanFactory(BeanFactory beanFactory) {
super.setBeanFactory(beanFactory);
Object proxy = getObject();
if (proxy instanceof Advised) {
Advised advised = (Advised) proxy;
advised.addAdvice(0, this);
}
}
@Override
public void setTargetBeanName(String targetBeanName) {
super.setTargetBeanName(targetBeanName);
this.targetBeanName = targetBeanName;
}
@Override
public Object invoke(MethodInvocation invocation) throws Throwable {
Method method = invocation.getMethod();
if (AopUtils.isEqualsMethod(method)
|| AopUtils.isToStringMethod(method)
|| AopUtils.isHashCodeMethod(method)
|| isScopedObjectGetTargetObject(method)) {
return invocation.proceed();
}
Object proxy = getObject();
Lock lock = locks.get(this.targetBeanName).readLock();
lock.lock();
try {
if (proxy instanceof Advised) {
Advised advised = (Advised) proxy;
ReflectionUtils.makeAccessible(method);
return ReflectionUtils.invokeMethod(method,
advised.getTargetSource().getTarget(),
invocation.getArguments());
}
return invocation.proceed();
}
finally {
lock.unlock();
}
}
private boolean isScopedObjectGetTargetObject(Method method) {
return method.getDeclaringClass().equals(ScopedObject.class)
&& method.getName().equals("getTargetObject")
&& method.getParameterTypes().length == 0;
}
}
}这里面我们先看一下RefreshScope的构造函数：
/**
* Create a scope instance and give it the default name: "refresh".
*/
public RefreshScope() {
super.setName("refresh");
}这里面创建了一个名字为refresh的scope。
紧接着在它的父类里我们可以看一下这个方法：
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
throws BeansException {
this.beanFactory = beanFactory;
beanFactory.registerScope(this.name, this);
setSerializationId(beanFactory);
}此方法中使用BeanFactory注册了一个refresh的范围，使得scope为refresh的bean生效。@RefreshScope标注的类还有一个特点：会使用代理对象并进行延迟加载。我们来看一下postProcessBeanDefinitionRegistry方法
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
throws BeansException {
for (String name : registry.getBeanDefinitionNames()) {
BeanDefinition definition = registry.getBeanDefinition(name);
if (definition instanceof RootBeanDefinition) {
RootBeanDefinition root = (RootBeanDefinition) definition;
if (root.getDecoratedDefinition() != null && root.hasBeanClass()
&& root.getBeanClass() == ScopedProxyFactoryBean.class) {
if (getName().equals(root.getDecoratedDefinition().getBeanDefinition()
.getScope())) {
root.setBeanClass(LockedScopedProxyFactoryBean.class);
}
}
}
}
}该方法遍历所有的bean定义 如果当前的bean的scope为refresh,那么就把当前的bean设置为 LockedScopedProxyFactoryBean的代理对象。
RefreshScope还会监听一个ContextRefreshedEvent，该事件会在ApplicationContext初始化或者refreshed时触发，我们来看一下代码：
@EventListener
public void start(ContextRefreshedEvent event) {
if (event.getApplicationContext() == this.context && this.eager
&& this.registry != null) {
eagerlyInitialize();
}
}
private void eagerlyInitialize() {
for (String name : this.context.getBeanDefinitionNames()) {
BeanDefinition definition = this.registry.getBeanDefinition(name);
if (this.getName().equals(definition.getScope()) && !definition.isLazyInit()) {
Object bean = this.context.getBean(name);
if (bean != null) {
bean.getClass();
}
}
}
}注意此处获取refreshscope的bean，其中getBean是一个复杂而又繁琐的过程，此处我们先不在这里讨论，只不过经过这个方法以后，其通过代理机制会在GernericScope的BeanLifecycleWrapperCache缓存里把这个@RefreshScope标记的bean添加进去。
最后我们回过头来看一看RefreshScope的refreshAll方法：
@ManagedOperation(description = "Dispose of the current instance of all beans in this scope and force a refresh on next method execution.")
public void refreshAll() {
super.destroy();
this.context.publishEvent(new RefreshScopeRefreshedEvent());
}
//.......GernericScope的destroy方法
@Override
public void destroy() {
List<Throwable> errors = new ArrayList<Throwable>();
Collection<BeanLifecycleWrapper> wrappers = this.cache.clear();
for (BeanLifecycleWrapper wrapper : wrappers) {
try {
Lock lock = locks.get(wrapper.getName()).writeLock();
lock.lock();
try {
wrapper.destroy();
}
finally {
lock.unlock();
}
}
catch (RuntimeException e) {
errors.add(e);
}
}
if (!errors.isEmpty()) {
throw wrapIfNecessary(errors.get(0));
}
this.errors.clear();
}这里的代码逻辑很简单清除与释放缓存里被@RefreshScope标记的bean 。
当我们要获取对象时，我们可以关注如下方法：
@Override
public Object get(String name, ObjectFactory<?> objectFactory) {
BeanLifecycleWrapper value = this.cache.put(name,
new BeanLifecycleWrapper(name, objectFactory));
locks.putIfAbsent(name, new ReentrantReadWriteLock());
try {
return value.getBean();
}
catch (RuntimeException e) {
this.errors.put(name, e);
throw e;
}
}
//..... BeanLifecycleWrapper的方法
public Object getBean() {
if (this.bean == null) {
synchronized (this.name) {
if (this.bean == null) {
this.bean = this.objectFactory.getObject();
}
}
}
return this.bean;
}BeanLifecycleWrapper这个是@RefreshScope标记bean的一个包装类，会被存储到缓存里，在这里取不到值的话就会从objectFactory里去拿
三、示例与总结
3.1、示例
创建AppConfig类代码如下：
package com.bdqn.lyrk.refresh.scope.server;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
@EnableConfigurationProperties(StudentConfig.class)
public class AppConfig {
@RefreshScope
@Bean
public Student student(StudentConfig config) {
Student student = new Student();
student.setName(config.getName());
return student;
}
}在这里，将Student设置为@RefreshScope 那么刷新以后会获取最新的Bean
启动类：
package com.bdqn.lyrk.refresh.scope.server;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@SpringBootApplication
@RestController
public class RefreshScopeApplication {
@Autowired
private Student student;
@GetMapping
public String student() {
return student.getName();
}
public static void main(String[] args) throws InterruptedException {
SpringApplication.run(RefreshScopeApplication.class, args);
}
}application.yml文件：
spring: application: name: refresh-scope-server endpoints: refresh: sensitive: false server: port: 8089 student: name: admin
这里把refresh端点开放出来，然后变更配置后就可以获取最新的对象了
3.2、总结
1) 当配置更新并通过refresh端点刷新后，会执行ContextRefresher的refresh方法，该方法会记录当前的Environment，而后构建一个简易的SpringApplicationBuilder并执行其run方法，此时ConfigFileApplicationListener会读取我们修改过后的配置并绑定到SpringApplication对象上，最后进行changes操作来变更已有的PropertySource
2) @RefreshScope最好配合@Bean使用，当且仅当变更配置后，需要重新获取最新的bean时使用。加上该注解的Bean会被代理并且延迟加载，所有的scope属性为Refresh的bean会被包装成BeanLifecycleWrapper存入缓存(ConcurrentHashMap)中,所有的读取，修改，删除都是基于该缓存的。
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