如何在Spring中使用MyBatis实现数据的读写分离？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。
其实现原理如下：
通过Spring AOP对dao层接口进行拦截，并对需要指定数据源的接口在ThradLocal中设置其数据源类型及名称
通过MyBatsi的插件，对根据更新或者查询操作在ThreadLocal中设置数据源（dao层没有指定的情况下）
继承AbstractRoutingDataSource类。
在此直接写死使用HikariCP作为数据源
其实现步骤如下：
定义其数据源配置文件并进行解析为数据源
定义AbstractRoutingDataSource类及其它注解
定义Aop拦截
定义MyBatis插件
整合在一起
1.配置及解析类
其配置参数直接使用HikariCP的配置，其具体参数可以参考HikariCP。
在此使用yaml格式，名称为datasource.yaml,内容如下：
dds: write: jdbcUrl: jdbc:mysql://localhost:3306/order password: liu123 username: root maxPoolSize: 10 minIdle: 3 poolName: master read: - jdbcUrl: jdbc:mysql://localhost:3306/test password: liu123 username: root maxPoolSize: 10 minIdle: 3 poolName: slave1 - jdbcUrl: jdbc:mysql://localhost:3306/test2 password: liu123 username: root maxPoolSize: 10 minIdle: 3 poolName: slave2
定义该配置所对应的Bean，名称为DBConfig,内容如下：
@Component
@ConfigurationProperties(locations = "classpath:datasource.yaml", prefix = "dds")
public class DBConfig {
private List<HikariConfig> read;
private HikariConfig write;
public List<HikariConfig> getRead() {
return read;
}
public void setRead(List<HikariConfig> read) {
this.read = read;
}
public HikariConfig getWrite() {
return write;
}
public void setWrite(HikariConfig write) {
this.write = write;
}
}把配置转换为DataSource的工具类，名称：DataSourceUtil，内容如下：
import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;
import javax.sql.DataSource;
import java.util.ArrayList;
import java.util.List;
public class DataSourceUtil {
public static DataSource getDataSource(HikariConfig config) {
return new HikariDataSource(config);
}
public static List<DataSource> getDataSource(List<HikariConfig> configs) {
List<DataSource> result = null;
if (configs != null && configs.size() > 0) {
result = new ArrayList<>(configs.size());
for (HikariConfig config : configs) {
result.add(getDataSource(config));
}
} else {
result = new ArrayList<>(0);
}
return result;
}
}2.注解及动态数据源
定义注解@DataSource，其用于需要对个别方法指定其要使用的数据源（如某个读操作需要在master上执行，但另一读方法b需要在读数据源的具体一台上面执行）
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DataSource {
/**
* 类型，代表是使用读还是写
* @return
*/
DataSourceType type() default DataSourceType.WRITE;
/**
* 指定要使用的DataSource的名称
* @return
*/
String name() default "";
}定义数据源类型，分为两种：READ,WRITE，内容如下：
public enum DataSourceType {
READ, WRITE;
}定义保存这此共享信息的类DynamicDataSourceHolder，在其中定义了两个ThreadLocal和一个map，holder用于保存当前线程的数据源类型（读或者写），pool用于保存数据源名称（如果指定），其内容如下：
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class DynamicDataSourceHolder {
private static final Map<String, DataSourceType> cache = new ConcurrentHashMap<>();
private static final ThreadLocal<DataSourceType> holder = new ThreadLocal<>();
private static final ThreadLocal<String> pool = new ThreadLocal<>();
public static void putToCache(String key, DataSourceType dataSourceType) {
cache.put(key,dataSourceType);
}
public static DataSourceType getFromCach(String key) {
return cache.get(key);
}
public static void putDataSource(DataSourceType dataSourceType) {
holder.set(dataSourceType);
}
public static DataSourceType getDataSource() {
return holder.get();
}
public static void putPoolName(String name) {
if (name != null && name.length() > 0) {
pool.set(name);
}
}
public static String getPoolName() {
return pool.get();
}
public static void clearDataSource() {
holder.remove();
pool.remove();
}
}动态数据源类为DynamicDataSoruce,其继承自AbstractRoutingDataSource，可以根据返回的key切换到相应的数据源，其内容如下：
import com.zaxxer.hikari.HikariDataSource;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ThreadLocalRandom;
public class DynamicDataSource extends AbstractRoutingDataSource {
private DataSource writeDataSource;
private List<DataSource> readDataSource;
private int readDataSourceSize;
private Map<String, String> dataSourceMapping = new ConcurrentHashMap<>();
@Override
public void afterPropertiesSet() {
if (this.writeDataSource == null) {
throw new IllegalArgumentException("Property 'writeDataSource' is required");
}
setDefaultTargetDataSource(writeDataSource);
Map<Object, Object> targetDataSource = new HashMap<>();
targetDataSource.put(DataSourceType.WRITE.name(), writeDataSource);
String poolName = ((HikariDataSource)writeDataSource).getPoolName();
if (poolName != null && poolName.length() > 0) {
dataSourceMapping.put(poolName,DataSourceType.WRITE.name());
}
if (this.readDataSource == null) {
readDataSourceSize = 0;
} else {
for (int i = 0; i < readDataSource.size(); i++) {
targetDataSource.put(DataSourceType.READ.name() + i, readDataSource.get(i));
poolName = ((HikariDataSource)readDataSource.get(i)).getPoolName();
if (poolName != null && poolName.length() > 0) {
dataSourceMapping.put(poolName,DataSourceType.READ.name() + i);
}
}
readDataSourceSize = readDataSource.size();
}
setTargetDataSources(targetDataSource);
super.afterPropertiesSet();
}
@Override
protected Object determineCurrentLookupKey() {
DataSourceType dataSourceType = DynamicDataSourceHolder.getDataSource();
String dataSourceName = null;
if (dataSourceType == null ||dataSourceType == DataSourceType.WRITE || readDataSourceSize == 0) {
dataSourceName = DataSourceType.WRITE.name();
} else {
String poolName = DynamicDataSourceHolder.getPoolName();
if (poolName == null) {
int idx = ThreadLocalRandom.current().nextInt(0, readDataSourceSize);
dataSourceName = DataSourceType.READ.name() + idx;
} else {
dataSourceName = dataSourceMapping.get(poolName);
}
}
DynamicDataSourceHolder.clearDataSource();
return dataSourceName;
}
public void setWriteDataSource(DataSource writeDataSource) {
this.writeDataSource = writeDataSource;
}
public void setReadDataSource(List<DataSource> readDataSource) {
this.readDataSource = readDataSource;
}
}3.AOP拦截
如果在相应的dao层做了自定义配置（指定数据源），则在些处理。解析相应方法上的@DataSource注解，如果存在，并把相应的信息保存至上面的DynamicDataSourceHolder中。在此对com.hfjy.service.order.dao包进行做拦截。内容如下：
import com.hfjy.service.order.anno.DataSource;
import com.hfjy.service.order.wr.DynamicDataSourceHolder;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;
import java.lang.reflect.Method;
/**
* 使用AOP拦截，对需要特殊方法可以指定要使用的数据源名称(对应为连接池名称）
*/
@Aspect
@Component
public class DynamicDataSourceAspect {
@Pointcut("execution(public * com.hfjy.service.order.dao.*.*(*))")
public void dynamic(){}
@Before(value = "dynamic()")
public void beforeOpt(JoinPoint point) {
Object target = point.getTarget();
String methodName = point.getSignature().getName();
Class<?>[] clazz = target.getClass().getInterfaces();
Class<?>[] parameterType = ((MethodSignature)point.getSignature()).getMethod().getParameterTypes();
try {
Method method = clazz[0].getMethod(methodName,parameterType);
if (method != null && method.isAnnotationPresent(DataSource.class)) {
DataSource datasource = method.getAnnotation(DataSource.class);
DynamicDataSourceHolder.putDataSource(datasource.type());
String poolName = datasource.name();
DynamicDataSourceHolder.putPoolName(poolName);
DynamicDataSourceHolder.putToCache(clazz[0].getName() + "." + methodName, datasource.type());
}
} catch (Exception e) {
e.printStackTrace();
}
}
@After(value = "dynamic()")
public void afterOpt(JoinPoint point) {
DynamicDataSourceHolder.clearDataSource();
}
}4.MyBatis插件
如果在dao层没有指定相应的要使用的数据源，则在此进行拦截，根据是更新还是查询设置数据源的类型，内容如下：
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import java.util.Properties;
@Intercepts({
@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class}),
@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class,
RowBounds.class, ResultHandler.class})
})
public class DynamicDataSourcePlugin implements Interceptor {
@Override
public Object intercept(Invocation invocation) throws Throwable {
MappedStatement ms = (MappedStatement)invocation.getArgs()[0];
DataSourceType dataSourceType = null;
if ((dataSourceType = DynamicDataSourceHolder.getFromCach(ms.getId())) == null) {
if (ms.getSqlCommandType().equals(SqlCommandType.SELECT)) {
dataSourceType = DataSourceType.READ;
} else {
dataSourceType = DataSourceType.WRITE;
}
DynamicDataSourceHolder.putToCache(ms.getId(), dataSourceType);
}
DynamicDataSourceHolder.putDataSource(dataSourceType);
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
if (target instanceof Executor) {
return Plugin.wrap(target, this);
} else {
return target;
}
}
@Override
public void setProperties(Properties properties) {
}
}5.整合
在里面定义MyBatis要使用的内容及DataSource，内容如下：
import com.hfjy.service.order.wr.DBConfig;
import com.hfjy.service.order.wr.DataSourceUtil;
import com.hfjy.service.order.wr.DynamicDataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import javax.annotation.Resource;
import javax.sql.DataSource;
@Configuration
@MapperScan(value = "com.hfjy.service.order.dao", sqlSessionFactoryRef = "sqlSessionFactory")
public class DataSourceConfig {
@Resource
private DBConfig dbConfig;
@Bean(name = "dataSource")
public DynamicDataSource dataSource() {
DynamicDataSource dataSource = new DynamicDataSource();
dataSource.setWriteDataSource(DataSourceUtil.getDataSource(dbConfig.getWrite()));
dataSource.setReadDataSource(DataSourceUtil.getDataSource(dbConfig.getRead()));
return dataSource;
}
@Bean(name = "transactionManager")
public DataSourceTransactionManager dataSourceTransactionManager(@Qualifier("dataSource") DataSource dataSource) {
return new DataSourceTransactionManager(dataSource);
}
@Bean(name = "sqlSessionFactory")
public SqlSessionFactory sqlSessionFactory(@Qualifier("dataSource") DataSource dataSource) throws Exception {
SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
sessionFactoryBean.setConfigLocation(new ClassPathResource("mybatis-config.xml"));
sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources("classpath*:mapper/*.xml"));
sessionFactoryBean.setDataSource(dataSource);
return sessionFactoryBean.getObject();
}
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