小编给大家分享一下java怎么复制非空对象属性值，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！
很多时候，我们需要通过对象拷贝，比如说VO类与数据库实体bean类、更新时非空对象不更新，对同一对象不同数据分开存储等
用于对象拷贝，spring 和 Apache都提供了相应的工具类方法，BeanUtils.copyProperties
但是对于非空属性拷贝就需要自己处理了
在这里借用spring中org.springframework.beans.BeanUtils类提供的方法
copyProperties(Object source, Object target, String... ignoreProperties)
/**
* Copy the property values of the given source bean into the given target bean,
* ignoring the given "ignoreProperties".
* <p>Note: The source and target classes do not have to match or even be derived
* from each other, as long as the properties match. Any bean properties that the
* source bean exposes but the target bean does not will silently be ignored.
* <p>This is just a convenience method. For more complex transfer needs,
* consider using a full BeanWrapper.
* @param source the source bean
* @param target the target bean
* @param ignoreProperties array of property names to ignore
* @throws BeansException if the copying failed
* @see BeanWrapper
*/
public static void copyProperties(Object source, Object target, String... ignoreProperties) throws BeansException {
copyProperties(source, target, null, ignoreProperties);
/**
* Copy the property values of the given source bean into the given target bean.
* <p>Note: The source and target classes do not have to match or even be derived
* from each other, as long as the properties match. Any bean properties that the
* source bean exposes but the target bean does not will silently be ignored.
* @param source the source bean
* @param target the target bean
* @param editable the class (or interface) to restrict property setting to
* @param ignoreProperties array of property names to ignore
* @throws BeansException if the copying failed
* @see BeanWrapper
*/
private static void copyProperties(Object source, Object target, Class<?> editable, String... ignoreProperties)
throws BeansException {
Assert.notNull(source, "Source must not be null");
Assert.notNull(target, "Target must not be null");
Class<?> actualEditable = target.getClass();
if (editable != null) {
if (!editable.isInstance(target)) {
throw new IllegalArgumentException("Target class [" + target.getClass().getName() +
"] not assignable to Editable class [" + editable.getName() + "]");
}
actualEditable = editable;
}
PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
List<String> ignoreList = (ignoreProperties != null ? Arrays.asList(ignoreProperties) : null);
for (PropertyDescriptor targetPd : targetPds) {
Method writeMethod = targetPd.getWriteMethod();
if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
if (sourcePd != null) {
Method readMethod = sourcePd.getReadMethod();
if (readMethod != null &&
ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
try {
if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
readMethod.setAccessible(true);
}
Object value = readMethod.invoke(source);
if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
writeMethod.setAccessible(true);
}
writeMethod.invoke(target, value);
}
catch (Throwable ex) {
throw new FatalBeanException(
"Could not copy property '" + targetPd.getName() + "' from source to target", ex);
}
}
}
}
}
}/**
* @author zml2015
* @Email zhengmingliang911@gmail.com
* @Time 2017年2月14日 下午5:14:25
* @Description <p>获取到对象中属性为null的属性名 </P>
* @param source 要拷贝的对象
* @return
*/
public static String[] getNullPropertyNames(Object source) {
final BeanWrapper src = new BeanWrapperImpl(source);
java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors();
Set<String> emptyNames = new HashSet<String>();
for (java.beans.PropertyDescriptor pd : pds) {
Object srcValue = src.getPropertyValue(pd.getName());
if (srcValue == null)
emptyNames.add(pd.getName());
}
String[] result = new String[emptyNames.size()];
return emptyNames.toArray(result);
}
/**
* @author zml2015
* @Email zhengmingliang911@gmail.com
* @Time 2017年2月14日 下午5:15:30
* @Description <p> 拷贝非空对象属性值 </P>
* @param source 源对象
* @param target 目标对象
*/
public static void copyPropertiesIgnoreNull(Object source, Object target) {
BeanUtils.copyProperties(source, target, getNullPropertyNames(source));
}如果项目中使用的框架有Hibernate的话，则可以通过在实体类上添加下面两条注解
@DynamicInsert(true) @DynamicUpdate(true)
如果想对该注解进一步了解的话，那么可以去官网看英文文档，文档解释的很清楚，在此不再赘述了
获取对象的属性和get、set方法进行复制；
import org.springframework.beans.BeanUtils; SourceObject sourceObject = new SourceObject(); TargetObject targetObject = new TargetObject(); BeanUtils.copyProperties(sourceObject, targetObject);
import net.sf.cglib.beans.BeanCopier; import net.sf.cglib.core.Converter; SourceObject sourceObject = new SourceObject(); TargetObject targetObject = new TargetObject(); BeanCopier beanCopier = BeanCopier.create(SourceObject.class, TargetObject.class, true);--第三个参数表示是否使用转换器，false表示不使用，true表示使用 Converter converter = new CopyConverter();--自定义转换器 beanCopier.copy(sourceObject, targetObject, converter);
转换器(当源对象属性类型与目标对象属性类型不一致时，使用转换器)：
import net.sf.cglib.core.Converter;
import org.apache.commons.lang3.StringUtils;
import java.math.BigDecimal;
import java.util.Date;
/**
* Created by asus on 2019/7/12.
*/
public class CopyConverter implements Converter {
@Override
public Object convert(Object value, Class target, Object context) {
{
String s = value.toString();
if (target.equals(int.class) || target.equals(Integer.class)) {
return Integer.parseInt(s);
}
if (target.equals(long.class) || target.equals(Long.class)) {
return Long.parseLong(s);
}
if (target.equals(float.class) || target.equals(Float.class)) {
return Float.parseFloat(s);
}
if (target.equals(double.class) || target.equals(Double.class)) {
return Double.parseDouble(s);
}
if(target.equals(Date.class)){
while(s.indexOf("-")>0){
s = s.replace("-", "/");
}
return new Date(s);
}
if(target.equals(BigDecimal.class)){
if(!StringUtils.isEmpty(s)&&!s.equals("NaN")){
return new BigDecimal(s);
}
}
return value ;
}
}
}中的org.springframework.cglib.beans.BeanCopier类（用法与第三种一样）
import org.springframework.cglib.beans.BeanCopier; import org.springframework.cglib.core.Converter; SourceObject sourceObject = new SourceObject(); TargetObject targetObject = new TargetObject(); Converter converter = new SpringCopyConverter(); BeanCopier beanCopier = BeanCopier.create(SourceObject.class, TargetObject.class, true); beanCopier.copy(sourceObject, targetObject, converter);
经过循环复制测试(源对象与目标对象各160个属性)：
第一种：Java反射通过判断属性类型，常用类型的属性值都能复制，但是不优化的前提下效率最慢；
第二种：属性类型不同时无法复制，且效率相对较慢；
第三种：耗时最少，不使用转换器时，属性类型不同时无法复制，使用转换器后，耗时会相对变长；
第四种：与第三种相似，但是耗时相对较长；
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