java 复制非空对象属性值 有更新!

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    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);
    						}
    					}
    				}
    			}
    		}
    	}
    

     

    然后封装一下得到以下方法:

    /**
    	 * @author 郑明亮
    	 * @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 郑明亮
    	 * @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));
    	}

     

    测试方法就不提供了,自行测试即可

     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

    https://www.mkyong.com/hibernate/hibernate-dynamic-insert-attribute-example/

     

     

     

     

     

     

     

     

     

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