使用res:bean属性复制避免null值覆盖版本

/**
 * 对象属性值拷贝，null 值覆盖修复版
 * @param beanSrc
 * @param beanDest
 */
public static void copyBeanPropertiesIgoreNull(Object beanSrc, Object beanDest){
 Class<?> clazzSrc = beanSrc.getClass();
 Class<?> clazzDest = beanDest.getClass();
 //获取所有属性，包括私有的和继承的
 List<Field> allFields = getAllFields(beanSrc);
 try {
 for(Field field:allFields) {
  String fieldName = field.getName(); //属性名
  if("serialVersionUID".equals(fieldName)) {
   continue;
  }
  PropertyDescriptor pd1 = getPropertyDescriptor(fieldName, clazzSrc);
  if(pd1!=null) {
   Method rMethod = pd1.getReadMethod();
   if(rMethod!=null) {
    Object fieldValue = rMethod.invoke(beanSrc); //属性值，引用类型，所以一般实体的属性用 Integer instead of int
    if(fieldValue!=null) { //关键：属性值为 null 就不要覆盖了
     PropertyDescriptor pd2 = getPropertyDescriptor(fieldName, clazzDest);
     if(pd2!=null) {
      Method wMethod = pd2.getWriteMethod();
      if(wMethod!=null) {
        wMethod.invoke(beanDest, fieldValue);
      }
     }
    }
   }
  }
 }
 } catch (IllegalAccessException | InvocationTargetException e) {
  e.printStackTrace();
  throw new RuntimeException(">> copyPropertiesIgoreNull exception", e);
 }
}

public static String[] getNullPropertyNames (Object source) {
        final BeanWrapper src = new BeanWrapperImpl(source);
        PropertyDescriptor[] pds = src.getPropertyDescriptors();
        Set<String> emptyNames = new HashSet<String>();
        for(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);
    }

BeanUtils.copyProperties(newdata,dbdata,getNullPropertyNames(newdata));

public static void main(String[] args) {
    U u = new U("1","zhangsan",null,null,null,"11");
    String[] nullPropertyNames = getNullPropertyNames(u);
    for (String nullPropertyName : nullPropertyNames) {
        System.out.println(nullPropertyName);
    }
}
public static String[] getNullPropertyNames (Object source) {
    final BeanWrapper src = new BeanWrapperImpl(source);
    PropertyDescriptor[] pds = src.getPropertyDescriptors();
    Set<String> emptyNames = new HashSet<String>();
    for(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);
}
class U {
        private String id;
        private String name;
        private String field1;
        private String field2;
        private String field3;
        private String field4;
        public U(String id, String name) {
            this.id = id;
            this.name = name;
        }
        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getField1() {
            return field1;
        }
        public void setField1(String field1) {
            this.field1 = field1;
        }
        public String getField2() {
            return field2;
        }
        public void setField2(String field2) {
            this.field2 = field2;
        }
        public String getField3() {
            return field3;
        }
        public void setField3(String field3) {
            this.field3 = field3;
        }
        public String getField4() {
            return field4;
        }
        public void setField4(String field4) {
            this.field4 = field4;
        }
        public U(String id, String name, String field1, String field2, String field3, String field4) {
            this.id = id;
            this.name = name;
            this.field1 = field1;
            this.field2 = field2;
            this.field3 = field3;
            this.field4 = field4;
        }
    }