Java cglib为实体类(javabean)动态添加属性方式

Java cglib为实体类(javabean)动态添加属性方式

1.应用场景

之前对接三方平台遇到一个参数名称是变化的，然后我就想到了动态javabean怎么生成，其实是我想多了，用个map就轻易解决了，但还是记录下动态属性添加的实现吧。

2.引入http://依赖

commons-beanutils

commons-beanutils

1.9.3

cglib

cglib-nodep

3.2.4

3.代码如下

import com.freemud.waimai.menu.dpzhcto.dto.DynamicBean;

import com.google.common.collect.Maps;

import org.apache.commons.beanutils.PropertyUtilsBean;

import java.beans.PropertyDescriptor;

import java.util.Map;

public class PicBeanAddPropertiesUtil {

public static Object getTarget(Object dest, Map addProperties) {

// get property map

PropertyUtilsBean propertyUtilsBean = new PropertyUtilsBean();

PropertyDescriptor[] descriptors = propertyUtilsBean.getPropertyDescriptors(dest);

Map propertyMap = Maps.newHashMap();

for (PropertyDescriptor d : descriptors) {

if (!"class".equalsIgnoreCase(d.getName())) {

propertyMap.put(d.getName(), d.getPropertyType());

}

}

// add extra properties

addProperties.forEach((k, v) -> propertyMap.put(k, v.getClass()));

// new dynamic bean

DynamicBean dynamicBean = new DynamicBean(dest.getClass(), propertyMap);

// add old value

propertyMap.forEach((k, v) -> {

try {

// filter extra properties

if (!addProperties.containsKey(k)) {

dynamicBean.setValue(k, propertyUtilsBean.getNestedProperty(dest, k));

}

} catch (Exception e) {

e.printStackTrace();

}

});

// add extra value

addProperties.forEach((k, v) -> {

try {

dynamicBean.setValue(k, v);

} catch (Exception e) {

e.printStackTrace();

}

});

Object target = dynamicBean.getTarget();

return target;

}

}

import net.sf.cglib.beans.BeanGenerator;

import net.sf.cglib.beans.BeanMap;

import java.util.Map;

public class DynamicBean {

/**

* 目标对象

*/

private Object target;

/**

* 属性集合

*/

private BeanMap beanMap;

public DynamicBean(Class superclass, Map propertyMap) {

this.target = generateBean(superclass, propertyMap);

this.beanMap = BeanMap.create(this.target);

}

/**

* bean 添加属性和值

*

* @param property

* @param value

*/

public void setValue(String property, Object value) {

beanMap.put(property, value);

}

/**

* 获取属性值

*

* @param property

* @return

*/

public Object getValue(String property) {

return beanMap.get(property);

}

/**

* 获取对象

*

* @return

*/

public Object getTarget() {

return this.target;

}

/**

* 根据属性生成对象

*

* @param superclass

* @param propertyMap

* @return

*/

private Object generateBean(Class superclass, Map propertyMap) {

BeanGenerator generator = new BeanGenerator();

if (null != superclass) {

generator.setSuperclass(superclass);

}

BeanGenerator.addProperties(generator, propertyMap);

return generator.create();

}

}

public static void main(String[] args) {

FinalPicBaseReqDto entity = new FinalPicBaseReqDto();

entity.setAppKey("eee");

entity.setContent("222");

Map addProperties = new HashMap() {{

put("动态属性名", "动态属性值");

}};

FinalPicBaseReqDto finalPicBaseReqVo = (FinalPicBaseReqDto) PicBeanAddPropertiesUtil.getTarget(entity, addProperties);

System.out.println(jsON.toJSONString(finalPicBaseReqVo));

}

可以看到实体类只有两个属性，但是最终是动态添加进去了新的属性。

声明：代码也是前人造的轮子，欢迎各位拿去使用，解决实际生产中遇到的相似场景问题

补充：JavaBean动态添加删除属性

1.cglib

BeanGenerator beanGenerator = new BeanGenerator();

beanGenerator.addProperty("id", Long.class);

beanGenerator.addProperty("username", String.class);

Object obj = beanGenerator.create();

BeanMap beanMap = BeanMap.create(obj);

BeanCopier copier = BeanCopier.create(User.class, obj.getClass(), false);

User user = new User();

user.setId(1L);

user.setUsername("name1");

user.setPassword("123");

copier.copy(user, obj, null);

System.out.println(beanMap.get("username"));Class clazz = obj.getClass();

Method[] methods = clazz.getDeclaredMethods();for (int i = 0; i < methods.length; i++) {

System.out.println(methods[i].getName());

}

输出结果:

name1

getId

getUsername

setId

setUsername

从输出结果可以看出最后生成的obj只有id和username两个属性

2.org.apache.commons.beanutils

DynaProperty property = new DynaProperty("id", Long.class);

DynaProperty property1 = new DynaProperty("username", String.class);

BasicDynaClass basicDynaClass = new BasicDynaClass("user", null, newDynaProperty[]{property, property1});

BasicDynaBean basicDynaBean = new BasicDynaBean(basicDynaClass);

User user = new User();

user.setId(1L);

user.setUsername("name1");

user.setPassword("123");

BeanUtils.copyProperties(basicDyhttp://naBean, user);Map map = basicDynaBean.getMap();

Iterator it = map.keySet().iterator();while (it.hasNext()) { String key = it.next();

System.out.println(key + ":" + map.get(key));

}

输入结果:

id:1username:name1

查看BasicDynaBean与BasicDynaClass之间的关系

DynaBean的源码

public interface DynaBean {

public boolean contains(String name, String key);

public Object get(String name);

public Object get(String name, int index);

public Object get(String name, String key);

public DynaClass getDynaClass();

public void remove(String name, String key);

public void set(String name, Object value);

public void set(String name, int index, Object value);

public void set(String name, String key, Object value);

}

主要是接口的定义

再来看看BasicDynaBean是怎么实现的,直接看public Object get(String name);

/**

* Return the value of a simple property with the specified name.

*

* @param name Name of the property whose value is to be retrieved

* @return The property's value

*

* @exception IllegalArgumentException if there is no property

* of the specified name

*/public Object get(String name) { // Return any non-null value for the specified property

Object value = values.get(name); if (value != null) { return (value);

} // Return a null value for a non-primitive property

Class> type = getDynaProperty(name).getType(); if (!type.isPrimitive()) { return(value);

} // Manufacture default values for primitive properties

if (type == Boolean.TYPE) { return (Boolean.FALSE);

} else if (type == Byte.TYPE) { return (new Byte((byte) 0));

} else if (type == Character.TYPE) { return (new Character((char) 0));

} else if (type == Double.TYPE) { return (new Double(0.0));

} else if (type == Float.TYPE) { return (new Float((float) 0.0));

} else if (type == Integer.TYPE) { return (new Integer(0));

} else if (type == Long.TYPE) { return (new Long(0));

} else if (type == Short.TYPE) { return (new Short((short) 0));

} else { return (null);

}

}

从以上代码可以看出是在values里取值的

/**

* The set of property values for this DynaBean, keyed by property name.

*/

protected HashMap values = new HashMap();

其实是用HashMap来实现的.

3.总结

用cglib动态删除添加属性时,虽然obj里有getUsername这个方法,却不能obj.getUsername()这样直接调用,想得到username的值只能通过beanMap.get("username")获取.

org.apache.commons.beanutils从源码来看是使用HashMap来实现的.

两种方式从操作角度来说和使用Map的区别不大.只是它们都提供了复制属性的工具方法.

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