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.引入依赖

commons-beanutilscommons-beanutils1.9.3cglibcglib-nodep3.2.4

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(basicDynaBean, 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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