Java cglib为实体类(javabean)动态添加属性方式
作者：writeanewworld
这篇文章主要介绍了Java cglib为实体类(javabean)动态添加属性方式，具有很好的参考价值，希望对大家有所帮助。一起跟随小编过来看看吧
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
<!--使用cglib 为javabean动态添加属性--> <dependency> <groupId>commons-beanutils</groupId> <artifactId>commons-beanutils</artifactId> <version>1.9.3</version> </dependency> <dependency> <groupId>cglib</groupId> <artifactId>cglib-nodep</artifactId> <version>3.2.4</version> </dependency>
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<String, Object> addProperties) {
// get property map
PropertyUtilsBean propertyUtilsBean = new PropertyUtilsBean();
PropertyDescriptor[] descriptors = propertyUtilsBean.getPropertyDescriptors(dest);
Map<String, Class> 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<String, Class> 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<String, Class> 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<String, Object> 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<String, Object> map = basicDynaBean.getMap();
Iterator<String> 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<String, Object> values = new HashMap<String, Object>();
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.