JavaBean動態新增刪除屬性

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

從輸出結果可以看出最後產生的obj只有id和username兩個屬性

2.org.apache.commons.beanutils

DynaProperty property = new DynaPropert
之間的關係

DynaBean的源碼

DynaProperty property = new DynaProperty("id", Long.class);
DynaProperty property1 = new DynaProperty("username", String.class);
BasicDynaClass basicDynaClass = new BasicDynaClass("user", null, new DynaProperty[]{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

主要是介面的定義

再來看看BasicDynaBean是怎麼實現的,直接看public Object get(String name);

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從以上是在values裡取值的

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);


}

其實是用HashMap來實現的.

3.總結

用cglib動態刪除添加屬性時,雖然obj裡有getUsername這個方法,卻不能obj.getUsername()這樣直接呼叫,想得到username的值只能透過beanMap.get("username")取得.

org.apache.commons.beanutils從源碼來看是使用HashMap來實現的.

使用Map的區別不大.只是它們都提供了複製屬性的工具方法.