JAVA动态代理和方法拦截（使用CGLib实现AOP、方法拦截、委托）

AOP用CGLib更简便、更可控。

动态代理的实现非常优雅。

 

实体类：

public class SampleClass {

public String MyFunction1(String input) {

System.out.println("MyFunction1方法被调用：Hello:" + input);
return "Hello:" + input;
}

public String MyFunction2(String input) {

System.out.println("MyFunction2方法被调用：Hello:" + input);
return "Hello:" + input;
}
}

 

import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Dispatcher;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.FixedValue;
import net.sf.cglib.proxy.LazyLoader;
import net.sf.cglib.proxy.NoOp;
import net.sf.cglib.proxy.ProxyRefDispatcher;

public class CgLibTest {

private static String MyName = "";

public static void main(String[] args) {

MyName = "王昕";

DoAOP();

Enhancer enhancer1 = EnhancerNoOp();
SampleClass proxy = (SampleClass) enhancer1.create();
String strOutput = proxy.MyFunction2("赵七");
System.out.println("EnhancerNoOp:"+strOutput);

Enhancer enhancer2 = EnhancerFixedValue();
SampleClass proxy2 = (SampleClass) enhancer2.create();
String strOutput2 = proxy2.MyFunction2("赵七");
System.out.println("EnhancerFixedValue:"+strOutput2);

}

private static void DoAOP() {
MyInterceptor cglib = new MyInterceptor();
SampleClass bookCglib = (SampleClass) cglib
.getInstance(new SampleClass());
bookCglib.MyFunction2("张三");
}

// 该回调将替代原类的方法实现
private static Enhancer EnhancerFixedValue() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(SampleClass.class);

enhancer.setCallback(new FixedValue() {
@Override
public Object loadObject() throws Exception {
//返回 MyName 作为输入参数的;
return new SampleClass().MyFunction2(MyName);
}
});
return enhancer;
}

//执行原（Super）类方法
private static Enhancer EnhancerNoOp() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(SampleClass.class);

enhancer.setCallback(NoOp.INSTANCE);
return enhancer;
}

//延迟加载
private static Enhancer EnhancerLazyLoader() {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(SampleClass.class);

enhancer.setCallback(new LazyLoader() {
@Override
public Object loadObject() throws Exception {
//return "回调后的返回值";
return new SampleClass().MyFunction2(MyName);
}
});
return enhancer;
}

private static Enhancer EnhancerProxyRefDispatcher(final String obj1) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(SampleClass.class);

enhancer.setCallback(new ProxyRefDispatcher() {
@Override
public Object loadObject(Object obj2) throws Exception {
return new SampleClass().MyFunction2(obj1 + (String)obj2);
}
});
return enhancer;
}

}

 

AOP拦截模拟类：

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class MyInterceptor implements MethodInterceptor {
private Object target;

public Object getInstance(Object target) {
this.target = target;
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(this.target.getClass());
// 回调方法
enhancer.setCallback(this);
// 创建代理对象
return enhancer.create();
}

@Override
// 回调方法
public Object intercept(Object obj, java.lang.reflect.Method method, Object[] args,
MethodProxy proxy) throws Throwable {
System.out.println("拦截前，做些事情");
proxy.invokeSuper(obj, args);
System.out.println("拦截后，再做些事情");
return null;

}

}

 

输出：

拦截前，做些事情

MyFunction2方法被调用：Hello:张三

拦截后，再做些事情

MyFunction2方法被调用：Hello:赵七

EnhancerNoOp:Hello:赵七

MyFunction2方法被调用：Hello:王昕

EnhancerFixedValue:Hello:王昕   

 

 

MethodDelegate

方法委托:  实现类似C#的委托。将方法调用绑定到某个接口的特定方法

public void testMethodDelegate() throws Exception {
SampleBean bean = new SampleBean();
bean.setValue("Hello cglib!");
BeanDelegate delegate = (BeanDelegate) MethodDelegate.create(bean,
"getValue", BeanDelegate.class);
assertEquals("Hello world!", delegate.getValueFromDelegate2());
}

public interface BeanDelegate {
//String getValueFromDelegate1();
String getValueFromDelegate2();
}

 

BulkBean 

使用数组访问bean的访问器方法调用

public void testBulkBean() throws Exception {
BulkBean bulkBean = BulkBean.create(SampleBean.class,
new String[] { "getValue" }, new String[] { "setValue" },
new Class[] { String.class });
SampleBean bean = new SampleBean();
bean.setValue("Hello world!");
assertEquals(1, bulkBean.getPropertyValues(bean).length);
assertEquals("Hello world!", bulkBean.getPropertyValues(bean)[0]);
bulkBean.setPropertyValues(bean, new Object[] { "Hello cglib!" });
assertEquals("Hello cglib!", bean.getValue());
}

public class SampleBean {
private String value;
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}