import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;public class ProxyHandler implements InvocationHandler { private Object obj; public Object bind(Object obj){
this.obj = obj;
return Proxy.newProxyInstance(obj.getClass().getClassLoader(),
obj.getClass().getInterfaces(),
this);
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object result = null;
System.out.println("before invoke!*****");
result = method.invoke(obj, args);
System.out.println("after invoke!-----");
return result;
}}
public class RealSubject implements Subject { @Override
public void dosomething() {
System.out.println(" call something! ");
}
}public interface Subject { public void dosomething();
}public class SubjectProxy implements Subject { @Override
public void dosomething() {
}
}
public class TestProxy { public static void main(String args[]){
ProxyHandler proxy = new ProxyHandler();
//绑定该类实现的所有接口
Subject sub = (Subject) proxy.bind(new RealSubject());
sub.dosomething();
}
}
具体这个代理类,java底层是如何实现的?
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;public class ProxyHandler implements InvocationHandler { private Object obj; public Object bind(Object obj){
this.obj = obj;
return Proxy.newProxyInstance(obj.getClass().getClassLoader(),
obj.getClass().getInterfaces(),
this);
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object result = null;
System.out.println("before invoke!*****");
result = method.invoke(obj, args);
System.out.println("after invoke!-----");
return result;
}}
public class RealSubject implements Subject { @Override
public void dosomething() {
System.out.println(" call something! ");
}
}public interface Subject { public void dosomething();
}public class SubjectProxy implements Subject { @Override
public void dosomething() {
}
}
public class TestProxy { public static void main(String args[]){
ProxyHandler proxy = new ProxyHandler();
//绑定该类实现的所有接口
Subject sub = (Subject) proxy.bind(new RealSubject());
sub.dosomething();
}
}
具体这个代理类,java底层是如何实现的?
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;import com.sun.xml.internal.ws.org.objectweb.asm.ClassReader;
import com.sun.xml.internal.ws.org.objectweb.asm.ClassWriter;
public class ProxyHander implements InvocationHandler {
private Object obj;
public Object bind(Object obj){
this.obj = obj;
return Proxy.newProxyInstance(obj.getClass().getClassLoader(),
obj.getClass().getInterfaces(),
this);
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result = null;
System.out.println("before invoke!*****");
result = method.invoke(obj, args);
System.out.println("after invoke!-----");
return result;
}
public static void main(String args[]){
RealSubject rs = new RealSubject();
ProxyHander proxy = new ProxyHander();
//绑定该类实现的所有接口
Subject obj = (Subject)proxy.bind(rs);
obj.dosomething();
Class<?> c = obj.getClass();
Field[] fs = c.getDeclaredFields();
//定义可变长的字符串,用来存储属性
StringBuffer sb = new StringBuffer();
//通过追加的方法,将每个属性拼接到此字符串中
//最外边的public定义
sb.append(Modifier.toString(c.getModifiers()) + " class " + c.getSimpleName() );
Class<?>[] interfaces = c.getInterfaces();
if(interfaces.length>0){
sb.append(" implements ");
}
for(Class<?> i:interfaces){
sb.append(i.getName()+" ");
}
sb.append("{\n");
//里边的每一个属性
for(Field field:fs){
field.setAccessible(true);
sb.append("\t");//空格
sb.append(Modifier.toString(field.getModifiers())+" ");//获得属性的修饰符,例如public,static等等
sb.append(field.getType().getSimpleName() + " ");//属性的类型的名字
sb.append(field.getName()+";\n");//属性的名字+回车
}
Method[] m = c.getDeclaredMethods();
for(Method method:m){
method.setAccessible(true);
sb.append("\t");//空格
sb.append(Modifier.toString(method.getModifiers())+" ");//获得属性的修饰符,例如public,static等等
sb.append(method.getReturnType().getName()+" ");
Class<?>[] param = method.getParameterTypes();//获取方法类返回型
sb.append(" "+method.getName()+" (");
for(int i=0;i<param.length;i++){
sb.append(param[i].getName()+" "+"arg"+i);
if(i!=param.length-1){
sb.append(",");
}
}
sb.append(")\n");
}
sb.append("}");
System.out.println(sb);
}
}
class RealSubject implements Subject {
@Override
public void dosomething() {
System.out.println(" call something! ");
}
}
interface Subject {
public void dosomething();
}
执行结果
before invoke!*****
call something!
after invoke!-----
public final class $Proxy0 implements Subject {
private static Method m1;
private static Method m3;
private static Method m0;
private static Method m2;
public final boolean equals (java.lang.Object arg0)
public final java.lang.String toString ()
public final int hashCode ()
public final void dosomething ()
}
从上面反射后的class内容可以知道他会用classwrite重新建一个Proxyxx的类并实现你的超类接口,你的dosometing会被重写。你可以把接口换成类试一下,这个代理就会失效了。所以框架注入时都会要求用户写接口也是这样来的。但现在的cglib 可以不写接口也能实现注入