java代理机制简单实现

     java代理分静态代理和动态代理，动态代理有jdk代理和cglib代理两种，在运行时生成新的子类class文件。本文主要练习下动态代理，代码用于备忘。对于代理的原理和机制，网上有很多写的很好的，就不班门弄斧了。

• jdk代理

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class ProxyFactory implements InvocationHandler {  
	  
    private Object tarjectObject;  
  
    public Object creatProxyInstance(Object obj) {  
        this.tarjectObject = obj;
        return Proxy.newProxyInstance(this.tarjectObject.getClass()  
                .getClassLoader(), this.tarjectObject.getClass()  
                .getInterfaces(), this);  
    }  
  
    @Override  
    public Object invoke(Object proxy, Method method, Object[] args)  
            throws Throwable { 
        Object result = null;  
        if (AssessUtils.isAssess()) {  
            result = method.invoke(this.tarjectObject, args);  
        }else{
        	throw new NoAssessException("This server cannot run this service.");
        }
        return result;  
    }
}

• cglib代理

import java.lang.reflect.Method;
import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;

public class ProxyCglibFactory implements MethodInterceptor {  
	  
    private Object tarjectObject;  
  
    public Object creatProxyInstance(Object obj) {  
        this.tarjectObject = obj;
        Enhancer enhancer=new Enhancer();
        enhancer.setSuperclass(this.tarjectObject.getClass());
        enhancer.setCallback(this);
        return enhancer.create();
    }

	@Override
	public Object intercept(Object obj, Method method, Object[] args,
			MethodProxy arg3) throws Throwable {
		Object result = null;  
        if (AssessUtils.isAssess()) {  
            result = method.invoke(this.tarjectObject, args);  
        }else{
        	throw new NoAssessException("This server cannot run this service.");
        }
        return result;  
	}
}

• Aspect注解

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class AssessInterceptor {
	@Pointcut(value="execution (* com..*.*(..))")
	private void anyMethod(){};
	
	@Before("anyMethod()")
	public void doBefore(JoinPoint joinPoint) throws NoAssessException{
		if (!AssessUtils.isAssess()) {  
			throw new NoAssessException("This server cannot run this service.");
		}
	}
	
	/**
	 * Around异常的时候调用
	 * @param pjp
	 * @throws Throwable
	 */
	@Around("anyMethod()")
	public void invoke(ProceedingJoinPoint pjp) throws Throwable{
		pjp.proceed();  
	}

}