（二十四）（项目篇）Netty准备之动态代理

Calculator.java

 

package bhz.uts.test;

/*计算器接口*/
public interface Calculator
{
    public double add(double num1, double num2) throws Exception;
    public double sub(double num1, double num2) throws Exception;
    public double div(double num1, double num2) throws Exception;
    public double mul(double num1, double num2) throws Exception;
}

 

 ArithmeticCalculator.java

 

package bhz.uts.test;

/*计算器接口的实现类,添加记录日志功能*/
public class ArithmeticCalculator implements Calculator
{
    @Override
    public double add(double num1, double num2) throws Exception
    {
        double result = num1 + num2;
        
        return result;
    }

    @Override
    public double sub(double num1, double num2) throws Exception
    {
        double result = num1 - num2;
        
        return result;
    }

    /*示意代码 暂时不考虑除数0的情况*/
    @Override
    public double div(double num1, double num2) throws Exception
    {
        double result = num1 / num2;
        
        return result;
    }

    @Override
    public double mul(double num1, double num2) throws Exception
    {
        double result = num1 * num2;
        
        return result;
    }
}

 

 

 

ArithmeticCalculatorInvocationHandler.java

 

package bhz.uts.test;

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

/*使用动态代理需要实现InvocationHandler接口*/
public class ArithmeticCalculatorInvocationHandler implements InvocationHandler
{
    /*要代理的对象，动态代理只有在运行时才知道代理谁，所以定义为Object类型，可以代理任意对象*/
    private Object target = null;
    
    /*通过构造函数传入原对象*/
    public ArithmeticCalculatorInvocationHandler(Object target)
    {
        this.target = target;
    }

    /*InvocationHandler接口的方法，proxy表示代理，method表示原对象被调用的方法，args表示方法的参数*/
    @Override
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable
    {
        /*原对象方法调用前处理日志信息*/
        System.out.println("the method ["+method.getName()+"]"+"begin with args ("+Arrays.toString(args)+")");
        
        Object result = method.invoke(this.target, args);
        
        /*原对象方法调用后处理日志信息*/
        System.out.println("the method ["+method.getName()+"]"+"end with result ("+result+")");
        
        return result;
    }
    
    /*获取代理类*/
    public Object getProxy()
    {
        return Proxy.newProxyInstance(this.target.getClass().getClassLoader(), this.target.getClass().getInterfaces(), this);
    }
}

 

 其实最关键的就是这个类在invoke方法中有代理的类对象，类的方法，有传递的参数

然后在通过调用Proxy.newProxyInstance这个方法来实现。

 

 clent

package bhz.uts.test;

public class Client
{
    public static void main(String[] args) throws Exception
    {
        /*获得代理*/
        Calculator arithmeticCalculatorProxy = (Calculator)new ArithmeticCalculatorInvocationHandler(
                 new ArithmeticCalculator()).getProxy(); 10         
        

        /*调用add方法*/
        arithmeticCalculatorProxy.add(10, 10);
    }
}

 

 

 

结果

the method [add]begin with args ([10.0, 10.0])
the method [add]end with result (20.0)

 

 

 

 

 

在上面的基础上其实还可以在代理的基础上在做代理如下：

 

ArithmeticCalculatorArgsInvocationHandler.java

 

package bhz.uts.test;

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

public class ArithmeticCalculatorArgsInvocationHandler implements
        InvocationHandler
{
    /*要代理的对象，动态代理只有在运行时才知道代理谁，所以定义为Object类型，可以代理任意对象*/
    private Object target = null;
    
    /*通过构造函数传入原对象*/
    public ArithmeticCalculatorArgsInvocationHandler(Object target)
    {
        this.target = target;
    }

    /*InvocationHandler接口的方法，proxy表示代理，method表示原对象被调用的方法，args表示方法的参数*/
    @Override
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable
    {
        System.out.println("begin valid method ["+method.getName()+"] with args "+Arrays.toString(args));
        
        for(Object arg : args)
        {
            this.argValidtor((Double)arg);
        }
        
        Object result = method.invoke(this.target, args);
        
        return result;
    }
    
    /*获取代理类*/
    public Object getProxy()
    {
        return Proxy.newProxyInstance(this.target.getClass().getClassLoader(), this.target.getClass().getInterfaces(), this);
    }
    
    private void argValidtor(double arg) throws Exception
    {
        if(arg < 0)
            throw new Exception("参数不能为负数！");
    }
}

 

 

 

package bhz.uts.test;

public class Client
{
    public static void main(String[] args) throws Exception
    {
        /*获得代理*/
        Calculator arithmeticCalculatorProxy = (Calculator)new ArithmeticCalculatorInvocationHandler(
                 new ArithmeticCalculator()).getProxy();
        
        Calculator argValidatorProxy = (Calculator)new ArithmeticCalculatorArgsInvocationHandler(arithmeticCalculatorProxy).getProxy();
12 
        /*调用add方法*/
        argValidatorProxy.add(-10, 10);
    }
}

 

加了一个负数的校验

我们可以看到，并没有改变原来代码的逻辑，只不过是有加了一个类

调用的时候直接加一行11行的代码，然后在用返回的对象调用就可以了。

 

结果

Java HotSpot(TM) 64-Bit Server VM warning: MaxNewSize (524288k) is equal to or greater than the entire heap (524288k).  A new generation size of 524224k will be used.
begin valid method [add] with args [-10.0, 10.0]
Exception in thread "main" java.lang.Exception: 参数不能为负数！
    at bhz.uts.test.ArithmeticCalculatorArgsInvocationHandler.argValidtor(ArithmeticCalculatorArgsInvocationHandler.java:46)
    at bhz.uts.test.ArithmeticCalculatorArgsInvocationHandler.invoke(ArithmeticCalculatorArgsInvocationHandler.java:29)
    at com.sun.proxy.$Proxy0.add(Unknown Source)
    at bhz.uts.test.Client.main(Client.java:14)