Java 动态代理

Java 动态代理

准备：maven依赖

  
    
        cglib
        cglib
        3.2.5
    

    
        javassist
        javassist
        3.12.1.GA
    

    
      junit
      junit
      3.8.1
      test
    
  

1，jdk方式实现

jdk方式的动态代理需要通过实现接口来实现，因此，先创建一个简单的接口及实现类：

接口：

package per.ym.proxy.jdk;

public interface BookStore {

    String add(String bookName);

    String delete(String bookName);
}

实现类：

package per.ym.proxy.jdk;

public class BookStoreImpl implements BookStore {

    public String add(String bookName) {
        System.out.println("增加书籍：" + bookName);
        return bookName;
    }

    public String delete(String bookName) {
        System.out.println("删除书籍：" + bookName);
        return bookName;
    }

}

创建代理类工厂：

package per.ym.proxy.jdk;

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

public class BookStoreJdkProxyFactory implements InvocationHandler{

    private BookStore bookStroe;

    public BookStoreJdkProxyFactory(BookStore bookStore) {
        this.bookStroe = bookStore;
    }

    public BookStore getProxy() {
        return (BookStore) Proxy.newProxyInstance(bookStroe.getClass().getClassLoader(),
                bookStroe.getClass().getInterfaces(), this);
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("调用方法：" + method.getName());

        String bookName = (String) method.invoke(bookStroe, args);

        System.out.println("方法：" + method.getName() + " 执行完成");

        return bookName;
    }

}

测试类：

package per.ym.proxy.jdk;

public class TestMain {

    public static void main(String[] args) {
         //将生成的代理类保存到文件中
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");

        BookStoreJdkProxyFactory factory = new BookStoreJdkProxyFactory(new BookStoreImpl());
        BookStore proxy = factory.getProxy();

        proxy.add("thinking in java");
        proxy.delete("spring in action");
    }

}

测试结果：

调用方法：add
增加书籍：thinking in java
方法：add 执行完成
调用方法：delete
删除书籍：spring in action
方法：delete 执行完成

工程目录下生成代理类文件：

反编译生成的代理类（避免篇幅过大，删除了equals,toString,hashCode方法）：

package com.sun.proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
import per.ym.proxy.jdk.BookStore;

public final class $Proxy0
  extends Proxy
  implements BookStore
{
  private static Method m1;
  private static Method m2;
  private static Method m3;
  private static Method m4;
  private static Method m0;

  public $Proxy0(InvocationHandler paramInvocationHandler)
  {
    super(paramInvocationHandler);
  }

  public final String add(String paramString)
  {
    try
    {
      return (String)this.h.invoke(this, m3, new Object[] { paramString });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final String delete(String paramString)
  {
    try
    {
      return (String)this.h.invoke(this, m4, new Object[] { paramString });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  static
  {
    try
    {
      m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
      m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
      m3 = Class.forName("per.ym.proxy.jdk.BookStore").getMethod("add", new Class[] { Class.forName("java.lang.String") });
      m4 = Class.forName("per.ym.proxy.jdk.BookStore").getMethod("delete", new Class[] { Class.forName("java.lang.String") });
      m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
      return;
    }
    catch (NoSuchMethodException localNoSuchMethodException)
    {
      throw new NoSuchMethodError(localNoSuchMethodException.getMessage());
    }
    catch (ClassNotFoundException localClassNotFoundException)
    {
      throw new NoClassDefFoundError(localClassNotFoundException.getMessage());
    }
  }
}

从以上得，代理类实现了被代理类的接口（因此使用jdk实现的动态代理需要被代理类实现接口），并持有传入的InvocationHandler，当调用代理类的方法时，都会转到InvocationHandler的invoke方法中，并传入自身，被调用方法及参数。

2，Cglib方式实现

Cglib是基于继承实现的代理，因此，被代理类不需要实现，直接使用一个类即可：

被代理类：

package per.ym.proxy.cglib;

public class BookStore {

    public String add(String bookName) {
        System.out.println("增加书籍：" + bookName);
        return bookName;
    }

    public String delete(String bookName) {
        System.out.println("删除书籍：" + bookName);
        return bookName;
    }

}

创建代理类工厂：

package per.ym.proxy.cglib;

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

import java.lang.reflect.Method;

public class BookStoreCglibProxyFactory implements MethodInterceptor {

    private BookStore bookStore;

    public BookStoreCglibProxyFactory(BookStore bookStore) {
        this.bookStore = bookStore;
    }

    public BookStore getProxy() {
        Enhancer enhancer = new Enhancer();

        //设置父类
        enhancer.setSuperclass(bookStore.getClass());

        //回调方法
        enhancer.setCallback(this);

        //创建代理
        return (BookStore) enhancer.create();
    }

    public Object intercept(Object obj, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
        System.out.println("调用方法：" + method.getName());

        String bookName = (String) methodProxy.invokeSuper(obj, args);

        System.out.println("方法：" + method.getName() + " 执行完成");

        return bookName;
    }
}

测试类：

package per.ym.proxy.cglib;

import net.sf.cglib.core.DebuggingClassWriter;

public class TestMain {

    public static void main(String[] args) {
        //将生成的代理类保存到指定目录下
        System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "D:\\proxy_test");

        BookStoreCglibProxyFactory factory = new BookStoreCglibProxyFactory(new BookStore());

        BookStore proxy = factory.getProxy();

        proxy.add("thinking in java");

        proxy.delete("spring in action");
    }

}

测试结果：

CGLIB debugging enabled, writing to 'D:\proxy_test'
调用方法：add
增加书籍：thinking in java
方法：add 执行完成
调用方法：delete
删除书籍：spring in action
方法：delete 执行完成

指定目录下生成的代理类class文件：

反编译生成的代理类（删除了一些注释的东西）：

package per.ym.proxy.cglib;

import java.lang.reflect.Method;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class BookStore$$EnhancerByCGLIB$$847c411a
  extends BookStore
  implements Factory
{
  private boolean CGLIB$BOUND;
  public static Object CGLIB$FACTORY_DATA;
  private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
  private static final Callback[] CGLIB$STATIC_CALLBACKS;
  private MethodInterceptor CGLIB$CALLBACK_0;
  private static Object CGLIB$CALLBACK_FILTER;
  private static final Method CGLIB$add$0$Method;
  private static final MethodProxy CGLIB$add$0$Proxy;
  private static final Object[] CGLIB$emptyArgs;
  private static final Method CGLIB$delete$1$Method;
  private static final MethodProxy CGLIB$delete$1$Proxy;
  private static final Method CGLIB$equals$2$Method;
  private static final MethodProxy CGLIB$equals$2$Proxy;
  private static final Method CGLIB$toString$3$Method;
  private static final MethodProxy CGLIB$toString$3$Proxy;
  private static final Method CGLIB$hashCode$4$Method;
  private static final MethodProxy CGLIB$hashCode$4$Proxy;
  private static final Method CGLIB$clone$5$Method;
  private static final MethodProxy CGLIB$clone$5$Proxy;

  final String CGLIB$add$0(String paramString)
  {
    return super.add(paramString);
  }

  public final String add(String paramString)
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null) {
      return (String)tmp17_14.intercept(this, CGLIB$add$0$Method, new Object[] { paramString }, CGLIB$add$0$Proxy);
    }
    return super.add(paramString);
  }

  final String CGLIB$delete$1(String paramString)
  {
    return super.delete(paramString);
  }

  public final String delete(String paramString)
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null) {
      return (String)tmp17_14.intercept(this, CGLIB$delete$1$Method, new Object[] { paramString }, CGLIB$delete$1$Proxy);
    }
    return super.delete(paramString);
  }

  final boolean CGLIB$equals$2(Object paramObject)
  {
    return super.equals(paramObject);
  }

  public final boolean equals(Object paramObject)
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
    {
      Object tmp41_36 = tmp17_14.intercept(this, CGLIB$equals$2$Method, new Object[] { paramObject }, CGLIB$equals$2$Proxy);
      tmp41_36;
      return tmp41_36 == null ? false : ((Boolean)tmp41_36).booleanValue();
    }
    return super.equals(paramObject);
  }

  final String CGLIB$toString$3()
  {
    return super.toString();
  }

  public final String toString()
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null) {
      return (String)tmp17_14.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy);
    }
    return super.toString();
  }

  final int CGLIB$hashCode$4()
  {
    return super.hashCode();
  }

  public final int hashCode()
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null)
    {
      Object tmp36_31 = tmp17_14.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
      tmp36_31;
      return tmp36_31 == null ? 0 : ((Number)tmp36_31).intValue();
    }
    return super.hashCode();
  }

  final Object CGLIB$clone$5()
    throws CloneNotSupportedException
  {
    return super.clone();
  }

  protected final Object clone()
    throws CloneNotSupportedException
  {
    MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
    if (tmp4_1 == null)
    {
      tmp4_1;
      CGLIB$BIND_CALLBACKS(this);
    }
    MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
    if (tmp17_14 != null) {
      return tmp17_14.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy);
    }
    return super.clone();
  }

  public BookStore$$EnhancerByCGLIB$$847c411a()
  {
    CGLIB$BIND_CALLBACKS(this);
  }

  public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] paramArrayOfCallback)
  {
    CGLIB$THREAD_CALLBACKS.set(paramArrayOfCallback);
  }

  public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] paramArrayOfCallback)
  {
    CGLIB$STATIC_CALLBACKS = paramArrayOfCallback;
  }

  private static final void CGLIB$BIND_CALLBACKS(Object paramObject)
  {
    847c411a local847c411a = (847c411a)paramObject;
    if (!local847c411a.CGLIB$BOUND)
    {
      local847c411a.CGLIB$BOUND = true;
      Object tmp23_20 = CGLIB$THREAD_CALLBACKS.get();
      if (tmp23_20 == null)
      {
        tmp23_20;
        CGLIB$STATIC_CALLBACKS;
      }
      local847c411a.CGLIB$CALLBACK_0 = (tmp31_28 == null ? tmp31_28 : (MethodInterceptor)((Callback[])tmp23_20)[0]);
    }
  }

  public Object newInstance(Callback[] paramArrayOfCallback)
  {
    CGLIB$SET_THREAD_CALLBACKS(paramArrayOfCallback);
    CGLIB$SET_THREAD_CALLBACKS(null);
    return new 847c411a();
  }

  public Object newInstance(Callback paramCallback)
  {
    CGLIB$SET_THREAD_CALLBACKS(new Callback[] { paramCallback });
    CGLIB$SET_THREAD_CALLBACKS(null);
    return new 847c411a();
  }

  public Callback getCallback(int paramInt)
  {
    CGLIB$BIND_CALLBACKS(this);
    switch (paramInt)
    {
    case 0: 
      break;
    }
    return null;
  }

  public void setCallback(int paramInt, Callback paramCallback)
  {
    switch (paramInt)
    {
    case 0: 
      this.CGLIB$CALLBACK_0 = ((MethodInterceptor)paramCallback);
      break;
    }
  }

  public Callback[] getCallbacks()
  {
    CGLIB$BIND_CALLBACKS(this);
    return new Callback[] { this.CGLIB$CALLBACK_0 };
  }

  public void setCallbacks(Callback[] paramArrayOfCallback)
  {
    this.CGLIB$CALLBACK_0 = ((MethodInterceptor)paramArrayOfCallback[0]);
  }

  static {}
}

这个看着就有点难受了，而且还生成了其他的class文件，不过能够看出来生成的代理类是通过继承被代理类实现的，当调用指定方法时会转到回调方法中，并传入自身，被调用方法，方法参数和一个MethodProxy，这个MethodProxy还没仔细去看是什么，不过猜测应该是封装了被调用方法相关的信息，最终也是通过反射调用被代理对象的相应方法，如果猜错了，不负责。

3，Javassist方式实现

javassist可以动态的生成一个class，关于它的更多信息，请到这里去：https://www.jianshu.com/p/43424242846b

被代理类：

package per.ym.proxy.javassist;

public class BookStore {

    public String add(String bookName) {
        System.out.println("增加书籍：" + bookName);
        return bookName;
    }

    public String delete(String bookName) {
        System.out.println("删除书籍：" + bookName);
        return bookName;
    }

}

创建代理类工厂：

package per.ym.proxy.javassist;

import java.lang.reflect.Method;

import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtField;
import javassist.CtNewMethod;

public class BookStoreJavassistProxyFactory {

    public static BookStore getProxy() throws Exception {
        ClassPool classPool = ClassPool.getDefault();

        //代理类名
        String proxyClassName = BookStore.class.getName() + "Proxy";

        //创建代理类
        CtClass ctClass = classPool.makeClass(proxyClassName);

        //设置父类为BookStore
        ctClass.setSuperclass(classPool.get(BookStore.class.getName()));

        //添加属性bookStore
        ctClass.addField(CtField.make("private " + BookStore.class.getName() + " bookStore = new " +
                BookStore.class.getName() + "();", ctClass));

        //保存整个方法信息
        StringBuilder methodSb = new StringBuilder();
        //保存方法参数信息
        StringBuilder paraSb1 = new StringBuilder();
        //保存调用被代理类方法的参数信息
        StringBuilder paraSb2 = new StringBuilder();
        //保存异常信息
        StringBuilder exceptionSb = new StringBuilder();
        Method[] methods = BookStore.class.getDeclaredMethods();
        for (Method m : methods) {
            if (m.getModifiers() == 2) {
                 continue;
            }

            methodSb.append(getModifier(m.getModifiers())).append(" ")
                    .append(m.getReturnType().getName()).append(" ")
                    .append(m.getName());

           Class[] clazzs = m.getParameterTypes();
           paraSb1.append("(");
           paraSb2.append("(");
           for (int i=0 ; i< clazzs.length ; i++) {
               if (paraSb1.length() > 1) {
                   paraSb1.append(",").append(clazzs[i].getName()).append(" ").append("arg" + i);
                   paraSb2.append(",").append("arg" + i);
               } else {
                   paraSb1.append(clazzs[i].getName()).append(" ").append("arg" + i);
                   paraSb2.append("arg" + i);
               }
           }
           paraSb1.append(")");
           paraSb2.append(")");

           methodSb.append(paraSb1);

           clazzs = m.getExceptionTypes();
           if (clazzs.length > 0) {
               methodSb.append(" throws ");
               for (int i=0; i < clazzs.length; i++) {
                   if (exceptionSb.length() > 0) {
                       exceptionSb.append(",").append(clazzs[i].getName());
                   } else {
                       exceptionSb.append(clazzs[i].getName());
                   }
               }
           }

           methodSb.append("{")
                   .append("System.out.println(\"执行方法：" + m.getName() + "\"" + ");")
                   .append(m.getReturnType().getName() + " result = bookStore." + m.getName() + paraSb2 + ";")
                   .append("System.out.println(\"方法：" + m.getName() + " 执行完成  \");")
                   .append("return result;")
                   .append("}");

           //添加方法到生成的代理类中
           ctClass.addMethod(CtNewMethod.make(methodSb.toString(), ctClass));

           methodSb.delete(0, methodSb.length());
           paraSb1.delete(0, paraSb1.length());
           paraSb2.delete(0, paraSb2.length());
           exceptionSb.delete(0, exceptionSb.length());
        }

        //保存生成的class信息到文件中
        ctClass.writeFile();

        //获取代理类class对象
        Class clazz = ctClass.toClass();
        return clazz.newInstance();
    }

    private static String getModifier(int modifier) {
        switch(modifier) {
            case 0:
                return "protected";
            case 1:
                return "public";
            case 2:
                return "private";
            case 4:
                return "";
            default:
                return "public";
        }
    }

}

测试类：

package per.ym.proxy.javassist;

public class TestMain {

    public static void main(String[] args) throws Exception {
        BookStore proxy = BookStoreJavassistProxyFactory.getProxy();
        proxy.add("thinking in java");
        proxy.delete("spring in action");
    }

}

测试结果：

执行方法：add
增加书籍：thinking in java
方法：add 执行完成  
执行方法：delete
删除书籍：spring in action
方法：delete 执行完成  

生成的代理类class文件：

反编译生成的代理类（格式化后的）：

package per.ym.proxy.javassist;

import java.io.PrintStream;

public class BookStoreProxy
  extends BookStore
{
  private BookStore bookStore = new BookStore();

  public String add(String paramString)
  {
    System.out.println("执行方法： add");
    String str = this.bookStore.add(paramString);
    System.out.println("方法： add 执行完成  ");
    return str;
  }

  public String delete(String paramString)
  {
    System.out.println("执行方法：delete");
    String str = this.bookStore.delete(paramString);
    System.out.println("方法：delete 执行完成 ");
    return str;
  }
}

不知道为啥方法参数名是paramString，而不是我设置的arg0?