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jdk动态代理源码分析过程

时间:2020-10-04 14:44:53 | 栏目:JAVA代码 | 点击:

代理对象的生成方法是:

Proxy.newProxyInstance(...) ,进入这个方法内部,一步一步往下走会发现会调用

ProxyGenerator.generateProxyClass() ,这个方法用来生成代理类的字节码。

下面通过调用 ProxyGenerator.generateProxyClass()方法在本地生成代理类。

1.首先要有一个接口

2.生成代理类的方法如下

3.将生成的代理类导入到idea中查看是长这样

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

import com.example.springboottest.config.OrderService;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;

protected static class $OrderService extends Proxy implements OrderService {
  private static Method m1;
  private static Method m3;
  private static Method m2;
  private static Method m0;

  public $OrderService(InvocationHandler var1) throws {
    super(var1);
  }

  public final boolean equals(Object var1) throws {
    try {
      return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
    } catch (RuntimeException | Error var3) {
      throw var3;
    } catch (Throwable var4) {
      throw new UndeclaredThrowableException(var4);
    }
  }

  public final void query() throws {
    try {
      super.h.invoke(this, m3, (Object[])null);
    } catch (RuntimeException | Error var2) {
      throw var2;
    } catch (Throwable var3) {
      throw new UndeclaredThrowableException(var3);
    }
  }

  public final String toString() throws {
    try {
      return (String)super.h.invoke(this, m2, (Object[])null);
    } catch (RuntimeException | Error var2) {
      throw var2;
    } catch (Throwable var3) {
      throw new UndeclaredThrowableException(var3);
    }
  }

  public final int hashCode() throws {
    try {
      return (Integer)super.h.invoke(this, m0, (Object[])null);
    } catch (RuntimeException | Error var2) {
      throw var2;
    } catch (Throwable var3) {
      throw new UndeclaredThrowableException(var3);
    }
  }

  static {
    try {
      m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
      m3 = Class.forName("com.example.springboottest.config.OrderService").getMethod("query");
      m2 = Class.forName("java.lang.Object").getMethod("toString");
      m0 = Class.forName("java.lang.Object").getMethod("hashCode");
    } catch (NoSuchMethodException var2) {
      throw new NoSuchMethodError(var2.getMessage());
    } catch (ClassNotFoundException var3) {
      throw new NoClassDefFoundError(var3.getMessage());
    }
  }
}

可以发现在代理类中的构造方法中传入了我们实现的InvocationHandler,在调用方法时会回调invoke方法。

还可以发现代理类中继承了Proxy,由于java中是单继承的,所以java动态代理是针对接口的。

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