Proxy是在何時調用InvocationHandler的invoke方法的

最近看到spring的動態代理，扒到深處看到時 Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);看到這一句，頓時比較懵逼，仍是沒有搞懂invoke方法的調用，而後搜索了一下，礙，碰見一位大神的文章

特來記錄一下，嘿嘿：首先這裏是原文連接

其實前面的能夠省略了（太晚啦，要睡覺啦），什麼建立接口、實現類、建立實現InvocationHandler的類（不建立也行）等等操做，直接上重點，代理對象執行invoke的地方：

首先，咱們編譯後，會得出一個代理對象的class文件，打開這個class文件就解開謎題了（當時也是懵逼了，這招沒想到，啊哈哈）：

咱們Proxy的類中，有一個受保護的InvocationHandler成員屬性：

 

public class Proxy implements java.io.Serializable {

    private static final long serialVersionUID = -2222568056686623797L;

    /** parameter types of a proxy class constructor */
    private static final Class<?>[] constructorParams =
        { InvocationHandler.class };

    /**
     * a cache of proxy classes
     */
    private static final WeakCache<ClassLoader, Class<?>[], Class<?>>
        proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());

    /**
     * the invocation handler for this proxy instance.
     * @serial
     */
    protected InvocationHandler h;//在這裏！

    /**
     * Prohibits instantiation.
     */
    private Proxy() {
    }

    /**
     * Constructs a new {@code Proxy} instance from a subclass
     * (typically, a dynamic proxy class) with the specified value
     * for its invocation handler.
     *
     * @param  h the invocation handler for this proxy instance
     *
     * @throws NullPointerException if the given invocation handler, {@code h},
     *         is {@code null}.
     */
    protected Proxy(InvocationHandler h) {
        Objects.requireNonNull(h);
        this.h = h;
    }

 

接着看代理對象的實現：

public final class $Proxy0 extends Proxy implements Subject（目標類，被代理的類） {  
    private static Method m1;  
    private static Method m0;  
    private static Method m3;  
    private static Method m2;  
  
    static {  
        try {  
            m1 = Class.forName("java.lang.Object").getMethod("equals",  
                    new Class[] { Class.forName("java.lang.Object") });  
  
            m0 = Class.forName("java.lang.Object").getMethod("hashCode",  
                    new Class[0]);  
  
            m3 = Class.forName("***.RealSubject").getMethod("request",  //代理方法名稱
                    new Class[0]);  
  
            m2 = Class.forName("java.lang.Object").getMethod("toString",  
                    new Class[0]);  
  
        } catch (NoSuchMethodException nosuchmethodexception) {  
            throw new NoSuchMethodError(nosuchmethodexception.getMessage());  
        } catch (ClassNotFoundException classnotfoundexception) {  
            throw new NoClassDefFoundError(classnotfoundexception.getMessage());  
        }  
    } //static  
  
    public $Proxy0(InvocationHandler invocationhandler) {  
        super(invocationhandler);  
    }  
  
    @Override  
    public final boolean equals(Object obj) {  
        try {  
            return ((Boolean) super.h.invoke(this, m1, new Object[] { obj })) .booleanValue();  
        } catch (Throwable throwable) {  
            throw new UndeclaredThrowableException(throwable);  
        }  
    }  
  
    @Override  
    public final int hashCode() {  
        try {  
            return ((Integer) super.h.invoke(this, m0, null)).intValue();  
        } catch (Throwable throwable) {  
            throw new UndeclaredThrowableException(throwable);  
        }  
    }  
  
    public final void request() {  //代理方法
        try {  
            super.h.invoke(this, m3, null);  
            return;  
        } catch (Error e) {  
        } catch (Throwable throwable) {  
            throw new UndeclaredThrowableException(throwable);  
        }  
    }  
  
    @Override  
    public final String toString() {  
        try {  
            return (String) super.h.invoke(this, m2, null);  
        } catch (Throwable throwable) {  
            throw new UndeclaredThrowableException(throwable);  
        }  
    }  
}  

看到這裏就明白了。新返回的代理對象，調用了父類（Proxy）h的方法，這裏也就是invoke方法與Proxy相關的地方啦。