关于JDK
与cglib
动态代理的使用不是本文关注的重点,如有不清楚的同学可以查询相关资料进行了解。本文主要是要讲一下在面对方法存在嵌套调用时JDK
与cglib
动态代理的区别以及原因。
先看下测试代码,注意下TestProxyJDKImpl
的test1
方法调用了test2
方法即可。
public class Test {
static interface TestProxyJDK{
void test1();
void test2();
}
static class TestProxyJDKImp implements TestProxyJDK{
@Override
public void test1() {
System.out.println("执行test1");
test2();
}
@Override
public void test2() {
System.out.println("执行test2");
}
}
public static void main(String[] args) throws NoSuchMethodException {
//输出代理类
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
//创建JDK动态代理对象
TestProxyJDKImp testProxyJDKImp = new TestProxyJDKImp();
TestProxyJDK testProxyJDK = (TestProxyJDK) Proxy.newProxyInstance(Test.class.getClassLoader(), TestProxyJDKImp.class.getInterfaces(), new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String name = method.getName();
System.out.println(name + "方法被拦截前执行方法");
method.invoke(testProxyJDKImp, args);
System.out.println(name + "方法被拦截后执行方法");
return null;
}
});
//调用test1方法
testProxyJDK.test1();
//输出代理类
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\cglib");
//创建cglib代理对象
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TestProxyJDKImp.class);
enhancer.setCallback(new MethodInterceptor() {
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println("CGLIB拦截前");
proxy.invokeSuper(obj,args);
System.out.println("CGLIB拦截后");
return null;
}
});
TestProxyJDK testProxyCglib = (TestProxyJDK) enhancer.create();
//调用test1f方法
testProxyCglib.test1();
}
}
为了更好说明情况,我们先把生成的代理类以文件的形式保存下来。对于JDK动态代理,只需要在代码里添加如下一行代码即可。
//设置系统属性 1.8还是这种写法
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
生成类如下,主要看下test1
和test2
方法的代码即可:
final class $Proxy0 extends Proxy implements TestProxyJDK {
private static Method m1;
private static Method m2;
private static Method m3;
private static Method m4;
private static Method m0;
public $Proxy0(InvocationHandler var1) throws {
super(var1);
}
public final boolean equals(Object var1) throws {
try {
// 这里的h就是我们创建的InvocationHandler对象
return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final String toString() throws {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final void test1() throws {
try {
super.h.invoke(this, m3, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final void test2() throws {
try {
super.h.invoke(this, m4, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final int hashCode() throws {
try {
return (Integer)super.h.invoke(this, m0, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
static {
try {
m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
m2 = Class.forName("java.lang.Object").getMethod("toString");
m3 = Class.forName("com.xxx.xxx.Test$TestProxyJDK").getMethod("test1");
m4 = Class.forName("com.xxx.xxx.Test$TestProxyJDK").getMethod("test2");
m0 = Class.forName("java.lang.Object").getMethod("hashCode");
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
}
如果是cglib
那么可以使用下面的方式输出代理类
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "your path");
cglib
生成的相关类不止一个,这里就贴一下生成的代理类,主要看下test1
和test2
方法的代码即可:
public class Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c extends TestProxyJDKImp implements Factory {
private boolean CGLIB$BOUND;
private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
private static final Callback[] CGLIB$STATIC_CALLBACKS;
private MethodInterceptor CGLIB$CALLBACK_0;
private static final Method CGLIB$test2$0$Method;
private static final MethodProxy CGLIB$test2$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
private static final Method CGLIB$test1$1$Method;
private static final MethodProxy CGLIB$test1$1$Proxy;
private static final Method CGLIB$finalize$2$Method;
private static final MethodProxy CGLIB$finalize$2$Proxy;
private static final Method CGLIB$equals$3$Method;
private static final MethodProxy CGLIB$equals$3$Proxy;
private static final Method CGLIB$toString$4$Method;
private static final MethodProxy CGLIB$toString$4$Proxy;
private static final Method CGLIB$hashCode$5$Method;
private static final MethodProxy CGLIB$hashCode$5$Proxy;
private static final Method CGLIB$clone$6$Method;
private static final MethodProxy CGLIB$clone$6$Proxy;
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
Class var0 = Class.forName("com.xxx.xxx.Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c");
Class var1;
Method[] var10000 = ReflectUtils.findMethods(new String[]{"finalize", "()V", "equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
CGLIB$finalize$2$Method = var10000[0];
CGLIB$finalize$2$Proxy = MethodProxy.create(var1, var0, "()V", "finalize", "CGLIB$finalize$2");
CGLIB$equals$3$Method = var10000[1];
CGLIB$equals$3$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$3");
CGLIB$toString$4$Method = var10000[2];
CGLIB$toString$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$4");
CGLIB$hashCode$5$Method = var10000[3];
CGLIB$hashCode$5$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$5");
CGLIB$clone$6$Method = var10000[4];
CGLIB$clone$6$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$6");
var10000 = ReflectUtils.findMethods(new String[]{"test2", "()V", "test1", "()V"}, (var1 = Class.forName("com.xxx.xxx.Test$TestProxyJDKImp")).getDeclaredMethods());
CGLIB$test2$0$Method = var10000[0];
CGLIB$test2$0$Proxy = MethodProxy.create(var1, var0, "()V", "test2", "CGLIB$test2$0");
CGLIB$test1$1$Method = var10000[1];
CGLIB$test1$1$Proxy = MethodProxy.create(var1, var0, "()V", "test1", "CGLIB$test1$1");
}
final void CGLIB$test2$0() {
super.test2();
}
public final void test2() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
var10000.intercept(this, CGLIB$test2$0$Method, CGLIB$emptyArgs, CGLIB$test2$0$Proxy);
} else {
super.test2();
}
}
final void CGLIB$test1$1() {
super.test1();
}
public final void test1() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
var10000.intercept(this, CGLIB$test1$1$Method, CGLIB$emptyArgs, CGLIB$test1$1$Proxy);
} else {
super.test1();
}
}
final void CGLIB$finalize$2() throws Throwable {
super.finalize();
}
protected final void finalize() throws Throwable {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
var10000.intercept(this, CGLIB$finalize$2$Method, CGLIB$emptyArgs, CGLIB$finalize$2$Proxy);
} else {
super.finalize();
}
}
final boolean CGLIB$equals$3(Object var1) {
return super.equals(var1);
}
public final boolean equals(Object var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var2 = var10000.intercept(this, CGLIB$equals$3$Method, new Object[]{var1}, CGLIB$equals$3$Proxy);
return var2 == null ? false : (Boolean)var2;
} else {
return super.equals(var1);
}
}
final String CGLIB$toString$4() {
return super.toString();
}
public final String toString() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$4$Method, CGLIB$emptyArgs, CGLIB$toString$4$Proxy) : super.toString();
}
final int CGLIB$hashCode$5() {
return super.hashCode();
}
public final int hashCode() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var1 = var10000.intercept(this, CGLIB$hashCode$5$Method, CGLIB$emptyArgs, CGLIB$hashCode$5$Proxy);
return var1 == null ? 0 : ((Number)var1).intValue();
} else {
return super.hashCode();
}
}
final Object CGLIB$clone$6() throws CloneNotSupportedException {
return super.clone();
}
protected final Object clone() throws CloneNotSupportedException {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? var10000.intercept(this, CGLIB$clone$6$Method, CGLIB$emptyArgs, CGLIB$clone$6$Proxy) : super.clone();
}
public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
String var10000 = var0.toString();
switch(var10000.hashCode()) {
case -1574182249:
if (var10000.equals("finalize()V")) {
return CGLIB$finalize$2$Proxy;
}
break;
case -1147892426:
if (var10000.equals("test1()V")) {
return CGLIB$test1$1$Proxy;
}
break;
case -1147862635:
if (var10000.equals("test2()V")) {
return CGLIB$test2$0$Proxy;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;")) {
return CGLIB$clone$6$Proxy;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return CGLIB$equals$3$Proxy;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return CGLIB$toString$4$Proxy;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return CGLIB$hashCode$5$Proxy;
}
}
return null;
}
public Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c() {
CGLIB$BIND_CALLBACKS(this);
}
public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
CGLIB$THREAD_CALLBACKS.set(var0);
}
public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
CGLIB$STATIC_CALLBACKS = var0;
}
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c var1 = (Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c)var0;
if (!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if (var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if (var10000 == null) {
return;
}
}
var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
}
}
public Object newInstance(Callback[] var1) {
CGLIB$SET_THREAD_CALLBACKS(var1);
Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c var10000 = new Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Callback var1) {
CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c var10000 = new Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
CGLIB$SET_THREAD_CALLBACKS(var3);
Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c var10000 = new Test$TestProxyJDKImp$$EnhancerByCGLIB$$62be832c;
switch(var1.length) {
case 0:
var10000.<init>();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
default:
throw new IllegalArgumentException("Constructor not found");
}
}
public Callback getCallback(int var1) {
CGLIB$BIND_CALLBACKS(this);
MethodInterceptor var10000;
switch(var1) {
case 0:
var10000 = this.CGLIB$CALLBACK_0;
break;
default:
var10000 = null;
}
return var10000;
}
public void setCallback(int var1, Callback var2) {
switch(var1) {
case 0:
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
default:
}
}
public Callback[] getCallbacks() {
CGLIB$BIND_CALLBACKS(this);
return new Callback[]{this.CGLIB$CALLBACK_0};
}
public void setCallbacks(Callback[] var1) {
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
}
static {
CGLIB$STATICHOOK1();
}
}
在方法1中调用方法2使用JDK
动态代理和使用cglib
动态代理有什么区别?
执行上面测试代码的main
方法,打印结果如下:
test1方法被拦截前执行方法
执行test1
执行test2
test1方法被拦截后执行方法
CGLIB拦截前
执行test1
CGLIB拦截前
执行test2
CGLIB拦截后
CGLIB拦截后
可以看到,使用JDK
代理的时候,在test1
方法里调用test2
时,test2
方法并未被拦截,调用的还是被代理类的test2
方法。使用cglib
代理的时候,在test1
方法里调用test2
时,test2
也被拦截,调用的是生成的代理类的test2
方法。
这是为什么呢?
回到我们生成的代理类,使用JDK
代理的时候,调用test1
方法,最终执行的是InvocationHandler
的invoke
方法.
super.h.invoke(this, m3, (Object[])null);
在invoke
方法里调用被代理的test1
方法
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String name = method.getName();
System.out.println(name + "方法被拦截前执行方法");
method.invoke(testProxyJDKImp, args);
System.out.println(name + "方法被拦截后执行方法");
return null;
}
注意这里使用 method.invoke(testProxyJDKImp, args)
使用的是被代理对象,那么在test1
方法里调用this.test2
时,这个this
自然就是被代理对象,那么test2
走的就是原始的方法;
而使用cglib
代理的时候,调用test1
方法最终执行的是
public final void test1() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
//这个this就是下面的obj,是代理对象
var10000.intercept(this, CGLIB$test1$1$Method, CGLIB$emptyArgs, CGLIB$test1$1$Proxy);
} else {
super.test1();
}
}
也就是我们实现的MethodInterceptor
的intercept
方法里
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println("CGLIB拦截前");
proxy.invokeSuper(obj,args);
System.out.println("CGLIB拦截后");
return null;
}
注意,cglib
代理时我们从头到尾并不需要被代理类的对象,这里的obj
是代理对象,那么自然在调用test1
方法时,它里面的this.test2
方法里的this
就是代理对象,自然执行的是被代理后的test2
方法。文章来源:https://www.toymoban.com/news/detail-707827.html
说到这里,你有没有想起@Transactional
的一种失效的使用场景呢?其实道理都是一样的。文章来源地址https://www.toymoban.com/news/detail-707827.html
到了这里,关于动态代理JDK与cglib的区别之:如何处理被代理方法中的This调用的文章就介绍完了。如果您还想了解更多内容,请在右上角搜索TOY模板网以前的文章或继续浏览下面的相关文章,希望大家以后多多支持TOY模板网!