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Cglib dynamic agent -- example / principle
2022-07-06 00:54:00 【It blade out of sheath】
Original website ：CGLIB A dynamic proxy -- example / principle _IT A blog with a sharp blade -CSDN Blog
brief introduction
explain
This article introduces with examples CGLIB Use of dynamic agents .
principle
CGLIB It's about classes that implement proxies .
The principle is to generate a subclass of the specified target class , And cover the methods to realize the enhancement , But because it's inheritance , So we can't be right final Decorated class to proxy .
Limit
JDK The dynamic proxy mechanism can only implement the class of the interface , Classes that cannot implement interfaces cannot implement JDK Dynamic proxy for .
example ： Count the execution time
rely on
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib</artifactId>
<version>3.2.5</version>
</dependency>The lower version of cglib This dependency may be required ：
<dependency>
<groupId>org.ow2.asm</groupId>
<artifactId>asm</artifactId>
<version>5.0.1</version>
</dependency>
Code
package org.example.a;
import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
// Surrogate class
class ExecutionTimeReality {
// Print out the task name here , And sleep 500ms The simulation task took a long time
public void dealTask(String taskName) {
System.out.println("Task is running: " + taskName);
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// Print out the task name here , And sleep 500ms The simulation task took a long time
public void sayHello(String name) {
System.out.println("hello: " + name);
}
}
// proxy class
class ExecutionTimeProxy implements MethodInterceptor {
@Override
public Object intercept(Object obj, Method method, Object[] args,
MethodProxy proxy) throws Throwable {
long startTime = System.currentTimeMillis();
proxy.invokeSuper(obj, args);
long endTime = System.currentTimeMillis();
System.out.println("Elapsed time: " + (endTime - startTime) + " ms");
return null;
}
}
// Factory methods get proxy objects
class DynamicProxyFactory {
public static Object getInstance() {
Object target = new ExecutionTimeReality();
ExecutionTimeProxy proxySubject = new ExecutionTimeProxy();
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(target.getClass());
enhancer.setCallback(proxySubject);
return enhancer.create();
}
}
public class Demo {
public static void main(String[] args) {
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\CglibProxyClass");
ExecutionTimeReality subject = (ExecutionTimeReality) DynamicProxyFactory.getInstance();
subject.dealTask("TestTask");
}
}Execution results
Task is running: TestTask
Elapsed time: 524 msprinciple
Process Overview
This part should be put to the end as a conclusion . But in order to quickly experience the overall process , Put it to the front .
Instantiation Enhancer And set the class and callback to proxy （MethodInterceptor Implementation class object of interface ）
Create a proxy class （ Inherited from the proxied class ）
Represented by dealTask Method （ Overridden by proxy class , Actually call the proxy class dealTask Method ）
Callback intercept Method （ExecutionTimeProxy.intercept） // The callback is passed in the first step
proxy.invokeSuper(obj, args); // Call the parent class invokeSuper The method is MethodProxy Declarative
this.init(); // If it does not exist FastClass, Generate a
this.fastClassInfo.f2.invoke(fci.i2, obj, args);
FastClass Of invoke Method
Compare the first parameter with the number , Execute the corresponding method
Manually generate the proxy class source code
Analysis of the source code , It depends on the generated proxy class source code , Generation method ： stay main Write this code at the beginning ：
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\CglibProxyClass");
After operation , Will generate E:/CglibProxyClass Folder , Its structure is as follows
E:\CGLIBPROXYCLASS
├─net
│ └─sf
│ └─cglib
│ ├─core
│ │ MethodWrapper$MethodWrapperKey$$KeyFactoryByCGLIB$$d45e49f7.class
│ │
│ └─proxy
│ Enhancer$EnhancerKey$$KeyFactoryByCGLIB$$7fb24d72.class
│
└─org
└─example
└─a
ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386$$FastClassByCGLIB$$bebee033.class
ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386.class
ExecutionTimeReality$$FastClassByCGLIB$$81389d66.classBecause the two one. $ stay CSDN The display in the is abnormal , So use one below $ Two $
ExecutionTimeReality$EnhancerByCGLIB$5a92c386$FastClassByCGLIB$bebee033.class
Quick class 1. This class will not be discussed for the time being . The code does not analyze .
ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class
proxy class , Will be called to ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class
ExecutionTimeReality$FastClassByCGLIB$81389d66.class
Quick class 2. Called by proxy class to .FastClass It is not generated with the proxy class , But in the first execution MethodProxy invoke/invokeSuper And put it in the cache .
ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package org.example.a;
import java.lang.reflect.Method;
import net.sf.cglib.core.ReflectUtils;
import net.sf.cglib.core.Signature;
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 ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 extends ExecutionTimeReality 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$dealTask$0$Method;
private static final MethodProxy CGLIB$dealTask$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
private static final Method CGLIB$sayHello$1$Method;
private static final MethodProxy CGLIB$sayHello$1$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;
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
Class var0 = Class.forName("org.example.a.ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386");
Class var1;
Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
CGLIB$equals$2$Method = var10000[0];
CGLIB$equals$2$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$2");
CGLIB$toString$3$Method = var10000[1];
CGLIB$toString$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$3");
CGLIB$hashCode$4$Method = var10000[2];
CGLIB$hashCode$4$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$4");
CGLIB$clone$5$Method = var10000[3];
CGLIB$clone$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$5");
var10000 = ReflectUtils.findMethods(new String[]{"dealTask", "(Ljava/lang/String;)V", "sayHello", "(Ljava/lang/String;)V"}, (var1 = Class.forName("org.example.a.ExecutionTimeReality")).getDeclaredMethods());
CGLIB$dealTask$0$Method = var10000[0];
CGLIB$dealTask$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "dealTask", "CGLIB$dealTask$0");
CGLIB$sayHello$1$Method = var10000[1];
CGLIB$sayHello$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "sayHello", "CGLIB$sayHello$1");
}
final void CGLIB$dealTask$0(String var1) {
super.dealTask(var1);
}
public final void dealTask(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
var10000.intercept(this, CGLIB$dealTask$0$Method, new Object[]{var1}, CGLIB$dealTask$0$Proxy);
} else {
super.dealTask(var1);
}
}
final void CGLIB$sayHello$1(String var1) {
super.sayHello(var1);
}
public final void sayHello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
var10000.intercept(this, CGLIB$sayHello$1$Method, new Object[]{var1}, CGLIB$sayHello$1$Proxy);
} else {
super.sayHello(var1);
}
}
final boolean CGLIB$equals$2(Object var1) {
return super.equals(var1);
}
public final boolean equals(Object var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var2 = var10000.intercept(this, CGLIB$equals$2$Method, new Object[]{var1}, CGLIB$equals$2$Proxy);
return var2 == null ? false : (Boolean)var2;
} else {
return super.equals(var1);
}
}
final String CGLIB$toString$3() {
return super.toString();
}
public final String toString() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy) : super.toString();
}
final int CGLIB$hashCode$4() {
return super.hashCode();
}
public final int hashCode() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var1 = var10000.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
return var1 == null ? 0 : ((Number)var1).intValue();
} else {
return super.hashCode();
}
}
final Object CGLIB$clone$5() throws CloneNotSupportedException {
return super.clone();
}
protected final Object clone() throws CloneNotSupportedException {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? var10000.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy) : super.clone();
}
public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
String var10000 = var0.toString();
switch(var10000.hashCode()) {
case -1165719922:
if (var10000.equals("dealTask(Ljava/lang/String;)V")) {
return CGLIB$dealTask$0$Proxy;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;")) {
return CGLIB$clone$5$Proxy;
}
break;
case 771401912:
if (var10000.equals("sayHello(Ljava/lang/String;)V")) {
return CGLIB$sayHello$1$Proxy;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return CGLIB$equals$2$Proxy;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return CGLIB$toString$3$Proxy;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return CGLIB$hashCode$4$Proxy;
}
}
return null;
}
public ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386() {
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) {
ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var1 = (ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386)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);
ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Callback var1) {
CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
CGLIB$SET_THREAD_CALLBACKS(var3);
ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386;
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();
}
}
You can see through the source code of the proxy class , The proxy class will get all the methods inherited from the parent class , And there will be MethodProxy With the corresponding , such as ：
private static final Method CGLIB$dealTask$0$Method;
private static final MethodProxy CGLIB$dealTask$0$Proxy;
private static final Method CGLIB$sayHello$1$Method;
private static final MethodProxy CGLIB$sayHello$1$Proxy;in addition , From the type of proxy class , It directly inherits the class to be represented , So classes without interfaces that can be proxied . Actually , It has nothing to do with interfaces , If there is an interface, it will not be used .
public class ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 extends ExecutionTimeReality implements FactoryMethod call
final void CGLIB$dealTask$0(String var1) {
super.dealTask(var1);
}
public final void dealTask(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
var10000.intercept(this, CGLIB$dealTask$0$Method, new Object[]{var1}, CGLIB$dealTask$0$Proxy);
} else {
super.dealTask(var1);
}
}FastClass Mechanism
Cglib The reason why the efficiency of dynamic agent execution method is better than JDK Because Cglib Adopted FastClass Mechanism , Its principle is simply ： Generate one for the proxy class and one for the proxied class Class, This Class A method of the proxy class or the proxied class is assigned a index(int type ). This index As a parameter ,FastClass You can directly locate the method to be called and call it directly , This saves reflection calls , So call efficiency ratio JDK Dynamic proxy calls high through reflection .
ExecutionTimeReality$FastClassByCGLIB$81389d66
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package org.example.a;
import java.lang.reflect.InvocationTargetException;
import net.sf.cglib.core.Signature;
import net.sf.cglib.reflect.FastClass;
public class ExecutionTimeReality$$FastClassByCGLIB$$81389d66 extends FastClass {
public ExecutionTimeReality$$FastClassByCGLIB$$81389d66(Class var1) {
super(var1);
}
public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case -1165719922:
if (var10000.equals("dealTask(Ljava/lang/String;)V")) {
return 0;
}
break;
case 771401912:
if (var10000.equals("sayHello(Ljava/lang/String;)V")) {
return 1;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return 2;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return 3;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 4;
}
}
return -1;
}
public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -2012993625:
if (var1.equals("sayHello")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 1;
}
}
}
break;
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 3;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 2;
}
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 4;
}
}
break;
case 510300177:
if (var1.equals("dealTask")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 0;
}
}
}
}
return -1;
}
public int getIndex(Class[] var1) {
switch(var1.length) {
case 0:
return 0;
default:
return -1;
}
}
public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
ExecutionTimeReality var10000 = (ExecutionTimeReality)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
var10000.dealTask((String)var3[0]);
return null;
case 1:
var10000.sayHello((String)var3[0]);
return null;
case 2:
return new Boolean(var10000.equals(var3[0]));
case 3:
return var10000.toString();
case 4:
return new Integer(var10000.hashCode());
}
} catch (Throwable var4) {
throw new InvocationTargetException(var4);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
ExecutionTimeReality var10000 = new ExecutionTimeReality;
ExecutionTimeReality var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.<init>();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public int getMaxIndex() {
return 4;
}
}
Other websites
Cglib Principle of dynamic agent implementation - Steamed buns with sugar beans - Blog Garden
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