前言
- 上篇博客spring 5.0.x源码学习系列六: 后置处理器ConfigurationClassPostProcessor之BeanDefinitionRegistryPostProcessor身份主要介绍了ConfigurationClassPostProcessor的BeanDefinitionRegistryPostProcessor身份, 为了精通spring, 我们还需要对它的第二个身份
BeanFactoryPostProcessor进行总结
一、ConfigurationClassPostProcessor之BeanFactoryPostProcessor身份
- 它的这个身份同样起到了非常重要的作用: 为全配置类添加cglib代理，防止以@Bean的方式创建bean时出现重复调用相同逻辑的问题。 接下来我们按照如下demo一起探究它。
二、项目demo
2.1 项目全景图
2.1.1 AppConfig
2.1.2 Bean1
2.1.3 Bean2
2.1.4 Entry
2.2 运行结果
2.2.1 AppConfig类中无@Configuration注解的运行结果
2.2.1 AppConfig类中有@Configuration注解的运行结果
2.3 解释运行结果
| 情形 | 运行结果 | 原因 |
|---|---|---|
| AppConfig中无@Configuration注解 | 打印了两次"creating bean1" | 运行的没有一点毛病, 按照正常逻辑, 执行了两次(spring创建Bean1的时候调用了一次, 创建Bean2的时候又调用了一次)创建bean的方法, 所以输出两次"creating bean1", 没毛病 |
| AppConfig中存在@Configuration注解 | 只打印了一次"creating bean1" | 是因为spring在执行BeanFactoryPostProcessor后置处理器时. 执行到了ConfigurationClassPostProcessor的postProcessBeanFactory方法, 此方法对所有的全注解类进行了CGLIB代理, 对方法进行了增强, 但此时只是将产生的cglib的class添加到了当前全配置类对应的beanDefinition的beanClass属性中(注意: 此时并没有产生bean, 只是改变了beanClass属性) |
2.4 查看cglib代理类内容
2.4.1 设置指定属性, 将cglib代理类保存至指定地方
// 将整个工程中产生的cglib代理类全部存入g盘的cglib文件夹中
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "g://cglib");2.4.2 运行项目并查看文件夹
2.4.3 将整个com文件夹copy至idea中可以解析class文件的目录下
- 因spring源码是用gradle编译的, 我copy进的是out文件夹中, 若是普通的maven项目, 把它copy至target文件夹中即可
- 生成的代理类文件夹结构如下:
代理类源码:
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package com.eugene.sumarry.csdn.invokeBeanFactoryPostProcessor3; import java.lang.reflect.Method; import org.springframework.beans.BeansException; import org.springframework.beans.factory.BeanFactory; import org.springframework.cglib.core.ReflectUtils; import org.springframework.cglib.core.Signature; import org.springframework.cglib.proxy.Callback; import org.springframework.cglib.proxy.MethodInterceptor; import org.springframework.cglib.proxy.MethodProxy; import org.springframework.cglib.proxy.NoOp; import org.springframework.context.annotation.ConfigurationClassEnhancer.EnhancedConfiguration; /** * 它继承了AppConfig, 所以断定它就是AppConfig类的cglib代理类 */ public class AppConfig$$EnhancerBySpringCGLIB$$912e823e extends AppConfig implements EnhancedConfiguration { 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$CALLBACK_0; private MethodInterceptor CGLIB$CALLBACK_1; private NoOp CGLIB$CALLBACK_2; private static Object CGLIB$CALLBACK_FILTER; private static final Method CGLIB$bean1$0$Method; private static final MethodProxy CGLIB$bean1$0$Proxy; private static final Object[] CGLIB$emptyArgs; private static final Method CGLIB$bean2$1$Method; private static final MethodProxy CGLIB$bean2$1$Proxy; private static final Method CGLIB$setBeanFactory$6$Method; private static final MethodProxy CGLIB$setBeanFactory$6$Proxy; public BeanFactory $$beanFactory; static void CGLIB$STATICHOOK1() { CGLIB$THREAD_CALLBACKS = new ThreadLocal(); CGLIB$emptyArgs = new Object[0]; Class var0 = Class.forName("com.eugene.sumarry.csdn.invokeBeanFactoryPostProcessor3.AppConfig$$EnhancerBySpringCGLIB$$912e823e"); Class var1; CGLIB$setBeanFactory$6$Method = ReflectUtils.findMethods(new String[]{"setBeanFactory", "(Lorg/springframework/beans/factory/BeanFactory;)V"}, (var1 = Class.forName("org.springframework.beans.factory.BeanFactoryAware")).getDeclaredMethods())[0]; CGLIB$setBeanFactory$6$Proxy = MethodProxy.create(var1, var0, "(Lorg/springframework/beans/factory/BeanFactory;)V", "setBeanFactory", "CGLIB$setBeanFactory$6"); Method[] var10000 = ReflectUtils.findMethods(new String[]{"bean1", "()Lcom/eugene/sumarry/csdn/invokeBeanFactoryPostProcessor3/Bean1;", "bean2", "()Lcom/eugene/sumarry/csdn/invokeBeanFactoryPostProcessor3/Bean2;"}, (var1 = Class.forName("com.eugene.sumarry.csdn.invokeBeanFactoryPostProcessor3.AppConfig")).getDeclaredMethods()); CGLIB$bean1$0$Method = var10000[0]; CGLIB$bean1$0$Proxy = MethodProxy.create(var1, var0, "()Lcom/eugene/sumarry/csdn/invokeBeanFactoryPostProcessor3/Bean1;", "bean1", "CGLIB$bean1$0"); CGLIB$bean2$1$Method = var10000[1]; CGLIB$bean2$1$Proxy = MethodProxy.create(var1, var0, "()Lcom/eugene/sumarry/csdn/invokeBeanFactoryPostProcessor3/Bean2;", "bean2", "CGLIB$bean2$1"); } final Bean1 CGLIB$bean1$0() { return super.bean1(); } /** * 代理增强的bean1方法 */ public final Bean1 bean1() { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (var10000 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } return var10000 != null ? (Bean1)var10000.intercept(this, CGLIB$bean1$0$Method, CGLIB$emptyArgs, CGLIB$bean1$0$Proxy) : super.bean1(); } final Bean2 CGLIB$bean2$1() { return super.bean2(); } /** * 代理增强的bean2方法 */ public final Bean2 bean2() { // 这里获取到产生cglib代理类时的方法拦截器 // 在spring中默认的方法拦截器有这三个: // private static final Callback[] CALLBACKS = new Callback[] { // new BeanMethodInterceptor(), // new BeanFactoryAwareMethodInterceptor(), // NoOp.INSTANCE // }; // 方法拦截器的具体作用没有去研究, 这里大致走的是方法拦截器, 在方法拦截器中对bean2方法进行了增强 MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (var10000 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } return var10000 != null ? (Bean2)var10000.intercept(this, CGLIB$bean2$1$Method, CGLIB$emptyArgs, CGLIB$bean2$1$Proxy) : super.bean2(); } final void CGLIB$setBeanFactory$6(BeanFactory var1) throws BeansException { super.setBeanFactory(var1); } public final void setBeanFactory(BeanFactory var1) throws BeansException { MethodInterceptor var10000 = this.CGLIB$CALLBACK_1; if (var10000 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_1; } if (var10000 != null) { var10000.intercept(this, CGLIB$setBeanFactory$6$Method, new Object[]{var1}, CGLIB$setBeanFactory$6$Proxy); } else { super.setBeanFactory(var1); } } public static MethodProxy CGLIB$findMethodProxy(Signature var0) { String var10000 = var0.toString(); switch(var10000.hashCode()) { case -1792804773: if (var10000.equals("bean2()Lcom/eugene/sumarry/csdn/invokeBeanFactoryPostProcessor3/Bean2;")) { return CGLIB$bean2$1$Proxy; } break; case 720662557: if (var10000.equals("bean1()Lcom/eugene/sumarry/csdn/invokeBeanFactoryPostProcessor3/Bean1;")) { return CGLIB$bean1$0$Proxy; } break; case 2095635076: if (var10000.equals("setBeanFactory(Lorg/springframework/beans/factory/BeanFactory;)V")) { return CGLIB$setBeanFactory$6$Proxy; } } return null; } public AppConfig$$EnhancerBySpringCGLIB$$912e823e() { CGLIB$BIND_CALLBACKS(this); } public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) { CGLIB$THREAD_CALLBACKS.set(var0); } public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) { CGLIB$STATIC_CALLBACKS = var0; } private static final void CGLIB$BIND_CALLBACKS(Object var0) { AppConfig$$EnhancerBySpringCGLIB$$912e823e var1 = (AppConfig$$EnhancerBySpringCGLIB$$912e823e)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; } } Callback[] var10001 = (Callback[])var10000; var1.CGLIB$CALLBACK_2 = (NoOp)((Callback[])var10000)[2]; var1.CGLIB$CALLBACK_1 = (MethodInterceptor)var10001[1]; var1.CGLIB$CALLBACK_0 = (MethodInterceptor)var10001[0]; } } static { CGLIB$STATICHOOK2(); CGLIB$STATICHOOK1(); } static void CGLIB$STATICHOOK2() { } }
三、总结
- ConfigurationClassPostProcessor之BeanFactoryPostProcessor身份最重要的就是为全注解类添加cglib代理了。当然除此之外, 还注册了一个类型为ImportAwareBeanPostProcessor的BeanPostProcessor，这里还未总结到它有何用。
- I am a slow walker, but I never walk backwards.
- github spring源码学习地址: https://github.com/AvengerEug/spring/tree/develop/resourcecode-study