spring aop 源码分析 @Scope注解创建代理对象

Posted 2020-12-19 yangxiaohui227

一.源码环境的搭建：

@Component
@Scope(scopeName = ConfigurableBeanFactory.SCOPE_SINGLETON,proxyMode = ScopedProxyMode.TARGET_CLASS)
public class MyMath implements Calc{

   public Integer add(int num1,int num2){
        return num1+num2;
    }
}

@Configuration
@ComponentScan("com.yang.xiao.hui.aop")
public class App
{
    public static void main( String[] args )
    {
        ApplicationContext ctx = new AnnotationConfigApplicationContext(App.class);
        MyMath myMath = (MyMath)ctx.getBean("myMath");
        System.out.println(myMath.getClass());
        System.out.println(ctx.getBean("scopedTarget.myMath").getClass());
    }
}

启动main方法：

 

二.源码分析，先看Scope注解：

 

 scope注解的proxyMode的属性决定了被该注解标注的类是否会被代理，这是一个枚举，有如下几个值：

 

 本次测试代码使用的是cglib代理，被Scope标注的对象，如果代理模式是jdk或者cglib代理的话，会在spring容器中产生2个bean,一个是代理的bean,一个是原始的bean,原始的bean的beanName被命名为：scopedTarget.xx:

debug调试：

 

 

 

 省略n步：

 

 我们在这个方法里面可以看到spring是如何解析主启动类，扫描到其他的bean的：

protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
            throws IOException {

        if (configClass.getMetadata().isAnnotated(Component.class.getName())) { //解析Component注解
            // Recursively process any member (nested) classes first
            processMemberClasses(configClass, sourceClass);
        }

        // Process any @PropertySource annotations
        for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
                sourceClass.getMetadata(), PropertySources.class,
                org.springframework.context.annotation.PropertySource.class)) {
            if (this.environment instanceof ConfigurableEnvironment) {
                processPropertySource(propertySource);
            }
            else {
                logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
                        "]. Reason: Environment must implement ConfigurableEnvironment");
            }
        }

        // Process any @ComponentScan annotations
        Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable( //解析Component注解ComponentScan.class
                sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
        if (!componentScans.isEmpty() &&
                !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
            for (AnnotationAttributes componentScan : componentScans) {
                // The config class is annotated with @ComponentScan -> perform the scan immediately
                Set<BeanDefinitionHolder> scannedBeanDefinitions =
                        this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName()); //componentScan解析器，对该注解进行解析
                // Check the set of scanned definitions for any further config classes and parse recursively if needed
                for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
                    BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
                    if (bdCand == null) {
                        bdCand = holder.getBeanDefinition();
                    }
                    if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
                        parse(bdCand.getBeanClassName(), holder.getBeanName());
                    }
                }
            }
        }


  //..............................省略部分代码
 }

 

 

 

 

 

 

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
        Assert.notEmpty(basePackages, "At least one base package must be specified");
        Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
        for (String basePackage : basePackages) {
            Set<BeanDefinition> candidates = findCandidateComponents(basePackage);//通过包名，扫描该包名下的所有bean的定义信息
            for (BeanDefinition candidate : candidates) {
                ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate); //scope注解解析器，获取Scope注解的属性信息，封装成ScopeMetadata 
                candidate.setScope(scopeMetadata.getScopeName());
                String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);//beanName生成器，这里是myMath
                if (candidate instanceof AbstractBeanDefinition) {
                    postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
                }
                if (candidate instanceof AnnotatedBeanDefinition) {
                    AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
                }
                if (checkCandidate(beanName, candidate)) {
                    BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                    definitionHolder =
                            AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); //这里处理scope注解，下面跟进这个
                    beanDefinitions.add(definitionHolder);
                    registerBeanDefinition(definitionHolder, this.registry);
                }
            }
        }
        return beanDefinitions;
    }

 

 

public static BeanDefinitionHolder createScopedProxy(BeanDefinitionHolder definition,
            BeanDefinitionRegistry registry, boolean proxyTargetClass) {

        String originalBeanName = definition.getBeanName();//原始的beanName: myMath
        BeanDefinition targetDefinition = definition.getBeanDefinition(); //原始的bean定义信息
        String targetBeanName = getTargetBeanName(originalBeanName); //scopedTarget.myMath

        // Create a scoped proxy definition for the original bean name,
        // "hiding" the target bean in an internal target definition.
        RootBeanDefinition proxyDefinition = new RootBeanDefinition(ScopedProxyFactoryBean.class); //创建一个代理对象
        proxyDefinition.setDecoratedDefinition(new BeanDefinitionHolder(targetDefinition, targetBeanName)); //将原始的bean定义信息作为被装饰的bean定义信息
        proxyDefinition.setOriginatingBeanDefinition(targetDefinition);//设置原始的bean定义信息
        proxyDefinition.setSource(definition.getSource());
        proxyDefinition.setRole(targetDefinition.getRole());

        proxyDefinition.getPropertyValues().add("targetBeanName", targetBeanName); 
        if (proxyTargetClass) {
            targetDefinition.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
            // ScopedProxyFactoryBean\'s "proxyTargetClass" default is TRUE, so we don\'t need to set it explicitly here.
        }
        else {
            proxyDefinition.getPropertyValues().add("proxyTargetClass", Boolean.FALSE);
        }

        // Copy autowire settings from original bean definition.
        proxyDefinition.setAutowireCandidate(targetDefinition.isAutowireCandidate());
        proxyDefinition.setPrimary(targetDefinition.isPrimary());
        if (targetDefinition instanceof AbstractBeanDefinition) {
            proxyDefinition.copyQualifiersFrom((AbstractBeanDefinition) targetDefinition);
        }

        // The target bean should be ignored in favor of the scoped proxy.
        targetDefinition.setAutowireCandidate(false);
        targetDefinition.setPrimary(false);

        // Register the target bean as separate bean in the factory.
        registry.registerBeanDefinition(targetBeanName, targetDefinition);//这里将原始的bean定义信息注册到了spring容器，而bean的名称是scopedTarget.myMath

        // Return the scoped proxy definition as primary bean definition
        // (potentially an inner bean).
        return new BeanDefinitionHolder(proxyDefinition, originalBeanName, definition.getAliases()); //这里将代理bean定义信息返回，bean的名称是原始的beanName,myMath,该beanHodler返回去后，会被注册到spring
    }

 

 总结：
一个被Scope注解标注的类，如果scope的proxyMode不是no 或者defualt,那么会在spring创建2个bean,一个是代理bean,类型为ScopedProxyFactoryBean.class，一个是原始的bean:

这里我们的MyMath类，生成了2个beanDefinition,一个是代理的beanDefinition,beanName为myMath,一个是原始的beanDefinition，beanName为scopedTarget.myMath；

下面我们要分析ScopedProxyFactoryBean的创建过程了，我们知道XXFactoryBean会有一个getObject()方法返回XX代理对象：先看ScopedProxyFactoryBean继承体系

 

 

 

 通过继承图，我们知道，ScopedProxyFactoryBean实现了BeanFactoryAware接口，因此在ScopedProxyFactoryBean的创建过程中，会回调setBeanFactory(BeanFactory beanFactory)，所以我们debug在该方法：

 

 

 我们详细看看该方法：

@Override
    public void setBeanFactory(BeanFactory beanFactory) {
        if (!(beanFactory instanceof ConfigurableBeanFactory)) {
            throw new IllegalStateException("Not running in a ConfigurableBeanFactory: " + beanFactory);
        }
        ConfigurableBeanFactory cbf = (ConfigurableBeanFactory) beanFactory;

        this.scopedTargetSource.setBeanFactory(beanFactory);

        ProxyFactory pf = new ProxyFactory(); //创建代理工厂
        pf.copyFrom(this);
        pf.setTargetSource(this.scopedTargetSource);

        Assert.notNull(this.targetBeanName, "Property \'targetBeanName\' is required");
        Class<?> beanType = beanFactory.getType(this.targetBeanName);//获取被代理类
        if (beanType == null) {
            throw new IllegalStateException("Cannot create scoped proxy for bean \'" + this.targetBeanName +
                    "\': Target type could not be determined at the time of proxy creation.");
        }
        if (!isProxyTargetClass() || beanType.isInterface() || Modifier.isPrivate(beanType.getModifiers())) {
            pf.setInterfaces(ClassUtils.getAllInterfacesForClass(beanType, cbf.getBeanClassLoader())); //获取被代理类的所有实现的接口
        }

        // Add an introduction that implements only the methods on ScopedObject.
        ScopedObject scopedObject = new DefaultScopedObject(cbf, this.scopedTargetSource.getTargetBeanName());
        pf.addAdvice(new DelegatingIntroductionInterceptor(scopedObject));//这里添加了一个增强器，在执行目标方法时，会拦截

        // Add the AopInfrastructureBean marker to indicate that the scoped proxy
        // itself is not subject to auto-proxying! Only its target bean is.
        pf.addInterface(AopInfrastructureBean.class);

        this.proxy = pf.getProxy(cbf.getBeanClassLoader());//创建代理对象
    }

 

 创建代理对象过程，跟之前aop源码分析一和源码分析二的时侯分析的一样了，这里不重复了