TargetSourceCreator源码分析
linlei
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06a981d273
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@ -213,6 +213,7 @@
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- [AdvisorAdapter](spring-aop/spring-aop-advisorAdapter/README.md)：适配不同类型通知到拦截器链。<img src="https://img.shields.io/badge/Level-%E4%B8%80%E8%88%AC-%23FF6347"></img>
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- [Advised](spring-aop/spring-aop-advised/README.md)：配置AOP代理的通知、通知器、目标等。<img src="https://img.shields.io/badge/Level-%E7%AE%80%E5%8D%95-0099ff"></img>
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- [TargetSource](spring-aop/spring-aop-targetSource/README.md)：管理AOP代理对象的获取与释放。<img src="https://img.shields.io/badge/Level-%E7%AE%80%E5%8D%95-0099ff"></img>
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- [TargetSourceCreator](spring-aop/spring-aop-targetSourceCreator/README.md)：创建特殊的目标源，定制代理对象的创建和管理。<img src="https://img.shields.io/badge/Level-%E4%B8%80%E8%88%AC-%23FF6347"></img>
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- [@EnableAspectJAutoProxy](spring-aop/spring-aop-enableAspectJAutoProxy/README.md)：启用AspectJ切面自动代理。<img src="https://img.shields.io/badge/Level-%E4%B8%80%E8%88%AC-%23FF6347"></img>
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- [@EnableLoadTimeWeaving](spring-aop/spring-aop-enableLoadTimeWeaving/README.md)：启用Spring加载时编织。<img src="https://img.shields.io/badge/Level-%E4%B8%80%E8%88%AC-%23FF6347"></img>
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- [AspectInstanceFactory](spring-aop/spring-aop-aspectInstanceFactory/README.md)：创建切面实例，支持多种实现方式。<img src="https://img.shields.io/badge/Level-%E4%B8%80%E8%88%AC-%23FF6347"></img>
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<module>spring-aop-advisorAdapterRegistry</module>
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<module>spring-aop-advised</module>
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<module>spring-aop-aopContext</module>
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<module>spring-aop-targetSourceCreator</module>
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</modules>
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<modelVersion>4.0.0</modelVersion>
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## TargetSourceCreator
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- [TargetSourceCreator](#TargetSourceCreator)
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- [一、基本信息](#一基本信息)
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- [二、基本描述](#二基本描述)
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- [三、主要功能](#三主要功能)
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- [四、接口源码](#四接口源码)
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- [五、主要实现](#五主要实现)
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- [六、最佳实践](#六最佳实践)
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- [七、源码分析](#七源码分析)
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- [八、常见问题](#八常见问题)
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### 一、基本信息
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✒️ **作者** - Lex 📝 **博客** - [掘金](https://juejin.cn/user/4251135018533068/posts) 📚 **源码地址** - [github](https://github.com/xuchengsheng/spring-reading)
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### 二、基本描述
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`TargetSourceCreator`接口，主要用于创建目标对象的代理。通过实现该接口，你可以自定义代理对象的创建逻辑，例如根据不同的条件返回不同的代理对象。这在AOP（面向切面编程）和代理模式中非常有用，可以灵活地控制代理对象的生成过程。
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### 三、主要功能
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1. **创建代理对象的目标源（TargetSource）**
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+ 该接口允许我们定义创建代理对象的逻辑，包括决定何时创建代理对象以及如何创建代理对象的目标源。
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2. **定制代理对象的创建过程**
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+ 通过实现该接口，你可以根据需要定制代理对象的创建过程。这包括根据不同的条件返回不同的目标源，或者在创建代理对象之前或之后执行特定的逻辑。
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3. **支持AOP的灵活配置**
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+ 在Spring框架中，AOP（面向切面编程）经常使用代理对象来实现横切关注点。`TargetSourceCreator`接口允许我们灵活地控制代理对象的生成过程，从而为AOP提供了更高的定制性和灵活性。
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### 四、接口源码
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`TargetSourceCreator`接口，它允许实现类创建特殊的目标源（TargetSource），例如池化目标源，用于特定的bean。实现类可以基于目标类的属性，如池化属性，来决定选择哪种类型的目标源。`AbstractAutoProxyCreator`可以支持多个`TargetSourceCreators`，它们将按顺序应用，为Spring框架中的代理对象创建提供了灵活性和定制性。
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```java
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/**
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* 实现类可以为特定的bean创建特殊的目标源，例如池化目标源。例如，它们可以根据目标类上的属性（例如池化属性）来选择目标源。
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*
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* <p>AbstractAutoProxyCreator 可以支持多个 TargetSourceCreators，它们将按顺序应用。
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*
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* @author Rod Johnson
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* @author Juergen Hoeller
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*/
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@FunctionalInterface
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public interface TargetSourceCreator {
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/**
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* 为给定的bean创建一个特殊的目标源（如果有的话）。
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* @param beanClass bean的类
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* @param beanName bean的名称
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* @return 特殊的目标源，如果此 TargetSourceCreator 不感兴趣于特定的bean，则返回 {@code null}
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*/
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@Nullable
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TargetSource getTargetSource(Class<?> beanClass, String beanName);
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}
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```
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### 五、主要实现
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1. **QuickTargetSourceCreator**
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+ 用于快速创建目标源。它适用于那些不需要延迟加载的情况，通过特定的条件或策略，可以快速地生成目标源，以提高性能或满足其他需求。
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2. **LazyInitTargetSourceCreator**
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+ 用于延迟创建目标源。它适用于需要延迟加载的场景，以减少启动时间或资源占用。根据特定的条件或策略，它会延迟地创建目标源，直到被请求时才进行加载。
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### 六、最佳实践
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使用Spring框架中的注解配置来创建应用程序上下文，并从上下文中获取`MyConnection` bean。然后，它打印了`MyConnection`实例的类名，并循环调用了`MyConnection`实例的`getName()`方法来获取实例的名称并打印输出。
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```java
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public class TargetSourceCreatorDemo {
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public static void main(String[] args) {
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// 创建一个基于注解的应用程序上下文
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AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
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// 从上下文中获取 MyConnection bean
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MyConnection myConnection = context.getBean(MyConnection.class);
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// 打印 MyConnection 实例的类名
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System.out.println("MyConnection Class = " + myConnection.getClass());
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// 循环调用 MyConnection 实例的 getName() 方法
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for (int i = 0; i < 10; i++) {
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// 打印 MyConnection 实例的名称
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System.out.println("MyConnection Name = " + myConnection.getName());
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}
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}
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}
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```
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通过`@EnableAspectJAutoProxy`注解启用了AspectJ自动代理功能，允许Spring框架创建和管理切面（Aspects）。同时，通过`@Configuration`注解标识这是一个配置类，并使用`@ComponentScan("com.xcs.spring")`注解来指定需要扫描的包，以便Spring能够自动装配Bean和发现组件。
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```java
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@EnableAspectJAutoProxy
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@Configuration
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@ComponentScan("com.xcs.spring")
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public class AppConfig {
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}
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```
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`SetMyTargetSourceCreator`类实现了Spring框架的`BeanPostProcessor`接口和`PriorityOrdered`接口。在`postProcessAfterInitialization`方法中，通过判断bean是否为`AbstractAutoProxyCreator`的实例，然后为其设置了自定义的目标源创建器`MyTargetSourceCreator`。通过实现`PriorityOrdered`接口并重写`getOrder`方法，确保了该后置处理器具有最高的优先级，以确保在其他后置处理器之前执行。
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```java
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@Component
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public class SetMyTargetSourceCreator implements BeanPostProcessor , PriorityOrdered {
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@Override
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public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
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if (bean instanceof AbstractAutoProxyCreator) {
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((AbstractAutoProxyCreator) bean).setCustomTargetSourceCreators(new MyTargetSourceCreator());
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}
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return bean;
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}
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@Override
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public int getOrder() {
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return Ordered.HIGHEST_PRECEDENCE;
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}
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}
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```
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`MyTargetSourceCreator`类实现了`TargetSourceCreator`接口。在`getTargetSource`方法中，它根据传入的bean类和bean名称来判断是否需要为特定的bean创建目标源。如果传入的bean类是`MyConnection`类或其子类，它将返回一个具有连接池功能的目标源`ConnectionPoolTargetSource`，并设置连接池的大小为3。
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```java
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public class MyTargetSourceCreator implements TargetSourceCreator {
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@Override
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public TargetSource getTargetSource(Class<?> beanClass, String beanName) {
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if (MyConnection.class.isAssignableFrom(beanClass)) {
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return new ConnectionPoolTargetSource(3);
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}
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return null;
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}
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}
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```
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`ConnectionPoolTargetSource` 类实现了 Spring 的 `TargetSource` 接口，用于管理自定义连接对象的连接池。在构造函数中，它会初始化一个固定大小的阻塞队列作为连接池，并填充连接对象。通过实现 `getTarget()` 方法，它能够从连接池中获取连接对象，并在 `releaseTarget()` 方法中释放连接对象。
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```java
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/**
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* 连接池目标源，用于管理自定义连接对象的连接池。
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*
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* @author xcs
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* @date 2024年4月9日15:26:28
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*/
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public class ConnectionPoolTargetSource implements TargetSource {
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/**
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* 连接池
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*/
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private final BlockingQueue<MyConnection> connectionPool;
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/**
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* 构造函数，初始化连接池。
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*
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* @param poolSize 连接池大小
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*/
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public ConnectionPoolTargetSource(int poolSize) {
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this.connectionPool = new ArrayBlockingQueue<>(poolSize);
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initializeConnectionPool(poolSize);
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}
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/**
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* 初始化连接池，填充连接对象。
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*
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* @param poolSize 连接池大小
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*/
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private void initializeConnectionPool(int poolSize) {
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for (int i = 0; i < poolSize; i++) {
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MyConnection connection = new MyConnection("Connection" + i);
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connectionPool.offer(connection);
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}
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}
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/**
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* 获取目标类的类型。
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*
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* @return 目标类的类型
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*/
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@Override
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public Class<?> getTargetClass() {
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return MyConnection.class;
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}
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/**
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* 判断目标对象是否是静态的。
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*
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* @return 如果目标对象是静态的，则返回true，否则返回false
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*/
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@Override
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public boolean isStatic() {
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return false;
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}
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/**
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* 获取连接对象。
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*
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* @return 连接对象
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* @throws Exception 如果获取连接对象时发生异常
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*/
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@Override
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public Object getTarget() throws Exception {
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return connectionPool.take();
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}
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/**
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* 释放连接对象。
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*
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* @param target 待释放的连接对象
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* @throws Exception 如果释放连接对象时发生异常
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*/
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@Override
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public void releaseTarget(Object target) throws Exception {
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if (target instanceof MyConnection) {
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connectionPool.offer((MyConnection) target);
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}
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}
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}
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```
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`MyConnection` 类代表了一个自定义的连接对象。
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```java
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public class MyConnection {
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private String name;
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public MyConnection(String name) {
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this.name = name;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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@Override
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public String toString() {
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return "MyConnection{" +
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"name='" + name + '\'' +
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'}';
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}
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}
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```
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运行结果，`MyTargetSourceCreator`类成功地为`MyConnection`类创建了一个连接池目标源。Spring框架通过CGLIB动态代理增强了`MyConnection`类，使其能够使用连接池功能。每次调用`getName()`方法时，都从连接池中获取连接，并返回连续的"Connection0"、"Connection1"和"Connection2"字符串，表明连接池的大小为3且连接名称在连接池中循环使用。
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```java
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MyConnection Class = class com.xcs.spring.MyConnection$$EnhancerBySpringCGLIB$$fb2fa879
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MyConnection Name = Connection0
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MyConnection Name = Connection1
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MyConnection Name = Connection2
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MyConnection Name = Connection0
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MyConnection Name = Connection1
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MyConnection Name = Connection2
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MyConnection Name = Connection0
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MyConnection Name = Connection1
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MyConnection Name = Connection2
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MyConnection Name = Connection0
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```
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### 七、源码分析
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在`org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#postProcessBeforeInstantiation`方法中，在Bean实例化之前进行处理。首先，它检查缓存中是否存在目标Bean的信息，如果存在则直接返回null，否则继续执行。然后，它检查Bean是否是基础设施类或是否应该被跳过，如果是，则将其标记为不需要增强，并返回null。最后，如果存在自定义的目标源（TargetSource），则创建代理对象，并使用自定义的目标源处理目标实例，从而避免不必要的默认实例化过程。
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```java
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@Override
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public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) {
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// 获取缓存键
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Object cacheKey = getCacheKey(beanClass, beanName);
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// 如果bean名称为空或不在目标源bean列表中，且缓存中存在该键，则返回null
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if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
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if (this.advisedBeans.containsKey(cacheKey)) {
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return null;
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}
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// 如果bean类是基础设施类或应跳过，则将其标记为不需要增强，并返回null
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if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
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this.advisedBeans.put(cacheKey, Boolean.FALSE);
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return null;
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}
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}
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// 如果存在自定义的目标源，则在此处创建代理：
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// 避免不必要的目标bean默认实例化：
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// 目标源将以自定义方式处理目标实例。
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TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
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if (targetSource != null) {
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// 如果bean名称不为空，则将其添加到目标源bean列表中
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if (StringUtils.hasLength(beanName)) {
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this.targetSourcedBeans.add(beanName);
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}
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// 获取适用于bean的特定拦截器和增强器
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Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
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// 创建代理对象
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Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
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// 将代理对象的类与缓存键关联
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this.proxyTypes.put(cacheKey, proxy.getClass());
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return proxy;
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}
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return null;
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}
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```
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在`org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#getCustomTargetSource`方法中，根据bean的类和名称创建目标源（TargetSource）。如果设置了自定义的TargetSourceCreators，并且bean工厂中包含了指定名称的bean，则会尝试使用这些TargetSourceCreators来创建目标源。方法会遍历所有的TargetSourceCreators，调用它们的getTargetSource方法来获取目标源。如果找到了匹配的目标源，则返回该目标源；否则返回null。
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```java
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/**
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* 为bean实例创建目标源。如果设置了任何TargetSourceCreators，则使用它们。
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* 如果不应使用自定义的TargetSource，则返回{@code null}。
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* <p>此实现使用"customTargetSourceCreators"属性。
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* 子类可以重写此方法以使用不同的机制。
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* @param beanClass bean的类
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* @param beanName bean的名称
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* @return 用于此bean的目标源
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* @see #setCustomTargetSourceCreators
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*/
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@Nullable
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protected TargetSource getCustomTargetSource(Class<?> beanClass, String beanName) {
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// 对于直接注册的单例bean，我们无法创建复杂的目标源。
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if (this.customTargetSourceCreators != null &&
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this.beanFactory != null && this.beanFactory.containsBean(beanName)) {
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// 遍历所有的TargetSourceCreators
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for (TargetSourceCreator tsc : this.customTargetSourceCreators) {
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// 通过TargetSourceCreator获取目标源
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TargetSource ts = tsc.getTargetSource(beanClass, beanName);
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// 如果找到匹配的目标源，则返回
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||||
if (ts != null) {
|
||||
// 找到了匹配的目标源。
|
||||
if (logger.isTraceEnabled()) {
|
||||
logger.trace("TargetSourceCreator [" + tsc +
|
||||
"] found custom TargetSource for bean with name '" + beanName + "'");
|
||||
}
|
||||
return ts;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// 没有找到自定义的目标源。
|
||||
return null;
|
||||
}
|
||||
```
|
||||
|
||||
### 八、常见问题
|
||||
|
||||
1. **如何在Spring应用程序中配置和使用TargetSourceCreator？**
|
||||
|
||||
- 配置`TargetSourceCreator`，创建一个实现`BeanPostProcessor`和`PriorityOrdered`接口的自定义类`SetMyTargetSourceCreator`，在其`postProcessAfterInitialization`方法中设置自定义的目标源创建器。
|
||||
|
|
@ -0,0 +1,14 @@
|
|||
<?xml version="1.0" encoding="UTF-8"?>
|
||||
<project xmlns="http://maven.apache.org/POM/4.0.0"
|
||||
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
||||
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
|
||||
<parent>
|
||||
<groupId>com.xcs.spring</groupId>
|
||||
<artifactId>spring-aop</artifactId>
|
||||
<version>0.0.1-SNAPSHOT</version>
|
||||
</parent>
|
||||
|
||||
<modelVersion>4.0.0</modelVersion>
|
||||
<artifactId>spring-aop-targetSourceCreator</artifactId>
|
||||
|
||||
</project>
|
||||
|
|
@ -0,0 +1,12 @@
|
|||
package com.xcs.spring;
|
||||
|
||||
import org.springframework.context.annotation.ComponentScan;
|
||||
import org.springframework.context.annotation.Configuration;
|
||||
import org.springframework.context.annotation.EnableAspectJAutoProxy;
|
||||
|
||||
@EnableAspectJAutoProxy
|
||||
@Configuration
|
||||
@ComponentScan("com.xcs.spring")
|
||||
public class AppConfig {
|
||||
|
||||
}
|
||||
|
|
@ -0,0 +1,86 @@
|
|||
package com.xcs.spring;
|
||||
|
||||
import org.springframework.aop.TargetSource;
|
||||
|
||||
import java.util.concurrent.ArrayBlockingQueue;
|
||||
import java.util.concurrent.BlockingQueue;
|
||||
|
||||
/**
|
||||
* 连接池目标源，用于管理自定义连接对象的连接池。
|
||||
*
|
||||
* @author xcs
|
||||
* @date 2024年4月9日15:26:28
|
||||
*/
|
||||
public class ConnectionPoolTargetSource implements TargetSource {
|
||||
|
||||
/**
|
||||
* 连接池
|
||||
*/
|
||||
private final BlockingQueue<MyConnection> connectionPool;
|
||||
|
||||
/**
|
||||
* 构造函数，初始化连接池。
|
||||
*
|
||||
* @param poolSize 连接池大小
|
||||
*/
|
||||
public ConnectionPoolTargetSource(int poolSize) {
|
||||
this.connectionPool = new ArrayBlockingQueue<>(poolSize);
|
||||
initializeConnectionPool(poolSize);
|
||||
}
|
||||
|
||||
/**
|
||||
* 初始化连接池，填充连接对象。
|
||||
*
|
||||
* @param poolSize 连接池大小
|
||||
*/
|
||||
private void initializeConnectionPool(int poolSize) {
|
||||
for (int i = 0; i < poolSize; i++) {
|
||||
MyConnection connection = new MyConnection("Connection" + i);
|
||||
connectionPool.offer(connection);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* 获取目标类的类型。
|
||||
*
|
||||
* @return 目标类的类型
|
||||
*/
|
||||
@Override
|
||||
public Class<?> getTargetClass() {
|
||||
return MyConnection.class;
|
||||
}
|
||||
|
||||
/**
|
||||
* 判断目标对象是否是静态的。
|
||||
*
|
||||
* @return 如果目标对象是静态的，则返回true，否则返回false
|
||||
*/
|
||||
@Override
|
||||
public boolean isStatic() {
|
||||
return false;
|
||||
}
|
||||
|
||||
/**
|
||||
* 获取连接对象。
|
||||
*
|
||||
* @return 连接对象
|
||||
* @throws Exception 如果获取连接对象时发生异常
|
||||
*/
|
||||
@Override
|
||||
public Object getTarget() throws Exception {
|
||||
return connectionPool.take();
|
||||
}
|
||||
|
||||
/**
|
||||
* 释放连接对象。
|
||||
*
|
||||
* @param target 待释放的连接对象
|
||||
* @throws Exception 如果释放连接对象时发生异常
|
||||
*/
|
||||
@Override
|
||||
public void releaseTarget(Object target) throws Exception {
|
||||
if (target instanceof MyConnection) {
|
||||
connectionPool.offer((MyConnection) target);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,28 @@
|
|||
package com.xcs.spring;
|
||||
|
||||
import org.springframework.stereotype.Service;
|
||||
|
||||
@Service
|
||||
public class MyConnection {
|
||||
|
||||
private String name;
|
||||
|
||||
public MyConnection(String name) {
|
||||
this.name = name;
|
||||
}
|
||||
|
||||
public String getName() {
|
||||
return name;
|
||||
}
|
||||
|
||||
public void setName(String name) {
|
||||
this.name = name;
|
||||
}
|
||||
|
||||
@Override
|
||||
public String toString() {
|
||||
return "MyConnection{" +
|
||||
"name='" + name + '\'' +
|
||||
'}';
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,14 @@
|
|||
package com.xcs.spring;
|
||||
|
||||
import org.springframework.aop.TargetSource;
|
||||
import org.springframework.aop.framework.autoproxy.TargetSourceCreator;
|
||||
|
||||
public class MyTargetSourceCreator implements TargetSourceCreator {
|
||||
@Override
|
||||
public TargetSource getTargetSource(Class<?> beanClass, String beanName) {
|
||||
if (MyConnection.class.isAssignableFrom(beanClass)) {
|
||||
return new ConnectionPoolTargetSource(3);
|
||||
}
|
||||
return null;
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,25 @@
|
|||
package com.xcs.spring;
|
||||
|
||||
import org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator;
|
||||
import org.springframework.beans.BeansException;
|
||||
import org.springframework.beans.factory.config.BeanPostProcessor;
|
||||
import org.springframework.core.Ordered;
|
||||
import org.springframework.core.PriorityOrdered;
|
||||
import org.springframework.stereotype.Component;
|
||||
|
||||
@Component
|
||||
public class SetMyTargetSourceCreator implements BeanPostProcessor , PriorityOrdered {
|
||||
|
||||
@Override
|
||||
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
|
||||
if (bean instanceof AbstractAutoProxyCreator) {
|
||||
((AbstractAutoProxyCreator) bean).setCustomTargetSourceCreators(new MyTargetSourceCreator());
|
||||
}
|
||||
return bean;
|
||||
}
|
||||
|
||||
@Override
|
||||
public int getOrder() {
|
||||
return Ordered.HIGHEST_PRECEDENCE;
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,19 @@
|
|||
package com.xcs.spring;
|
||||
|
||||
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
|
||||
|
||||
public class TargetSourceCreatorDemo {
|
||||
public static void main(String[] args) {
|
||||
// 创建一个基于注解的应用程序上下文
|
||||
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
|
||||
// 从上下文中获取 MyConnection bean
|
||||
MyConnection myConnection = context.getBean(MyConnection.class);
|
||||
// 打印 MyConnection 实例的类名
|
||||
System.out.println("MyConnection Class = " + myConnection.getClass());
|
||||
// 循环调用 MyConnection 实例的 getName() 方法
|
||||
for (int i = 0; i < 10; i++) {
|
||||
// 打印 MyConnection 实例的名称
|
||||
System.out.println("MyConnection Name = " + myConnection.getName());
|
||||
}
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue