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<a href="/文章/当我们在讨论CQRS时，我们在讨论些神马？.md.html">当我们在讨论CQRS时，我们在讨论些神马？.md.html</a>
|
||
</li>
|
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|
||
<li>
|
||
|
||
|
||
<a href="/文章/彻底理解 MySQL 的索引机制.md.html">彻底理解 MySQL 的索引机制.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/最全的 116 道 Redis 面试题解答.md.html">最全的 116 道 Redis 面试题解答.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/有赞权限系统(SAM).md.html">有赞权限系统(SAM).md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/有赞零售中台建设方法的探索与实践.md.html">有赞零售中台建设方法的探索与实践.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/服务注册与发现原理剖析（Eureka、Zookeeper、Nacos）.md.html">服务注册与发现原理剖析（Eureka、Zookeeper、Nacos）.md.html</a>
|
||
</li>
|
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|
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<li>
|
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|
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|
||
<a href="/文章/深入浅出Cache.md.html">深入浅出Cache.md.html</a>
|
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</li>
|
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|
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<li>
|
||
|
||
|
||
<a href="/文章/深入理解 MySQL 底层实现.md.html">深入理解 MySQL 底层实现.md.html</a>
|
||
</li>
|
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|
||
<li>
|
||
|
||
|
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<a href="/文章/漫画讲解 git rebase VS git merge.md.html">漫画讲解 git rebase VS git merge.md.html</a>
|
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<li>
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<a href="/文章/生成浏览器唯一稳定 ID 的探索.md.html">生成浏览器唯一稳定 ID 的探索.md.html</a>
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<li>
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<a href="/文章/缓存 如何保证缓存与数据库的双写一致性？.md.html">缓存 如何保证缓存与数据库的双写一致性？.md.html</a>
|
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<li>
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<a href="/文章/网易严选怎么做全链路监控的？.md.html">网易严选怎么做全链路监控的？.md.html</a>
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<li>
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<a href="/文章/美团万亿级 KV 存储架构与实践.md.html">美团万亿级 KV 存储架构与实践.md.html</a>
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||
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|
||
<li>
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||
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||
|
||
<a href="/文章/美团点评Kubernetes集群管理实践.md.html">美团点评Kubernetes集群管理实践.md.html</a>
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||
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||
<li>
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||
|
||
|
||
<a href="/文章/美团百亿规模API网关服务Shepherd的设计与实现.md.html">美团百亿规模API网关服务Shepherd的设计与实现.md.html</a>
|
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||
<li>
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||
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|
||
<a href="/文章/解读《阿里巴巴 Java 开发手册》背后的思考.md.html">解读《阿里巴巴 Java 开发手册》背后的思考.md.html</a>
|
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||
<li>
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||
|
||
|
||
<a href="/文章/认识 MySQL 和 Redis 的数据一致性问题.md.html">认识 MySQL 和 Redis 的数据一致性问题.md.html</a>
|
||
</li>
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||
<li>
|
||
|
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|
||
<a href="/文章/进阶：Dockerfile 高阶使用指南及镜像优化.md.html">进阶：Dockerfile 高阶使用指南及镜像优化.md.html</a>
|
||
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||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/铁总在用的高性能分布式缓存计算框架 Geode.md.html">铁总在用的高性能分布式缓存计算框架 Geode.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
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||
|
||
<a href="/文章/阿里云PolarDB及其共享存储PolarFS技术实现分析（上）.md.html">阿里云PolarDB及其共享存储PolarFS技术实现分析（上）.md.html</a>
|
||
</li>
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||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/阿里云PolarDB及其共享存储PolarFS技术实现分析（下）.md.html">阿里云PolarDB及其共享存储PolarFS技术实现分析（下）.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/面试最常被问的 Java 后端题.md.html">面试最常被问的 Java 后端题.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/领域驱动设计在互联网业务开发中的实践.md.html">领域驱动设计在互联网业务开发中的实践.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/领域驱动设计的菱形对称架构.md.html">领域驱动设计的菱形对称架构.md.html</a>
|
||
</li>
|
||
|
||
<li>
|
||
|
||
|
||
<a href="/文章/高效构建 Docker 镜像的最佳实践.md.html">高效构建 Docker 镜像的最佳实践.md.html</a>
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
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</div>
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<div class="sidebar-toggle" onclick="sidebar_toggle()" onmouseover="add_inner()" onmouseleave="remove_inner()">
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<div class="sidebar-toggle-inner"></div>
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</div>
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<script>
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function add_inner() {
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let inner = document.querySelector('.sidebar-toggle-inner')
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inner.classList.add('show')
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}
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function remove_inner() {
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let inner = document.querySelector('.sidebar-toggle-inner')
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inner.classList.remove('show')
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}
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function sidebar_toggle() {
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let sidebar_toggle = document.querySelector('.sidebar-toggle')
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let sidebar = document.querySelector('.book-sidebar')
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let content = document.querySelector('.off-canvas-content')
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if (sidebar_toggle.classList.contains('extend')) { // show
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sidebar_toggle.classList.remove('extend')
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sidebar.classList.remove('hide')
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content.classList.remove('extend')
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} else { // hide
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sidebar_toggle.classList.add('extend')
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||
|
||
sidebar.classList.add('hide')
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content.classList.add('extend')
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}
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}
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function open_sidebar() {
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let sidebar = document.querySelector('.book-sidebar')
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sidebar.classList.add('show')
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overlay.classList.add('show')
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function hide_canvas() {
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let sidebar = document.querySelector('.book-sidebar')
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let overlay = document.querySelector('.off-canvas-overlay')
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sidebar.classList.remove('show')
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overlay.classList.remove('show')
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}
|
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</script>
|
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<div class="off-canvas-content">
|
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|
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<div class="columns">
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|
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<div class="column col-12 col-lg-12">
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<div class="book-navbar">
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<!-- For Responsive Layout -->
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<header class="navbar">
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<section class="navbar-section">
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<a onclick="open_sidebar()">
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<i class="icon icon-menu"></i>
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</a>
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</section>
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</header>
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||
</div>
|
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<div class="book-content" style="max-width: 960px; margin: 0 auto;
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||
overflow-x: auto;
|
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|
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overflow-y: hidden;">
|
||
|
||
<div class="book-post">
|
||
|
||
<p id="tip" align="center"></p>
|
||
|
||
<div><h1>Spring MyBatis和Spring整合的奥秘</h1>
|
||
|
||
<p><em>本篇博客源码分析基于Spring 5.1.16.RELEASE，mybatis-spring 2.0.0，较高版本的mybatis-spring源码有较大区别。</em></p>
|
||
|
||
<p>Spring之所以是目前Java最受欢迎的框架，几乎所有的Java项目都在使用，就是因为它良好的生态，很多技术可以与之整合，为什么其他技术可以和Spring相整合，就是因为Spring拥有很多扩展点，阅读Spring源码，有一部分原因就是有必要清楚的知道Spring提供了哪些扩展点，而怎么合理的利用这些扩展点，就需要了解其他技术是如何利用这些扩展点的。</p>
|
||
|
||
<p>今天我就来带着大家看下，国内最流行的数据库框架MyBatis是如何利用Spring的扩展点的，从而双剑合璧，让Spring+MyBatis成为国内最流行的技术搭配。</p>
|
||
|
||
<h3>前置知识</h3>
|
||
|
||
<p>为了后面的故事可以顺利展开，很有必要先给大家介绍下，阅读mybatis-spring源码的前置知识，没有这些前置知识阅读mybatis-spring源码是寸步难行。</p>
|
||
|
||
<h4>mybatis-spring使用</h4>
|
||
|
||
<p>因为现在有了SpringBoot，所以Mybatis和Spring的整合变得非常简单，但是如果没有SpringBoot，该怎么整合呢？我翻阅了百度的前几页，不知道是不是搜索关键词问题，几乎全是用XML的方式去整合Mybatis和Spring的，零XML配置，它不香吗？</p>
|
||
|
||
<p>代码结构：
|
||
|
||
<img src="assets/15100432-c2a982e6c0145a65.png" alt="image.png" /></p>
|
||
|
||
<p>具体实现：</p>
|
||
|
||
<pre><code> <dependencies>
|
||
|
||
<dependency>
|
||
|
||
<groupId>org.mybatis</groupId>
|
||
|
||
<artifactId>mybatis-spring</artifactId>
|
||
|
||
<version>2.0.0</version>
|
||
|
||
</dependency>
|
||
|
||
<!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
|
||
|
||
<dependency>
|
||
|
||
<groupId>org.springframework</groupId>
|
||
|
||
<artifactId>spring-context</artifactId>
|
||
|
||
<version>5.1.16.RELEASE</version>
|
||
|
||
</dependency>
|
||
|
||
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
|
||
|
||
<dependency>
|
||
|
||
<groupId>org.mybatis</groupId>
|
||
|
||
<artifactId>mybatis</artifactId>
|
||
|
||
<version>3.4.0</version>
|
||
|
||
</dependency>
|
||
|
||
<!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
|
||
|
||
<dependency>
|
||
|
||
<groupId>org.springframework</groupId>
|
||
|
||
<artifactId>spring-jdbc</artifactId>
|
||
|
||
<version>5.1.10.RELEASE</version>
|
||
|
||
</dependency>
|
||
|
||
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
|
||
|
||
<dependency>
|
||
|
||
<groupId>mysql</groupId>
|
||
|
||
<artifactId>mysql-connector-java</artifactId>
|
||
|
||
<version>6.0.5</version>
|
||
|
||
</dependency>
|
||
|
||
</dependencies>
|
||
|
||
@MapperScan("com.codebear.mapper")
|
||
|
||
@ComponentScan
|
||
|
||
public class AppConfig {
|
||
|
||
@Bean
|
||
|
||
public SqlSessionFactory sqlSessionFactory() throws Exception {
|
||
|
||
DriverManagerDataSource dataSource = new DriverManagerDataSource();
|
||
|
||
dataSource.setDriverClassName("com.mysql.jdbc.Driver");
|
||
|
||
dataSource.setUrl("jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC");
|
||
|
||
dataSource.setUsername("root");
|
||
|
||
dataSource.setPassword("123456");
|
||
|
||
SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
|
||
|
||
factoryBean.setDataSource(dataSource);
|
||
|
||
return factoryBean.getObject();
|
||
|
||
}
|
||
|
||
}
|
||
|
||
@Repository
|
||
|
||
public interface StudentMapper {
|
||
|
||
@Select("select * from student")
|
||
|
||
List<Student> getList();
|
||
|
||
}
|
||
|
||
public class Main {
|
||
|
||
public static void main(String[] args) {
|
||
|
||
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
|
||
|
||
System.out.println(applicationContext.getBean(StudentMapper.class).getList());
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>运行结果：</p>
|
||
|
||
<pre><code>[Student{id=1, name='疫苗王', age=20}, Student{id=2, name='阿修罗独角仙', age=18}, Student{id=3, name='地底王', age=18}]
|
||
|
||
</code></pre>
|
||
|
||
<h4>Import注解</h4>
|
||
|
||
<p>如果我们想把一个类注册到Spring容器中，可以采用的方法有很多，其中一种是利用Import注解，Import注解有三种用法，mybatis-spring利用的是其中一种用法，Import了ImportBeanDefinitionRegistrar类，所以我们这里只看Import ImportBeanDefinitionRegistrar。</p>
|
||
|
||
<h5>如何使用</h5>
|
||
|
||
<pre><code>public class MyBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
|
||
|
||
public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) {
|
||
|
||
System.out.println(annotationMetadata.getAnnotationTypes());
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>写一个类实现ImportBeanDefinitionRegistrar ，重写其中的registerBeanDefinitions方法。</p>
|
||
|
||
<pre><code>@Import(MyBeanDefinitionRegistrar.class)
|
||
|
||
@ComponentScan
|
||
|
||
@MapperScan("com.codebear.mapper")
|
||
|
||
public class AppConfig {
|
||
|
||
@Bean
|
||
|
||
public SqlSessionFactory sqlSessionFactory() throws Exception {
|
||
|
||
DriverManagerDataSource dataSource = new DriverManagerDataSource();
|
||
|
||
dataSource.setDriverClassName("com.mysql.jdbc.Driver");
|
||
|
||
dataSource.setUrl("jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC");
|
||
|
||
dataSource.setUsername("root");
|
||
|
||
dataSource.setPassword("123456");
|
||
|
||
SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
|
||
|
||
factoryBean.setDataSource(dataSource);
|
||
|
||
return factoryBean.getObject();
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>在配置上加上@Import注解，写上刚才写的MyBeanDefinitionRegistrar类。</p>
|
||
|
||
<p>运行结果：</p>
|
||
|
||
<pre><code>[org.springframework.context.annotation.Import, org.springframework.context.annotation.ComponentScan, org.mybatis.spring.annotation.MapperScan]
|
||
|
||
</code></pre>
|
||
|
||
<p>从registerBeanDefinitions两个入参的命名来看，第一个参数，Spring把注解元数据给你了，而第二个参数，Spring是直接把beanDefinition的注册器给你了。</p>
|
||
|
||
<h5>追本溯源</h5>
|
||
|
||
<p>下面我们来看看Spring在什么时候处理@Import注解的，又是什么时候调用registerBeanDefinitions方法的，当然这里不是Spring源码分析，我不会详细一行行翻译，而是简单的找到源头。</p>
|
||
|
||
<pre><code>//AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(Class<?>... componentClasses)
|
||
|
||
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
|
||
|
||
this();
|
||
|
||
register(componentClasses);
|
||
|
||
refresh();
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>进入第三行的refresh()方法。</p>
|
||
|
||
<p>refresh方法做了很多事情，我们只需要关心invokeBeanFactoryPostProcessors方法：</p>
|
||
|
||
<pre><code>//AbstractApplicationContext#refresh
|
||
|
||
invokeBeanFactoryPostProcessors(beanFactory);
|
||
|
||
</code></pre>
|
||
|
||
<p>执行invokeBeanFactoryPostProcessors方法，顾名思义，这个方法是执行BeanFactoryPostProcessor的。什么，你不知道什么是BeanFactoryPostProcessor？你可以简单的理解为Spring遵循插件化式的开发，其中有一个插件叫ConfigurationClassPostProcessor，实现了BeanDefinitionRegistryPostProcessor，同时BeanDefinitionRegistryPostProcessor又实现了BeanFactoryPostProcessor，通过ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry的方法，Spring完成了扫描。</p>
|
||
|
||
<pre><code>//PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors
|
||
|
||
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
|
||
|
||
</code></pre>
|
||
|
||
<p>这一步传入了BeanDefinitionRegistryPostProcessor的集合，要执行BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法，集合有一个元素是我们关心的，就是上面提到的ConfigurationClassPostProcessor。</p>
|
||
|
||
<pre><code>//PostProcessorRegistrationDelegate#invokeBeanDefinitionRegistryPostProcessors
|
||
|
||
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
|
||
|
||
postProcessor.postProcessBeanDefinitionRegistry(registry);
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>循环传入的BeanDefinitionRegistryPostProcessor集合，调用postProcessBeanDefinitionRegistry方法，我们直接进入到ConfigurationClassPostProcessor的processConfigBeanDefinitions方法，找到关键解析代码：</p>
|
||
|
||
<pre><code>//ConfigurationClassPostProcessor#processConfigBeanDefinitions
|
||
|
||
parser.parse(candidates);
|
||
|
||
//ConfigurationClassParser#parse
|
||
|
||
parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
|
||
|
||
//ConfigurationClassParser#processConfigurationClass
|
||
|
||
doProcessConfigurationClass(configClass, sourceClass);
|
||
|
||
//ConfigurationClassParser#doProcessConfigurationClass
|
||
|
||
processImports(configClass, sourceClass, getImports(sourceClass), true);
|
||
|
||
</code></pre>
|
||
|
||
<p>重点来了，终于找到了我们的目标：处理@Import注解。</p>
|
||
|
||
<pre><code>//ConfigurationClassParser#processImports
|
||
|
||
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
|
||
|
||
//ConfigurationClass#addImportBeanDefinitionRegistrar
|
||
|
||
this.importBeanDefinitionRegistrars.put(registrar, importingClassMetadata);
|
||
|
||
</code></pre>
|
||
|
||
<p>这个importBeanDefinitionRegistrars就是一个Map：</p>
|
||
|
||
<pre><code>//ConfigurationClass
|
||
|
||
private final Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> importBeanDefinitionRegistrars = new LinkedHashMap<>();
|
||
|
||
</code></pre>
|
||
|
||
<p>让我们就监视下configClass：
|
||
|
||
<img src="assets/15100432-df700f54b54cb88d.png" alt="image.png" />
|
||
|
||
可以看到我们写的MyBeanDefinitionRegistrar被放入了importBeanDefinitionRegistrars ，我们需要记住这个集合，至于还有一个什么，这里不用关心，当然，聪明的小伙伴肯定知道这是什么了。</p>
|
||
|
||
<p>我们写的MyBeanDefinitionRegistrar只是被放入了一个Map，并没有执行，下面我们要找找它是在哪里执行的。</p>
|
||
|
||
<p>我们需要回到ConfigurationClassPostProcessor的processConfigBeanDefinitions方法：</p>
|
||
|
||
<pre><code>//ConfigurationClassPostProcessor#processConfigBeanDefinitions
|
||
|
||
this.reader.loadBeanDefinitions(configClasses);
|
||
|
||
//ConfigurationClassBeanDefinitionReader#loadBeanDefinitions
|
||
|
||
loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
|
||
|
||
//ConfigurationClassBeanDefinitionReader#loadBeanDefinitionsForConfigurationClass
|
||
|
||
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
|
||
|
||
</code></pre>
|
||
|
||
<p>这个集合是不是有点眼熟，就是我在上面让大家记住的集合，这个集合就存放着我们的写的MyBeanDefinitionRegistrar类，让我们继续点进去：</p>
|
||
|
||
<pre><code>//ConfigurationClassBeanDefinitionReader#loadBeanDefinitionsFromRegistrars
|
||
|
||
private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {
|
||
|
||
registrars.forEach((registrar, metadata) ->
|
||
|
||
registrar.registerBeanDefinitions(metadata, this.registry));
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>循环传入的ImportBeanDefinitionRegistrar集合，调用registerBeanDefinitions方法，我的天，终于找到执行方法了。</p>
|
||
|
||
<h4>FactoryBean</h4>
|
||
|
||
<p>Spring就像是一个魔术师的袋子，而FactoryBean就是被魔术师装进袋子的香蕉，当魔术师打开袋子，发现香蕉变成鸽子了。</p>
|
||
|
||
<h5>如何使用</h5>
|
||
|
||
<pre><code>@Component
|
||
|
||
public class MyFactoryBean implements FactoryBean<Teacher> {
|
||
|
||
public Teacher getObject() {
|
||
|
||
Teacher teacher = new Teacher();
|
||
|
||
teacher.setName("琦玉老师");
|
||
|
||
return teacher;
|
||
|
||
}
|
||
public Class<?> getObjectType() {
|
||
|
||
return Teacher.class;
|
||
|
||
}
|
||
|
||
}
|
||
|
||
public class Main {
|
||
|
||
public static void main(String[] args) {
|
||
|
||
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
|
||
|
||
System.out.println(applicationContext.getBean(MyFactoryBean.class));
|
||
|
||
System.out.println(applicationContext.getBean(Teacher.class));
|
||
System.out.println(applicationContext.getBean("&myFactoryBean"));
|
||
|
||
System.out.println(applicationContext.getBean("myFactoryBean"));
|
||
System.out.println(applicationContext.getBean("myFactoryBean").hashCode());
|
||
|
||
System.out.println(applicationContext.getBean("myFactoryBean").hashCode());
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>运行结果：</p>
|
||
|
||
<pre><code><a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="85e6eae8abe6eae1e0e7e0e4f7abc8fcc3e4e6f1eaf7fcc7e0e4ebc5b1e0e0b7b5b6e0e7">[email protected]</a>
|
||
|
||
Teacher{name='琦玉老师'}
|
||
|
||
<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c6a5a9abe8a5a9a2a3a4a3a7b4e88bbf80a7a5b2a9b4bf84a3a7a886f2a3a3f4f6f5a3a4">[email protected]</a>
|
||
|
||
Teacher{name='琦玉老师'}
|
||
|
||
442125849
|
||
|
||
442125849
|
||
|
||
</code></pre>
|
||
|
||
<p>可以很清楚的看到从FactoryBean里面又生产出了一个Bean，生产出来的Bean就是FactoryBean中getObject方法返回的。</p>
|
||
|
||
<h5>追本溯源</h5>
|
||
|
||
<p>和上面一样，我们也要看看FactoryBean中的getObject是在哪里执行的，我们先来做个试验：</p>
|
||
|
||
<p>我们在getObject里面加上一句打印的代码：</p>
|
||
|
||
<pre><code>@Component
|
||
|
||
public class MyFactoryBean implements FactoryBean<Teacher> {
|
||
|
||
public Teacher getObject() {
|
||
|
||
System.out.println("getObject");
|
||
|
||
Teacher teacher = new Teacher();
|
||
|
||
teacher.setName("琦玉老师");
|
||
|
||
return teacher;
|
||
|
||
}
|
||
public Class<?> getObjectType() {
|
||
|
||
return Teacher.class;
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>然后只保留main方法中的创建ApplicationContext方法：</p>
|
||
|
||
<pre><code>public class Main {
|
||
|
||
public static void main(String[] args) {
|
||
|
||
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>运行后，你会发现，控制台没有任何输出，我们大胆的猜想，FactoryBean生产出来的Bean并不是预先加载的，而是采用懒加载的机制，也就是只有需要，才会去加载。</p>
|
||
|
||
<p>我们继续改下main方法：</p>
|
||
|
||
<pre><code> public static void main(String[] args) {
|
||
|
||
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
|
||
|
||
System.out.println(applicationContext.getBean(Teacher.class));
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>运行结果：</p>
|
||
|
||
<pre><code>getObject
|
||
|
||
Teacher{name='琦玉老师'}
|
||
|
||
</code></pre>
|
||
|
||
<p>所以我们的猜想是正确的，这次入口是getBean。</p>
|
||
|
||
<p>下面还是枯燥无味的寻找，这次的寻找之旅更复杂：</p>
|
||
|
||
<pre><code>//org.springframework.beans.factory.support.DefaultListableBeanFactory#getBean(java.lang.Class<T>)
|
||
|
||
public <T> T getBean(Class<T> requiredType) throws BeansException {
|
||
|
||
return getBean(requiredType, (Object[]) null);
|
||
|
||
}
|
||
|
||
// org.springframework.beans.factory.support.DefaultListableBeanFactory#getBean(java.lang.Class<T>, java.lang.Object...)
|
||
|
||
Object resolved = resolveBean(ResolvableType.forRawClass(requiredType), args, false);
|
||
|
||
//org.springframework.beans.factory.support.DefaultListableBeanFactory#resolveBean
|
||
|
||
NamedBeanHolder<T> namedBean = resolveNamedBean(requiredType, args, nonUniqueAsNull);
|
||
|
||
//org.springframework.beans.factory.support.DefaultListableBeanFactory#resolveNamedBean(org.springframework.core.ResolvableType, java.lang.Object[], boolean)
|
||
|
||
String[] candidateNames = getBeanNamesForType(requiredType);
|
||
|
||
//org.springframework.beans.factory.support.DefaultListableBeanFactory#getBeanNamesForType(org.springframework.core.ResolvableType)
|
||
|
||
return getBeanNamesForType(resolved, true, true);
|
||
|
||
//org.springframework.beans.factory.support.DefaultListableBeanFactory#getBeanNamesForType(java.lang.Class<?>, boolean, boolean)
|
||
|
||
resolvedBeanNames = doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, true);
|
||
|
||
</code></pre>
|
||
|
||
<p>这个方法里面有一步是循环beanDefinitionNames，当循环到myFactoryBean的时候，判断这是一个FactoryBean：</p>
|
||
|
||
<pre><code>boolean isFactoryBean = isFactoryBean(beanName, mbd);
|
||
|
||
</code></pre>
|
||
|
||
<p>随后执行isTypeMatch(beanName, type)方法：</p>
|
||
|
||
<pre><code>//org.springframework.beans.factory.support.AbstractBeanFactory#isTypeMatch(java.lang.String, org.springframework.core.ResolvableType)
|
||
|
||
Class<?> type = getTypeForFactoryBean((FactoryBean<?>) beanInstance);
|
||
|
||
//org.springframework.beans.factory.support.FactoryBeanRegistrySupport#getTypeForFactoryBean
|
||
|
||
return factoryBean.getObjectType();
|
||
|
||
</code></pre>
|
||
|
||
<p>当执行到这里，我们写的MyFactoryBean的getObjectType方法被调用了，返回Teacher.class，而我们现在要找的也是Teacher.class，所以匹配。</p>
|
||
|
||
<p>随后回到DefaultListableBeanFactory#doGetBeanNamesForType，把beanName放入一个集合中：</p>
|
||
|
||
<pre><code>if (matchFound) {
|
||
|
||
result.add(beanName);
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>随后返回集合。</p>
|
||
|
||
<p>再回到DefaultListableBeanFactory#resolveNamedBean，会判断返回出来的集合的元素的个数，显然只返回一个，执行</p>
|
||
|
||
<pre><code>//org.springframework.beans.factory.support.DefaultListableBeanFactory#resolveNamedBean
|
||
|
||
if (candidateNames.length == 1) {
|
||
|
||
String beanName = candidateNames[0];
|
||
|
||
return new NamedBeanHolder<>(beanName, (T) getBean(beanName, requiredType.toClass(), args));
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>继续点开getBean方法：</p>
|
||
|
||
<pre><code>//org.springframework.beans.factory.support.AbstractBeanFactory#getBean(java.lang.String, java.lang.Class<T>, java.lang.Object...)
|
||
|
||
return doGetBean(name, requiredType, args, false);
|
||
|
||
//org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean
|
||
|
||
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
|
||
|
||
//org.springframework.beans.factory.support.AbstractBeanFactory#getObjectForBeanInstance
|
||
|
||
object = getObjectFromFactoryBean(factory, beanName, !synthetic);
|
||
|
||
//org.springframework.beans.factory.support.FactoryBeanRegistrySupport#getObjectFromFactoryBean
|
||
|
||
doGetObjectFromFactoryBean(factory, beanName);
|
||
|
||
//org.springframework.beans.factory.support.FactoryBeanRegistrySupport#doGetObjectFromFactoryBean
|
||
|
||
object = factory.getObject();
|
||
|
||
</code></pre>
|
||
|
||
<p>直到这里，才执行了我们写的MyFactoryBean的getObject方法，拿到了我们返回的Teacher对象后。</p>
|
||
|
||
<p>因为有缓存机制如果我们再去拿，就不会再次调用getObject方法了，这个缓存机制就不再继续分析了，比较复杂，就算不了解也不影响我们今天的主题。</p>
|
||
|
||
<h4>JDK动态代理</h4>
|
||
|
||
<p>我以前写过JDK动态代理的博客，大家可以找来看一看 ，这里就不阐述了。</p>
|
||
|
||
<h3>mybatis-spring源码分析</h3>
|
||
|
||
<p>前置知识介绍完成，有了上面的前置知识，我们就可以一探MyBatis和Spring整合的奥秘。</p>
|
||
|
||
<p>Mybatis和Spring整合的入口很好找，就是我们再配置上添加的@MapperScan注解，当我们点开@MapperScan：</p>
|
||
|
||
<pre><code>@Retention(RetentionPolicy.RUNTIME)
|
||
|
||
@Target(ElementType.TYPE)
|
||
|
||
@Documented
|
||
|
||
@Import(MapperScannerRegistrar.class)
|
||
|
||
@Repeatable(MapperScans.class)
|
||
|
||
public @interface MapperScan {
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>你会发现一个很熟悉的注解，就是我们上面讲的Import注解，Import了MapperScannerRegistrar。</p>
|
||
|
||
<p>通过上面的源码分析明白，Spring会执行到registerBeanDefinitions方法：</p>
|
||
|
||
<pre><code>@Override
|
||
|
||
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
|
||
|
||
// 拿到我们写的MapperScan注解上带的东西，我们写的，只有一个Value字段。
|
||
|
||
AnnotationAttributes mapperScanAttrs = AnnotationAttributes
|
||
|
||
.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName()));
|
||
|
||
if (mapperScanAttrs != null) {
|
||
|
||
registerBeanDefinitions(mapperScanAttrs, registry);
|
||
|
||
}
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>继续深入registerBeanDefinitions方法：</p>
|
||
|
||
<pre><code>// 创建了一个扫描器，这个扫描器继承了Spring定义的扫描器：ClassPathBeanDefinitionScanner，
|
||
|
||
// 扫描的主要是主要作用就是扫描，把bean放到map中去
|
||
|
||
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
|
||
|
||
//省略
|
||
|
||
basePackages.addAll(
|
||
|
||
Arrays.stream(annoAttrs.getStringArray("value"))
|
||
|
||
.filter(StringUtils::hasText)
|
||
|
||
.collect(Collectors.toList()));
|
||
|
||
//省略
|
||
|
||
scanner.registerFilters();
|
||
|
||
scanner.doScan(StringUtils.toStringArray(basePackages));
|
||
|
||
</code></pre>
|
||
|
||
<p>这里主要是创建了一个扫描器，传入了一些规则。</p>
|
||
|
||
<p>scanner.registerFilters()中有一行代码，比较重要：</p>
|
||
|
||
<pre><code>// mybatis定义的扫描器最终的扫描任务是交给Spring的扫描器执行的，
|
||
|
||
// Spring的扫描器中定义了includeFilters，只有符合规则的最终才可以被扫描出来，
|
||
|
||
// 这里意味着mybatis告诉spring，任何东西你都要给我扫描出来。
|
||
|
||
addIncludeFilter((metadataReader, metadataReaderFactory) -> true);
|
||
|
||
</code></pre>
|
||
|
||
<p>让我们看下 scanner.doScan(StringUtils.toStringArray(basePackages))方法：</p>
|
||
|
||
<pre><code> @Override
|
||
|
||
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
|
||
|
||
//交给Spring执行扫描任务，返回beanDefinition、beanName的包装对象，这里就把我们
|
||
|
||
//@MapperScan注解中给定的com.codebear.mapper包中所有的内容都扫描
|
||
|
||
//并且返回出来了。
|
||
|
||
Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
|
||
if (beanDefinitions.isEmpty()) {
|
||
|
||
LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration.");
|
||
|
||
} else {
|
||
|
||
processBeanDefinitions(beanDefinitions);
|
||
|
||
}
|
||
return beanDefinitions;
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>继续看processBeanDefinitions方法：</p>
|
||
|
||
<pre><code>// 省略
|
||
|
||
for (BeanDefinitionHolder holder : beanDefinitions) {
|
||
|
||
definition.setBeanClass(this.mapperFactoryBean.getClass());
|
||
|
||
}
|
||
|
||
//省略
|
||
|
||
</code></pre>
|
||
|
||
<p>这个循环中，有一行代码很是重要，把扫描出来的bean的BeanClass都设置成了mapperFactoryBean，这个mapperFactoryBean是何方神圣呢？没错，它就是我们上面分析过的FactoryBean，通过实验和分析，我们知道了最终产生的bean对象是FactoryBean中的getObject返回的对象。</p>
|
||
|
||
<pre><code> public T getObject() throws Exception {
|
||
|
||
return getSqlSession().getMapper(this.mapperInterface);
|
||
|
||
}
|
||
|
||
public SqlSession getSqlSession() {
|
||
|
||
return this.sqlSessionTemplate;
|
||
|
||
}
|
||
|
||
//org.mybatis.spring.SqlSessionTemplate#getMapper
|
||
|
||
public <T> T getMapper(Class<T> type) {
|
||
|
||
return getConfiguration().getMapper(type, this);
|
||
|
||
}
|
||
|
||
//org.apache.ibatis.binding.MapperRegistry#getMapper
|
||
|
||
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
|
||
|
||
MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory)this.knownMappers.get(type);
|
||
|
||
if (mapperProxyFactory == null) {
|
||
|
||
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
|
||
|
||
} else {
|
||
|
||
try {
|
||
|
||
return mapperProxyFactory.newInstance(sqlSession);
|
||
|
||
} catch (Exception var5) {
|
||
|
||
throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);
|
||
|
||
}
|
||
|
||
}
|
||
|
||
}
|
||
|
||
//org.apache.ibatis.binding.MapperProxyFactory#newInstance(org.apache.ibatis.session.SqlSession)
|
||
|
||
//sqlSession是SqlSessionTemplate
|
||
|
||
public T newInstance(SqlSession sqlSession) {
|
||
|
||
// 这里需要用到JDK动态代理的知识，传入了SqlSessionTemplate，Mapper类（接口）
|
||
|
||
MapperProxy<T> mapperProxy = new MapperProxy(sqlSession, this.mapperInterface, this.methodCache);
|
||
|
||
return this.newInstance(mapperProxy);
|
||
|
||
}
|
||
|
||
// 生成了代理对象
|
||
|
||
protected T newInstance(MapperProxy<T> mapperProxy) {
|
||
|
||
return Proxy.newProxyInstance(this.mapperInterface.getClassLoader(), new Class[]{this.mapperInterface}, mapperProxy);
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>最终我们调用代理对象的方法，会执行到MapperProxy的invoke方法：</p>
|
||
|
||
<pre><code> public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
|
||
|
||
if (Object.class.equals(method.getDeclaringClass())) {
|
||
|
||
try {
|
||
|
||
return method.invoke(this, args);
|
||
|
||
} catch (Throwable t) {
|
||
|
||
throw ExceptionUtil.unwrapThrowable(t);
|
||
|
||
}
|
||
|
||
}
|
||
|
||
final MapperMethod mapperMethod = cachedMapperMethod(method);
|
||
|
||
return mapperMethod.execute(sqlSession, args);
|
||
|
||
}
|
||
|
||
</code></pre>
|
||
|
||
<p>当我们点开mapperMethod.execute方法，你会觉得一切是那么的熟悉。</p>
|
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