高级Spring之ApplicationContext 实现

我就是我 2024-03-27 08:59 142阅读 0赞

以四个比较典型的实现类为例:

### 1.较为经典的容器, 基于 classpath 下 xml 格式的配置文件来创建 ###

private static void testClassPathXmlApplicationContext() {
            ClassPathXmlApplicationContext context =
                    new ClassPathXmlApplicationContext("a02.xml");
    
            for (String name : context.getBeanDefinitionNames()) {
                System.out.println(name);//bean1 bean2
            }
    
            System.out.println(context.getBean(Bean2.class).getBean1());
            //com.tangyuan.a02.A02Appilcation$Bean1@5542c4ed
        }

xml文件配置：

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
        
        <bean id="bean1" class="com.tangyuan.a02.A02.Bean1"/>
    
        
        <bean id="bean2" class="com.tangyuan.a02.A02.Bean2">
            
            <property name="bean1" ref="bean1"/>
        </bean>
    </beans>

### 2.基于磁盘路径下 xml 格式的配置文件来创建 ###

private static void testFileSystemXmlApplicationContext() {
            FileSystemXmlApplicationContext context =
                    new FileSystemXmlApplicationContext(
                            "src\\main\\resources\\a02.xml");
            for (String name : context.getBeanDefinitionNames()) {
                System.out.println(name);
            }
    
            System.out.println(context.getBean(Bean2.class).getBean1());
        }

**基于磁盘路径下 xml 格式的配置文件来创建----->内部是如何工作的---->过程代码演示**

DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
            System.out.println("读取之前...");
            for (String name : beanFactory.getBeanDefinitionNames()) {
                System.out.println(name);
            }
            System.out.println("读取之后...");
          //读取内部信息存放到哪里
            XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(beanFactory);
            //文件路径
            reader.loadBeanDefinitions(new FileSystemResource("src\\main\\resources\\a02.xml"));
            for (String name : beanFactory.getBeanDefinitionNames()) {
                System.out.println(name);
            }

### 3.较为经典的容器, 基于 java 配置类来创建 ###

private static void testAnnotationConfigApplicationContext() {
            AnnotationConfigApplicationContext context =
                    new AnnotationConfigApplicationContext(Config.class);
    
            for (String name : context.getBeanDefinitionNames()) {
                System.out.println(name);
            }
    
            System.out.println(context.getBean(Bean2.class).getBean1());
        }

**配置类信息定义：**

@Configuration
        static class Config {
            @Bean
            public Bean1 bean1() {
                return new Bean1();
            }
    
            @Bean
            public Bean2 bean2(Bean1 bean1) {
                Bean2 bean2 = new Bean2();
                bean2.setBean1(bean1);
                return bean2;
            }
        }

![d17ee8a78935494e9c0830cf3cfb9d6e.png][]

与上面的两种方式相对比，除了基本的bean，还将config类作为bean配置进去了，这个bean的作用是提供更多的beandefinition进行配置，还有五个后处理器，提供解析注解的能力，与普通的方式相对比，效率更高

### 4.较为经典的容器, 基于 java 配置类来创建, 用于 web 环境 ###

private static void testAnnotationConfigServletWebServerApplicationContext() {
            AnnotationConfigServletWebServerApplicationContext context =
                    new AnnotationConfigServletWebServerApplicationContext(WebConfig.class);
            for (String name : context.getBeanDefinitionNames()) {
                System.out.println(name);
            }
        }

**config配置类:**

@Configuration
        static class WebConfig {
            @Bean//产生内部Tomcat容器
            public ServletWebServerFactory servletWebServerFactory(){
                return new TomcatServletWebServerFactory();
            }
            @Bean//前控制器
            public DispatcherServlet dispatcherServlet() {
                return new DispatcherServlet();
            }
            @Bean//将DispatcherServlet注册到Tomcat服务器
            public DispatcherServletRegistrationBean registrationBean(DispatcherServlet dispatcherServlet) {
                return new DispatcherServletRegistrationBean(dispatcherServlet, "/");
            }
            @Bean("/hello")//控制器
            public Controller controller1() {
                return (request, response) -> {
                    response.getWriter().print("hello");
                    return null;
                };
            }
        }

#### 总结： ####

学到了什么?

1.  常见的 ApplicationContext 容器实现
2.  内嵌容器、DispatcherServlet 的创建方法、作用

[d17ee8a78935494e9c0830cf3cfb9d6e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/a02dd5924bfe48dcb74cb89ee9fefd4b.png