本篇博客为作者学习spring的源码所做的学习笔记。
1、ApplicationContextApplicationContext继承了MessageSource、RosourcePatternResolver、ApplicationEventPublisher、EnvironmentCapable四个接口。
1.1、MessageSourceMessageSource主要用来实现语言国际化.
System.out.println(context.getMessage("hi", null, Locale.CHINA));
System.out.println(context.getMessage("hi", null, Locale.ENGLISH));
1.2、RosourcePatternResolver
ReourcePatternResolver主要用作获取一些配置文件，例如properties、factories、xml、yml、yaml等之类的配置文件。
Resource[] resources = context.getResources("classpath:application.properties");
for (Resource resource : resources) {
System.out.println(resource.getURL());
}
Resource[] contextResources = context.getResources("classpath*:META-INF/spring.factories");
for (Resource contextResource : contextResources) {
System.out.println(contextResource);
}
1.3、ApplicationEventPublisher
此接口可以实现事件的发布和订阅。
Component1
@Component
public class Component1 {
private static final Logger log = LoggerFactory.getLogger(Component1.class);
@Autowired
private ApplicationEventPublisher context;
public void register() {
log.debug("用户注册");
context.publishEvent(new UserRegisteredEvent(this));
}
}
Component2
@Component
public class Component2 {
private static final Logger log = LoggerFactory.getLogger(Component2.class);
@EventListener
public void aaa(UserRegisteredEvent event) {
log.debug("{}", event);
log.debug("发送短信");
}
}
1.4、EnvironmentCapable
使用EnvironmentCapable可以获取一些环境变量的配置。
ConfigurableEnvironment environment = context.getEnvironment();
System.out.println(environment.getProperty("JAVA_HOME"));
2、容器化的实现
2.1、BeanFactory
public class TestBeanFactory {
public static void main(String[] args) {
DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
// bean 的定义（class, scope, 初始化, 销毁）
AbstractBeanDefinition beanDefinition =
BeanDefinitionBuilder.genericBeanDefinition(Config.class).setScope("singleton").getBeanDefinition();
beanFactory.registerBeanDefinition("config", beanDefinition);
// 给 BeanFactory 添加一些常用的后处理器
AnnotationConfigUtils.registerAnnotationConfigProcessors(beanFactory);
// BeanFactory 后处理器主要功能，补充了一些 bean 定义
beanFactory.getBeansOfType(BeanFactoryPostProcessor.class).values().forEach(beanFactoryPostProcessor -> {
beanFactoryPostProcessor.postProcessBeanFactory(beanFactory);
});
// Bean 后处理器, 针对 bean 的生命周期的各个阶段提供扩展, 例如 @Autowired @Resource ...
beanFactory.getBeansOfType(BeanPostProcessor.class).values().stream()
.sorted(beanFactory.getDependencyComparator())
.forEach(beanPostProcessor -> {
System.out.println(">>>>" + beanPostProcessor);
beanFactory.addBeanPostProcessor(beanPostProcessor);
});
for (String name : beanFactory.getBeanDefinitionNames()) {
System.out.println(name);
}
beanFactory.preInstantiateSingletons(); // 准备好所有单例
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ");
// System.out.println(beanFactory.getBean(Bean1.class).getBean2());
System.out.println(beanFactory.getBean(Bean1.class).getInter());
System.out.println("Common:" + (Ordered.LOWEST_PRECEDENCE - 3));
System.out.println("Autowired:" + (Ordered.LOWEST_PRECEDENCE - 2));
}
@Configuration
static class Config {
@Bean
public Bean1 bean1() {
return new Bean1();
}
@Bean
public Bean2 bean2() {
return new Bean2();
}
@Bean
public Bean3 bean3() {
return new Bean3();
}
@Bean
public Bean4 bean4() {
return new Bean4();
}
}
interface Inter {
}
static class Bean3 implements Inter {
}
static class Bean4 implements Inter {
}
static class Bean1 {
private static final Logger log = LoggerFactory.getLogger(Bean1.class);
public Bean1() {
log.debug("构造 Bean1()");
}
@Autowired
private Bean2 bean2;
public Bean2 getBean2() {
return bean2;
}
@Autowired
@Resource(name = "bean4")
private Inter bean3;
public Inter getInter() {
return bean3;
}
}
static class Bean2 {
private static final Logger log = LoggerFactory.getLogger(Bean2.class);
public Bean2() {
log.debug("构造 Bean2()");
}
}
}
2.2、ApplicationContext
2.2.1、ClassPathXMLApplicationContext
ClassPathXMLApplicationContext读取类路径下面的xml的配置文件。
// ⬇️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);
}
System.out.println(context.getBean(Bean2.class).getBean1());
}
2.2.2、FileSystemXmlApplicationContext
FileSystemXmlApplicationContext读取文件系统的xml配置文件。
// ⬇️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());
}
2.2.3、AnnotationConfigApplicationContext
AnnotationConfigApplicationContext读取注解配置
// ⬇️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());
}
2.2.4、AnnotationConfigServletWebServerApplicationContext
读取web环境下面的配置类
// ⬇️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);
}
}
@Configuration
static class WebConfig {
@Bean
public ServletWebServerFactory servletWebServerFactory(){
return new TomcatServletWebServerFactory();
}
@Bean
public DispatcherServlet dispatcherServlet() {
return new DispatcherServlet();
}
@Bean
public DispatcherServletRegistrationBean registrationBean(DispatcherServlet dispatcherServlet) {
return new DispatcherServletRegistrationBean(dispatcherServlet, "/");
}
@Bean("/hello")
public Controller controller1() {
return (request, response) -> {
response.getWriter().print("hello");
return null;
};
}
}
2.2.5、ApplicationContext容器实现的完整代码
public class A02 {
private static final Logger log = LoggerFactory.getLogger(A02.class);
public static void main(String[] args) {
testClassPathXmlApplicationContext();
// testFileSystemXmlApplicationContext();
// testAnnotationConfigApplicationContext();
// testAnnotationConfigServletWebServerApplicationContext();
}
// ⬇️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);
}
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
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());
}
// ⬇️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());
}
// ⬇️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);
}
}
@Configuration
static class WebConfig {
@Bean
public ServletWebServerFactory servletWebServerFactory(){
return new TomcatServletWebServerFactory();
}
@Bean
public DispatcherServlet dispatcherServlet() {
return new DispatcherServlet();
}
@Bean
public DispatcherServletRegistrationBean registrationBean(DispatcherServlet dispatcherServlet) {
return new DispatcherServletRegistrationBean(dispatcherServlet, "/");
}
@Bean("/hello")
public Controller controller1() {
return (request, response) -> {
response.getWriter().print("hello");
return null;
};
}
}
@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;
}
}
static class Bean1 {
}
static class Bean2 {
private Bean1 bean1;
public void setBean1(Bean1 bean1) {
this.bean1 = bean1;
}
public Bean1 getBean1() {
return bean1;
}
}
}
bean的生命周期创建、依赖注入、初始化、销毁
