三种context
ClassPathXmlApplicationContext
根据 xml 获取bean
<?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">
<!-- 定义一个Employee类型的bean -->
<bean id="employee" class="org.example.Employee">
<constructor-arg value="John Doe"/>
<constructor-arg value="30"/>
</bean>
</beans>
对应对象
public class Employee {
private String name;
private int age;
public Employee(String name, int age) {
this.name = name;
this.age = age;
}
public void work() {
System.out.println(name + " is working.");
}
}
测试
private static void testClassPathXmlApplicationContext() {
// 根据 xml 获取bean
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("b01.xml");
for (String beanDefinitionName : context.getBeanDefinitionNames()) {
System.out.println(beanDefinitionName);
}
}
AnnotationConfigApplicationContext
bean
@Configuration
static class Config{
@Bean
public Bean1 test(){
return new Bean1();
}
@Bean
public Bean2 test2(){
return new Bean2();
}
}
测试
private static void testAnnotationConfigApplicationContext() {
AnnotationConfigApplicationContext context3 = new AnnotationConfigApplicationContext(BeanFactoryTest.Config.class);
for (String beanDefinitionName : context3.getBeanDefinitionNames()) {
System.out.println(beanDefinitionName);
}
}
AnnotationConfigServletWebApplicationContext
Bean
@Configuration
static class WebConfig{
// 内嵌服务器
@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;
};
}
}
测试
private static void testAnnotationConfigServletWebApplicationContext() {
AnnotationConfigServletWebApplicationContext context4 = new AnnotationConfigServletWebApplicationContext(WebConfig.class);
}
Bean的生命周期
用一个bean告诉你
public class LifeCycleBean {
private static final Logger logger = LoggerFactory.getLogger(LifeCycleBean.class);
private LifeCycleBean() {
logger.info("构造");
}
@Autowired
public void autoWire(@Value("${JAVA_HOME}") String home) {
logger.info("依赖注入:" + home);
}
@PostConstruct
public void init() {
logger.info("初始化");
}
@PreDestroy
public void destroy() {
logger.info("销毁");
}
}
启动类
@SpringBootApplication
public class Application {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(Application.class, args);
context.close();
}
}
