applicationcontext实现类

╰半橙微兮° 2022-05-06 07:21 158阅读 0赞

ClassPathXmlApplicationContext:类路径加载  
FileSystemXmlApplicationContext:文件系统路径加载  
AnnotationConfigApplicationContext:用于基于注解的配置  
WebApplicationContext:专门为web应用准备的，从相对于Web根目录的路径中装载配置文件完成初始化

ApplicationContext ac = new ClassPathXmlApplicationContext("com/zzm/context/beans.xml");//等同路径:"classpath:com/zzm/context/beans.xml"
    ac.getBean("abc",abc.calss);//就可以获得bean了
    
    ApplicationContext ac = new FileSystemXmlApplicationContext("com/zzm/context/beans.xml");//等同路径:"file:com/zzm/context/beans.xml"
    ac.getBean("abc",abc.calss);//就可以获得bean了

基于注解

@Coniguration
    public class Beans{
        @Bean(name="man")
        public Man newMan(){
        Man man = new Man();
        man.setName("小明");
        }
    ｝

ApplicationContext ac = new AnnotationConfigApplicationContext(Beans.class);
    Man man = ac.getBean("man",Man.class);

WebApplicationContext初始化需要ServletContext事例，即必须先有Web容器才能完成启动工作，可在web.xml中配置自启动Servlet或定义Web容器监听器(ServletContextListener)。

通过Web容器监听器：

web.xml:
    
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/zzm-service.xml</param-value>
        
    </context-param>
    
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

通过自启动的Servlet引导

<context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/zzm-service.xml</param-value>
    </context-param>
    <!--声明自启动的Servlet容器>
    <servlet>
        <servlet-name>sprinfContextLoaderServlet</servlet-name>
        <servlet-class>org.springframework.web.context.ContextLoaderServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

WebApplicationContext Spring提供WebApplicationContextUtils通过该类的getWebApplicationContext(ServletContext sc)方法获取，即可从ServletContext中获取WebApplicationContext。  
新增3作用域：request，session，global session

public class ACLFilter implements Filter{
    
    private ServletContext sc;
    private ApplicationContext ctx;
    private UserService userService;
    
    /**
     * 过滤器初始化
     */
    public void init(FilterConfig cfg)
        throws ServletException {
    
        sc= cfg.getServletContext();//获取Spring容器
        ctx=WebApplicationContextUtils.getWebApplicationContext(sc);//从容器中获取 UserService 对象
        userService=ctx.getBean("userService",UserService.class);
    }
    public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain)throws IOException, ServletException {
        /**/
        chain.doFilter(request, response); 
    }
    
    public void destroy() {
    }