Spring-具有依赖项注入的启动代码

Question

I'm working on a simple web application using spring-mvc framework.

My configuration only has one single mvc-dispatcher Servlet, ( org.springframework.web.servlet.DispatcherServlet ), and all my configuration is in the META-INF\\mvc-dispatcher-servlet.xml ; I don't have any application.xml .

Especially, the mvc-dispatcher-servlet.xml autowire all my beans.

I would like to execute a piece of code at the startup of my web application, and this code need some beans that I need to inject.

All the examples that I've found advice to implement WebApplicationInitializer or ServletContextListener . But the problem for me is that both these interface allow to execute my code before the start-up of my main unique Servlet, and therefore, before that my beans are auto-wired.

@WebListener
public class MyCustomListener implements ServletContextListener {

    @Autowired
    private MyBean myBean;

    @Override
    public void contextInitialized(ServletContextEvent sce) {

        // I have tried the following to inject the beans:
        SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(sce.getServletContext());

        WebApplicationContextUtils
            .getRequiredWebApplicationContext(sce.getServletContext())
            .getAutowireCapableBeanFactory()
            .autowireBean(this);

        WebApplicationContextUtils
            .getWebApplicationContext(sce.getServletContext())
            .getAutowireCapableBeanFactory()
            .autowireBean(this);

        myBean.doStuff(); //NullPointerException
    }


    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
    }
}

I've tried to inject my dependencies into the Listener, using something like WebApplicationContextUtils or SpringBeanAutowiringSupport , but my webapplication context is always null; if I'm not mistaken, it's because the FrameworkServlet of spring hasn't read the mvc-dispatcher-servlet.xml and created the webApplicationContext yet:

From FrameworkServlet.initServletBean :

// this code that create the WebapplicationContext
// is executed after my custom listener
this.webApplicationContext = initWebApplicationContext();

What is the standard way to execute code that require beans in my case (ie with only a single DispatcherServlet that handle all the configuration)?

Edit:

My web.xml is pretty standard:

<web-app ... >

    <display-name>Spring MVC Application</display-name>

    <servlet>
        <servlet-name>mvc-dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>0</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>mvc-dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

I tried to implement the ApplicationListener<ContextRefreshedEvent> , but the ContextRefreshedEvent is never fired when I start my server:

@WebListener
public class MyCustomListener implements ApplicationListener<ContextRefreshedEvent> { 

    @Autowired
    private MyBean myBean;

    // I don't know why this event is never fired?
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        myBean.doStuff();
    }
}

Is there a parameter that I should add in my web.xml and/or mvc-dispatcher-servlet.xml to trigger the event ?

Answer 1

It seems you need to execute some code after Spring context is initialized. and not before it. You could use ContextRefreshedEvent event of the ApplicationListener .

public class CustomInitializerClass implements ApplicationListener{

 public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent ) { } }