Java 春天不是'；t，我做错了什么？

我只是想尝试一下Spring，但我似乎错过了一些东西。它似乎很好地加载了Spring和Bean，但是当涉及到用autowired注入这些Bean时，它不起作用。有人有线索吗

Spring和mainServlet的web.xml部分：

    <welcome-file-list>
        <welcome-file>/login.jsp</welcome-file>
    </welcome-file-list>

    <!-- Spring Dependency Injection -->

     <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>

  <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
    </listener-class>

 @Service
public class MainServlet extends HttpServlet {

    @Autowired
    @Qualifier("UserManager")
    private UserManagerInterface userManager;
    Logger log;

    public MainServlet() {
        log = Logger.getLogger(getClass());
    }

    public boolean userLoggedIn(String username, String password) {     
        return SecurityManager.getInstance().credentialsValid(username, password);
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp);
    }

    public void processRequest(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {

        HttpSession session = ((HttpServletRequest) request).getSession();

        String username = (String) session.getAttribute("username");
        boolean authenticated = (boolean) session.getAttribute("authenticated");

        User user = userManager.getUserByEmail(username);

        WelcomeGenerator welcomeGenerator = new WelcomeGenerator();

        if (authenticated) {
            generateResponse(response, welcomeGenerator.WelcomeMessage(user), "The secret code is " + session.getAttribute("secretParameter"));
        } else {
            generateResponse(response, welcomeGenerator.wrongCredentialsMessage(username), "Secret code is hidden, because authentication failed");
        }
    }

    public void generateResponse(HttpServletResponse response, String welcomeMessage, String additionalData) throws IOException {       
        HtmlGenerator generator = new HtmlGenerator("PIRS");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        out.write(generator.printHeader());
        out.write(generator.printCenter(welcomeMessage));
        out.write(generator.printCenter(additionalData));
        out.write(generator.printFooter());
    }

    public UserManagerInterface getUserManager() {
        return userManager;
    }

    public void setUserManager(UserManagerInterface userManager) {
        this.userManager = userManager;
    }               
}

MainServlet：

    <welcome-file-list>
        <welcome-file>/login.jsp</welcome-file>
    </welcome-file-list>

    <!-- Spring Dependency Injection -->

     <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>

  <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
    </listener-class>

 @Service
public class MainServlet extends HttpServlet {

    @Autowired
    @Qualifier("UserManager")
    private UserManagerInterface userManager;
    Logger log;

    public MainServlet() {
        log = Logger.getLogger(getClass());
    }

    public boolean userLoggedIn(String username, String password) {     
        return SecurityManager.getInstance().credentialsValid(username, password);
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp);
    }

    public void processRequest(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {

        HttpSession session = ((HttpServletRequest) request).getSession();

        String username = (String) session.getAttribute("username");
        boolean authenticated = (boolean) session.getAttribute("authenticated");

        User user = userManager.getUserByEmail(username);

        WelcomeGenerator welcomeGenerator = new WelcomeGenerator();

        if (authenticated) {
            generateResponse(response, welcomeGenerator.WelcomeMessage(user), "The secret code is " + session.getAttribute("secretParameter"));
        } else {
            generateResponse(response, welcomeGenerator.wrongCredentialsMessage(username), "Secret code is hidden, because authentication failed");
        }
    }

    public void generateResponse(HttpServletResponse response, String welcomeMessage, String additionalData) throws IOException {       
        HtmlGenerator generator = new HtmlGenerator("PIRS");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        out.write(generator.printHeader());
        out.write(generator.printCenter(welcomeMessage));
        out.write(generator.printCenter(additionalData));
        out.write(generator.printFooter());
    }

    public UserManagerInterface getUserManager() {
        return userManager;
    }

    public void setUserManager(UserManagerInterface userManager) {
        this.userManager = userManager;
    }               
}

结果当然是调用userManager时出现了一个空指针异常，这应该是由Spring注入的

java.lang.NullPointerException
    at com.nortal.pirs.presentation.web.MainServlet.processRequest(MainServlet.java:58)
    at com.nortal.pirs.presentation.web.MainServlet.doPost(MainServlet.java:47)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)

然而Spring确实加载了bean，它只是不注入bean，也不抛出任何错误，这是为什么呢

2013-03-08 03:48:42,834 [localhost-startStop-1] INFO  org.springframework.beans.factory.support.DefaultListableBeanFactory - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@6a4ac9fb: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalPersistenceAnnotationProcessor,org.springframework.context.config.internalBeanConfigurerAspect,mainController,SecurityManager,**UserManager**,VisitManager,**mainServlet**,org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor#0,org.springframework.context.annotation.CommonAnnotationBeanPostProcessor#0,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchy

---

您的servlet不可配置。因为它的生命周期不是由Spring控制的，所以这是让它自动连接的唯一方法

---

哦，您的servlet肯定不是

@服务

，这是因为servlet是由Spring容器管理的。 Servlet由Servlet容器管理

但幸运的是，Spring提供了一种实用方法来获取SpringApplicationContext，从而从Servlet中获取bean。 这是通过使用

示例代码

ApplicationContext ctx = 
                    WebApplicationContextUtils.
                          getWebApplicationContext(session.getServletContext());
UserManagerInterface userManager = (UserManagerInterface )ctx.getBean("UserManager");

---

不止这些。您的servlet不是由spring管理的，因此它不能将其他bean注入其中。@Sotirios:那不是真的。看见它的目标是域对象，但对任何对象都有效。在这个问题的上下文中，servlet容器将实例化他的

MainServlet

，那么Spring如何知道将任何内容自动连接到其中？@Sotirios:使用AspectJ构建时或加载时字节码编织，您可以让Spring控制任何对象的构造，它管理的不仅仅是豆子。我之前评论中的链接是参考指南中描述其工作原理的部分。我也尝试了可配置，没有任何变化，除了将服务更改为可配置之外，还需要做什么？还有，我怎样才能使所有这些servlet Spring易于管理？为什么不使用控制器而不是servlet

@service

注释并不适用于servlet。请查看此内容。应该与您的问题相同。

2013-03-08 03:48:42,834 [localhost-startStop-1] INFO  org.springframework.beans.factory.support.DefaultListableBeanFactory - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@6a4ac9fb: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalPersistenceAnnotationProcessor,org.springframework.context.config.internalBeanConfigurerAspect,mainController,SecurityManager,**UserManager**,VisitManager,**mainServlet**,org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor#0,org.springframework.context.annotation.CommonAnnotationBeanPostProcessor#0,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchy

ApplicationContext ctx = 
                    WebApplicationContextUtils.
                          getWebApplicationContext(session.getServletContext());
UserManagerInterface userManager = (UserManagerInterface )ctx.getBean("UserManager");