Question

我试图简单地尝试Spring，但我似乎错过了一些东西。它似乎加载Spring和bean就好了，但是当涉及到使用自动装配注入这些bean时，它不起作用。有人有线索吗？

Spring的web.xml部分和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>

<!-- Login Filter -->
<filter>
    <filter-name>LoginFilter</filter-name>
    <filter-class>com.nortal.pirs.presentation.web.LoginFilter</filter-class>
    <init-param>
        <param-name>secretParameter</param-name>
        <param-value>8392</param-value>
    </init-param>
</filter>

<filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <url-pattern>/MainServlet</url-pattern>
        <servlet-name>MainServlet</servlet-name>
</filter-mapping>

<!-- Main Servlet -->
<servlet>
<servlet-name>MainServlet</servlet-name>
<servlet-class>com.nortal.pirs.presentation.web.MainServlet</servlet-class>

<servlet-mapping>
    <servlet-name>MainServlet</servlet-name>
    <url-pattern>/main/*</url-pattern>
</servlet-mapping>

Spring应用程序上下文文件（虽然我认为我也加载了太多不必要的垃圾，但是因为它不起作用而出于绝望：）

    <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop 
        http://www.springframework.org/schema/aop/spring-aop-3.1.xsd
        http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context-3.1.xsd">

    <context:annotation-config />

    <!-- Turn on AspectJ @Configurable support -->
    <context:spring-configured />

    <context:component-scan base-package="com.nortal.pirs.test.independent" />
    <context:component-scan base-package="com.nortal.pirs.businesslogic.logic" />
    <context:component-scan base-package="com.nortal.pirs.presentation.vaadin" />
    <context:component-scan base-package="com.nortal.pirs.presentation.vaadin.views" />
    <context:component-scan base-package="com.nortal.pirs.presentation.web" />

    <!-- Turn on @Autowired, @PostConstruct etc support -->
    <bean
        class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />
    <bean
        class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />

</beans>

UserManagerLogic（必须在以后使用@autowired在MainServlet中注入的bean）：

@Component("UserManager")
public class UserManagerLogic implements UserManagerInterface {

MainServlet：

 @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;
    }               
}

结果是在调用userManager时出现空指针异常，当然应该由Spring注入？

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会加载bean，它只会注入它们并且不会抛出任何错误，为什么会这样？

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

Answer 1

您的servlet不是@Configurable。由于它的生命周期不受Spring的控制，因此这是您将其自动装配的唯一方式。

哦，你的servlet肯定不是@Service。

Answer 2

这是因为Servlet由Spring Container管理。 Servlet由Servlet容器管理。

但幸运的是，Spring提供了一种实用工具方法来获取SpringApplicationContext以从Servlet中获取bean。这是使用WebApplicationContextUtils

完成的

示例代码

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

春天不是注射豆子，我做错了什么？

2 个答案: