Question

我的应用程序使用Spring Security，在启动期间崩溃。跟踪应用程序的执行情况，我可以在MainWebAppInitializer类的方法onStartup中验证错误：

public class MainWebAppInitializer implements WebApplicationInitializer {

    /**
     * Register and configure all Servlet container components necessary to power the web application.
     */
    @Override
    public void onStartup(final ServletContext sc) throws ServletException {
        // Create the 'root' Spring application context
        final AnnotationConfigWebApplicationContext root = new AnnotationConfigWebApplicationContext();
        root.scan("com.spring.web.config");

        // Manages the lifecycle of the root application context
        sc.addListener(new ContextLoaderListener(root));

        // Handles requests into the application
        final ServletRegistration.Dynamic appServlet = sc.addServlet("horariolivreapp", new DispatcherServlet(new GenericWebApplicationContext()));
        appServlet.setLoadOnStartup(1);
        final Set<String> mappingConflicts = appServlet.addMapping("/");
        if (!mappingConflicts.isEmpty()) {
            throw new IllegalStateException("'appServlet' could not be mapped to '/' due " + "to an existing mapping. This is a known issue under Tomcat versions " + "<= 7.0.14; see https://issues.apache.org/bugzilla/show_bug.cgi?id=51278");
        }
    }

}

更具体地说，错误发生在行

中

appServlet.setLoadOnStartup(1)

触发NullPointerException。遵循它是我的配置文件，供参考：

的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns="http://java.sun.com/xml/ns/javaee" 
   xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
   xsi:schemaLocation="

http://java.sun.com/xml/ns/javaee

      http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
   id="WebApp_ID" version="3.0">

   <display-name>HorarioLivre</display-name>

   <!-- Spring MVC -->
   <servlet>
      <servlet-name>horariolivreapp</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <load-on-startup>1</load-on-startup>
   </servlet>
   <servlet-mapping>
      <servlet-name>horariolivreapp</servlet-name>
      <url-pattern>*.html</url-pattern>
   </servlet-mapping>

   <context-param>
      <param-name>contextClass</param-name>
      <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
   </context-param>
   <context-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>com.spring.web.config</param-value>
   </context-param>
   <listener>
      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
   </listener>

   <!-- Spring Security -->
   <filter>
      <filter-name>springSecurityFilterChain</filter-name>
      <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
   </filter>
   <filter-mapping>
      <filter-name>springSecurityFilterChain</filter-name>
      <url-pattern>/*</url-pattern>
   </filter-mapping>

</web-app>

horariolivreap-servlet.xml中

<?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:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:component-scan base-package="com.horariolivreapp.controller" />
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>
</beans>

webSecurityConfig.xml

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

http://www.springframework.org/schema/security


http://www.springframework.org/schema/security/spring-security-3.1.xsd


http://www.springframework.org/schema/beans

      http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">

   <http use-expressions="true">
      <intercept-url pattern="/login*" access="isAnonymous()" />
      <intercept-url pattern="/**" access="isAuthenticated()"/>

      <form-login 
         login-page='/form_login.html' 
         login-processing-url="/usuario_login.html"
         default-target-url="/usuario_start.html" 
         authentication-failure-url="/form_login"
         always-use-default-target="true"/>

      <logout logout-success-url="/login.html" />

   </http>
   <authentication-manager>
      <authentication-provider>
         <user-service>
            <user name="user1" password="user1Pass" authorities="ROLE_USER" />
         </user-service>
      </authentication-provider>
   </authentication-manager>
</beans:beans>

查看这些文件，有人可以找到出现此问题的原因吗？

更新1 这是我的Controller（DispatcherServlet）类：

package com.horariolivreapp.controller;

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ImportResource;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

import com.horariolivreapp.core.Sessao;
import com.horariolivreapp.data.UsuarioDAO;
@Controller
public class HorarioLivreController {

    private Sessao sessao;

    @RequestMapping("/cadastra_evento")
    public ModelAndView cadastra_evento() {
        return null;
    }
    @RequestMapping(value="/listagem_evento", method=RequestMethod.GET)
    public ModelAndView listagem_evento() {
        return null;
    }
    @RequestMapping("/cadastra_horario")
    public ModelAndView cadastra_horario() {
        return null;
    }
    @RequestMapping("/listagem_horario")
    public ModelAndView listagem_horario() {
        return null;
    }
    @RequestMapping("/cadastra_usuario")
    public ModelAndView cadastra_usuario() {
        return null;
    }
    @RequestMapping("/listagem_usuario")
    public ModelAndView listagem_usuario() {
        return null;
    }
    @RequestMapping("/cadastra_tipo")
    public ModelAndView cadastra_tipo() {
        return null;
    }
    @RequestMapping("/cadastra_campo")
    public ModelAndView cadastra_campo() {
        return null;
    }
    @RequestMapping("/cadastra_autorizacao")
    public ModelAndView cadastra_autorizacao() {
        return null;
    }
    @RequestMapping("/usuario_perfil")
    public ModelAndView usuario_perfil() {
        return null;
    }
    @RequestMapping("/usuario_config")
    public ModelAndView usuario_config() {
        return null;
    }
    @RequestMapping(value="/usuario_login", method=RequestMethod.POST)
    public ModelAndView usuario_login(@RequestParam("j_username") String username, @RequestParam("j_password") String password) {
        UsuarioDAO usuario = new UsuarioDAO(username, password);
        if(usuario.getUsuario() != null) {
            this.sessao = new Sessao(usuario.getUsuario());
        }
        return new ModelAndView("usuario_start","usuario",usuario.getUsuario());
    }
    @Configuration
    @ImportResource({ "classpath:webSecurityConfig.xml" })
    public class SecSecurityConfig {
       public SecSecurityConfig() {
          super();
       }
    }
}

Answer 1

此时的NPE意味着appServlet为空，这反过来意味着sc.addServlet(...)返回null。

addServlet的Javadoc说：

“返回：可用于进一步配置给定servlet的ServletRegistration对象，如果此null已包含完整ServletContext，则为ServletRegistration具有给定servletName的servlet，或者是否已在同一容器中向此帐户或另一个ServletContext注册了相同的servlet实例。“

现在您正在实例化Servlet对象，因此以前无法注册。但是可能是另一个具有相同名称的Servlet ......这可能是造成问题的直接原因。

事实上，通过在web.xml文件中声明它，已经已经注册了一个名为“horariolivreapp”的servlet。

基于Spring Security的Web应用程序在启动期间崩溃（NullPointerException）

1 个答案: