Spring MVC简易Java Web项目运行出现404页面未找到问题求助

Hey there! Let's break down why you're hitting that frustrating 404 error when running your simple Java Web project. I've seen this a hundred times—usually it's one of a handful of common misconfigurations. Let's go through the checks step by step:

1. Verify Your Controller Setup #

First, make sure your Controller is actually being recognized by Spring:

• Check Controller Annotations: Did you add @Controller (for view-based responses) or @RestController (for JSON responses) to your controller class? Without these, Spring won't register it as a request handler.
• Double-Check Request Mappings: Let's say your controller method has @GetMapping("/greet")—your full request URL should be http://localhost:8080/[your-project-context]/greet. Don't forget the project context path (usually the name of your deployed WAR file).
• Ensure Package Scanning is Enabled: In your dispatcher-servlet.xml, you need to tell Spring to scan your controller package. Add this line if it's missing:

  <context:component-scan base-package="controller"/>
  

  Without this, Spring will never find your controller class.

2. Validate dispatcher-servlet.xml Configurations #

This file is the heart of your Spring MVC setup—let's make sure it's correct:

• Enable Annotation-Driven Support: Add <mvc:annotation-driven/> to enable Spring's MVC annotation processing (like @RequestMapping, @GetMapping, etc.). Without this, your mappings won't be detected.
• Check View Resolver (if using JSPs): If your controller returns a view name (like "home"), you need a view resolver to map that to the actual JSP file. Example configuration:

  <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
      <property name="prefix" value="/WEB-INF/views/"/>
      <property name="suffix" value=".jsp"/>
  </bean>
  

  If your JSP is at /WEB-INF/views/home.jsp, returning "home" will work—but if the prefix/suffix is wrong, or the file doesn't exist, you'll get a 404.
• Handle Static Resources: If you're loading CSS/JS/images and getting 404s for those too, add <mvc:default-servlet-handler/> to let the server's default servlet handle static files (since your DispatcherServlet is mapped to /).

3. Check web.xml Configurations #

The web.xml defines how your server handles requests—let's confirm these settings:

• DispatcherServlet Mapping: Avoid using /* as the url-pattern (it intercepts all requests, including JSPs). Use / instead, which maps to all requests except JSPs and static resources. Example:

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

• Confirm DispatcherServlet Initialization: Make sure you're pointing to the correct dispatcher-servlet.xml path in the init-param:

  <servlet>
      <servlet-name>dispatcher</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <init-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>/WEB-INF/dispatcher-servlet.xml</param-value>
      </init-param>
      <load-on-startup>1</load-on-startup>
  </servlet>
  

  If the path is wrong, the servlet won't load your configuration, and no mappings will be registered.
• Project Context Path: If you didn't set a custom context path, it's usually the name of your deployed project. So if your WAR is named my-web-app.war, your base URL is http://localhost:8080/my-web-app/.

4. Check Project Deployment & Structure #

• Confirm Deployment: Navigate to your Tomcat (or whatever server you're using) webapps directory—your project folder/WAR should be present there. If not, re-deploy the project.
• Verify File Locations: JSPs should typically be under /WEB-INF/views/ (matches the view resolver prefix), and static resources under /resources/ or /static/ in your web root.

Quick Debug Tip #

If none of the above fixes it, check your server's logs (Tomcat's logs/catalina.out or similar). Look for errors like "Could not find controller class" or "Failed to parse dispatcher-servlet.xml"—these will point you directly to the problem.

内容的提问来源于stack exchange，提问作者Zaim Busuladzic