Java Web客户端index.jsp关联Restful接口出现HTTP 404 Not Found问题排查

Hey there! Let's break down why you're hitting that frustrating 404 error when interacting with your RESTful interface. A 404 means the server can't locate the resource your client is requesting, so let's walk through the most common fixes using your provided code snippet as a guide.

Common Culprits & Fixes #

• Verify Servlet Mapping Configuration
  Your form uses action="calcular.do", so you need to make sure this path is correctly mapped to your backend Servlet:

  • If you're using annotations, check that your Servlet class has @WebServlet("/calcular.do") (note the leading slash, which ensures it's mapped relative to the app root).
  • If you're using web.xml, confirm the <url-pattern> for your Servlet is set to /calcular.do, and the <servlet-name> matches the corresponding <servlet-class> entry.
    Pro tip: HTTP paths are case-sensitive, so double-check that "calcular.do" matches exactly what's configured on the server.

• Confirm Servlet Class is Properly Deployed
  Ensure your Servlet class is compiled and placed in the WEB-INF/classes directory of your deployed application. A missing or misnamed class will prevent the server from finding the resource. Also, check for typos in the class name or package structure in your configuration.

• Check Application Context Path
  If your web app is deployed with a context path (e.g., http://localhost:8080/your-factorial-app/), your form action needs to account for this. You can either:

  • Use an absolute path: action="/your-factorial-app/calcular.do"
  • Use a relative path that correctly resolves from your index.jsp location (if index.jsp is in the app root, calcular.do works; if it's in a subfolder, you may need ../calcular.do).

• Validate Request Method Matching
  Your form doesn't specify a method attribute, so it defaults to GET. Make sure your Servlet handles GET requests:

  • If you've overridden doGet() in your Servlet class, ensure it's properly implemented (not empty or throwing an unhandled error).
  • If you're only handling POST requests in doPost(), update your form to include method="POST" or add doGet() logic to your Servlet.

• Inspect Server Logs
  Take a look at your server's access logs (e.g., Tomcat's localhost_access_log.*.txt). These logs will show the exact URL the server received, like:

  GET /your-factorial-app/calcular.do HTTP/1.1 404
  

  This can help you spot discrepancies between the URL your client is sending and what the server expects.

内容的提问来源于stack exchange，提问作者Ives Rodriguez