Ajax请求Servlet返回404错误排查求助

Hey there, let's break down your 404 issue step by step—since it works locally but fails on AWS EC2, we can narrow down the root cause pretty effectively. Here's what to check:

Since you suspect firewall problems after configuring SSL, start here:

• AWS Security Group Check: Make sure your EC2 security group allows inbound traffic on your Tomcat HTTPS port (default is 8443, or whatever custom port you set in server.xml). Double-check the source IP range isn't restricted to only your local machine.
• Ubuntu UFW Firewall: Run sudo ufw status to confirm the HTTPS port is allowed. If not, add it with sudo ufw allow 8443/tcp.
• Test Port Connectivity: From your local machine, run curl -v https://<your-ec2-public-ip>:8443/your-api-endpoint or telnet <your-ec2-public-ip> 8443. If the connection times out, the problem is definitely network/firewall-related.

Mismatched SSL settings between local and EC2 often cause silent failures:

• Compare server.xml Configs: Check your EC2 server.xml's SSL Connector block against your local one. Ensure:
  • The port number matches what you're using in AJAX requests
  • The keystore path is an absolute path (Linux doesn't recognize relative paths the same way as Windows)
  • The Tomcat user has read permissions for the keystore file (run sudo chown tomcat:tomcat /path/to/your/keystore.jks if needed)
• Check Tomcat Logs: Look at /var/log/tomcat9/catalina.out (adjust path for your Tomcat version) for SSL initialization errors or request-related warnings. Logs will tell you if requests are even reaching Tomcat.

Linux is case-sensitive, which is a common gotcha when moving from local Windows/macOS:

• Verify AJAX Request URL: Ensure the URL in your JS code uses the correct EC2 public IP/domain, HTTPS, and port. For example, if local uses http://localhost:8080/api/data, EC2 should be https://<ec2-ip>:8443/api/data—no typos, no missing context paths.
• Check Backend Route Annotations: If you're using Spring MVC/JAX-RS, confirm your @RequestMapping (or equivalent) path exactly matches the AJAX request path. A lowercase/uppercase mismatch (e.g., /Api/Data vs /api/data) will cause 404 on Linux but work locally.

Here are key web.xml settings to verify:

• Servlet Mappings: Ensure your Java backend servlet's <url-pattern> covers your AJAX endpoint. For example, if your servlet maps to /rest/*, your AJAX request should target https://<ec2-ip>:8443/rest/data, not /api/data.
• Context Path: If you deployed your app to a non-ROOT context on EC2 (e.g., /myapp), your AJAX requests must include this prefix. Local might use ROOT, so you won't notice the difference until deployment.
• Filter Interactions: Check if any security filters (like CORS filters) are blocking HTTPS requests. Make sure filter mappings apply to your API paths and don't restrict access to local-only traffic.

To rule out backend vs network issues:

• SSH into your EC2 instance and run curl https://localhost:8443/your-api-endpoint directly on the server.
  • If this returns a valid response: The backend works—problem is in external network access or AJAX URL configuration.
  • If this also returns 404: The issue is with your backend routing or Tomcat deployment, not the firewall.

内容的提问来源于stack exchange，提问作者Tyler