基于Eclipse+Tomcat开发Servlet出现404错误求助

Hey there, let's break down why you're seeing that 404 when accessing http://localhost:8080/MosheAPI_Project/rest/hello—it's almost always a mapping or configuration issue with JAX-RS. Let's go through the common fixes step by step.

First, Let's Clarify Your Code Context #

From what you shared, your servlet has both @Path("/hello") (JAX-RS annotation) and @WebServlet("/hello") (standard Servlet annotation)—that's a red flag right there. Let's fix that and other potential issues.

1. Remove Conflicting Annotations #

JAX-RS uses its own routing system, so mixing it with @WebServlet will cause mapping conflicts. Delete the @WebServlet("/hello") annotation from your servlet class. Your servlet should only use JAX-RS annotations for routing.

2. Add a Proper JAX-RS Application Class #

You mentioned @ApplicationPath, but you need a dedicated class to define your API's root path. Create this class in your MyPackage:

package MyPackage;
import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;

@ApplicationPath("/rest") // This sets your API's base path
public class MyApiApplication extends Application {
    // No need for extra code here—JAX-RS will auto-scan your package for resources
}

This tells JAX-RS that all your @Path endpoints will be under /rest (matching the URL you're trying to access).

3. Verify Your Servlet Class is Complete #

Make sure your hello endpoint has the proper JAX-RS annotations for HTTP method and response type. Here's a full working example:

package MyPackage;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/hello")
public class HelloApi {

    @GET // Specifies this responds to GET requests
    @Produces(MediaType.TEXT_PLAIN) // Sets the response content type
    public String getHelloMessage() {
        return "Hello from your JAX-RS API!";
    }
}

4. Check Web.xml (If You're Using It) #

If you're not relying on annotation-based configuration (the Application class above), you need to configure the JAX-RS servlet in web.xml. Here's the correct setup (assuming you're using Jersey, the most common JAX-RS implementation):

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <servlet>
        <servlet-name>Jersey REST Service</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <!-- Tell Jersey which package to scan for JAX-RS resources -->
        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>MyPackage</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Jersey REST Service</servlet-name>
        <url-pattern>/rest/*</url-pattern> <!-- Matches your base path -->
    </servlet-mapping>
</web-app>

Note: Make sure you have Jersey's core JARs in your project's WEB-INF/lib folder (or added via Maven/Gradle).

5. Double-Check Deployment & Context Path #

• Confirm your MosheAPI_Project is successfully deployed to Tomcat: Check the Tomcat webapps folder—you should see a MosheAPI_Project directory there.
• Verify the context root: In Eclipse, right-click your project → Properties → Web Project Settings—ensure the Context Root is set to MosheAPI_Project (matches your URL).
• Restart Tomcat after making configuration changes—sometimes changes don't take effect until the server is restarted.

Once you've applied these fixes, try accessing http://localhost:8080/MosheAPI_Project/rest/hello again—it should return your hello message instead of a 404.

内容的提问来源于stack exchange，提问作者Yuri Zach