Ubuntu14.04 html 上的 Tomcat7 可以工作，但 servlet 出现 404 错误

Question

I'm new to servlets. I've installed Tomcat7 in Ubuntu14.04 and the service runs fine. But it gives 404(not found) error for servlet ( http://localhost:8080/hello/HelloServlet ). The html within the application runs fine. So are the Tomcat managerial tools.

Any idea of what I'm doing wrong?

Tomcat webapps structure: /var/lib/tomcat7/webapps

webapps
|-- ROOT
    |-- hello
    |   |-- index.html
    |   `-- WEB-INF
    |       |-- classes
    |       |   |-- HelloServlet.class
    |       |   `-- HelloServlet.java
    |       |-- lib
    |       `-- web.xml
    |-- index.html
    `-- META-INF
        `-- context.xml

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
     version="2.5">
<servlet>
    <servlet-name>HelloServlet</servlet-name>
    <servlet-class>HelloServlet</servlet-class>
</servlet>

<servlet-mapping>
     <servlet-name>HelloServlet</servlet-name>
     <url-pattern>/HelloServlet</url-pattern>
</servlet-mapping>
</web-app>

HelloServlet.java:

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.WebServlet;

@WebServlet(name="HelloServlet", urlPatterns={"/HelloServlet"})

public class HelloServlet extends HttpServlet{
  private String message;
  public void init() throws ServletException{
      message = "Hello World";
  }
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
      response.setContentType("text/html");
      PrintWriter out = response.getWriter();
      out.println("<h1>" + message + "</h1>");
  }
  public void destroy(){

  }
}

Answer 1

Finally I got it running :)

It was the directory structuring that was creating the problem. The application directory should be just outside the 'webapps/ROOT' directory. To be specific, just put the application directory directly under the 'webapps' (Seems to be specific case for Tomcat7 and Ubuntu 14.04LTS)

The corrected structure:

webapps
|-- ROOT
`-- hello
    |-- index.html
    `-- WEB-INF
        |-- classes
        |   |-- HelloServlet.class
        |   `-- HelloServlet.java
        |-- lib
        `-- web.xml

The previous structure (with error):

webapps
|-- ROOT
    |-- hello
    |   |-- index.html
    |   `-- WEB-INF
    |       |-- classes
    |       |   |-- HelloServlet.class
    |       |   `-- HelloServlet.java
    |       |-- lib
    |       `-- web.xml
    |-- index.html
    `-- META-INF
        `-- context.xml

Answer 2

The java source file should not be in the /WEB-INF folder. Servlet is a regular java file and should be located in the /src/... folder. also, once you annotate the class as @WebServlet - u can remove the web.xml file ( although it has many other usage, using it for 'servlet-mapping' can be ignored for simplification).

├───build
│   └───classes
│       └───pkg
│               HelloServlet.class
│
├───src
│   └───pkg
│           HelloServlet.java
│
└───WebContent
    ├───META-INF
    │       MANIFEST.MF
    │
    └───WEB-INF
        └───lib

Answer 3

你的java类文件位置不对，把你的java类文件改成src文件夹。