@WebServlet注释不适用于Tomcat 8

问题描述

我想在运行于Tomcat 8的Java EE Web应用程序中使用@WebServlet批注.

I want to use the @WebServlet annotation in a Java EE webapp which runs on Tomcat 8.

我已经阅读到我需要在web.xml中声明Servlet版本3.1，并且我的Servlet需要扩展HttpServlet.我做了所有这些，但是@WebServlet仍然不起作用.我正在获取HTTP404.

I have read that I need to declare Servlet Version 3.1 in my web.xml and that my Servlet needs to extend HttpServlet. I did all that but still the @WebServlet doesn't work. I am getting a HTTP 404.

我还尝试在web.xml中使用metadata-complete="false"进行配置，但是仍然没有成功.

I also tried my configuration with metadata-complete="false" in my web.xml, but still no success.

这是我的web.xml和Servlet.

Here is my web.xml and Servlet.

完整的示例代码可以在GitHub上找到.

The complete sample code can be found on GitHub.

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app
  version="3.1"
  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_3_1.xsd">

  <context-param>
    <param-name>facelets.DEVELOPMENT</param-name>
    <param-value>true</param-value>
  </context-param>

  <!-- http://stackoverflow.com/a/7924117/451634 -->
  <!-- Put "-1" to disable this feature -->
  <context-param>
    <param-name>facelets.REFRESH_PERIOD</param-name>
    <param-value>1</param-value>
  </context-param>

  <servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.xhtml</welcome-file>
  </welcome-file-list>

  <!-- JSF -->
  <listener>
    <listener-class>org.apache.myfaces.webapp.StartupServletContextListener</listener-class>
  </listener>

  <!-- CDI -->
  <listener>
    <listener-class>org.apache.webbeans.servlet.WebBeansConfigurationListener</listener-class>
  </listener>

</web-app>

TestServlet.java

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(name = "TestServlet", urlPatterns = {"*.serve"})
public class TestServlet extends HttpServlet {

  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
          throws ServletException, IOException {
    try (ServletOutputStream out = resp.getOutputStream()) {
      out.write("Hello World".getBytes());
      out.flush();
    }
  }

}

推荐答案

我知道了.我必须扩展启动Tomcat 8.0.12服务器的方式.

I got it working. I had to extend the way I started my Tomcat 8.0.12 server.

但是，必须完成三件事:

Nevertheless, there are three main things that must be done:

web.xml 中的
1. web-app version必须至少为3.0(我使用的是3.1 )
web.xml 中的
2. metadata-complete可能不正确(default is "false")
开始之前，必须将
3. classes目录添加到嵌入式Tomcat

1. web-app version in web.xml has to be at least 3.0 (I used 3.1)
2. metadata-complete in web.xml may not be true (default is "false")
3. classes directories have to be added to the embedded Tomcat before start

以下是 web.xml 文件的示例:

<?xml version="1.0" encoding="UTF-8"?>
<web-app
  version="3.1"
  metadata-complete="false"
  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_3_1.xsd">

  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>

</web-app>

这是我的Tomcat主类的外观(现在支持@WebServlet注释):

This is how my Tomcat main class looks like (which supports now @WebServlet annotations):

public static void main(String[] args) throws Exception {
  String contextPath = "/";
  String webappDirLocation = "src/main/webapp/";
  String baseDirectory = new File(webappDirLocation).getAbsolutePath();

  Tomcat tomcat = new Tomcat();
  tomcat.setPort(8080);
  StandardContext context = (StandardContext) tomcat.addWebapp(contextPath, baseDirectory);

  // Additions to make @WebServlet work
  String buildPath = "target/classes";
  String webAppMount = "/WEB-INF/classes";

  File additionalWebInfClasses = new File(buildPath);
  WebResourceRoot resources = new StandardRoot(context);
  resources.addPreResources(new DirResourceSet(resources, webAppMount, additionalWebInfClasses.getAbsolutePath(), contextPath));
  context.setResources(resources);
  // End of additions

  tomcat.start();
  tomcat.getServer().await();
}

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