1.Hello World

Create a new Maven webapp project in Eclipse

File->New->Maven Project，保持默认选项。Click "Next" to continue
选择Maven项目的原型(archetype)，Catalog选择Internal，Artifact Id选择maven-archetype-webapp。Click "Next" to continue
填写Artifact Id等信息，如下。Click "Finish"。

Maven项目创建完成。由于servlet-api的jar没有添加到classpath，eclipse会提示编译错误。在pom.xml中添加该jar包的依赖。另外，在src/main目录下新建java目录。

pom.xml

 1 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 2     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 3     <modelVersion>4.0.0</modelVersion>
 4     <groupId>com.xuan.flight.tutorial</groupId>
 5     <artifactId>hello-world-web</artifactId>
 6     <packaging>war</packaging>
 7     <version>1.0.0</version>
 8     <name>hello-world-web Maven Webapp</name>
 9     <url>http://maven.apache.org</url>
10     <dependencies>
11         <dependency>
12             <groupId>junit</groupId>
13             <artifactId>junit</artifactId>
14             <version>4.8.1</version>
15             <scope>test</scope>
16         </dependency>
17         <dependency>
18             <groupId>javax.servlet</groupId>
19             <artifactId>javax.servlet-api</artifactId>
20             <version>3.1.0</version>
21             <scope>provided</scope>
22         </dependency>
23     </dependencies>
24     <build>
25         <finalName>hello-world-web</finalName>
26     </build>
27 </project>

Add Hello World Servlet

Create Servlet, then click "Finish"。此时Servlet的配置信息已经自动添加到web.xml文件中

web.xml

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
  <display-name>Archetype Created Web Application</display-name>
  <servlet>
    <servlet-name>HelloWorld</servlet-name>
    <display-name>HelloWorld</display-name>
    <description></description>
    <servlet-class>com.xuan.flight.tutorial.web.HelloWorld</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>/HelloWorld</url-pattern>
  </servlet-mapping>
</web-app>

Edit the source code: "HelloWorld.java"

HelloWorld.java

 1 package com.xuan.flight.tutorial.web;
 2 import java.io.IOException;
 3 import javax.servlet.ServletException;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 /**
 8  * Servlet implementation class HelloWorld
 9  */
10 public class HelloWorld extends HttpServlet
11 {
12     private static final long serialVersionUID = 1L;
13     /**
14      * @see HttpServlet#HttpServlet()
15      */
16     public HelloWorld()
17     {
18         super();
19         // TODO Auto-generated constructor stub
20     }
21     /**
22      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
23      *      response)
24      */
25     protected void doGet(HttpServletRequest request, HttpServletResponse response)
26         throws ServletException, IOException
27     {
28         response.getWriter().println("Hello World");
29         response.getWriter().append("Served at: ").append(request.getContextPath());
30     }
31     /**
32      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
33      *      response)
34      */
35     protected void doPost(HttpServletRequest request, HttpServletResponse response)
36         throws ServletException, IOException
37     {
38         // TODO Auto-generated method stub
39         doGet(request, response);
40     }
41 }

进入项目所在目录(pom.xml文件所在位置)，运行命令mvn clean package。在target目录下生成了文件hello-world-web.war。
将hello-world-web.war文件copy到${TOMCAT_HOME}/webapps目录下，重启tomcat。
在浏览器中访问http://localhost:8080/hello-world-web/HelloWorld，可以看到如下输出。
```
Hello World
Served at: /hello-world-web
```