Servlet入门（第一个Servlet的Web程序）

新建maven项目，注意项目的类型

工程名为ServletExample

点击Finish，建立maven项目完成如下

生成后的目录没有java源码目录，按照maven的约定，还要新建src/main/java的源码目录。选中项目，点击鼠标右键

不知道为什么，新建src/main/java目录时，eclipse报这个目录已经存在。没办法，先建立src/main/java2，然后再重构为src/main/java

配置maven的构建文件pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<projectxmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://maven.apache.org/POM/4.0.0http://maven.apache.org/maven-v4_0_0.xsd">
       <modelVersion>4.0.0</modelVersion>
       <packaging>war</packaging>
       <name>ServletExample</name>
       <groupId>com.ydoing</groupId>
       <artifactId>ServletExample</artifactId>
       <version>0.0.1-SNAPSHOT</version>
 
       <build>
              <plugins>
                    <plugin>
                           <groupId>org.apache.maven.plugins</groupId>
                           <artifactId>maven-compiler-plugin</artifactId>
                           <version>3.1</version>
                           <configuration>
                                  <source>1.7</source>
                                  <target>1.7</target>
                           </configuration>
                    </plugin>
              </plugins>
       </build>
       <dependencies>
              <dependency>
                    <groupId>javax.servlet</groupId>
                    <artifactId>javax.servlet-api</artifactId>
                    <version>3.0.1</version>
              </dependency>
       </dependencies>
 
</project>

更新maven项目

新增HelloServlet

代码如下，该类核心代码是doGet，作用是向客户端返回“Hello, world!”

package com.ydoing.helloapp;
 
import java.io.IOException;
import java.io.PrintWriter;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servletimplementation class HelloServlet
 */
publicclassHelloServletextendsHttpServlet{
       privatestaticfinallongserialVersionUID =1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    publicHelloServlet(){
        super();
        // TODO Auto-generated constructor stub
    }
 
       /**
        * @see HttpServlet#doGet(HttpServletRequestrequest, HttpServletResponse response)
        */
       protectedvoid doGet(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{
              // TODO Auto-generated method stub
              response.setContentType("text/html");
              PrintWriter out = response.getWriter();
              String msg ="Hello, world!";
              out.println("<h1>"+ msg +"</h1>");
       }
 
       /**
        * @see HttpServlet#doPost(HttpServletRequestrequest, HttpServletResponse response)
        */
       protectedvoid doPost(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{
              // TODO Auto-generated method stub
       }
 
}

修改web.xml文件。作用是将URI映射到指定的Servlet上

<?xml version="1.0" encoding="UTF-8"?>
<web-appxmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://java.sun.com/xml/ns/javaee"
       xsi:schemaLocation="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
       id="WebApp_ID"version="3.0">
 
       <servlet>
              <servlet-name>HelloServlet</servlet-name>
              <servlet-class>com.ydoing.helloapp.HelloServlet</servlet-class>
       </servlet>
       <servlet-mapping>
              <servlet-name>HelloServlet</servlet-name>
              <url-pattern>/hello</url-pattern>
       </servlet-mapping>
 
</web-app>

运行在Tomcat上

运行结果如下