servlet是一个普通的Java类，它继承了HTTP Servlet类，servlet中的程序可以叫作基于http协议的servlet程序。 servlet程序需要交给Tomcat服务器运行，所以需要下载Tomcat服务器并导入到eclipse中。 servlet的创建： 1.在WebDemo下的src中创建一个工程包，这里将包命名为com.test.servlet，在这个包中创建一个名为TestHello的servlet；
package com.test.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class TestHello */ public class TestHello extends HttpServlet { //在这里可以看出，servlet就是一个继承了HttpServlet的Java类 private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public TestHello() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } }2.拼一个用h1标题写的Hello World
package com.test.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class TestHello */ public class TestHello extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public TestHello() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); //目的是让doPost和doGet执行同一个逻辑 } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { StringBuffer buff = new StringBuffer();//创建一个拼接字符串的对象buff buff.append("<html><body>");//拼接html文件，省略head buff.append("<h1>Hello World</h1>"); buff.append("</body></html>");//html文件的结尾 response.getWriter().write(buff.toString()); //将html文件输出到浏览器上 } }3.在浏览器中访问servlet http://localhost:8080/WebDemo 这一块表明是访问本地机Tomcat服务器下的WebDemo文件； 接下来想要访问哪个servlet，就在WebDemo下的WebContent下的WEB-INF下的web.xml中找到对应的url-pattern。
