servlet(1)

本文介绍如何使用Java Servlet创建一个简单的HTTP GET请求响应,包括HTML页面的生成与输出。

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package org.xiaoyukid.servlet;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;


public class HelloServlet extends HttpServlet{
	public void doGet(HttpServletRequest req,HttpServletResponse resp)throws ServletException,IOException{
		PrintWriter out = null;
		out = resp.getWriter();
		out.println("<html>") ;
		out.println("<head><title>hello</title></head>") ;
		out.println("<body>") ;
		out.println("<h1><font color=\"red\">");
		out.println("HELLO WORLD!") ;
		out.println("</font></h1>") ;
		out.println("</body>") ;
		out.println("</html>") ;
		out.close() ;
	}

}

classpath 需要找到tomcat下得lib,或者把tomca中得servlet-api.jar复制到C:\jdk6.0\jre\lib\ext中

映射

<servlet>
		<servlet-name>hello</servlet-name>
		<servlet-class>org.xiaoyukid.servlet.HelloServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>hello</servlet-name>
		<url-pattern>/demo</url-pattern>
	</servlet-mapping>



在Java Web项目中,可以通过多种方式实现多个Servlet共享数据。以下是使用`HttpSession`共享数据的示例: 1. **Servlet1**:设置共享对象`name`。 2. **Servlet2**:修改共享对象`name`的值。 3. **Servlet3**:读取共享对象`name`的值。 ### Servlet1.java ```java import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; @WebServlet("/servlet1") public class Servlet1 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 设置共享对象name HttpSession session = request.getSession(); session.setAttribute("name", "Tom"); response.getWriter().write("Servlet1: name set to Tom"); } } ``` ### Servlet2.java ```java import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; @WebServlet("/servlet2") public class Servlet2 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 修改共享对象name的值 HttpSession session = request.getSession(); session.setAttribute("name", "Jerry"); response.getWriter().write("Servlet2: name changed to Jerry"); } } ``` ### Servlet3.java ```java import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; @WebServlet("/servlet3") public class Servlet3 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 读取共享对象name的值 HttpSession session = request.getSession(); String name = (String) session.getAttribute("name"); response.getWriter().write("Servlet3: name is " + name); } } ``` ### 说明 1. **Servlet1**:通过`HttpSession`设置一个名为`name`的属性,值为`Tom`。 2. **Servlet2**:通过`HttpSession`修改`name`属性的值为`Jerry`。 3. **Servlet3**:通过`HttpSession`读取`name`属性的值并返回。 ### 访问顺序 1. 访问`http://localhost:8080/yourapp/servlet1` 2. 访问`http://localhost:8080/yourapp/servlet2` 3. 访问`http://localhost:8080/yourapp/servlet3` ### 结果 1. Servlet1: name set to Tom 2. Servlet2: name changed to Jerry 3. Servlet3: name is Jerry
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