java_ServletContext 应用源码

目录概要：

1. 写出获取ServletContext的两种方式

2.使用ServletContext实现两个Servlet数据共享

3.设置ServletContext初始化参数，然后对其之。

4. 编写一个转发

5.通过ServletContext读取配置文件的内容。（使用两种方式）

6.通过一般的java类读取配置文件的内容。

原码：----------------------------------------------------------------------------------------

一、写出获取ServletContext的两种方式

package com.hbsi.context;

import java.io.IOException;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Context1 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//获取ServletContext方法1

ServletContext context1 = this.getServletConfig().getServletContext();

//获取ServletContext方法2

ServletContext context2 = this.getServletContext();

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}

package com.hbsi.context;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Context2 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//多个Servlet实现数据共享

String data="abcd";

this.getServletContext().setAttribute("data1", data);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}

package com.hbsi.context;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Context3 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//配合Context2使用

String value = (String) this.getServletContext().getAttribute("data1");

System.out.println(value);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}

package com.hbsi.context;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Context4 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

System.out.println(this.getServletContext().getInitParameter("data"));

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}

package com.hbsi.context;

import java.io.IOException;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Context5 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//实现转发

this.getServletContext().setAttribute("username","zhangsan");

RequestDispatcher rd = this.getServletContext().getRequestDispatcher("/index.jsp");

rd.forward(request, response);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}

-------------------------------------------------------

//链接数据库

driver=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/test

username=root

password=root

----------------------------------------------------------

//JSP

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<base href="<%=basePath%>">

<title>My JSP 'index.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">

<meta http-equiv="cache-control" content="no-cache">

<meta http-equiv="expires" content="0">

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

<meta http-equiv="description" content="This is my page">

<!--

<link rel="stylesheet" type="text/css" href="styles.css">

-->

</head>

<body>

//嵌入java代码

<%=application.getAttribute("username") %>

</body>

</html>

package com.hbsi.context;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.util.Properties;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.hbsi.dao.StudentDao;

public class Context6 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// 传统的方式错误了

/*

* FileInputStream fis = new FileInputStream("src/db.properties");

*

* Properties prop = new Properties(); prop.load(fis);

*

* String driver = prop.getProperty("driver");

* System.out.println(driver);

*/

StudentDao dao = new StudentDao();

dao.delete();

}

// 通过ServletContext读取配置文件 方法1

public void test1() throws IOException {

InputStream in = this.getServletContext().getResourceAsStream(

"/WEB-INF/classes/db.properties");

Properties prop = new Properties();

prop.load(in);

String driver = prop.getProperty("driver");

String url = prop.getProperty("url");

String username = prop.getProperty("username");

String password = prop.getProperty("password");

System.out.println(url);

}

// 通过ServletContext读取配置文件 方法2,获取了文件的绝对路径

public void test2() throws IOException {

String path = this.getServletContext().getRealPath(

"/WEB-INF/classes/db.properties");

int i = path.lastIndexOf("\\");

System.out.println(path.substring(i + 1));

FileInputStream fis = new FileInputStream(path);

Properties prop = new Properties();

prop.load(fis);

String driver = prop.getProperty("driver");

System.out.println(driver);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}

package com.hbsi.dao;

import java.io.IOException;

import java.io.InputStream;

import java.sql.Connection;

import java.util.Properties;

public class StudentDao {

private static String driver;

static{

//如果读取配置文件不是Servlet，而是一般的类，使用类加载器。

InputStream in = StudentDao.class.getClassLoader().getResourceAsStream("db.properties");

Properties prop = new Properties();

try {

prop.load(in);

} catch (IOException e) {

e.printStackTrace();

}

driver = prop.getProperty("driver");

String url = prop.getProperty("url");

String username = prop.getProperty("username");

String password = prop.getProperty("password");

}

public static Connection getConnection(){

return null;

}

public void insert(){

}

public void update(){

}

public void delete(){

}

}