java_ServletContext 应用

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);
}
}

二、使用ServletContext实现两个Servlet数据共享
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);
}
}
三、设置ServletContext初始化参数，然后对其之。
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);
}

}
四、编写一个转发

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">

</head>

<body>
//嵌入java代码
    <%=application.getAttribute("username") %>
</body>
</html>

5.通过ServletContext读取配置文件的内容。（使用两种方式）

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(

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