ServletContext共享数据

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今天观看视频复习得时候学到了ServletContext相关知识，发现它可以实现servlet之间得数据共享，可以在servlet中传递数据，我还记得原来做老师布置的项目的时候因为这个问题，我把数据都存在session域再在需要的servlet取用，那样特别麻烦，还是源于自己之前学的不踏实。

所有的servlet都共用一个servletcontext的对象，利用它存取数据：

 

 下面我贴一下我使用其的例子：

<html>
<body>
<h2>Hello World!</h2>
<form action="servlet_01">
<input type="submit" value="queding">
</form>
</body>
</html>
index.jsp
import java.io.IOException;
import java.io.Writer;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class servlet_01
 */
public class servlet_01 extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public servlet_01() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           Writer writer =  response.getWriter();
           writer.append("hello servlet");
           ServletContext context = this.getServletContext();
           context.setAttribute("username", "一个程序猿！");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
servlet-01.java
package frist_test;

import java.io.IOException;
import java.io.Writer;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class servlet_02
 */
public class servlet_02 extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public servlet_02() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
//        response.setHeader("utf-8", "text/html");
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        String name = (String)context.getAttribute("username");
        response.getWriter().append(name);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
servlet-02.java

 

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