在每个web容器中,都会有一个对应的ServletContext对象,它代表着这个web应用。

利用ServletContext对象实现数据的共享,也就是说我们在一个servlet中存放的数据,可以在另外一个servlet中拿到。

 

1.建立数据存放的类 PutServlet

 1 package com.jms.servlet;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.ServletContext;
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 
11 public class PutServlet extends HttpServlet{
12 
13     @Override
14     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
15         
16         ServletContext context = this.getServletContext();//获取这个web的ServletContext对象
17         context.setAttribute("username", "金木三");//将一个数据存放到这个ServletContext中,其中名为“username”,值为“金木三”
18     }
19 
20     @Override
21     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
22         doGet(req, resp);
23     }
24 
25 }

 

2.建立一个数据读取的类 GetServlet

 1 package com.jms.servlet;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.ServletContext;
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 
11 public class GetServlet extends HttpServlet{
12 
13     @Override
14     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
15         
16         ServletContext context = this.getServletContext();//获取这个web的ServletContext对象
17         String name = (String)context.getAttribute("username");//通过名找到对应的值
18         resp.setCharacterEncoding("utf-8");//设置响应编码
19         resp.setContentType("text/html");//设置格式
20         resp.getWriter().print(name);
21     }
22 
23     @Override
24     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
25         doGet(req, resp);
26     }
27     
28 }

 

 

3.修改web.xml文件,添加以下内容

  <!--注册Servlet-->
    <servlet>
        <servlet-name>gets</servlet-name>
        <servlet-class>com.jms.servlet.GetServlet</servlet-class>
    </servlet>
    <!--Servlet的请求路径-->
    <servlet-mapping>
        <servlet-name>gets</servlet-name>
        <url-pattern>/gets</url-pattern>
    </servlet-mapping>
    
        <!--注册Servlet-->
    <servlet>
        <servlet-name>puts</servlet-name>
        <servlet-class>com.jms.servlet.PutServlet</servlet-class>
    </servlet>
    <!--Servlet的请求路径-->
    <servlet-mapping>
        <servlet-name>puts</servlet-name>
        <url-pattern>/puts</url-pattern>
    </servlet-mapping>

 

4.进行测试

我们首先直接访问gets进行数据的读取,看能否读到数据

 

此时我们读的数据为null,因为我们还没有存放数据

那么我们尝试一下先访问puts,再访问gets尝试一下

 

 

 

此时成功的读取到了ServletContext中的数据

 

(本文仅作个人学习记录用,如有纰漏,敬请指正)