多应用共享session

发表于 | 分类于 | |

在Java web开发中，我们经常使用Tomcat来作为Java web应用的容器。关于web开发中web容器的作用，可以参考这篇文章

特别情况下，我们可能需要部署在Tomcat中的多个应用共享session，以方便在不同的应用中共享存储在session中的内容。本文介绍了如何基于Tomcat实现多应用共享session。

tomcat 配置

修改Tomcat/conf/server.xml文件

把

1
2
3
4
5
6
7
8
<Host appBase="webapps" autoDeploy="true" name="localhost" unpackWARs="true" xmlNamespaceAware="false" x mlValidation="false"></Host>
``` 
修改为
```XML
<Host appBase="webapps" autoDeploy="true" name="localhost" unpackWARs="true" xmlNamespaceAware="false" x mlValidation="false">
<Context path="/project_a" reloadable="false" crossContext="true"></Context>
<Context path="/project_b" reloadable="false" crossContext="true"></Context>
</Host>

注意 crossContext 属性：设置为true，说明你可以调用另外一个WEB应用程序，通过ServletContext.getContext() 获得ServletContext 然后再调用其getAttribute() 得到你要的对象。

编写项目代码

project_a项目

1
2
3
4
5
6
7
8
9
10
11
PrintWriter out = response.getWriter();

HttpSession session = request.getSession();
session.setAttribute("name", "user");
session.setMaxInactiveInterval(1800);

ServletContext ContextA = request.getSession().getServletContext();
ContextA.setAttribute("session", session);

//测试
out.println("in session put name : " + session.getAttribute("name"));

project_b项目

1
2
3
4
5
6
7
8
9
10
11
PrintWriter out = response.getWriter();

HttpSession session = request.getSession();
ServletContext contextB = session.getServletContext();

// 这里面传递的是 Project_A 的虚拟路径
ServletContext context = contextB.getContext("/project_a");
HttpSession sessionA= (HttpSession) context.getAttribute("session");

//测试
out.println("in session put name : " + sessionA.getAttribute("name"));

进阶：共享socket套接字

project_a项目

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
PrintWriter out = response.getWriter();

HttpSession session = request.getSession();
session.setAttribute("name", "user");
session.setMaxInactiveInterval(1800);

ServletContext ContextA = request.getSession().getServletContext();
ContextA.setAttribute("session", session);

Socket socket = new Socket("127.0.0.1", 8889);
ContextA.setAttribute("socket", socket);

PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true);
ContextA.setAttribute("printWriter", printWriter);

//测试
out.println("in session put name : " + session.getAttribute("name"));

project_b项目

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PrintWriter out = response.getWriter();

HttpSession session = request.getSession();
ServletContext contextB = session.getServletContext();

// 这里面传递的是 Project_A 的虚拟路径
ServletContext context = contextB.getContext("/project_a");
HttpSession sessionA= (HttpSession) context.getAttribute("session");
PrintWriter printWriter = (PrintWriter) context.getAttribute("printWriter");

String ipRequest = "B:" + System.currentTimeMillis();
printWriter.println(ipRequest);
printWriter.flush();

//测试
out.println("in session put name : " + sessionA.getAttribute("name"));

socket服务端

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
public static void main(String[] args) {
   try {
       ServerSocket ss = new ServerSocket(8889);
       while (true) {
            Socket socket = ss.accept();
            receive(socket);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public static void receive(final Socket socket){
   new Thread(){
       public void run(){
           while(true){
                try {
                    BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                    String line = in.readLine();
                    System.out.println("收到消息:" + line);
                    //返回处理信息
                    PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                    out.println("发送信息:" + System.currentTimeMillis());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }.start();
}

同一Tomcat下不同Web应用之间共享Session会话