在 Java EE Web 应用程序中更新注销数据

Question

我有一个使用 jsp/servlets 构建的 Web 应用程序。Web 应用程序会话在 web.xml 中设置的用户闲置 5 分钟后设置为超时。

现在我想在此会话超时发生之前更新一些与会话超时的用户有关的详细信息。

假设用户已经登录并且由于用户选择在这种情况下保持不活动状态的时间，我需要为会话超时的用户更新一些信息。

我如何做到这一点。

package com.student.track;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
import javax.servlet.http.HttpSessionEvent; 
import javax.servlet.http.HttpSessionListener; 

public class sessionInfo implements HttpSessionListener {


    public void sessionCreated(HttpSessionEvent event) { 

    } 
    public void sessionDestroyed(HttpSessionEvent event) { 

        String query = "insert into SessionInfo values(?)";
        try
        {
        runQuery(query);
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

    } 

    public static void runQuery(String query)  throws Exception

    {
        Connection conn=null;
        int result=0;
        try
        {
            conn = getConnection();
            PreparedStatement stat=null;
            stat = conn.prepareStatement(query); 
            stat.setString(1,"first");
            result = stat.executeUpdate(query);
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
        catch(SQLException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try 
            {
                conn.close();
            } 
            catch (SQLException e) 
            {
                throw e;
            }
        }

    }

    public static Connection getConnection() throws SQLException, IOException, Exception
    {
        Properties props = new Properties();
        FileInputStream in = new FileInputStream("database.properties");
        props.load(in);
        in.close();

        String drivers = props.getProperty("dbcb.jdbcDriver");
        try
        {
            Class.forName(drivers);
        }
        catch(Exception e)
        {
            throw e;
        }

        if (drivers != null)
            System.setProperty("jdbc.drivers", drivers);

            String url = props.getProperty("dbcb.jdbcURL");
            String username = props.getProperty("dbcb.dbUser");
            String password = props.getProperty("dbcb.dbPassword");
            return DriverManager.getConnection(url, username, password);
    }


    }

还有 web.xml

    <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
    <servlet>
    <servlet-name>InitServlet</servlet-name>
    <servlet-class>com.student.track.InitServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
    <servlet-mapping>
    <servlet-name>InitServlet</servlet-name>
    <url-pattern>/InitServlet</url-pattern>
  </servlet-mapping>
  <taglib>
    <taglib-uri>/orataglib</taglib-uri>
    <taglib-location>tlds/orataglib_1_0_2.tld</taglib-location>
  </taglib>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
  <resource-ref>
 <description>Sybase Datasource example</description>
 <res-ref-name>jdbc/mysybase</res-ref-name>
 <res-type>javax.sql.DataSource</res-type>
 <res-auth>Container</res-auth>
</resource-ref>

<listener> 
<description>sessionListener</description> 
<listener-class> com.student.track.sessionInfo </listener-class> 
</listener>  
</web-app>

Answer 1

相当简单，实现HttpSessionListener。如果容器决定从其缓存中删除会话，它将触发sessionDestroyed()。

例子：

@WebListener /* or reister it in web.xml */
public final class MySessionListener implements HttpSessionListener {

    @Override
    public void sessionCreated(final HttpSessionEvent se) { }

    @Override
    public void sessionDestroyed(final HttpSessionEvent se) {

        // obtain HTTP session
        HttpSession session = se.getSession();

        /* as you cannot retrieve the user ID from the
         * HTTP session, getRemoteUser() is not available, you must
         * read the user ID from a custom parameter
         */
        String user = (String) session.getAttribute("myCustomAttribute");

        // work with it

    }

}

更新。要在 web.xml 中指定侦听器，请将以下标签添加到 web.xml：

<listener>
  <listener-class>com.test.MySessionListener</listener-class>
</listener>