Tomcat下的数据库连接池的配置与使用

实验环境：Eclipse Neon.3 (4.6.3)、MySQL、Tomcat 9.0

一、在web应用下的META-INF下新建context.xml文件，配置数据源。

<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <Resource name="DBPool"
    type="javax.sql.DataSource" 
    auth="Container"
    driverClassName="com.mysql.jdbc.Driver" 
    url="jdbc:mysql://localhost:3306/newsdb" 
    username="root"
    password="root" 
    maxActive="5" 
    maxIdle="2" 
    maxWait="6000" />
</Context>

二、使用JNDI访问数据库连接池

package com.drathin.db;

import java.sql.*;

import javax.naming.*;
import javax.sql.DataSource;


public class Dbpool {

    protected static Statement s = null;
    protected static ResultSet rs = null;
    protected static Connection conn = null;
    
    public static Connection getConnection()
    {
        try
        {
            //Context是javax.name包中的一个接口，用于查找数据库连接池的配置文件
            Context ctx = new InitialContext();  //向上转型
            ctx = (Context) ctx.lookup("java:comp/env");
            
            DataSource ds = (DataSource) ctx.lookup("DBPool");
            conn = ds.getConnection();
        }catch(Exception e)
        {
            e.printStackTrace();
            //System.out.println("FAil");
        }
        return conn;
    }

    public static Statement getS() {
        return s;
    }

    public static void setS(Statement s) {
        Dbpool.s = s;
    }

    public static ResultSet getRs() {
        return rs;
    }

    public static void setRs(ResultSet rs) {
        Dbpool.rs = rs;
    }

    public static Connection getConn() {
        return conn;
    }

    public static void setConn(Connection conn) {
        Dbpool.conn = conn;
    }

    

}

三、用JSP脚本测试

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"
    import="com.drathin.db.Dbpool"
    import="java.sql.*"
    %>
<!DOCTYPE html>
<html>
<head>

<title>Tomcat连接池测试</title>
</head>
<body>
<%
    Dbpool.setConn(Dbpool.getConnection());    

    
    try {
        Dbpool.setS(Dbpool.getConn().createStatement());
        Dbpool.setRs(Dbpool.getS().executeQuery("select * from user"));
        while(Dbpool.getRs().next()){
            out.print("  id：" + Dbpool.getRs().getInt(1));
            out.print(";  username：" + Dbpool.getRs().getString(2));
            out.print(";  password：" + Dbpool.getRs().getString(3));
            out.print("\n");
        }
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
%>

</body>
</html>

注意：测试程序切勿用java应用程序，因为这是Tomcat的数据库连接池，如果在eclipse下run运行，会导致Tomcat关闭，而运行抛出异常，也可以用servlet去实现，然后运行在Tomcat下。

package com.drathin.db;

import java.io.IOException;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet("/DBPoolServlet")
public class DBPoolServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public DBPoolServlet() {
        super();

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        response.getWriter().append("Served at: ").append(request.getContextPath());
        Dbpool.setConn(Dbpool.getConnection());    

        try {
            Dbpool.setS(Dbpool.getConn().createStatement());
            Dbpool.setRs(Dbpool.getS().executeQuery("select * from user"));
            while(Dbpool.getRs().next()){
                System.out.print("  id：" + Dbpool.getRs().getInt(1));
                System.out.print(";  username：" + Dbpool.getRs().getString(2));
                System.out.print(";  password：" + Dbpool.getRs().getString(3));
                System.out.print("\n");
            }
        } catch (SQLException e) {
        
            e.printStackTrace();
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        doGet(request, response);
    }

}