JDBC创建mysql连接池代码

1、底层实现类（DBConnection）

　　

package JDBC.JDBCPool.MyJDBCPool;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Enumeration;
import java.util.Vector;

/**
 * Created by Administrator on 2018/3/10 0010.
 */
public class DBConnection {
    private String password;
    private String url;
    private String user;
    private int normalConn;
    private int maxConn;
    private Vector<Connection> freeConnections = new Vector<Connection>();
    private static int num = 0;// 空闲的连接数
    private static int numActive = 0;// 当前的连接数
    private int checkedOut;

    public DBConnection(String password, String url, String user,
                            int normalConn, int maxConn) {
        this.password = password;
        this.url = url;
        this.user = user;
        this.maxConn = maxConn;
        this.normalConn = normalConn;
        for (int i = 0; i < normalConn; i++) { // 初始normalConn个连接
            Connection c = newConnection();
            if (c != null) {
                freeConnections.addElement(c);
                num++;
            }
        }
    }
    // 创建一个新连接

    private Connection newConnection() {
        Connection con = null;
        try {
            if (user == null) { // 用户,密码都为空
                con = DriverManager.getConnection(url);
            } else {
                con = DriverManager.getConnection(url, user, password);
            }
            System.out.println("连接池创建一个新的连接");
        } catch (SQLException e) {
            System.out.println("无法创建这个URL的连接" + url);
            return null;
        }
        return con;
    }

    public synchronized Connection getConnection() {
      Connection con=null;
      if(freeConnections.size()>0) {
          num--;//调用之后，空闲的连接就减少一个
          con = (Connection) freeConnections.firstElement();
          freeConnections.removeElementAt(0);
          try {
              if (con.isClosed()) {
                  System.out.println("从连接池删除了一个无效连接");
                  con = getConnection();
              }
          } catch (SQLException e) {
              System.out.println("从连接池删除了一个无效连接");
              con = getConnection();
          }
      }else if(maxConn==0||checkedOut<maxConn){
          con=newConnection();
      }
      if(con!=null){//当前连接数+1
            checkedOut++;
      }
      numActive++;
      return con;
    }

    public int getnumActive() {
        return numActive;
    }

    public int getnum(){//获取空闲连接数目
        return num;
    }

    public synchronized  void release(){
        Enumeration allConnections=freeConnections.elements();
        while(allConnections.hasMoreElements()){
            Connection con=(Connection)allConnections.nextElement();
            try {
                con.close();
                num--;
            } catch (SQLException e) {
                System.out.println("无法关闭连接池中的连接");
            }
        }
        freeConnections.removeAllElements();
        numActive=0;
    }//释放空闲的链接

    public synchronized  void freeConnection(Connection con){
        freeConnections.addElement(con);
        num++;//空闲的链接增加一个
        checkedOut--;
        numActive--;
        notifyAll();
    }
}

2、连接池接口代码

　　

package JDBC.JDBCPool.MyJDBCPool;


import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
 * Created by Administrator on 2018/3/10 0010.
 */
public class DBPool {
    private String password = "root";// 密码
    private String url = "jdbc:mysql://localhost/bz?useSSL=false";// 连接URL
    private String user = "root";// 用户名
    private String driverName = "com.mysql.jdbc.Driver";// 驱动类
    private int normalConnect = 10;// 保持连接数
    private int maxConn=0;
    private DBConnection dbPool=null;
    private static DBPool instance = null; // 定义唯一实例
    Driver driver = null;// 驱动变量

    private DBPool(){
        loadDrivers(driverName);
        createPool();
    }

    public void loadDrivers(String driverName){
        String driverClassName=driverName;
        try {
            driver =(Driver)Class.forName(driverClassName).newInstance();
            DriverManager.registerDriver(driver);//注册驱动需要的是驱动程序的实例
            System.out.println("成功注册JDBC驱动程序" + driverClassName);
        } catch(Exception e){
            System.out.println("注册JDBC驱动程序失败");
        }
    }

    public void createPool(){
        dbPool=new DBConnection(password,url,user,normalConnect,maxConn);
        if(dbPool!=null){
            System.out.println("数据库连接池成功创建");
        }else{
            System.out.println("数据库连接池创建失败");
        }
    }//创建一个连接池

    public static synchronized DBPool getInstance() {
        if (instance == null) {
            instance = new DBPool();
        }
        return instance;
    }//调用构造函数返回一个独有的连接池

    public Connection getConnection() {
        if (dbPool!= null) {
            return dbPool.getConnection();
        }
        return null;
    }

    public int getnumActive() {
        return dbPool.getnumActive();
    }//获取有效连接数目

    public int getnum(){
        return dbPool.getnum();
    }//获取空闲连接数目

    public void freeConnection(Connection con) {
        if (dbPool != null) {
            dbPool.freeConnection(con);
        }
    }

    public synchronized void release(){
        dbPool.release();
        try {
            DriverManager.deregisterDriver(driver);
            System.out.println("撤销JDBC驱动程序"+driver.getClass().getName()+"成功");
        } catch (SQLException e) {
            System.out.println("无法撤销JDBC驱动程序的注册："+driver.getClass().getName());
        }
    }
}

三、测试类

　　

package JDBC.JDBCPool.MyJDBCPool;

import java.sql.Connection;

/**
 * Created by Administrator on 2018/3/10 0010.
 */
public class Test {
    public Test(){}

    public static void main(String[] args) {
        DBPool dbPool=DBPool.getInstance();
        System.out.println(dbPool.getnumActive());
        System.out.println(dbPool.getnum());
        Connection con1=dbPool.getConnection();
        System.out.println(dbPool.getnumActive());
        System.out.println(dbPool.getnum());
        dbPool.release();
    }
}