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();
    }
}