JDBC的单例模式

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
*
*
*
*/
public final class JDBCSingleton  {

private String url = "jdbc:mysql://localhost:3306/jdbc";

private String username = "root";

private String password = "root";

// 构造函数私有
private JDBCUtilSingle() {
}

// 构造私有实例
private static JDBCUtilSingle instance = null;

public static JDBCUtilSingle getInstance() {
  //延迟加载 
  if (instance == null) {
   //加锁 防止线程并发
   synchronized (JDBCUtilSingle.class) {
    //必须有的判断
    if(instance == null){
     instance = new JDBCUtilSingle();
    }    
   }  
  }
  return instance;
}

// 注册驱动
static {
  try {
   Class.forName("com.mysql.jdbc.Driver");
  } catch (ClassNotFoundException e) {
   throw new ExceptionInInitializerError(e);
  }
}

// 获取连接
public Connection getConnection() throws SQLException {
  return DriverManager.getConnection(instance.url, instance.username,
    instance.password);
}

// 释放资源
public static void free(ResultSet rs, Statement stmt, Connection conn) {
  try {
   if (rs != null) {
    rs.close();
   }
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   try {
    if (stmt != null) {
     stmt.close();
    }
   } catch (SQLException e) {
    e.printStackTrace();
   } finally {
    try {
     if (conn != null) {
      conn.close();
     }
    } catch (SQLException e) {
     e.printStackTrace();
    }
   }
  }
}
}

评论

1 楼 taoge2121 2011-09-20  

不错，不错！