用单例模式实现的java连接MySql数据库

package com.adrop.util;



import java.sql.*;



public class DBManager {

//用户名

private String user = "";

//密码

private String password = "";

//主机

private String host = "";

//数据库名字

private String database = "";

//private DBManager dbm=null;



/*

private String url="jdbc:mysql://"+host+"/"+"useUnicode=true&characterEncoding=GB2312";

*/

private String url ="";

private Connection con = null;



Statement stmt;

/**

* 私有的构造方法，保证外部不能实例化，只能由DBManager自己能提供自

* 己的实例，并且只能有一个。

* 根据主机、数据库名称、数据库用户名、数据库用户密码取得连接。

* @param host String

* @param database String

* @param user String

* @param password String

*/

private DBManager(String host, String database, String user, String password) {



this.host = host;

this.database = database;

this.user = user;

this.password = password;

//显示中文

this.url = "jdbc:mysql://" + host + "/" + database +

"?useUnicode=true&characterEncoding=GB2312";



try {

Class.forName("org.gjt.mm.mysql.Driver");

}

catch (ClassNotFoundException e) {

System.err.println("class not found:" + e.getMessage());

}



try {

con = DriverManager.getConnection(this.url, this.user, this.password);

//连接类型为ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY

stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,

ResultSet.CONCUR_READ_ONLY);

}

catch (SQLException a) {

System.err.println("sql exception:" + a.getMessage());

}

}

/**

* 静态工厂方法，来获得一个DBManager实例

*/

public static DBManager getInstance(String host, String database, String user, String password){

if(dbm==null){

dbm=new DBManager(host,database,user,password);

}

return dbm;

}

/**

* 返回取得的连接

*/

public Connection getCon() {

return con;

}

/**

* 执行一条简单的查询语句

* 返回取得的结果集

*/

public ResultSet executeQuery(String sql) {

ResultSet rs = null;

try {

rs = stmt.executeQuery(sql);

}

catch (SQLException e) {

e.printStackTrace();

}

return rs;

}

/**

* 执行一条简单的更新语句

* 执行成功则返回true

*/

public boolean executeUpdate(String sql) {

boolean v = false;

try {

v = stmt.executeUpdate(sql) > 0 ? true : false;

}

catch (SQLException e) {

e.printStackTrace();

}

finally {

return v;

}

}



}

原文转自：http://www.ltesting.net