dbmanager.java

音乐信息管理系统

package music;

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 static 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; 

} 

} 



}