database.java

图书管管理系统是基于JAVA的 很好的

package h6.action;

import java.sql.*;

/**
 * 数据库最底层的操作，提供查找，删除和更新等基本操作
 * @author lee
 * @version 0.5
 * 
 *
 */
public class DataBase {
	private SystemParameter conf = new SystemParameter();
	private String driverName = conf.getDateBaseDriver();
	private String userName = conf.getDateBaseUser();
	private String userPasswd = conf.getDateBasePassword();
	private String dbName= conf.getDateBaseName();
	private String url = conf.getDateBaseUrl()+dbName;
	private Connection connection;
	private Statement statement;
  
	public DataBase(){
		try{
			Class.forName(driverName );
		}catch ( ClassNotFoundException cnfex ) {
			  System.err.println( "装载 JDBC/ODBC 驱动程序失败。" );
			  cnfex.printStackTrace();
			  System.exit( 1 ); // terminate program
		  }
	}

	public String getUserName(){
		return userName;
	}
	
	public String getDbName(){
		return dbName;
	}
	
	public String getPassWord(String pass){
		return userPasswd;
	}
	
	/**	
	 *	从表中查找，返回查找结果的记录集ResultSet
	 * 	@param table	要查找的表的名字
	 * 	@param attr		要查找的表中的所有属性安查找顺序放入此数组		
	 * 	@param where	sql语句中条件部分，即where部分
	 * 	@return 	从数据库查找得到的ResultSet
	 *  例：	select name,age from student where nation='china'
	 *  	String table = "student";
	 *  	String attr[] = {"name","age"};
	 *  	String where = "nation='china'";
	 */
	public ResultSet search(String table,String[] attr,String where){

		int i = 0,j = attr.length;
		ResultSet rs = null;
		getConnection();
		try{
			  statement = connection.createStatement();
			  String sql="SELECT ";
			  for(i=0;i < j;i++){
				  if(i == 0)
					  sql += attr[i];
				  else
					  sql += ","+attr[i];
			  }
			  
			  if(where.length()>0)
				  sql += " FROM "+table+" where "+where;
			  else
				  sql += " FROM "+table;
			  
			  
			  rs = statement.executeQuery(sql); 
			  
			  
			  return rs;
		  }catch(Exception e){
			  System.out.println("查找数据时出错！");
			  System.out.println(e);
			  closeConnection();
			  return null;
		  }
	}
	
	/**
	 * 从表中删除相应的记录，删除成功则返回true,否则返回false
	 * @param table		要进行删除操作的表的名字		
	 * @param where		sql语句中条件部分，即where部分
	 * @return		执行操作成功与否，成功则返回true,否则返回false
	 * 例：	delete from student where age=20
	 * 		String table = "student";
	 * 		String where = "age=20";
	 */
	public boolean delete(String table,String where){
		String sql = "DELETE FROM " + table + " where " + where;
		getConnection();
		try{
			statement = connection.createStatement();
			statement.execute(sql);
		}catch(Exception e){
			System.out.println("删除数据库里数据里出错！");
			System.out.println(e);
			closeConnection();
			return false;
		}
		closeConnection();
		return true;
	}

	/**
	 * 插入相应的记录到表中，操作成功则返回true,否则返回false
	 * @param table		要进行插入操作的表的名字		
	 * @param value		插入各属性的值
	 * @return		执行操作成功与否，成功则返回true,否则返回false
	 * 例：	insert into student values ('小明',20,‘男’)
	 * 		String table = "student";
	 * 		String value = "'小明',20,‘男’";
	 */
	public boolean insert(String table,String value){
		String sql = "INSERT INTO " + table + " VALUES (" + value + ") ";
		System.out.println(sql);
		getConnection();
		try{
			statement = connection.createStatement();
			statement.execute("SET NAMES 'GBK'");
			statement.execute(sql);
		}catch(Exception e){
			System.out.println("往数据库里插入数据时出错！");
			System.out.println(e);
			closeConnection();
			return false;
		}
		closeConnection();
		return true;
	}
	
	/**
	 * 更新表中的记录，操作成功则返回true,否则返回false
	 * @param table			要进行更新操作的表的名字		
	 * @param setValue		更新的相应属性经及更新后的值
	 * @param where			sql语句中条件部分，即where部分
	 * @return		执行操作成功与否，成功则返回true,否则返回false
	 * 例：	update student set name='大明',age=22 where name='小明'
	 * 		String table = "student";
	 * 		String setValue = "name='大明',age=22“;
	 * 		String where = "name='小明'";
	 */
	public boolean update (String table,String setValue,String where){
		String sql = "UPDATE " + table + " SET " + setValue;
		getConnection();
		if (where.length() > 0){
			sql += " WHERE " + where;
		}
		
		try{
			statement = connection.createStatement();
			statement.execute("SET NAMES 'GBK'");
			statement.execute(sql);
		}catch(Exception e){
			System.out.println("更新数据库数据时出错！");
			System.out.println(e);
			closeConnection();
			return false;
		}
		closeConnection();
		return true;
	}
	

	 private void getConnection(){//取得与数据库的连接
		  try {
			  connection = DriverManager.getConnection(
			  url, userName, userPasswd );
			  }
			  //捕获连接数据库异常
			  catch ( SQLException sqlex ) {
				  System.err.println( "无法连接数据库" );
				  sqlex.printStackTrace();
				  System.exit( 1 ); // terminate program
			  } 
	  }
	 
	 public void closeConnection(){
		 try{
                        if(null != statement)
                            statement.close();
                        if(null != connection)
                            connection.close();
			 statement = null;
			 connection = null;
		 }catch(Exception e){
			 e.printStackTrace();
		 }
	 }
}