Java 学习 - 写了个简单的数据库操作类

老师要求将数据库操作封装成一个类
简单写了一个，感觉用处不大，单纯为了考试
考完试后更：这个我记得有点BUG

package gui.zyl;

import java.sql.*;
import java.util.ArrayList;
import java.util.Vector;
import java.awt.*;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;

public class DButil {
	private boolean ConnectStatus = false;
	private Connection conn = null;
	
	public DButil() {}
	
	public boolean getConnectStatus() {
		return ConnectStatus;
	}
	
	public void connectDB(String dbName,String user,String password) {
		/*
		 *  Connect to database
		 * 	Sample Parameters: "myshop","root",""
		 */
		try {
			if(conn != null && !conn.isClosed()) {
				conn.close();
			}
			conn = DriverManager.getConnection("jdbc:mysql://localhost/"+dbName+"?serverTimezone=GMT%2B8&characterEncoding=utf8",user, password);
			ConnectStatus = true;
		} catch (SQLException e) {
			JOptionPane.showConfirmDialog(null,"数据库连接建立失败,程序即将关闭","系统消息",JOptionPane.CLOSED_OPTION);
			e.printStackTrace();
			System.exit(0);
		} 
	}
	
	
	public void disconnectDB() {
		/*
		 * Disconnect database
		 */
		try {
			if(ConnectStatus == false) {
				JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			}else {
				ConnectStatus = false;
				conn.close();
			}
		} catch (SQLException e) {
			JOptionPane.showConfirmDialog(null,"数据库连接关闭失败","系统消息",JOptionPane.CLOSED_OPTION);
			e.printStackTrace();
		}
	}
	
	
	
	public ResultSet queryAll(String tableName) throws SQLException{
		/*
		 * query all the rows in table 'tableName'
		 * if query succeed,return a ResultSet
		 * return null otherwise
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return null;
		}else {
			Statement stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery("select * from " + tableName);
			return rs;	
		}
	}
	
	public ResultSet queryAll(String tableName,String booleanExpression) throws SQLException {
		/*
		 * query all the rows in 'tableName' that make 'booleanExpression' true
		 * if query succeed,return a ResultSet
		 * return null otherwise
		 * 
		 * Sample Parameters: "items","price > 10" / "items","id like '%001%'"
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return null;
		}else {
			Statement stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery("select * from " + tableName + " where " + booleanExpression);
			return rs;
		}
	}
	
	public ResultSet queryByCol(String tableName,String colNames) throws SQLException {
		/*
		 * query selected columns in 'tableName' 
		 * if query succeed,return a ResultSet
		 * return null otherwise
		 * 
		 * Sample Parameters:"items","id" / "items","id,name,price"
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return null;
		}else {
			Statement stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery("select " + colNames + " from " + tableName);
			return rs;
		}
	}
	
	public ResultSet queryByCol(String tableName,String colNames,String booleanExpression) throws SQLException {
		/*
		 * query selected columns in 'tableName' that make 'booleanExpression' true 
		 * if query succeed,return a ResultSet
		 * return null otherwise
		 * 
		 * Sample Parameters:"items","id" / "items","id,name,price"
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return null;
		}else {
			Statement stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery("select " + colNames + " from " + tableName + " where " + booleanExpression);
			return rs;
		}
	}
	
	
	public int insertRow(String tableName,String ... args) throws SQLException {
		/*
		 * insert a row into 'tableName' 
		 * if insert succeed,return 1;if insert failed,return 0
		 * return -1 otherwise(for example,sql synatx error)
		 * 
		 * Sample Parameters:"items","'001'" / "items","'001'","'car'","12.8"
		 * 
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return -1;
		}else {
			int first = 1;
			String para = "";
			for(String arg : args) {
				if(first == 1) first = 0; else para += ",";
				para += arg;
			}
			Statement stmt = conn.createStatement();
			int affected = stmt.executeUpdate("insert into " + tableName + " values(" + para + ")");
			return affected;
		}
	}
	
	
	
	public int setRow(String tableName,String updateInfo) throws SQLException {
		/*
		 * update all rows in 'tableName' 
		 * if update succeed,return 1;if update failed,return 0
		 * return -1 otherwise(for example,sql synatx error)
		 * 
		 * Sample Parameters:"items","set id = '1'" / "items","set id='1',price=10"
		 * 
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return -1;
		}else {
			Statement stmt = conn.createStatement();
			int affected = stmt.executeUpdate("update " + tableName +" set " + updateInfo);
			return affected;
		}
	}
	
	
	public int setRow(String tableName,String updateInfo,String booleanExpression) throws SQLException {
		/*
		 * update all rows in 'tableName' 
		 * if update succeed,return 1;if update failed,return 0
		 * return -1 otherwise(for example,sql synatx error)
		 * 
		 * Sample Parameters:"items","set id = '1'","price < 10"/ "items","set id='1',price=10","price = 100"
		 * 
		 */
		if(ConnectStatus == false) {
			JOptionPane.showConfirmDialog(null,"数据库连接尚未建立","系统消息",JOptionPane.CLOSED_OPTION);
			return -1;
		}else {
			Statement stmt = conn.createStatement();
			int affected = stmt.executeUpdate("update " + tableName +" set " + updateInfo + " where " + booleanExpression);
			return affected;
		}
	}
	
	
	public TableModel createTableModel(ResultSet rs,ArrayList<String> colNames) {
		/*
		 * write data to a tablemodel
		 * usage:
		 * DButil dbu = new DButil();
		 * dbu.connectDB(...);
		 * ResultSet rs = dbu.queryAll(...);
		 * TabelModel tb = rs.createTableModel(rs,colNames);
		 */
		try {
			Vector<String> colparas = new Vector<String>();
			for(String s:colNames) {
				colparas.add(s);
			}
			DefaultTableModel df = new DefaultTableModel(colparas,0);
			while(rs.next()) {
				String[] line = {
						rs.getString(1),
						rs.getString(2),
						String.valueOf(rs.getInt(3)),
						String.valueOf(rs.getInt(4)),
						String.valueOf(rs.getInt(5))
						};
				
				df.addRow(line);
			}
			
			return df;
		} catch (SQLException e) {
			JOptionPane.showConfirmDialog(null,"发生意外错误","系统消息",JOptionPane.CLOSED_OPTION);
			e.printStackTrace();
			return null;
		}
	}
}