Java数据库连接工具类

import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JdbcUtils {
	private static String url;
	private static String user;
	private static String password;
	  //静态代码块
    static{
        //加载资源
        try {
            Class.forName("com.mysql.jdbc.Driver");
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");
            //System.out.println(in);
            Properties p = new Properties();
            p.load(in);
            url = p.getProperty("url");
            user = p.getProperty("user");
            password = p.getProperty("password");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获得数据库连接
    public static Connection getConnection() throws SQLException{
       return DriverManager.getConnection(url, user, password);
       
    }//关闭资源
    public static void closeAll(Connection conn, PreparedStatement ps, ResultSet rs){
        if (conn !=null){
            try {
                conn.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (ps !=null){
            try {
                ps.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (rs !=null){
            try {
                rs.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }

    }
}

实现查询

public class  USerDaoImpl implements UserDao{

	@Override
	public boolean login(UserDamain userDamain) {
		//查询
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		//调用JdbcUtils工具类
		try {
			conn = JdbcUtils.getConnection();
			String sql="select id from user where username=? and password=?";
			ps = conn.prepareStatement(sql);
			ps.setString(1,userDamain.getUsername());
			ps.setString(2,userDamain.getPassword());
			rs = ps.executeQuery();
			
			
			if (rs.next()) {
				return true;
			}else{
				return false;
			}
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			JdbcUtils.closeAll(conn, ps, rs);
		}
		
		return false;
	}