java_jdbc_3层 解耦

Dao - 提供接口

DaoImpl - 实现

DaoFactory - 工厂模式获取实现

DaoExcetpion - jdbc异常处理 实现runtime exception类即可

TestDemo - 主函数

User - bean

daoconfig.properties - 配置文件

package cn.itcast.user;public interface Dao {public User findById(int id);}

 

package cn.itcast.user;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import cn.itcast.JdbcUtils;public class DaoImpl implements Dao {@Overridepublic User findById(int id) {Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;User user=null;String sql = "select * from t_user where id=?";try{conn = JdbcUtils.getConnection();ps = conn.prepareStatement(sql);ps.setInt(1, id);rs=ps.executeQuery();while(rs.next()){user = new User();user.setId(rs.getInt("id"));user.setName(rs.getString("username"));user.setPassword(rs.getString("password"));}}catch(SQLException e){throw new DaoExcetpion(e.getMessage(),e);}finally{JdbcUtils.free(rs, ps, conn);}return user;}}

 

 

package cn.itcast.user;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.util.Properties;public class DaoFactory {private static Dao dao = null;private static DaoFactory intance = new DaoFactory();private DaoFactory() {try {Properties prop = new Properties();InputStream inStream = DaoFactory.class.getClassLoader().getResourceAsStream("daoconfig.properties");prop.load(inStream);String userDaoClass = prop.getProperty("userDaoClass");dao=(Dao)Class.forName(userDaoClass).newInstance();} catch (Exception e) {// TODO Auto-generated catch blockthrow new ExceptionInInitializerError(e);}}public static DaoFactory getInstance() {return intance;}public Dao getUserDao() {return dao;}}

 

 

package cn.itcast.user;public class TestDemo {public static void main(String[] args) {// TODO Auto-generated method stub//Dao dao = new DaoImpl();Dao dao = DaoFactory.getInstance().getUserDao();User user = dao.findById(2);System.out.println(user.getId());System.out.println(user.getName());}}

 

//配置文件

userDaoClass=cn.itcast.user.DaoImpl