JDBC学习之路（五）基于MVC框架的JDBC异常与设计模式处理

以前写JDBC时候，根本没有考虑过底层JDBC的SQLException异常如何处理，有时候直接放在那里就不动了，但是这样的做法非常不正确，今天看了一下JDBC的视频，知道了正确的JDBC处理办法，还有一些正规的处理模式，现在感觉以后做东西还是得正规一些好。下面将代码贴出来研究研究

首先得写一个类，他实现了对JDBC类的封装，这样中间层进行访问的时候能和Java的面向对对象技术切合起来，本例子以User为例

package com.bird.jdbc.domain;

import java.util.Date;

/**
 * 
 * @use 对一个表的面向对象的封装
 * 
 * @author bird
 * 
 */
public class User {
	private int id;
	private String name;
	private Date birthday;
	private float money;
	
	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

然后建立一个接口，将需要的操作都放入到接口中进行声明，以便以后更改数据访问层的时候能不改变中间层的东西

package com.bird.jdbc.dao;

import com.bird.jdbc.domain.user;
/**
 * 
 * @use  对方法的进行接口的封装
 * 
 * @author bird
 * 
 */
public interface UserDao {//可以看到，传递的东西都是对象，不再是JDBC的一个个表
	public void addUser(User user);

	public User getUser(int userId);

	public User findUser(String loginName, String password);

	public void update(User user);

	public void delete(User user);

}

下面是对本接口的实现，要单独开辟一个包出来

package com.bird.jdbc.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import cn.itcast.jdbc.JdbcUtils;
import cn.itcast.jdbc.dao.DaoException;
import cn.itcast.jdbc.dao.UserDao;
import cn.itcast.jdbc.domain.User;

/**
 * 
 * @use 对接口的实现
 * 
 * @author Bird
 * 
 */
public class UserDaoJdbcImpl implements UserDao {

	public void addUser(User user) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "insert into user(name,birthday, money) values (?,?,?) ";
			ps = conn.prepareStatement(sql);
			ps.setString(1, user.getName());
			ps.setDate(2, new java.sql.Date(user.getBirthday().getTime()));
			ps.setFloat(3, user.getMoney());
			ps.executeUpdate();
		} catch (SQLException e) {
			throw new DaoException(e.getMessage(), e);//注意一定要将异常抛出，
		} finally {//这样就将编译错误改编成运行错误，让中间层不用强制处理，当他想要处理的时候再处理
			JdbcUtils.free(rs, ps, conn);
		}
	}

	public void delete(User user) {
		Connection conn = null;
		Statement st = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			st = conn.createStatement();
			String sql = "delete from user where id=" + user.getId();
			st.executeUpdate(sql);
		} catch (SQLException e) {
			throw new DaoException(e.getMessage(), e);
		} finally {
			JdbcUtils.free(rs, st, conn);
		}

	}

	public User findUser(String loginName, String password) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		User user = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "select id, name, money, birthday  from user where name=?";
			ps = conn.prepareStatement(sql);
			ps.setString(1, loginName);
			rs = ps.executeQuery();
			while (rs.next()) {
				user = mappingUser(rs);
			}
		} catch (SQLException e) {
			throw new DaoException(e.getMessage(), e);
		} finally {
			JdbcUtils.free(rs, ps, conn);
		}
		return user;
	}

	public User getUser(int userId) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		User user = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "select id, name, money, birthday  from user where id=?";
			ps = conn.prepareStatement(sql);
			ps.setInt(1, userId);
			rs = ps.executeQuery();
			while (rs.next()) {
				user = mappingUser(rs);
			}
		} catch (SQLException e) {
			throw new DaoException(e.getMessage(), e);
		} finally {
			JdbcUtils.free(rs, ps, conn);
		}
		return user;
	}

	private User mappingUser(ResultSet rs) throws SQLException {
		User user = new User();
		user.setId(rs.getInt("id"));
		user.setName(rs.getString("name"));
		user.setMoney(rs.getFloat("money"));
		user.setBirthday(rs.getDate("birthday"));
		return user;
	}

	public void update(User user) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "update user set name=?, birthday=?, money=? where id=? ";
			ps = conn.prepareStatement(sql);
			ps.setString(1, user.getName());
			ps.setDate(2, new java.sql.Date(user.getBirthday().getTime()));
			ps.setFloat(3, user.getMoney());
			ps.setInt(4, user.getId());
			ps.executeUpdate();
		} catch (SQLException e) {
			throw new DaoException(e.getMessage(), e);
		} finally {
			JdbcUtils.free(rs, ps, conn);
		}
	}

}

写一个类继承运行异常，再以后抛出，要单独进行处理才可以

package com.bird.jdbc.dao;

/**
 *
 * @use 继承自RuntimeException

 *
 * @author Bird
 *
 */
public class DaoException extends RuntimeException {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public DaoException() {
		// TODO Auto-generated constructor stub
	}

	public DaoException(String message) {
		super(message);
		// TODO Auto-generated constructor stub
	}

	public DaoException(Throwable cause) {
		super(cause);
		// TODO Auto-generated constructor stub
	}

	public DaoException(String message, Throwable cause) {//过会调用的就是这个方法
		super(message, cause);
		// TODO Auto-generated constructor stub
	}

}

看样子以后得这样写MVC的JDBC才行