TMaize Blog

DAO开发模式

概念

一般的信息系统的开发架构如下

DAO就是Data Access Object的简称,主要就是对数据进行操作,对应上面的层级实时数据层。 在数据操作过程中,主要是以面向接口编程为主。一般将DAO划分为下面几个部分:

DAO开发

项目结构如下图

p1

User.java

import java.sql.Date;

public class User {
	
	String name;
	Date birthday;
	int sex;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public int getSex() {
		return sex;
	}
	public void setSex(int sex) {
		this.sex = sex;
	}
}

db-config.properties

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/tian?characterEncoding=utf-8
user=root
password=123456

DBConnection.java

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

public class DBConnection {
	
	private static String driverClass = null;
	private static String url = null;
	private static String user = null;
	private static String password = null;

	private Connection conn = null;
	
	static {
		InputStream inputStream = DBConnection.class.getClassLoader().getResourceAsStream("db-config.properties");
		Properties properties = new Properties();
		try {
			properties.load(inputStream);
			driverClass = properties.getProperty("driverClass");
			url = properties.getProperty("url");
			user = properties.getProperty("user");
			password = properties.getProperty("password");
		} catch (IOException e) {
			throw new ExceptionInInitializerError("Load 'SqlConfig.properties' Error!!!");
		}
	}
	
	public DBConnection() throws Exception{
		try {
			Class.forName(driverClass);
			this.conn = DriverManager.getConnection(url, user, password);
		} catch (Exception e) {
			throw e;
		}
	}
	
	public Connection getConnection(){
		return this.conn;
	}
	
	public void close() throws Exception{
		if (this.conn!=null) {
			try {
				this.conn.close();
			} catch (Exception e) {
				throw e;
			}
		}
	}
}

UserDao.java

import java.util.List;

import pojo.User;

public interface UserDao {
	
	/**
	 * 加入一个用户
	 * @param user 要添加的对象
	 * @return 是否增加成功的标记
	 * @throws Exception 如果有异常将直接抛出
	 */
	public boolean addUser(User user) throws Exception;

	/**
	 * 列出所有的用户
	 * @return 所有的用户
	 * @throws Exception 失败将抛出异常
	 */
	public List<User> listAll() throws Exception;
}

UserDaoImpl.java

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.util.List;
import pojo.User;

public class UserDaoImpl implements UserDao{

	private Connection conn = null;
	private PreparedStatement pstmt;
	
	public UserDaoImpl(Connection conn) {
		this.conn = conn;
	}
	
	@Override
	public boolean addUser(User user) throws Exception {

		boolean flag = false;
		
		String sql = "insert into user(xxx,xxx,xxx) values(?,?,?)";
		this.pstmt = this.conn.prepareStatement(sql);
		
		this.pstmt.setString(1, user.getName());
		this.pstmt.setDate(2, user.getBirthday());
		this.pstmt.setInt(3, user.getSex());
		
		if (this.pstmt.executeUpdate()>0) {
			flag = true;
		}
		
		//关闭
		this.pstmt.close();
		return flag;
	}

	@Override
	public List<User> listAll() throws Exception {
		//实现....
		return null;
	}

}

UserService.java

import java.util.List;
import dao.UserDao;
import dao.UserDaoImpl;
import db.DBConnection;
import pojo.User;

public class UserService implements UserDao{
	
	private DBConnection dbconn = null;
	private UserDao dao = null;
	
	public UserService () throws Exception{
		this.dbconn = new DBConnection();
		//用dao来代理daoimpl
		this.dao = new UserDaoImpl(this.dbconn.getConnection());
	}

	@Override
	public boolean addUser(User user) throws Exception {
		boolean flage = false;
		
		//业务逻辑,如先检查是否存在同名用户,直接返回false拒绝出现同名用户
		
		flage = this.addUser(user);
		
		//关闭数据库连接
		this.dbconn.close();
		
		return flage;
	}

	@Override
	public List<User> listAll() throws Exception {

		//业务逻辑....
		
		List<User> list = this.dao.listAll();
		
		//关闭数据库连接
		this.dbconn.close();
		
		return list;
	}

}

DAOFactory.java

import dao.UserDao;
import service.UserService;

public class DAOFactory {
	
	public static UserDao getUserDaoInstance() throws Exception{
		
		return new UserService();
	}

}

UserDaoTest.java

这里使用junit做测试

import java.sql.Date;
import java.util.List;
import org.junit.Test;
import factory.DAOFactory;
import pojo.User;

public class UserDaoTest {
	
	@Test
	public void addUser(){
		User user = new User();
		user.setName("name");
		user.setBirthday(new Date(1996, 4, 11));
		user.setSex(0);
		try {
			DAOFactory.getUserDaoInstance().addUser(user);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	@Test
	public void listAllUser(){
		List<User> list;
		try {
			list = DAOFactory.getUserDaoInstance().listAll();
			for (User user : list) {
				System.out.println(user.toString());
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}