[Java] DAO设计模式

背景

• B/S（Browser/Server）：浏览器/服务器架构，用于广域网
• C/S（Client/Server）：客户机/服务器架构，用于局域网

 

业务分析

• 前端
• 控制层
  • 调用业务层
• 业务层（Business Object BO）
  • 调用数据层实现业务操作
  • 业务层需要明确地知道数据层的操作方法，但不需要知道它的具体实现
  • 使用代理模式（动态代理）进行业务控制，Sprint、Struct框架中会提供
  • 定义操作协议（接口）
  • 定义业务实现类，控制数据库的打开和关闭，取得数据层接口对象，调用数据层操作
  • 定义业务工厂类，用于供控制层实例化，隐藏具体实现
• 数据层（Data Access Object DAO，持久层）
  • 把具体的业务“翻译”成数据库的原子操作（增删改查）
  • 定义接口，对业务层隐藏子类，一个数据表对应一个接口
  • 定义简单Java类（POJO），对数据表中的数据进行包装，以便在不同层之间传递数据
  • 定义实现类，一个类实现一个接口，类中一个方法实现一个具体的SQL操作
  • 定义工厂类，用于其它层实例化接口对象，隐藏具体实现
• 数据库

 

 

实例

功能

• 连接mysql，为雇员表增加一行数据

项目结构

 

项目代码

• 数据库连接类 -- DatabaseConnection.java

 1 package dbc;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.SQLException;
 6 
 7 public class DatabaseConnection {
 8     private static final String DBDRIVER = "com.mysql.cj.jdbc.Driver";
 9     private static final String DBURL = "jdbc:mysql://127.0.0.1:3306/company?serverTimezone=GMT%2B8&characterEncoding=UTF-8&useSSL=false";
10     private static final String DBUSER = "root";
11     private static final String PASSWORD = "Chen1227+";
12     private Connection conn = null;
13     
14     // 连接数据库
15     public DatabaseConnection() {
16         try {
17             Class.forName(DBDRIVER);
18         } catch (ClassNotFoundException e1) {
19             e1.printStackTrace();
20         }
21         try {
22             this.conn = DriverManager.getConnection(DBURL,DBUSER,PASSWORD);
23         } catch (SQLException e) {
24             e.printStackTrace();
25         }
26     }
27     
28     // 取得数据库的连接对象
29     public Connection getConnection() {
30         return this.conn;
31     }
32     
33     // 关闭数据库
34     public void close() {
35         if(this.conn != null) {
36             try {
37                 this.conn.close();
38                 //System.out.print("close success!");
39             } catch (SQLException e) {
40                 e.printStackTrace();
41             }
42         }
43     }
44 }

• POJO类 -- Emp.java

 1 package vo;
 2 
 3 import java.io.Serializable;
 4 import java.util.Date;
 5 
 6 
 7 @SuppressWarnings("serial")
 8 public class Emp implements Serializable{
 9     private Integer empno;
10     private String ename;
11     private String job;
12     private Date hiredate;
13     private Double sal;
14     private Double comm;
15     
16     public Integer getEmpno() {
17         return empno;
18     }
19     public void setEmpno(Integer empno) {
20         this.empno = empno;
21     }
22     public String getEname() {
23         return ename;
24     }
25     public void setEname(String name) {
26         this.ename = name;
27     }
28     public String getJob() {
29         return job;
30     }
31     public void setJob(String job) {
32         this.job = job;
33     }
34     public Date getHiredate() {
35         return hiredate;
36     }
37     public void setHiredate(Date hiredate) {
38         this.hiredate = hiredate;
39     }
40     public Double getSal() {
41         return sal;
42     }
43     public void setSal(Double sal) {
44         this.sal = sal;
45     }
46     public Double getComm() {
47         return comm;
48     }
49     public void setComm(Double comm) {
50         this.comm = comm;
51     }
52 }

• 数据层
  • 数据层接口 -- IEmpDAO.java

 1 package dao;
 2 
 3 import java.util.List;
 4 import java.util.Set;
 5 
 6 import vo.Emp;
 7 
 8 public interface IEmpDAO {
 9     public boolean doCreate(Emp vo) throws Exception;
10     public boolean doUpdata(Emp vo) throws Exception;
11     public boolean doRemoveBatch(Emp vo) throws Exception;
12     public boolean doRemoveBatch(Set<Integer> ids) throws Exception;
13     public Emp findById(Integer id) throws Exception;
14     public List<Emp> findAll() throws Exception;
15     public List<Emp> findAll(Integer currentPage, Integer LineSize, String column, String keyWord) throws Exception;
16     public Integer getAllCount(String column, String keyWord) throws Exception;
17  }

• • 数据层实现类 -- EmpDAOImpl.java

 1 package dao.impl;
 2 
 3 import java.sql.Connection;
 4 import java.sql.PreparedStatement;
 5 import java.util.List;
 6 import java.util.Set;
 7 
 8 import dao.IEmpDAO;
 9 import vo.Emp;
10 
11 public class EmpDAOImpl implements IEmpDAO{
12     private Connection conn;
13     private PreparedStatement pstmt;
14     
15     public EmpDAOImpl(Connection conn) {
16         this.conn = conn;
17     }
18     
19     @Override
20     public boolean doCreate(Emp vo) throws Exception {
21         String sql = "INSERT INTO emp(empno,ename,job,hiredate,sal,comm) VALUES (?,?,?,?,?,?)";
22         this.pstmt = this.conn.prepareStatement(sql);
23         this.pstmt.setInt(1, vo.getEmpno());
24         this.pstmt.setString(2, vo.getEname());
25         this.pstmt.setString(3, vo.getJob());
26         this.pstmt.setDate(4, new java.sql.Date(vo.getHiredate().getTime()));
27         this.pstmt.setDouble(5, vo.getSal());
28         this.pstmt.setDouble(6, vo.getComm());
29         // System.out.println("insert success!");
30         return this.pstmt.executeUpdate() > 0;
31     }
32 
33     @Override
34     public boolean doUpdata(Emp vo) throws Exception {
35         return false;
36     }
37 
38     @Override
39     public boolean doRemoveBatch(Emp vo) throws Exception {
40         return false;
41     }
42 
43     @Override
44     public boolean doRemoveBatch(Set<Integer> ids)
45             throws Exception {
46         return false;
47     }
48 
49     @Override
50     public Emp findById(Integer id) throws Exception {
51         return null;
52     }
53 
54     @Override
55     public List<Emp> findAll() throws Exception {
56         return null;
57     }
58 
59     @Override
60     public List<Emp> findAll(Integer currentPage,
61             Integer LineSize, String column, String keyWord)
62             throws Exception {
63         return null;
64     }
65 
66     @Override
67     public Integer getAllCount(String column,
68             String keyWord) throws Exception {
69         return null;
70     }
71     
72 }

• • 数据层工厂类 -- DAOFactory.java

 1 package factory;
 2 
 3 import java.sql.Connection;
 4 import dao.IEmpDAO;
 5 import dao.impl.EmpDAOImpl;
 6 
 7 public class DAOFactory {
 8     public static IEmpDAO getIEmpDAOInstance(Connection conn) {
 9         return new EmpDAOImpl(conn);
10     }
11 }

• 业务层
  • 业务层接口 -- IEmpService.java

1 package service;
2 import vo.Emp;
3 
4 public interface IEmpService {
5     public boolean insert(Emp vo) throws Exception;
6 }

• • 业务层实现类 -- EmpServiceImpl.java

 1 package service.impl;
 2 
 3 import dbc.DatabaseConnection;
 4 import factory.DAOFactory;
 5 import service.IEmpService;
 6 import vo.Emp;
 7 
 8 public class EmpServiceImpl implements IEmpService{
 9     private DatabaseConnection dbc = new DatabaseConnection();
10 
11     @Override
12     public boolean insert(Emp vo) throws Exception {
13         try {
14             if(DAOFactory.getIEmpDAOInstance(this.dbc.getConnection()).findById(vo.getEmpno()) == null ) {
15                 return DAOFactory.getIEmpDAOInstance(this.dbc.getConnection()).doCreate(vo);
16             }
17             System.out.println("insert false!");
18             return false;
19         }catch(Exception e) {
20             throw e;
21         }finally {
22             this.dbc.close();
23         }
24     }
25 }

• • 业务层工厂类 -- ServiceFactory.java

 1 package factory;
 2 
 3 import service.IEmpService;
 4 import service.impl.EmpServiceImpl;
 5 
 6 public class ServiceFactory {
 7     public static IEmpService getIEmpServiceInstance() {
 8         return new EmpServiceImpl();
 9     }
10 }

• 测试类
  • main()测试

 1 package test;
 2 
 3 import java.util.Date;
 4 import factory.ServiceFactory;
 5 import vo.Emp;
 6 
 7 public class TestEmpInsert {
 8     public static void main(String[] args) throws Exception{
 9         Emp vo = new Emp();
10         vo.setEmpno(8888);
11         vo.setEname("Lucy");
12         vo.setJob("Teacher");
13         vo.setHiredate(new Date());
14         vo.setSal(8900.0);
15         vo.setComm(5600.0);
16         System.out.println(ServiceFactory.getIEmpServiceInstance().insert(vo));
17     }
18 }

• • Junit测试

 1 package test.junit;
 2 
 3 import java.util.Date;
 4 import org.junit.Test;
 5 import factory.ServiceFactory;
 6 import junit.framework.TestCase;
 7 import vo.Emp;
 8 
 9 public class IEmpServiceTest {
10     
11     @Test
12     public void testInsert() throws Exception {
13         Emp vo = new Emp();
14         vo.setEmpno(8888);
15         vo.setEname("Lucy");
16         vo.setJob("Teacher");
17         vo.setHiredate(new Date());
18         vo.setSal(8900.0);
19         vo.setComm(5600.0);
20         TestCase.assertTrue(ServiceFactory.getIEmpServiceInstance().insert(vo));
21     }
22 }

 

参考

B/S与C/S的区别

https://zhidao.baidu.com/question/3711387.html

java中PreparedStatement和Statement详细讲解

https://blog.csdn.net/czh500/article/details/88202971

class.forName()做了什么

https://blog.csdn.net/u012292938/article/details/81033660

来源：https://www.cnblogs.com/cxc1357/p/12470244.html