JAVA DAO

最新推荐文章于 2023-06-30 18:37:00 发布

mimixi666

最新推荐文章于 2023-06-30 18:37:00 发布

阅读量1k

点赞数

分类专栏：设计模式文章标签：数据库 Java DAO设计模式

本文链接：https://blog.youkuaiyun.com/mimixi666/article/details/8810590

版权

设计模式专栏收录该内容

1 篇文章

订阅专栏

DAO的组成
1.实体
    一个java类，这个类与数据库中的表对应。
    比如，table_user表与User类对应:
    对应关系指的是:
    table_user表名与User类名对应
    table_user表的列(column)与User类的属性对应

table_user表中的一条记录与User类的一个实例对应

2.数据库

数据库的创建，链接。

3.dao接口
   声明一系列方法（即对数据库进行哪些操作--crud），
   这些方法应该与具体的技术无关。
3.dao实现

实现dao接口的一个具体类DaoImpl

4.dao的代理

对象访问的管理

5.工厂
提供符合接口定义的对象，调用者不用关心对象的创建细节。

也就是说，通过工厂，可以将调用者与要调用的对象解耦了。

显示层->DAO.HTML:

<html>
<head><title>DAO</title></head>
<body>
	<form action="createEmp.jsp" method="post">
		<table>
			<tr>
				<td>用户名：</td>
				<td><input  type="text" name="user" width="20px"/></td>
			</tr>
			<tr>
				<td>密码：</td>
				<td><input  type="password" name="password"/></td>
			</tr>
			<tr>
				<td>邮箱：</td>
				<td><input  type="text" name="email"/></td>
			</tr>
			<tr>
				<td><input type="submit" value=" 注册"/></td>
				<td><input  type="reset" value="重置"/></td>
			</tr>									
		</table>
	</form>
</body>
</html>

控制层->createEmp.jsp

<%@page contentType="text/html" pageEncoding="GBK"%>
<%@page import="DAO.VO.Emp"%>
<html>
<head><title>createEmp</title></head>

<body>
<center>hello</center>
	<jsp:useBean id="emp" class="DAO.VO.Emp" />
	<jsp:useBean id="factory" class="DAO.Factory.EmpDAOFactory" />
	<%
		String user  = request.getParameter("user");
		String pass  = request.getParameter("password");
		String email = request.getParameter("email");
		emp = new Emp(user,pass,email);
		/*emp.setUser(user);
		emp.setPassword(pass);
		emp.setEmail(email);*/
		factory.instance().createEmp(emp);
	%>
	
	<%="user->"+user%><br />
	<%="pass->"+pass%><br />
	<%="email->"+email%><br />
</body>
</html>

实体VO->emp.java:

package DAO.VO;
public class Emp
{
	private int id;
	private String user;
	private String password;
	private String email;
	public Emp(){

	}
	public Emp(String user,String password,String email){
		this.user = user;
		this.password = password;
		this.email = email;
	}
	public Emp(int id,String user,String password,String email){
		this.id = id;
		this.user = user;
		this.password = password;
		this.email = email;
	}
	public void setID(int id){
		this.id = id;
	}
	public void setUser(String user){
		this.user = user;
	}
	public void setPassword(String password){
		this.password = password;
	}
	public void setEmail(String email){
		this.email = email;
	}
	public int getID(){
		return this.id;
	}
	public String getUser(){
		return user;
	}
	public String getPassword(){
		return password;
	}
	public String getEmail(){
		return email;
	}
	/*public static void main(String[] args){
		Emp e = new Emp();
		e.setID(2);
		e.setUser("hua");
		e.setPassword("aaaaa.0");
		e.setEmail("980914629@qq.com");
		println("ID:"+e.getID());
		println("User:"+e.getUser());
		println("Password:"+e.getPassword());
		println("Email:"+e.getEmail());
	}
	public static void println(Object obj){
		System.out.println(obj);
	}*/

}

数据库->DatabaseConnection.java:

package DAO.DBC;
import java.sql.*;
public class DatabaseConnection 
{
	private static final String DRIVER     = "org.gjt.mm.mysql.Driver";
	private static final String DBURL      = "jdbc:mysql://localhost:3306/emp";
	private static final String DBUSER	   = "scott";
	private static final String DBPASSWORD = "tiger";
	private static Connection conn;
	public DatabaseConnection()throws Exception{
		Class.forName(DRIVER);//驱动加载
		conn = DriverManager.getConnection(DBURL,DBUSER,DBPASSWORD);//连接数据库
	}
	public Connection getConnection(){
		return conn;
	}
	public void close()throws Exception{
		conn.close();
	}
	/*public static void main(String[] args)throws Exception 
	{
		DatabaseConnection dc = new DatabaseConnection();
		dc.connection();
		printf(dc.getConnection());

		Connection conn  = dc.getConnection();
		Statement state  = conn.createStatement();
		state.executeUpdate("use study");//首先要使用哪个数据库
		ResultSet result = state.executeQuery("select * from emp");
		while(result.next()){
			printf(result.getObject("id"));
			printf(result.getObject("user"));
			printf(result.getObject("password"));
			printf(result.getObject("email"));
		}

		dc.close();
	}
	public static void printf(Object obj){
		System.out.println(obj);
	}*/
}

DAO接口->IEmpDAO.java:

package DAO.IEmpDAO;
import  DAO.VO.*;
import java.util.*;
public interface IEmpDAO
{
	public boolean createEmp(Emp emp)throws Exception;
	public List<Emp> findAll(String keyWord)throws Exception;
	public Emp findByID(int id)throws Exception;
}

DAO实现类->EmpDAOImpl.java:

package DAO.EmpDAOImpl;
import DAO.VO.*;
import DAO.IEmpDAO.*;
import java.util.*;
import java.sql.*;
public class  EmpDAOImpl implements IEmpDAO 
{
	private Connection conn;
	PreparedStatement preStatement;
	ResultSet result;
	public EmpDAOImpl(Connection conn){		
		preStatement = null;
		result = null;
		this.conn = conn;
	}
	public boolean createEmp(Emp e)throws Exception{						
		
		preStatement = conn.prepareStatement("INSERT INTO emp(user,password,email) VALUES(?,?,?)");
		preStatement.setString(1,e.getUser());
		preStatement.setString(2,e.getPassword());
		preStatement.setString(3,e.getEmail());
		preStatement.execute("use study");//先使用哪个数据库
		preStatement.execute();		
		preStatement.close();		
		return true;
	}
	public List<Emp> findAll(String keyWord)throws Exception{
		List <Emp> emps = new ArrayList<Emp>();
		preStatement = conn.prepareStatement("select * from emp where user like ? or password like ?");
		preStatement.setString(1,"%"+keyWord+"%");
		preStatement.setString(2,"%"+keyWord+"%");
		preStatement.execute("use study");//先使用哪个数据库
		result = preStatement.executeQuery();
		while(result.next()){
			Emp emp = new Emp(result.getInt("id"),
							  result.getString("user"),
				              result.getString("password"),
							  result.getString("email")
							  );
			emps.add(emp);
			}		
		preStatement.close();
		return emps;
	}
	public Emp findByID(int id)throws Exception{	
		Emp emp = null;
		preStatement = conn.prepareStatement("select * from emp where id=?");
		preStatement.setInt(1,id);
		result = preStatement.executeQuery();
		while(result.next()){
			emp = new Emp(result.getInt("id"),
						  result.getString("user"),
						  result.getString("password"),
						  result.getString("email")
						);
		}
		preStatement.close();
		return emp;
	}
	public boolean findEmp(String user)throws Exception{
		List <Emp> emps = new ArrayList<Emp>();
		preStatement = conn.prepareStatement("select * from emp where user=?");
		preStatement.setString(1,user);		
		preStatement.execute("use study");
		result = preStatement.executeQuery();
		while(result.next()){		
			 String userTemp = result.getString("user");
			 if(user.equals(userTemp)){
				preStatement.close();
				return true;
			 }
			}		
		preStatement.close();
		return false;
	}
	/*public static void main(String[] args)throws Exception{
		EmpDAOImpl edi = new EmpDAOImpl(new DatabaseConnection().getConnection());
		edi.createEmp(new Emp("hua1","aaaaa.0","435501646@qq.com"));

		List <Emp> emps = edi.findAll("hu");
		for(int i=0;i<emps.size();i++){
			printf(emps.get(i).getID()+" ");
			printf(emps.get(i).getUser()+" ");
			printf(emps.get(i).getPassword()+" ");
			printfln(emps.get(i).getEmail());
		}

		Emp emp;
		emp = edi.findByID(5);
		printf(emp.getID()+" ");
		printf(emp.getUser()+" ");
		printf(emp.getPassword()+" ");
		printfln(emp.getEmail());
	}
	public static void printf(Object obj){
		System.out.print(obj);
	}
	public static void printfln(Object obj){
		System.out.println(obj);
	}*/
}

DAO代理->EmpDAOProxy.java:

package DAO.EmpProxy;
import DAO.VO.*;
import DAO.IEmpDAO.*;
import DAO.DBC.*;
import DAO.EmpDAOImpl.*;
import java.util.*;
public class EmpDAOProxy implements IEmpDAO
{
	private DatabaseConnection dc;
	private EmpDAOImpl edi;
	public EmpDAOProxy()throws Exception{
		dc  = new DatabaseConnection();
		edi = new EmpDAOImpl(dc.getConnection());	
	}
	public boolean createEmp(Emp emp){		
		try
		{			
			if(!edi.findEmp(emp.getUser()))
				edi.createEmp(emp);	
			else
				return false;
		}
		catch (Exception e)
		{
			
		}
		finally
		{
			try
			{
				dc.close();	
			}
			catch (Exception e)
			{
			}			
		}				
		return true;
	}
	public List<Emp> findAll(String keyWord){
		List<Emp> emps = new ArrayList<Emp>();
		try
		{
			emps = edi.findAll(keyWord);
		}
		catch (Exception e)
		{
		}
		return emps;
	}
	public Emp findByID(int id){
		Emp emp = null;
		try
		{
			emp = edi.findByID(id);
		}
		catch (Exception e)
		{
		}
		return emp;
	}
	/*public static void main(String[] args){
		System.out.println("Hello World!");
	}*/
	public static void printf(Object obj){
		System.out.print(obj);
	}
	public static void printfln(Object obj){
		System.out.println(obj);
	}
}

DAO工厂->EmpDAOFactory.java:

package DAO.Factory;
import DAO.VO.*;
import DAO.EmpProxy.*;
public class EmpDAOFactory 
{
	public static EmpDAOProxy instance()throws Exception{
		return new EmpDAOProxy();
	}
}

我觉得对于初学者，如果是为了测试一下这种的设计模式，最后一步一步来，免得出麻烦，搞到头都大，像我那些注释的那样，

都是一步一步来的，虽然可能有点慢，但是自己会更加注意那些细节，而且如果一下子写完的话，如果出错了，那时候头就大了，

不要看到那些代码都是一下子出现你面前，你就要一下子写完它，应该理解之后，再一步一步慢慢写，这样才能有好的收获的。

<pre name="code" class="java"><pre name="code" class="java"><pre name="code" class="java"><pre name="code" class="java"><pre name="code" class="java"><pre>