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README.md

DAO(数据访问对象)

程序的标准架构为:

客户层(Client)-> 显示层(jsp/servlet)-> 业务层(BO) -> 数据层(BAO) -> 资源层(DataBase)

1,组成部分(Java命名规范)

  • 1,DatabaseConnection: 专门负责数据库打开和关闭操作的类;(xxx.dbc.DatabaseConnection)
  • 2,VO:主要由属性、setter、geter组成,VO类中的属性与表中的字段相对应。(xxx.vo.Xxx)
  • 3,DAO: 主要定义操作的接口,定义一系列的数据库的原子性操作,如,增删改查。(xxx.dao.XxxDAO)
  • 4,Impl:DAO接口的真实实现类,完成具体的数据库操作,但是不负责数据库的打开和关闭。(xxx.dao.impl.XxxDAOImpl)
  • 5,Proxy:代理实现类,主要完成数据库的打开和关闭,并且调用真实实现类对象的操作。(xxx.dao.proxy.XxxDAOProxy)
  • 6,Factory:工厂类,通过工厂类获得一个DAO的实例化对象。(xxx.factory.DAOFactory)

2,DAO的实例开发

项目结构:

image-20210325170339548

2.1,数据库脚本建立(使用PostgreSQL)

数据库名为:jsp

create table emp (
    empno int  primary key,
    ename varchar(10),
    job varchar(9),
    hiredate date,
    sal decimal
);

2.2,编写与数据库对应的OV类(Emp.java)

package com.hcfly.vo;

import java.math.BigDecimal;
import java.util.Date;

public class Emp {
	private int empno;
	private String ename;
	private String job;
	private Date hiredate;
	private float sal;
	
	public int getEmpno() {
		return empno;
	}
	public void setEmpno(int empno) {
		this.empno = empno;
	}
	public String getEname() {
		return ename;
	}
	public void setEname(String ename) {
		this.ename = ename;
	}
	public String getJob() {
		return job;
	}
	public void setJob(String job) {
		this.job = job;
	}
	public Date getHiredate() {
		return hiredate;
	}
	public void setHiredate(Date hiredate) {
		this.hiredate = hiredate;
	}
	public float getSal() {
		return sal;
	}
	public void setSal(float sal) {
		this.sal = sal;
	}
}

2.3, 编写数据库连接类(DatabaseConnection.java)

这个地方可以将DatabaseConnection抽象为一个接口,并且用不同的数据库去实现它,来达到通用的水平。

package com.hcfly.dbc;

import java.sql.Connection;
import java.sql.DriverManager;

public class DatabaseConnection {
	// 数据库连接类
	private static final String DBDRIVER = "org.postgresql.Driver";
	private static final String DBURL = "jdbc:postgresql://localhost/jsp";
	private static final String DBUSER = "postgres";
	private static final String DBPASSWORD = "miaomiao";
	private Connection connection = null;
	
	public DatabaseConnection() throws Exception{
		try {
			Class.forName(DBDRIVER);
			this.connection = DriverManager.getConnection(DBURL, DBUSER, DBPASSWORD);
//			System.out.println("连接成功");
		} catch (Exception e) {
			throw e;
			// TODO: handle exception
		}
	
	}
	
	public Connection getConnection() {
		return this.connection;
	}
	
	public void close() throws Exception {
		if(this.connection != null) {
			try {
				this.connection.close();
			} catch (Exception e) {
				throw e;
				// TODO: handle exception
			}
		}
	}

}

2.4,定义DAO操作标准(IEmpDAO.java)

package com.hcfly.dao;

import java.util.List;

import com.hcfly.vo.Emp;

public interface IEmpDAO { // 定义DAO操作
	/**
	 * 定义DAO的标准操作
	 * 
	 */
	public boolean doCreate(Emp emp) throws Exception;
	/**
	 * @param emp要增加的数据对象
	 */
	public List<Emp> findAll(String keyWord) throws Exception;
	/**
	 * 根据查询关键字进行搜索
	 */
	public Emp findById(int empno) throws Exception;

}

2.5,真实主题实现类(EmpDAOImpl.java)

package com.hcfly.dao.impl;

import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.hcfly.dao.IEmpDAO;
import com.hcfly.vo.Emp;

public class EmpDAOImpl implements IEmpDAO{
	/**
	 * 真实主题类
	 */
	private Connection connection = null;
	private PreparedStatement pstmt = null;
	
	public EmpDAOImpl(Connection connection) {
		// 获取数据库连接
		this.connection = connection;
	}

	@Override
	public boolean doCreate(Emp emp) throws Exception {
		boolean flag = false;
		String sql = "INSERT INTO emp (empno, ename, job, hiredate, sal) VALUES (?,?,?,?,?)";
		this.pstmt = this.connection.prepareStatement(sql);
		this.pstmt.setInt(1, emp.getEmpno());
		this.pstmt.setString(2, emp.getEname());
		this.pstmt.setString(3, emp.getJob());
		this.pstmt.setDate(4, new Date(emp.getHiredate().getTime()));
		this.pstmt.setFloat(5, emp.getSal());
		
		if(this.pstmt.executeUpdate() > 0) {	// 更新记录行数大于1
			flag = true;
		}
		this.pstmt.close();
		return flag;
	}

	@Override
	public List<Emp> findAll(String keyWord) throws Exception {
		
		List<Emp> all = new ArrayList<Emp>();
		String sql = "SELECT empno, ename, job, hiredate, sal FROM emp WHERE ename LIKE ? OR job LIKE ?";
		this.pstmt = this.connection.prepareStatement(sql);
		this.pstmt.setString(1, "%"+keyWord +"%");
		this.pstmt.setString(2, "%"+keyWord +"%");
		ResultSet rSet = this.pstmt.executeQuery();
		Emp emp = null;
		while (rSet.next()) {
			emp = new Emp();
			emp.setEmpno(rSet.getInt("empno"));
			emp.setEname(rSet.getString("ename"));
			emp.setHiredate(rSet.getDate("hiredate"));
			emp.setJob(rSet.getString("job"));
			emp.setSal(rSet.getFloat("sal"));
			all.add(emp);
			
		}
		this.pstmt.close();
		// TODO Auto-generated method stub
		return all;
	}

	@Override
	public Emp findById(int empno) throws Exception {
		String sql = "SELECT empno, ename, job, hiredate, sal FROM emp WHERE empno=?";
		this.pstmt = this.connection.prepareStatement(sql);
		this.pstmt.setInt(1, empno);
		ResultSet rSet = this.pstmt.executeQuery();
		Emp emp = null;
		if(rSet.next()) {
			emp = new Emp();
			emp.setEmpno(rSet.getInt("empno"));
			emp.setEname(rSet.getString("ename"));
			emp.setHiredate(rSet.getDate("hiredate"));
			emp.setJob(rSet.getString("job"));
			emp.setSal(rSet.getFloat("sal"));
		}
		this.pstmt.close();
		// TODO Auto-generated method stub
		return emp;
	}

}

2.5,代理主题实现类(IEmpDAOProxy.java)

package com.hcfly.dao.proxy;

import java.util.List;

import com.hcfly.dao.IEmpDAO;
import com.hcfly.dao.impl.EmpDAOImpl;
import com.hcfly.dbc.DatabaseConnection;
import com.hcfly.vo.Emp;

public class EmpDAOProxy implements IEmpDAO{
	/**
	 * 代理主题实现类
	 */
	
	private DatabaseConnection dbc = null;
	private IEmpDAO dao = null;
	
	public EmpDAOProxy() throws Exception{
		this.dbc = new DatabaseConnection(); // 连接到数据库
		this.dao = new EmpDAOImpl(this.dbc.getConnection());
	}

	@Override
	public boolean doCreate(Emp emp) throws Exception {
		boolean flag = false;
		
		try {
			if(this.dao.findById(emp.getEmpno()) == null) {
				flag = this.dao.doCreate(emp);
			}
		} catch (Exception e) {
			throw e;
		}finally {	
			this.dbc.close();	// 无论是否成功,将连接关闭
		}
		// TODO Auto-generated method stub
		return flag;
	}

	@Override
	public List<Emp> findAll(String keyWord) throws Exception {
		List<Emp> all = null;
		try {
			all = this.dao.findAll(keyWord);
		} catch (Exception e) {
			throw e;
		} finally {
			this.dbc.close();
		}
		return all;
	}

	@Override
	public Emp findById(int empno) throws Exception {
		Emp emp = null;
		try {
			emp = this.dao.findById(empno);
		} catch (Exception e) {
			throw e;
		}finally {
			this.dbc.close();
		}
		return emp;
	}

}

2.6,DAO工厂类(DAOFactory.java)

package com.hcfly.factory;

import com.hcfly.dao.IEmpDAO;
import com.hcfly.dao.proxy.EmpDAOProxy;

public class DAOFactory {
	/**
	 * 工厂类
	 * @return
	 * @throws Exception
	 */
	public static IEmpDAO getIEmpDAOInstance() throws Exception{
		return new EmpDAOProxy();
	}
}

2.7,测试类(TestDAOInsert.java)

package com.hcfly.dao.test;

import java.util.Date;

import com.hcfly.factory.DAOFactory;
import com.hcfly.vo.Emp;

public class TestDAOInsert {

	public static void main(String[] args) throws Exception{
		// TODO Auto-generated method stub
		Emp emp = null;
		for(int x = 0; x < 5; x++) {
			emp = new Emp();
			emp.setEmpno(1000+x);
			emp.setEname("张憨憨" + x);
			emp.setJob("程序员 - " + x);
			emp.setHiredate(new Date());
			emp.setSal(500 * x);
//			DAOFactory.getIEmpDAOInstance().doCreate(emp);
			
		}
		System.out.println(DAOFactory.getIEmpDAOInstance().findById(1001));

	}

}

2.8,总结

DAO 只是提供了一个数据的操作平台,不管在Application还是Web程序中,此DAO程序都不用做修改。

3,DAO的web使用实例(开发工具为Ecplise,如果要运行,请先配置数据库)

从注册页面提交信息给数据库,然后读出来,展示到表格中。

3.1, 登录注册页面(增加数据表单)(emp_insert.jsp)

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>注册</title>
</head>
<body>
    <form action="emp_insert_do.jsp" method="post" >
        雇员编号:<input type="text" name="empno" id=""><br/>
        雇员姓名:<input type="text" name="ename" id=""><br/>
        雇员职位:<input type="text" name="job" id=""><br/>
        雇员日期:<input type="text" name="hiredate" id=""><br/>
        雇员工资:<input type="text" name="sal" id=""><br/>
        <input type="submit" value="注册">
        <input type="reset" value="重置">
    </form>
    <a href="emp_list.jsp">跳转到列表页面</a>
</body>
</html>

3.2, 处理数据页面(emp_insert_do.jsp)

<%@page import="com.hcfly.factory.DAOFactory"%>
<%@page import="java.text.SimpleDateFormat"%>
<%@page import="com.hcfly.vo.Emp"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>处理表单</title>
<%request.setCharacterEncoding("utf-8"); 
	response.setHeader("refresh", "3;URL=emp_list.jsp");	// 设置跳转时间为3秒
%>
</head>
<body>
<%
Emp emp = new Emp();
emp.setEmpno(Integer.parseInt(request.getParameter("empno")));
emp.setEname(request.getParameter("ename"));
emp.setJob(request.getParameter("job"));
emp.setHiredate(new SimpleDateFormat("yyyy-MM-dd").parse(request.getParameter("hiredate")));
emp.setSal(Float.parseFloat(request.getParameter("sal")));
try{
	if(DAOFactory.getIEmpDAOInstance().doCreate(emp)){
		out.print("<h3>雇员信息添加成功</h3>");
	}else{
		out.print("<h3>雇员信息添加失败</h3>");
	}
}catch(Exception e){
	e.printStackTrace();
}

%>
<h3>3秒后跳转到列表页</h3>
</body>
</html>

3.3,列表页面(emp_list.jsp)

<%@page import="com.hcfly.vo.Emp"%>
<%@page import="java.util.List"%>
<%@page import="org.apache.jasper.tagplugins.jstl.core.Catch"%>
<%@page import="java.util.Iterator"%>
<%@page import="com.hcfly.factory.DAOFactory"%>
<%@page import="java.util.Dictionary"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>列表</title>
<% request.setCharacterEncoding("utf-8"); %>
</head>
<body>
<%
	try{
		String keyWord = request.getParameter("kw");
		if(keyWord == null){
			keyWord = "";
		}
		List<Emp> all = DAOFactory.getIEmpDAOInstance().findAll(keyWord);
		Iterator<Emp> iter = all.iterator();
	
%>
<center>
        <form action="" method="post">
            <input type="text" name="kw">
            <input type="submit" value="查询">

        </form>
        <table border="1" width="80%">
            <tr>
                <td>雇员编号:</td>
                <td>雇员姓名:</td>
                <td>雇员工作:</td>
                <td>雇员工资:</td>
                <td>雇员日期:</td>
            </tr>
            <% while(iter.hasNext()){
            	Emp emp = iter.next();
            	
            	%>
            <tr>
                <td><%= emp.getEmpno() %></td>
                <td><%= emp.getEname() %></td>
                <td><%= emp.getJob() %></td>
                <td><%= emp.getSal() %></td>
                <td><%= emp.getHiredate() %></td>
            </tr>
            <%
            }
            %>
        </table>
        
        <a href="emp_insert.jsp">跳转到插入页面</a>

    </center>
    <%
    }catch(Exception e){
    	e.printStackTrace();
    }
    %>
</body>
</html>

3.4,结果展示

3.4.1 数据库

3.4.2,注册界面

3.4.3,列表页面

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使用DAO(数据访问对象)的设计模式,来开发了一个数据访问接口(PostgreSQL)。 使用JSP简单使用了这个接口。 客户层(Client)-> 显示层(jsp/servlet)-> 业务层(BO) -> 数据层(BAO) -> 资源层(DataBase) expand collapse
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