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  2. 三层架构定义及代码（二）

三层架构定义及代码（二）

由 邮差的信 提交于 2020-01-21 02:26:41

这是对上一个三层架构定义及代码（二）后面例子的完善，
之前例子只有增加功能，现在一步步完善全部功能，但是代码已经全部写完了，只能一步步整理整个过程。

目录

项目目录图示

在这里插入图片描述

一. 目的及实现情况

设计一个对学生的增删改查

1.1. index.jsp

在这里插入图片描述

1.2. add.jsp

在这里插入图片描述

1.3. studentInfo.jsp

在这里插入图片描述

1.4. 基本流程

index.jsp 展示基础信息，点击删除按钮直接删除对应学号的信息，并自动刷新；
点击新增链接跳转到add.jsp，增加后返回index.jsp，并提示增加成功与否；
点击学号超链接，进入对应学号的全部信息页面studentInfo.jsp，可以修改除学号之外的所有，修改后返回首页。

二. 项目接口与实现类规范

2.1. 基本规范

  1. 建议面向接口开发：先接口-再实现类
  2. 加入接口的地方：ervice、dao加入接口
接口起名形式 例如 位于的包名 对应类起名形式 例如 位于的包名
I实体类Service（Service） IStudentService xxx.service 实体类ServiceImpl StudentServiceImpl xx.dao
I实体类Dao（Dao） IStudentDao xxx.service.impl 实体类DaoImpl StudentDaoImpl xx.dao.impl
  1. 代码规范：
    以后使用接口/实现类时，推荐写法：
    接口 x = new 实现类()
    IStudentDao studentDao = new StudentDaoImpl();

2.2. IStudentDao.java接口

Dao层与Service层都对应接口

package org.student.dao;

import java.util.List;

import org.student.entity.Student;

public interface IStudentDao {
	//删除学生，根据学号删除学生
		public boolean deleteStudentBysno(int sno) ;	
//		修改学生,根据学号，修改学生信息
		public boolean updateStudentBysno(int sno,Student student) ;
//		添加学生
		public boolean addStudent(Student student) ;
//		通过学号，返回学生是否存在
		public boolean isExist(int sno) ;
//		查询全部学生,返回的是一个集合
		public List<Student> queryAllStudents() ;
//		根据姓名查询
		
//		根据年龄查
		
//		通过学号，返回学生
		public Student queryStudentBysno(int sno) ;	
}

三. IStudentService.java接口

package org.student.service;

import java.util.List;
import org.student.entity.Student;

public interface IStudentService {
//	根据学号查学生
	public Student queryStudentBySno(int sno) ;
//	查询全部学生
	public List<Student> queryAllStudents() ;
//	改
	public boolean updeteStudentBySno(int sno,Student student) ;
//	删除
	public boolean deleteStudentBySno(int sno) ;
//	增加学生
	public boolean addstudent(Student student) ;
}

四. Servlet类实现

  1. 每一个功能，对应一个servlet
  2. 现在有增删改查（查全部，查一个），所以对应5个servlet
  3. AddStudentServlet
  4. DeleteStudentServlet
  5. UpdateStudentServlet
  6. QueryAllStudentServlet
  7. QueryStudentBySnoServlet

五. Servlet类功能验证(不需前端)

  1. 页面的跳转都会跳转到对应的 /xxxServlet，直接在后面写上对应的传入数据，通过打印，验证功能的实现
  2. ? = &
  3. http://localhost:8080/ThreeTierSample/AddStudentServlet
  4. http://localhost:8080/ThreeTierSample/DeleteStudentServlet?sno=3
  5. http://localhost:8080/ThreeTierSample/UpdateStudentServlet?sno=2&sname=李四&sage=55&saddress=中国
  6. http://localhost:8080/ThreeTierSample/QueryAllStudentServlet
  7. http://localhost:8080/ThreeTierSample/QueryStudentBySnoServlet?sno=1

六. 流程解释

  1. index.jsp总是在QueryAllStudentServlet执行后，在获取数据展示，所以应该先执行QueryAllStudentServlet，在跳转到index.jsp。
  2. 解决：在启动时先执行QueryAllStudentServlet，修改Web.xml
    <welcome-file>QueryAllStudentServlet</welcome-file>
  3. QueryAllStudentServlet在最后通过请求转发到index.jsp页面
  4. 许多Servlet在最后都需要跳转到QueryAllStudentServlet，重新执行查询全部，传入值，在跳转到index.jsp
  5. 对于判断是否增加成功，删除成功，修改成功；就针对是否增加成功来说：分三种情况，1.直接访问首页 2.删除成功返回首页 3.删除失败返回首页，所以在DeleteStudentServlet中要设置标志位，对于删除成功，失败设置不同标志位：
			if (!result) {  //增加失败  
//				加入标识符
				request.setAttribute("error", "addError");
			}else {
				request.setAttribute("error", "noAddError");
			}
			request.getRequestDispatcher("QueryAllStudentServlet").forward(request, response);

在首页获取代码：

<%
				//  1.增加失败 	2.增加成功	3.直接访问查询全部页面
				String error = (String)request.getAttribute("error");
		      //  在不是直接访问查询全部页面情况下  进入判断,否则不提示
				if(error != null){
					if(error.equals("addError")){  //增加失败
						out.print("增加失败");
					}else{
						out.print("增加成功");
					}
				}
		%>

七. 具体代码

7.1. index.jsp

<body>
		<%
				//  1.增加失败 	2.增加成功	3.直接访问查询全部页面
				String error = (String)request.getAttribute("error");
		      //  在不是直接访问查询全部页面情况下  进入判断,否则不提示
				if(error != null){
					if(error.equals("addError")){  //增加失败
						out.print("增加失败");
					}else{
						out.print("增加成功");
					}
				}
		%>

	<table border = "1px">
		<tr>
				<th>学号</th>
				<th>姓名</th>
				<th>年龄</th>		
				<th>操作</th>	
		</tr>
		<%
		// 从QueryAllStudentServlet跳转过来的（在xml里改过了），
		//需要先查询，再显示数据，因为这里要获取数据
		
		// 获取request域里的数据,Object类型转换
		List<Student> students = (List<Student>) request.getAttribute("students");
		for(Student student : students ){
			%>
					<tr>
					<!-- 学号跳转查询此人信息 -->
						<th><a href="QueryStudentBySnoServlet?sno=<%=student.getSno() %>"><%=student.getSno() %></a></th>
						<th><%=student.getSname() %></th>
						<th><%=student.getSage() %></th>
						<th><a href="DeleteStudentServlet?sno=<%=student.getSno() %>">删除</a></th>
					</tr>
				<%	
		}
		%>
		
	</table>
<a href="add.jsp">新增</a>
</body>

7.2. studentInfo.jsp

<body>
		<%
			Student student = (Student) request.getAttribute("student");
		%>
		<!-- 通过表单展示，易于修改 -->
		<form action="UpdateStudentServlet">
		<!-- readonly 不可改 -->
			学号：<input type="text" name="sno" value="<%=student.getSno()%>" readonly="readonly"/><br/>
			姓名：<input type="text" name="sname" value="<%=student.getSname()%>"/><br/>
			年龄：<input type="text" name="sage" value="<%=student.getSage()%>"/><br/>
			地址：<input type="text" name="saddress" value="<%=student.getSaddress()%>"/><br/>
			<input type="submit" value="修改"/>
			<a href="QueryAllStudentServlet">返回</a>
		</form>
</body>

7.3. add.jsp

<body>
	<form action="AddStudentServlet"  method="post">
			学号：<input type = "text" name = "sno" /> <br/>
			姓名：<input type = "text" name = "sname" /> <br/>
			年龄：<input type = "text" name = "sage" /> <br/>
			地址：<input type = "text" name = "saddress" /> <br/>
			<input type = "submit" value="新增" /> <br/>
	</form>
</body>

7.4. AddStudentServlet.java

package org.student.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.student.entity.Student;
import org.student.service.IStudentService;
import org.student.service.impl.StudentServiceImpl;

public class AddStudentServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8"); //请求编码
		
			int no = Integer.parseInt(request.getParameter("sno"));
			String name = request.getParameter("sname");
			int age = Integer.parseInt(request.getParameter("sage"));
			String address = request.getParameter("saddress");
			
			Student student = new Student(no,name,age,address);
			
//			接口 X = new 实现类();
			IStudentService studentService = new StudentServiceImpl();
			
			boolean result = studentService.addstudent(student);
//			1.先设置响应编码 
			response.setContentType("text/html; charset=UTF-8"); 
			response.setCharacterEncoding("utf-8");
//			2. 再响应     ----------注意1,2先后顺序
			PrintWriter out = response.getWriter();   //响应对象
			if (!result) {  //增加失败  
//				加入标识符
				request.setAttribute("error", "addError");
			}else {
				request.setAttribute("error", "noAddError");
			}
			request.getRequestDispatcher("QueryAllStudentServlet").forward(request, response);
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doGet(request, response);
	}
}

7.5. DeleteStudentServlet .java

package org.student.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.student.service.IStudentService;
import org.student.service.impl.StudentServiceImpl;

public class DeleteStudentServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//  删除
		request.setCharacterEncoding("utf-8");
//		接收传过来的学号
		int sno = Integer.parseInt(request.getParameter("sno"));
		IStudentService service = new StudentServiceImpl();
		boolean result = service.deleteStudentBySno(sno);
//		1.先设置响应编码 
		response.setContentType("text/html; charset=UTF-8"); 
		response.setCharacterEncoding("utf-8");
//		2. 再响应     ----------注意1,2先后顺序
		PrintWriter out = response.getWriter();   //响应对象
		if (result) {
//			response.getWriter().println("删除成功");  //跳转太快，没有用
			response.sendRedirect("QueryAllStudentServlet"); //重新查询全部
		}else {
			response.getWriter().println("删除失败");
		}
	}
	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
			this.doGet(request, response);
	}
}

7.6. QueryAllStudentServlet .java

package org.student.servlet;

import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.student.entity.Student;
import org.student.service.IStudentService;
import org.student.service.impl.StudentServiceImpl;

public class QueryAllStudentServlet extends HttpServlet {
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		
		IStudentService service = new StudentServiceImpl();
		List<Student> students = service.queryAllStudents();
		System.out.println(students);
//		存入数据
		request.setAttribute("students", students);
//		因为request中有数据，通过请求转发（重定向丢失request），跳转到index.jsp显示数据
		request.getRequestDispatcher("index.jsp").forward(request, response);
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
}

7.7. QueryStudentBySnoServlet .java

package org.student.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.student.entity.Student;
import org.student.service.IStudentService;
import org.student.service.impl.StudentServiceImpl;

public class QueryStudentBySnoServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	request.setCharacterEncoding("utf-8");
	int sno = Integer.parseInt(request.getParameter("sno"));
	IStudentService service = new StudentServiceImpl();
	Student student = service.queryStudentBySno(sno);
	System.out.println(student);
//	将此人的数据通过前台jsp显示 ---studentInfo.jsp
	request.setAttribute("student", student);  //放信息
//	如果request域没有数据，使用重定向跳转respose.sendRedirect()
//	如果request域有数据(request.setArrribute()),使用请求转发跳转
	request.getRequestDispatcher("studentInfo.jsp").forward(request, response);
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

7.8. UpdateStudentServlet .java

package org.student.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.student.entity.Student;
import org.student.service.IStudentService;
import org.student.service.impl.StudentServiceImpl;

public class UpdateStudentServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//  修改
			request.setCharacterEncoding("utf-8");
//			接收传过来的学号
			int sno = Integer.parseInt(request.getParameter("sno"));
			String sname = request.getParameter("sname");
			int sage = Integer.parseInt(request.getParameter("sage"));
			String saddress = request.getParameter("saddress");
//			封装到javaBean
			Student student = new Student(sname, sage, saddress);
			
			IStudentService service = new StudentServiceImpl();
			boolean result = service.updeteStudentBySno(sno, student);
//			1.先设置响应编码 
			response.setContentType("text/html; charset=UTF-8"); 
			response.setCharacterEncoding("utf-8");
//			2. 再响应     ----------注意1,2先后顺序
			PrintWriter out = response.getWriter();   //响应对象
			if (result) {
//				response.getWriter().println("修改成功");
				response.sendRedirect("QueryAllStudentServlet"); //重新查询全部
			}else {
				response.getWriter().println("修改失败");
			}
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

7.9. StudentDaoImpl .java

package org.student.dao.impl;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.LinkedList;
import java.util.List;

import org.student.dao.IStudentDao;
import org.student.entity.Student;

//数据访问层 ：原子性的增删改查
public class StudentDaoImpl implements IStudentDao{
	private final String URL = "jdbc:mysql://localhost:3306/mvc";
	private final String USERNAME = "root";
	private final String PASSWORD = "root";
//删除学生，根据学号删除学生
	public boolean deleteStudentBysno(int sno) { 
		PreparedStatement pstmt = null;
		Connection connection = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
			String sql = "delete from student where sno=?";
			pstmt = connection.prepareStatement(sql);
			pstmt.setInt(1, sno);
			int count = pstmt.executeUpdate();
			if (count >0 ) {
				return true;
			}else {
				return false;
			}
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
			return false;
		} catch (SQLException e) {
			e.printStackTrace();
			return false;
		}catch (Exception e) {
			e.printStackTrace();
			return false;
		}finally {
			try {
				if (pstmt != null) pstmt.close();
				if (connection != null) connection.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
	
//	修改学生,根据学号，修改学生信息
		public boolean updateStudentBysno(int sno,Student student) { 
			PreparedStatement pstmt = null;
			Connection connection = null;
			try {
				Class.forName("com.mysql.jdbc.Driver");
				connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
				String sql = "update  student set sname = ?  , sage = ? , saddress = ? where sno = ?";
				pstmt = connection.prepareStatement(sql);
//				修改后的值
				pstmt.setString(1, student.getSname());
				pstmt.setInt(2, student.getSage());
				pstmt.setString(3, student.getSaddress());
//				要修改的学号
			    pstmt.setInt(4, sno);
				int count = pstmt.executeUpdate();
				if (count >0 ) {
					return true;
				}else {
					return false;
				}
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
				return false;
			} catch (SQLException e) {
				e.printStackTrace();
				return false;
			}catch (Exception e) {
				e.printStackTrace();
				return false;
			}finally {
				try {
					if (pstmt != null) pstmt.close();
					if (connection != null) connection.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
	
//	添加学生
	public boolean addStudent(Student student) { // zs 23 xm
		PreparedStatement pstmt = null;
		Connection connection = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
			String sql = "insert into student(sno,sname,sage,saddress) values(?,?,?,?)";
			pstmt = connection.prepareStatement(sql);
			pstmt.setInt(1, student.getSno());
			pstmt.setString(2, student.getSname());
			pstmt.setInt(3, student.getSno());
			pstmt.setString(4, student.getSaddress());
			int count = pstmt.executeUpdate();
			if (count >0 ) {
				return true;
			}else {
				return false;
			}
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
			return false;
		} catch (SQLException e) {
			e.printStackTrace();
			return false;
		}catch (Exception e) {
			e.printStackTrace();
			return false;
		}finally {
			try {
				if (pstmt != null) pstmt.close();
				if (connection != null) connection.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
//	通过学号，返回学生是否存在
	public boolean isExist(int sno) {  // true:存在   false:不存在
		return queryStudentBysno(sno) == null ? false : true;
	}
//	查询全部学生,返回的是一个集合
	public List<Student> queryAllStudents() {
		List<Student> students = new LinkedList<Student>();
		Student student = null;
		Connection connection = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
			String sql = "select * from student ";
			pstmt = connection.prepareStatement(sql);
			rs = pstmt.executeQuery();
			while(rs.next()) {
				int no = rs.getInt("sno");
				String name = rs.getString("sname");
				int age = rs.getInt("sage");
				String address = rs.getString("saddress");
				student = new Student(no, name, age,address);
				students.add(student);
			}
			return students;
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
			return null;
		} catch (SQLException e) {
			e.printStackTrace();
			return null;
		}catch (Exception e) {
			e.printStackTrace();
			return null;
		}finally {
			try {
				if (rs != null) rs.close();
				if (pstmt != null) pstmt.close();
				if (connection != null) connection.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
//	根据姓名查询
//	根据年龄查
//	通过学号，返回学生
	public Student queryStudentBysno(int sno) {
		Student student = null;
		Connection connection = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
			String sql = "select * from student where sno = ?";
			pstmt = connection.prepareStatement(sql);
			pstmt.setInt(1, sno);
			rs = pstmt.executeQuery();
			if (rs.next()) {
				int no = rs.getInt("sno");
				String name = rs.getString("sname");
				int age = rs.getInt("sage");
				String address = rs.getString("saddress");
				student = new Student(no, name, age,address);
			}
			return student;
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
			return null;
		} catch (SQLException e) {
			e.printStackTrace();
			return null;
		}catch (Exception e) {
			e.printStackTrace();
			return null;
		}finally {
			try {
				if (rs != null) rs.close();
				if (pstmt != null) pstmt.close();
				if (connection != null) connection.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

7.10. StudentServiceImpl .java

package org.student.service.impl;

import java.util.List;
import org.student.dao.IStudentDao;
import org.student.dao.impl.StudentDaoImpl;
import org.student.entity.Student;
import org.student.service.IStudentService;

// 业务逻辑层：逻辑性增删改查（ 增：查+增）,对dao层进行组装
public class StudentServiceImpl implements IStudentService{
		IStudentDao studentDao = new StudentDaoImpl();
//		根据学号查学生
		public Student queryStudentBySno(int sno) {
			return studentDao.queryStudentBysno(sno);
		}
//		查询全部学生
		public List<Student> queryAllStudents() {
				return studentDao.queryAllStudents();      
		}
//		改
		public boolean updeteStudentBySno(int sno,Student student) {
			if (studentDao.isExist(sno)) { //存在
				studentDao.updateStudentBysno(sno, student);       //改
				return true;      // 返回true
			}
				return false;
		}
//		删除
		public boolean deleteStudentBySno(int sno) {
			if (studentDao.isExist(sno)) { //存在
				studentDao.deleteStudentBysno(sno);       //删
				return true;      // 返回true
			}
				return false;
		}
//		增加学生
		public boolean addstudent(Student student) {
			if (!studentDao.isExist(student.getSno())) {  //不存在
				studentDao.addStudent(student);      // 进行添加
				return true;
			}else {
				System.out.println("此人已经存在");
				return false;
			}
		}
}

7.11. Student .java

package org.student.entity;

public class Student {
private int sno;
private String sname;
private int sage;
private String saddress;

public Student() {
}
public Student( String sname, int sage, String saddress) {
	super();
	this.sname = sname;
	this.sage = sage;
	this.saddress = saddress;
}
public Student(int sno, String sname, int sage, String saddress) {
	super();
	this.sno = sno;
	this.sname = sname;
	this.sage = sage;
	this.saddress = saddress;
}

@Override
public String toString() {
	return "Student [sno=" + sno + ", sname=" + sname + ", sage=" + sage + ", saddress=" + saddress + "]";
}
public int getSno() {
	return sno;
}
public void setSno(int sno) {
	this.sno = sno;
}
public String getSname() {
	return sname;
}
public void setSname(String sname) {
	this.sname = sname;
}
public int getSage() {
	return sage;
}
public void setSage(int sage) {
	this.sage = sage;
}
public String getSaddress() {
	return saddress;
}
public void setSaddress(String saddress) {
	this.saddress = saddress;
}

}
标签
三层架构
实体类
接口
dao
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