三層架構與 MVC 設計模式很類似。
三層步驟
1、前臺代碼獲取用戶數據
2、編寫與數據庫表機構對應的JavaBean
3、servlet 獲取用戶數據並組裝成 Javabean
4、編寫dao 的原子操作
5、service 創建dao對象，組裝dao原子，形成邏輯
6、servlet 創建service 對象， 把組裝好的Javabean傳入service
一、視圖層
前臺
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="AddStudentServlet" method = "post">
學號：<input type="text" name="sno"/><br/>
姓名：<input type="text" name="sname"/><br/>
年齡：<input type="text" name="sage"/><br/>
地址：<input type="text" name="saddress"/><br/>
<input type="submit" value = "新增"/><br/>
</form>
</body>
</html>
servlet
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.apache.jasper.tagplugins.jstl.core.Out;
import org.student.entity.Student;
import org.student.service.StudentService;
//視圖層後臺servlet
public class AddStudentServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
int no = Integer.parseInt(request.getParameter("sno"));
String name = request.getParameter("sname");
int age = Integer.parseInt(request.getParameter("sage"));
String address = request.getParameter("saddress");
//封裝實體類
Student student = new Student(no,name,age,address);
//servlet依賴於service層，需要調用service的函數
StudentService studentService = new StudentService();
boolean result = studentService.addStudent(student);
//設置響應編碼
response.setContentType("text/html; charset=UTF-8");
response.setCharacterEncoding("utf-8");
//jsp:out內置對象
PrintWriter out = response.getWriter();
if(result) {
out.println("增加成功！");
}else {
out.println("增加失敗！！");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
javabean
package org.student.entity;
public class Student {
private int sno;
private String sname;
private int sage;
private String 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;
}
public Student(int sno, String sname, int sage, String saddress) {
this.sno = sno;
this.sname = sname;
this.sage = sage;
this.saddress = saddress;
}
public Student( String sname, int sage, String saddress) {
this.sname = sname;
this.sage = sage;
this.saddress = saddress;
}
public Student(){
}
}
二、數據訪問層
dao層存在大量代碼相同，因此可以優化，此處不展示。
package org.student.dao;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.student.entity.Student;
//數據訪問層
public class StudentDao {
private final String URL="jdbc:mysql://120.76.156.19:3306/STD2017?useUnicode=true&characterEncoding=utf-8";
private final String USERNAME="STD2017";
private final String PASSWORD="STD20171QAZ";
//增加學生
public boolean addStudent(Student student) {
Connection connection = null;
PreparedStatement pstmt = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
String sql = "insert into student values(?,?,?,?)";
pstmt = connection.prepareStatement(sql);//預處理
pstmt.setInt(1, student.getSno());
pstmt.setString(2, student.getSname());
pstmt.setInt(3, student.getSage());
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();
}
}
}
//是否存在
public boolean isExist(int sno) {
return queryStudentBysno(sno)==null?false:true;
}
//根據學號查人
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);//預處理
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) {
e.printStackTrace();
}
}
}
}
三、業務邏輯層
package org.student.service;
import org.student.dao.StudentDao;
import org.student.entity.Student;
//業務邏輯層(簡單對dao層組裝)
public class StudentService {
//業務邏輯層依賴於dao層，需要dao層對象
StudentDao studentDao=new StudentDao();
//增加：查+ 增
public boolean addStudent(Student student) {
if(!studentDao.isExist(student.getSno() ) ) {
studentDao.addStudent(student);
return true;
}else {
System.out.println("此人已經存在!");
return false;
}
}
}
此案例只是簡單的案例，用於學習和理解。