饭前点心:
该程序采用三层架构的模式实现对用户信息的增删改查,功能尚未完善,不过实现基本的要求应该是没问题的。
采用的数据库是 Mysql.
前置知识:
三层架构
三层架构流程(通过增加用户举例):
Code:
表示层前台:
index.jsp:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import = "java.util.List" %>
<%@ page import = "org.entity.Student" %>
Insert title here
<%
// 增加 一个标记,用作提示是否增加成功
String error = (String)request.getAttribute("error");
if(error != null ) {
if(error.equals("addError")){
out.print("增加失败");
} else if(error.equals("successAdd")){
out.print("增加成功");
}
}
%>
学号
姓名
年龄
性别
地址
操作
<%
// 后台通过 request 进行请求转发将所有用户传输到前台,通过 getAttribute(),setAttribute()可以添加请求中的信息
List students = (List)request.getAttribute("students");
for(Student student:students) {
%>
<%=student.getSno() %>
<%=student.getName()%>
<%=student.getAge() %>
<%=student.getSex() %>
<%=student.getSad() %>
删除
<%
}
%>
注册
studentInfo.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import = "org.entity.Student" %>
Insert title here
<%
// 获取从后台传过来的数据域(根据 Key 取 Value)
Student student = (Student)request.getAttribute("student");
%>
add.jsp:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
Insert title here
表示层后台(一个Servlet 对应一个功能):
AddStudentServlet.java:
package org.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.entity.Student;
import org.service.StudentService;
@WebServlet("/AddStudentServlet")
public class AddStudentServlet extends HttpServlet {
/*
* 增加用户
* 用户在前台输入信息,在Servlet中将用户信息封装成一个实体类
* 通过Service(业务逻辑层)将用户信息添加到数据库
*
* */
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 一定要设置成统一的编码
request.setCharacterEncoding("utf-8");
int sno = Integer.parseInt(request.getParameter("sno"));
String sname = request.getParameter("sname");
int age = Integer.parseInt(request.getParameter("sage"));
String sex = request.getParameter("ssex");
String address = request.getParameter("sad");
// 将用户信息封装成一个实体类,便于传递
Student student = new Student(sno,sname,age,sex,address);
// new 一个 StudentService 对象(业务逻辑层)
StudentService studentService = new StudentService();
// 调用方法实现增加用户的信息(在业务逻辑层实现逻辑,具体功能在 Dao 层实现)
boolean result = studentService.addStudent(student);
// 响应时编码问题进行统一
response.setContentType("text/html; charset=UTF-8");
response.setCharacterEncoding("utf-8");
if(!result) {
request.setAttribute("error", "addError");
} else {
request.setAttribute("error", "successAdd");
}
// 无论增加成功与失败都要将结果返回到前台,通过请求转发的形式,不会丢失数据
request.getRequestDispatcher("QueryAllStudentServlet").forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
DeleteStudentServlet.java
package org.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.service.StudentService;
@WebServlet("/DeleteStudentServlet")
public class DeleteStudentServlet extends HttpServlet {
/*
* 功能: 根据学号删除某个学生
*
* */
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
int sno = Integer.parseInt(request.getParameter("sno"));
StudentService studentService = new StudentService();
// 设置响应时编码
response.setContentType("text/html; charset=UTF-8");
response.setCharacterEncoding("utf-8");
boolean result = studentService.deleteStudent(sno);
if(result) {
response.getWriter().println("删除成功");
response.sendRedirect("QueryAllStudentServlet");
} else {
response.getWriter().println("删除失败");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
QueryAllStudentServlet:
package org.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.entity.Student;
import org.service.StudentService;
@WebServlet("/QueryAllStudentServlet")
public class QueryAllStudentServlet extends HttpServlet {
/*
* 功能:查询所有用户信息
* 所有用户肯定要用一个 List集合来存储
*
* */
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
StudentService studentService = new StudentService();
List students = studentService.queryAllStudents();
System.out.println(students);
// 将数据内容存在数据域中
request.setAttribute("students", students);
// 将数据内容通过跳转的方式传输到 index.jsp
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);
}
}
QueryStudentStudent.java
package org.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.entity.Student;
import org.service.StudentService;
@WebServlet("/QueryStudentStudent")
public class QueryStudentStudent extends HttpServlet {
/*
* 功能: 根据学号查询用户信息
*
* */
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
int no = Integer.parseInt(request.getParameter("sno"));
StudentService studentService = new StudentService();
Student student = studentService.queryStudentBySno(no);
System.out.println(student);
// 将用户的信息通过 request 进行请求转发的方式跳转到另一个页面
// 通过 setAttribute()方法增加请求信息,另一个页面通过前面的 key("student") 取到后面的 value
request.setAttribute("student",student);
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);
}
}
UpdateStudentServlet.java
package org.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.entity.Student;
import org.service.StudentService;
@WebServlet("/UpdateStudentServlet")
public class UpdateStudentServlet extends HttpServlet {
/*
* 功能: 根据用户的学号更新用户的其他信息
*
* */
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
int sno = Integer.parseInt(request.getParameter("sno"));
String name = request.getParameter("sname");
int age = Integer.parseInt(request.getParameter("sage"));
String sex = request.getParameter("ssex");
String sad = request.getParameter("sad");
// 将要修改的内容封装到一个实体类中
Student student = new Student(sno,name,age,sex,sad);
StudentService studentService = new StudentService();
// 设置响应时编码
response.setContentType("text/html; charset=UTF-8");
response.setCharacterEncoding("utf-8");
boolean result = studentService.updateStudent(sno, student);
if(result) {
response.getWriter().println("修改成功");
// 修改成功后返回到所有用户的界面
response.sendRedirect("QueryAllStudentServlet");
} 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);
}
}
业务逻辑层(Service):
StudentService.java
package org.service;
import java.util.List;
// 业务逻辑层
import org.dao.StudentDao;
import org.entity.Student;
/*
* 业务逻辑层:组合各种信息,返回给 Servlet
* 实现功能:
* 1、增加用户(增加用户之前需要先判断用户是否已经存在)
* 2、删除用户(删除用户之前需要先判断用户是否已经存在)
* 3、更新用户(更新用户之前需要先判断用户是否已经存在)
* 4、根据用户号查询用户信息
* 5、查询所有用户信息
* 具体来说,每一个功能都对应一个 Servlet。
* */
public class StudentService {
// 所有的具体功能都通过 StudentDao 进行实现
StudentDao stu = new StudentDao();
// 根据用户号查询用户信息
public Student queryStudentBySno(int sno) {
return stu.queryStudentBySno(sno);
}
// 查询所有用户信息
public List queryAllStudents() {
return stu.queryAllStudents();
}
// 更新用户(更新用户之前需要先判断用户是否已经存在)
public boolean updateStudent(int sno,Student student) {
if(stu.isExist(sno)) {
return stu.updateStudentBySno(sno, student);
}
return false;
}
// 删除用户(删除用户之前需要先判断用户是否已经存在)
public boolean deleteStudent(int sno) {
if(stu.isExist(sno)) {
return stu.deleteStudentBySno(sno);
}
return false;
}
// 增加用户(增加用户之前需要先判断用户是否已经存在)
public boolean addStudent(Student student) {
// 不存在时返回 true, 存在时返回false
if(!stu.isExist(student.getSno())) {
stu.addStudent(student);
return true;
} else {
return false;
}
}
}
数据访问(Dao 层):
package org.dao;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import org.entity.Student;
public class StudentDao {
private static final String URL = "jdbc:mysql://localhost:3306/sqltest";
private static final String User = "root";
private static final String Password = "root";
// 判断该用户是否存在
public boolean isExist(int sno) {
// 查询该学生的学号是否存在,存在就返回true,不存在则返回 false
return queryStudentBySno(sno) == null ? false : true;
}
// 添加新用户
public boolean addStudent(Student student) {
Connection conn = null;
PreparedStatement pstam = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(URL,User,Password);
String sql = "insert into student values (?,?,?,?,?)";
pstam = conn.prepareStatement(sql);
pstam.setInt(1, student.getSno());
pstam.setString(2, student.getName());
pstam.setInt(3, student.getAge());
pstam.setString(4,student.getSex());
pstam.setString(5, student.getSad());
int result = pstam.executeUpdate();
if(result > 0) return true;
else return false;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(pstam != null )
try {
pstam.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(conn != null )
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return false;
}
// 根据学生学号修改学生信息
public boolean updateStudentBySno(int sno,Student student) {
Connection conn = null;
PreparedStatement pstam = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(URL,User,Password);
String sql = "update student set sname = ?,sage = ?,ssex = ?,sad = ? where sno = ?";
pstam = conn.prepareStatement(sql);
pstam.setString(1, student.getName());
pstam.setInt(2, student.getAge());
pstam.setString(3,student.getSex());
pstam.setString(4,student.getSad());
pstam.setInt(5, sno);
int result = pstam.executeUpdate();
if(result > 0) return true;
else return false;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(pstam != null )
try {
pstam.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(conn != null )
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return false;
}
// 删除用户
public boolean deleteStudentBySno(int sno) {
Connection conn = null;
PreparedStatement pstam = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(URL,User,Password);
String sql = "delete from student where sno = ?";
pstam = conn.prepareStatement(sql);
pstam.setInt(1, sno);
int result = pstam.executeUpdate();
if(result > 0) return true;
else return false;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
} catch (Exception e) {
e.printStackTrace();
return false;
} finally {
if(pstam != null )
try {
pstam.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(conn != null )
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
// 查询所有用户
public List queryAllStudents() {
Connection conn = null;
PreparedStatement pstam = null;
ResultSet rs = null;
List students = new ArrayList<>();
Student student = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(URL,User,Password);
String sql = "select * from student";
pstam = conn.prepareStatement(sql);
rs = pstam.executeQuery();
while(rs.next()) {
int no = rs.getInt("sno");
String name = rs.getString("sname");
int age = rs.getInt("sage");
String sex = rs.getString("ssex");
String sad = rs.getString("sad");
// 将每个用户的信息封装成一个实体类,便于传递
student = new Student(no,name,age,sex,sad);
// 将每个用户添加到集合中进行返回
students.add(student);
}
return students;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(rs != null )
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(pstam != null )
try {
pstam.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(conn != null )
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
// 通过学号查询学生信息(返回值是一个学生,如果学生不存在返回 Null)
public Student queryStudentBySno(int sno) {
Connection conn = null;
PreparedStatement pstam = null;
ResultSet rs = null;
Student student = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(URL,User,Password);
String sql = "select * from student where sno = ?";
pstam = conn.prepareStatement(sql);
pstam.setInt(1, sno);
rs = pstam.executeQuery();
if(rs.next()) {
int no = rs.getInt("sno");
String name = rs.getString("sname");
int age = rs.getInt("sage");
String sex = rs.getString("ssex");
String sad = rs.getString("sad");
student = new Student(no,name,age,sex,sad);
return student;
} else {
return null;
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(rs != null )
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(pstam != null )
try {
pstam.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(conn != null )
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
}
实体类(用户封装用户信息):
package org.entity;
public class Student {
/* 实体类:对应 数据库中的一张表
*
* */
private int sno;
private String name;
private int age;
private String sex;
private String sad;
// 无参的构造
public Student() {
}
public Student(int sno, String name, int age, String sex, String sad) {
this.sno = sno;
this.name = name;
this.age = age;
this.sex = sex;
this.sad = sad;
}
public int getSno() {
return sno;
}
public void setSno(int sno) {
this.sno = sno;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getSad() {
return sad;
}
public void setSad(String sad) {
this.sad = sad;
}
@Override
public String toString() {
return "Student [sno=" + sno + ", name=" + name + ", age=" + age + ", sex=" + sex + ", sad=" + sad + "]";
}
}
客官勿踩坑:
运行改代码时首先访问的页面应该是 QueryAllStudent.java ,因为本系统首先映入眼帘的是各个用户的信息。
不过不用担心，QueryAllStudent.java 中会以请求转发的方式跳转到首页。
您也可以在 web.xml 中 将 QueryAllStudent 设置为第一个即可。
客官请看:
index:
studentinfo:
delete:
update:
add:
客官留步:
本人深知，该系统还有很多的 Bug 及不足,如需要源代码及文件包,请私信我。
客官有任何问题可以在下方留言,共同学习交流,交个朋友。
感谢您的光顾。