javaweb03
Javaweb03
使用DAO层对学生管理系统进行处理
1.准备工作
创建DAOUtil工具类，封装JDBC
package com.grg.util;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* @Author Grg
* @Date 2023/8/23 13:23
* @PackageName:com.grg.util
* @ClassName: DAOUtil
* @Description: 又是码代码的一天
* @Version plus max 宇宙无敌终极版本
*/
public class DAOUtil {
//消除魔法值
private static final String CLASSNAME = "com.mysql.cj.jdbc.Driver";
private static final String URL = "jdbc:mysql:///jdbctest";
private static final String USERNAME = "root";
private static final String PASSWORDS = "123456";
//加载驱动
static {
try {
Class.forName(CLASSNAME);
} catch (ClassNotFoundException e) {
throw new RuntimeException(e);
}
}
//建立连接
public static Connection getConnection() throws Exception {
return DriverManager.getConnection(URL, USERNAME, PASSWORDS);
}
//增删改
public static int executeUpdate(String sql,Object[] data){
Connection conn = null;
try {
conn = DAOUtil.getConnection();
PreparedStatement ps = conn.prepareStatement(sql);
for (int i = 0; i < data.length; i++) {
ps.setObject(i+1,data[i]);
}
return ps.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if(conn != null) {
conn.close();
}
}catch (Exception e){
e.printStackTrace();
}
}
return 0;
}
//查
public static List<Map<String,Object>> executeQuery(String sql, Object... arr){
List<Map<String,Object>> data = new ArrayList<>();
Connection conn = null;
try {
conn = DAOUtil.getConnection();
PreparedStatement ps = conn.prepareStatement(sql);
for (int i = 0; i < arr.length; i++) {
ps.setObject(i+1,arr[i]);
}
ResultSet set = ps.executeQuery();
int columnCount = set.getMetaData().getColumnCount();
while (set.next()){
HashMap<String, Object> map = new HashMap<>();
for( int i=0;i<columnCount;i++){
map.put( set.getMetaData().getColumnLabel(i+1) , set.getObject(i+1) );
}
data.add(map);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if(conn != null) {
conn.close();
}
}catch (Exception e){
e.printStackTrace();
}
}
return data;
}
}
创建学生类，当进行多参数传递时，利用对象传参
package com.grg.dto;
import java.io.Serializable;
/**
* @Author Grg
* @Date 2023/8/23 13:22
* @PackageName:com.grg.dto
* @ClassName: Student
* @Description: 又是码代码的一天
* @Version plus max 宇宙无敌终极版本
*/
public class Student implements Serializable {
private Integer id ;
private String name;
private Integer age;
private String address;
public Student(Integer id, String name, Integer age, String address) {
this.id = id;
this.name = name;
this.age = age;
this.address = address;
}
public Student() {
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "student{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", address='" + address + '\'' +
'}';
}
}
POM文件
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>StudentDAO</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>StudentDAO Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.33</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>taglibs</groupId>
<artifactId>standard</artifactId>
<version>1.1.2</version>
</dependency>
</dependencies>
<build>
<finalName>StudentDAO</finalName>
</build>
</project>
2.DAO
创建StudentDAO接口,其中写了所需要用到的方法
package com.grg.dao;
import com.grg.dto.Student;
import java.util.List;
import java.util.Map;
/**
* @Author Grg
* @Date 2023/8/23 13:20
* @PackageName:com.grg.dao
* @ClassName: StudentDAO
* @Description: 又是码代码的一天
* @Version plus max 宇宙无敌终极版本
*/
public interface StudentDAO {
/**
* 查询所有学生
* @return
*/
List<Map<String, Object>> listAllStudents();
/**
* 删除学生
* @param id
* @return
*/
int delStudentById(String id);
/**
* 添加学生
* @param s
* @return
*/
int addStudent(Student s);
/**
* 更新学生
* @param s
* @return
*/
int updateStudent(Student s);
/**
* 获取需要更新数据
* @param id
* @return
*/
List<Map<String, Object>> getStudentId(String id);
}
创建StudentDAOImpl实现类
package com.grg.dao.impl;
import com.grg.dao.StudentDAO;
import com.grg.dto.Student;
import com.grg.util.DAOUtil;
import java.util.List;
import java.util.Map;
/**
* @Author Grg
* @Date 2023/8/23 13:19
* @PackageName:com.grg.dao.impl
* @ClassName: studentDAOImpl
* @Description: 又是码代码的一天
* @Version plus max 宇宙无敌终极版本
*/
public class StudentDAOImpl implements StudentDAO {
@Override
public List<Map<String, Object>> listAllStudents() {
String sql = "select * from student";
return DAOUtil.executeQuery(sql);
}
@Override
public int delStudentById(String id) {
String sql = "delete from student where id = ?";
Object[] data = {id};
return DAOUtil.executeUpdate(sql, data);
}
@Override
public int addStudent(Student s) {
String sql = "insert into student values (null,?,?,?)";
Object[] data = {s.getName(), s.getAge(), s.getAddress()};
return DAOUtil.executeUpdate(sql, data);
}
@Override
public int updateStudent(Student s) {
String sql = "update student set name=?,age=?,address=? where id = ?";
Object[] data = { s.getName(), s.getAge(), s.getAddress(),s.getId()};
return DAOUtil.executeUpdate(sql, data);
}
@Override
public List<Map<String, Object>> getStudentId(String id) {
String sql = "select * from student where id = " + id;
return DAOUtil.executeQuery(sql);
}
}
3.Servlet
展示数据创建StudentServlet
@WebServlet("/stu")
public class StudentServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
StudentDAO studentDAO = new StudentDAOImpl();
//查找所有学生
List<Map<String, Object>> data = studentDAO.listAllStudents();
//传递
req.setAttribute("aaa",data);
req.getRequestDispatcher("student.jsp").forward(req,resp);
}
}
添加数据创建AddStuServlet
@WebServlet("/addStu")
public class AddStuServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.接收请求参数
req.setCharacterEncoding("UTF-8");
String name = req.getParameter("name");
String age = req.getParameter("age");
String address = req.getParameter("address");
//用student对象作为参数传递
Student student = new Student(null, name, Integer.parseInt(age), address);
StudentDAO studentDAO = new StudentDAOImpl();
int i = studentDAO.addStudent(student);
//传递
req.setAttribute("msg", i > 0 ? "添加成功" : "添加失败");
req.getRequestDispatcher("addStu.jsp").forward(req, resp);
}
}
删除数据创建DelStuServlet
@WebServlet("/delStu")
public class DelStuServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//接收参数
String id = req.getParameter("id");
//删除数据
StudentDAO studentDAO = new StudentDAOImpl();
int i = studentDAO.delStudentById(id);
//传递
req.getRequestDispatcher("stu").forward(req,resp);
}
}
修改数据创建ToUpdateServlet和UpdateStuServlet
@WebServlet("/toUpdate")
public class ToUpdateServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//接收参数
String id = req.getParameter("id");
//查询学生
StudentDAO studentDAO = new StudentDAOImpl();
List<Map<String, Object>> data = studentDAO.getStudentId(id);
//传递
if(data.size()>0){
req.setAttribute("student",data.get(0));
}
req.getRequestDispatcher("updateStu.jsp").forward(req,resp);
}
}
@WebServlet("/updateStu")
public class UpdateStuServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//接收参数
req.setCharacterEncoding("UTF-8");
String id = req.getParameter("id");
String name = req.getParameter("name");
String age = req.getParameter("age");
String address = req.getParameter("address");
//修改数据 使用student对象来传递参数
Student student = new Student(Integer.parseInt(id), name, Integer.parseInt(age), address);
StudentDAO studentDAO = new StudentDAOImpl();
int i = studentDAO.updateStudent(student);
//传递
req.setAttribute("msg", i>0 ? "修改成功" : "修改失败");
req.getRequestDispatcher("updateStu.jsp").forward(req,resp);
}
}
4.JSP
student.jsp
<%--
Created by IntelliJ IDEA.
User: asus
Date: 2023/8/23
Time: 13:39
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
Title
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
编号
姓名
年龄
住址
操作
${s.id}
${s.name}
${s.age}
${s.address}
修改
addStu.jsp
<%--
Created by IntelliJ IDEA.
User: asus
Date: 2023/8/23
Time: 13:41
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
Title