基于maven采用MVC三层架构实现数据库数据显示到前端网页表单中。
文章目录
- 前言
- 一、数据库和实体类的建立
-
- 1.数据库的创建
- 2.实体类的创建
- 二、dao、service、servlet和前端jsp的编写
-
- 1.dao层
-
- 1.编写链接数据库、以及查询、更新、释放等代码
- 2.编写接口
- 2.service层
- 3.servlet层
- 3.jsp前端
- 二、运行截图
- 总结
前言
这里主要讲述一些采用mvc三层架构的方式，编写dao、service、servlet、前端jsp代码来实现提取数据库数据显示到前端网页表单中。这里以获取数据库中准考证信息为例子。
所用的编译器idea、基于maven的javaweb、服务器是tomcat、mysql版本8.0.22。
一、数据库和实体类的建立
1.数据库的创建
提示：这里只是示例我本人自己的数据库：
数据库名称、表名称、以及内容（示例）：
2.实体类的创建
StudentInfo.java代码如下（示例）：
package edu.login.pojo;
public class StudentInfo {
String name;
String candidate_number;
String id_number;
String gender;
String subject;
String address;
String time;
String seat;
String email;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCandidate_number() {
return candidate_number;
}
public void setCandidate_number(String candidate_number) {
this.candidate_number = candidate_number;
}
public String getId_number() {
return id_number;
}
public void setId_number(String id_number) {
this.id_number = id_number;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getSubject() {
return subject;
}
public void setSubject(String subject) {
this.subject = subject;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}
public String getSeat() {
return seat;
}
public void setSeat(String seat) {
this.seat = seat;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "StudentInfo{" +
"name='" + name + '\'' +
", candidate_number='" + candidate_number + '\'' +
", id_number='" + id_number + '\'' +
", gender='" + gender + '\'' +
", subject='" + subject + '\'' +
", address='" + address + '\'' +
", time='" + time + '\'' +
", seat='" + seat + '\'' +
", email='" + email + '\'' +
'}';
}
}
二、dao、service、servlet和前端jsp的编写
1.dao层
过程图示：
在编写dao层的时候，这里初始化连接参数,从配置文件里获得
创建db.properties文件如图
文件内容：
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/test?useSSL=false&serverTimezone=UTC&useUnicode=true&characterEncoding=utf8&characterSetResults=utf8
user=root
password=
filters=stat
initialSize=2
maxActive=300
maxWait=60000
timeBetweenEvictionRunsMillis=60000
minEvictableIdleTimeMillis=300000
validationQuery=SELECT 1
testWhileIdle=true
testOnBorrow=false
testOnReturn=false
poolPreparedStatements=false
maxPoolPreparedStatementPerConnectionSize=200
注意：
- driver，根据mysql的版本不同是不一样的，例如：如果是5.0的版本需要用，driver=“com.mysql.jdbc.Driver”
- url，选择本地数据库就行，这里的test是我的数据库名字，后面的“？&”这些链接的是来防止乱码问题的
- 本数据库root没有设置密码，所以我这里的password等于空
- 其余复制下来就行
1.编写链接数据库、以及查询、更新、释放等代码
创建BaseDao.java代码如下，用来链接数据库
package edu.login.dao;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
/**
* 操作数据库的基类--静态类
* @author Administrator
*
*/
public class BaseDao {
//静态代码块,在类加载的时候执行
static{
init();
}
private static String driver;
private static String url;
private static String user;
private static String password;
//初始化连接参数,从配置文件里获得
public static void init(){
Properties params=new Properties();
String configFile = "db.properties";
InputStream is= BaseDao.class.getClassLoader().getResourceAsStream(configFile);
try {
params.load(is);
} catch (IOException e) {
e.printStackTrace();
}
driver=params.getProperty("driver");
url=params.getProperty("url");
user=params.getProperty("user");
password=params.getProperty("password");
}
/**
* 获取数据库连接
* @return
*/
public static Connection getConnection(){
Connection connection = null;
try {
Class.forName(driver);
connection = DriverManager.getConnection(url, user, password);
System.out.println("suceess ");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return connection;
}
/**
* 查询操作
* @param connection
* @param pstm
* @param rs
* @param sql
* @param params
* @return
*/
public static ResultSet execute(Connection connection,PreparedStatement pstm,ResultSet rs,
String sql,Object[] params) throws Exception{
pstm = connection.prepareStatement(sql);
for(int i = 0; i < params.length; i++){
pstm.setObject(i+1, params[i]);
}
rs = pstm.executeQuery();
return rs;
}
/**
* 更新操作
* @param connection
* @param pstm
* @param sql
* @param params
* @return
* @throws Exception
*/
public static int execute(Connection connection,PreparedStatement pstm,
String sql,Object[] params) throws Exception{
int updateRows = 0;
pstm = connection.prepareStatement(sql);
for(int i = 0; i < params.length; i++){
pstm.setObject(i+1, params[i]);
}
updateRows = pstm.executeUpdate();
return updateRows;
}
/**
* 释放资源
* @param connection
* @param pstm
* @param rs
* @return
*/
public static boolean closeResource(Connection connection,PreparedStatement pstm,ResultSet rs){
boolean flag = true;
if(rs != null){
try {
rs.close();
rs = null;//GC回收
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
flag = false;
}
}
if(pstm != null){
try {
pstm.close();
pstm = null;//GC回收
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
flag = false;
}
}
if(connection != null){
try {
connection.close();
connection = null;//GC回收
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
flag = false;
}
}
return flag;
}
}
代码如下（示例）：
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import warnings
warnings.filterwarnings('ignore')
import ssl
ssl._create_default_https_context = ssl._create_unverified_context
2.编写接口
创建接口：UserDao.java
package edu.login.dao.user;
import edu.login.pojo.ScoreInfo;
import edu.login.pojo.StudentInfo;
import edu.login.pojo.User;
import java.sql.Connection;
public interface UserDao {
//获取学生准考证信息
public StudentInfo findAll(Connection connection ,String candidate_number) throws Exception;
}
实现接口里面的方法：UserDaoIml.java
package edu.login.dao.user;
import edu.login.dao.BaseDao;
import edu.login.pojo.ScoreInfo;
import edu.login.pojo.StudentInfo;
import edu.login.pojo.User;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class UserDaoIml implements UserDao {
@Override
public StudentInfo findAll(Connection connection, String candidate_number) throws Exception {
PreparedStatement pstm = null;//搭桥者
ResultSet rs = null;
StudentInfo studentInfo = null;
if (null != connection) {
String sql = "select * from t_admission_ticket where candidate_number=?";
Object[] params = {candidate_number};
rs = BaseDao.execute(connection, pstm, rs, sql, params);//得到结果集
if (rs.next()) {//把搜索到数据库中的内容读写到实体类中
studentInfo = new StudentInfo();
studentInfo.setName(rs.getString("name"));
studentInfo.setEmail(rs.getString("email"));
studentInfo.setSeat(rs.getString("seat"));
studentInfo.setTime(rs.getString("time"));
studentInfo.setAddress(rs.getString("address"));
studentInfo.setSubject(rs.getString("subject"));
studentInfo.setCandidate_number(rs.getString("candidate_number"));
studentInfo.setGender(rs.getString("gender"));
studentInfo.setId_number(rs.getString("id_number"));
}
BaseDao.closeResource(null, pstm, rs);
} else {
System.out.println("fail");
System.out.println("fail");
System.out.println("fail");
}
return studentInfo;
}
}
2.service层
过程图示：
创建接口：UserService.java
package edu.login.service.user;
import edu.login.pojo.ScoreInfo;
import edu.login.pojo.StudentInfo;
import edu.login.pojo.User;
public interface UserService {
//获取学生准考证信息
public StudentInfo FindAll(String candidate_number);
}
实现接口方法：UserServiceImpl.java
package edu.login.service.user;
import edu.login.dao.BaseDao;
import edu.login.dao.user.UserDao;
import edu.login.dao.user.UserDaoIml;
import edu.login.pojo.ScoreInfo;
import edu.login.pojo.StudentInfo;
import edu.login.pojo.User;
import java.sql.Connection;
import java.sql.SQLException;
public class UserServiceImpl implements UserService{
//业务层都会调用Dao层，所以要引入Dao层
private UserDao userDao;
public UserServiceImpl(){
userDao = new UserDaoIml();
}
@Override
public StudentInfo FindAll(String candidate_number) {
Connection connection = null;
StudentInfo studentInfos=null;
try {
connection = BaseDao.getConnection();
studentInfos= userDao.findAll(connection, candidate_number);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
BaseDao.closeResource(connection, null, null);
}
return studentInfos;
}
3.servlet层
过程图示：
ShowInfoServlet.java代码如下
这里把要查询的学号candidate_number静态设置为100101，也可以通过从req前端获取或者session获取。
package edu.login.servlet.user;
import edu.login.pojo.StudentInfo;
import edu.login.pojo.User;
import edu.login.service.user.UserService;
import edu.login.service.user.UserServiceImpl;
import edu.login.util.Constants;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class ShowInfoServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//调用service方法，进行用户匹配
UserService userService=new UserServiceImpl();
String candidate_number="10010";//这里的值可以从前端获取，可以从session里面获取，这里简单设置一下。
StudentInfo studentInfos=userService.FindAll(candidate_number);
System.out.println();
System.out.println(studentInfos);//后端验证
//把实体类转换成list
List<StudentInfo>StudentList= Collections.singletonList(studentInfos);
System.out.println();
System.out.println(StudentList);//后端验证
//将数据保存到数据域中
req.setAttribute("StudentList",StudentList);
//转发调转到准考证查询
req.getRequestDispatcher("showStudentInfo.jsp").forward(req,resp);
}
}
web,xml配置：
<servlet>
<servlet-name>ShowInfoServletservlet-name>
<servlet-class>edu.login.servlet.user.ShowInfoServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>ShowInfoServletservlet-name>
<url-pattern>/ShowInfo.dourl-pattern>
servlet-mapping>
3.jsp前端
这里我只显示直接前端jsp代码，因为实际上我加了许多css、js格式只为了美化表单。
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <div class="container">
<table class="table table-bordered table-hover">
<tr class="success">
<th>姓名</th>
<th>学号</th>
<th>身份证号</th>
<th>性别</th>
<th>考场</th>
<th>邮箱</th>
<th>数学</th>
<th>英语</th>
<th>专业课</th>
</tr>
<jsp:useBean id="ScoreList" scope="request" type="java.util.List"/>
<c:forEach var="li" items="${ScoreList}" varStatus="s">
<tr>
<!--切记不能用打写例如：li.Name-->
<td>${li.name}</td>
<td>${li.candidate_number}</td>
<td>${li.id_number}</td>
<td>${li.gender}</td>
<td>${li.address}</td>
<td>${li.email}</td>
<td>${li.math}</td>
<td>${li.english}</td>
<td>${li.scources}</td>
</tr>
</c:forEach>
</table>
</div>
二、运行截图
总结
愿自学的小伙伴们，今天依旧是收获满满的一天。