SpringBoot is paired with the PageHelper paging plug-in

First, SpringBoot framework construction

[1] Go to File –> Module, choose Spring Initializr, and click the next one

[2] The options on this page are to select the boot dependencies required by SpringBoot. There are many options available here. Here, select Web and Mysql and click Next

[3] Save the path and click Finish

Second, the configuration

1. Introduce Pagehelper pagination in POM files

<! -- Paging plugin -->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.2.12</version>
</dependency>
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2. Configure the paging plug-in

Change the application.properties configuration file to the yml suffix, that is, application.yml, and perform the following configuration

spring:
  datasource:
    url: JDBC: mysql: / / 127.0.0.1:3306 / pagehelperdemodat? useUnicode=true&characterEncoding=UTF-8&serverTimezone=CST
    username: root
    password: 806188
    driver-class-name: com.mysql.cj.jdbc.Driver

  thymeleaf:
    prefix: classpath:/templates/
    check-template-location: true
    suffix: .html
    mode: HTML
    encoding: UTF-8
    cache: false

mybatis:
  mapper-locations: classpath*:mapper/*.xml

pagehelper:
  helper-dialect: mysql
  params: count=countSql
  reasonable: true
  support-methods-arguments: true
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Create a database

Let’s take the user database as an example to test, database creation is as follows:

CREATE DATABASE pagehelperdemodat;

USE pagehelperdemodat;

CREATE TABLE users(
    id INT PRIMARY KEY AUTO_INCREMENT COMMENT 'id primary key', 
    username VARCHAR(20) NOT NULL COMMENT 'Username'.PASSWORD  VARCHAR(20) NOT NULL COMMENT'User password'
);

INSERT INTO users (username,PASSWORD) VALUES("onestar"."123");
INSERT INTO users (username,PASSWORD) VALUES("twostar"."456");
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Insert multiple pieces of data to facilitate paging view

Third, code writing

Create User entity class: User

package com.star.entity;

/ * * *@Description: user entity class *@Author: ONESTAR
 * @Date: Created in 22:57 2020/3/27
 * @QQ: 316392836
 * @URL: http://122.51.28.187:8080/ * /
public class User {

    private Integer id;
    private String username;
    private String PASSWORD;

    public Integer getId(a) {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername(a) {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPASSWORD(a) {
        return PASSWORD;
    }

    public void setPASSWORD(String PASSWORD) {
        this.PASSWORD = PASSWORD;
    }

    @Override
    public String toString(a) {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\' ' +
                ", PASSWORD='" + PASSWORD + '\' ' +
                '} '; }}Copy the code

Create user persistence layer interface: UserDao

package com.star.dao;

import com.star.entity.User;
import org.apache.ibatis.annotations.Select;

import java.util.List;

/ * * *@Description: User persistence layer interface *@Author: ONESTAR
 * @Date: Created in 22:59 2020/3/27
 * @QQ: 316392836
 * @URL: http://122.51.28.187:8080/ * /
public interface UserDao {

    // Query all users
    @Select("select * from users")
    List<User> getAllUser(a);

}
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3. Create the business layer interface and implementation classes UserService and UserServiceImpl

package com.star.service;

import com.star.entity.User;

import java.util.List;

/ * * *@Description: User business layer interface *@Author: ONESTAR
 * @Date: Created in 23:04 2020/3/27
 * @QQ: 316392836
 * @URL: http://122.51.28.187:8080/ * /
public interface UserService {

    // Query all users
    List<User> getAllUser(a);
}
package com.star.service.impl;

import com.star.dao.UserDao;
import com.star.entity.User;
import com.star.service.UserService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

/ * * *@Description: User business layer interface implementation class *@Author: ONESTAR
 * @Date: Created in 23:06 2020/3/27
 * @QQ: 316392836
 * @URL: http://122.51.28.187:8080/ * /
@Service
public class UserServiceImpl implements UserService {

    @Resource
    UserDao userDao;


    @Override
    public List<User> getAllUser(a) {
        returnuserDao.getAllUser(); }}Copy the code

Create a user control layer: UserController

package com.star.controller;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.star.entity.User;
import com.star.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import java.util.List;

/ * * *@Description: User control layer *@Author: ONESTAR
 * @Date: Created in 23:07 2020/3/27
 * @QQ: 316392836
 * @URL: http://122.51.28.187:8080/ * /
@Controller
public class UserController {

    @Autowired
    UserService userService;

    @GetMapping("/findUser")
    public String findUser(Model model,@RequestParam(defaultValue = "1",value = "pageNum") Integer pageNum){
        PageHelper.startPage(pageNum,5);
        List<User> list = userService.getAllUser();
        PageInfo<User> pageInfo = new PageInfo<User>(list);
        model.addAttribute("pageInfo",pageInfo);
        return "index"; }}Copy the code

Pagehelper. startPage(int PageNum,int PageSize): pageHelper. startPage(int PageNum,int PageSize): this is used to set the position of the page and the number of data items to display. PageInfo is used to encapsulate the page information and return it to the foreground interface. Some PageInfo parameters:

/ / the current page
 private int pageNum;
 // Number of pages per page
 private int pageSize;
 // The number of current pages
 private int size;
 // The starting line of the data displayed on the current page
 private int startRow;
 // The end line of the data displayed on the current page
 private int endRow;
 // Total records - the number of pieces of data that need to be paged
 private long total;
 / / the total number of pages
 private int pages;
 // The result set of the page display, for example, the current page is to display 20 data, then the list is the 20 data
 private List<T> list;
 // The previous page number
 private int prePage;
 // Next page number
 private int nextPage;
 // If it is the first page, the default is false. If it is the first page, the default is true
 private boolean isFirstPage ;
 // Last page defaults to false, or true if it is the last page
 private boolean isLastPage ;
 // Whether there is a previous page, the default is false, if there is a previous page set to true
 private boolean hasPreviousPage ;
 // If there is a next page, the default is false and if there is a next page, the default is true
 private boolean hasNextPage ;
 // The number of navigation pages is the number of pages displayed on the page.
 // If there are two pages of data, set this value to 2
 private int navigatePages;
 // all navigation page numbers are [1,2]
 private int[] navigatepageNums;
 // The first page of the navigation bar
 private int navigateFirstPage;
 // The last page of the navigation bar
 private int navigateLastPage;
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5. Add MapperScan annotations

Add MapperScan annotations to the Application class.

package com.star;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan({"com.star.dao"})
public class PagehelperdemoApplication {

    public static void main(String[] args) { SpringApplication.run(PagehelperdemoApplication.class, args); }}Copy the code

6. Create the index.xml page

      
<html lang="en" xmlns:th="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="UTF-8">
    <title>Paging testing</title>
</head>
<body>
<H3>Querying All Users</H3>
    <table border="1">
        <tr>
            <th>id</th>
            <th>name</th>
            <th>password</th>
        </tr>
        <tr th:each="user:${pageInfo.list}">
            <td th:text="${user.id}"></td>
            <td th:text="${user.username}"></td>
            <td th:text="${user.PASSWORD}"></td>
        </tr>
    </table>
    <p>The current<span th:text="${pageInfo.pageNum}"></span>Page, the total<span th:text="${pageInfo.pages}"></span>Page,<span th:text="${pageInfo.total}"></span>records</p>
    <a th:href="@{/findUser}">Home page</a>
    <a th:href="@{/findUser(pageNum=${pageInfo.hasPreviousPage}? ${pageInfo.prePage}:1)}">The previous page</a>
    <a th:href="@{/findUser(pageNum=${pageInfo.hasNextPage}? ${pageInfo.nextPage}:${pageInfo.pages})}">The next page</a>
    <a th:href="@{/findUser(pageNum=${pageInfo.pages})}">back</a>
</body>
</html>

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4. Run tests

Enter http://localhost:8080/findUser start SpringBoot project, in the browser, you can see page displays user information table, click on the back page can switch on the page