Paging plug-in -- PageHelper

mybatis The paging query of can be passed through PageHelper Plug-in implementation

 In the database, we use paging query sql Statement for ：
select * from  Table name  [where  Conditions ] limit (page-1)*pageSize, pageSize;
page:  The current page number 
pageSize:  Number of entries per page .

But when we use PageHelper We don't need to calculate the page number after the plug-in We can get what we want by directly using the functions in it . Such as ： Total number of articles Total number of pages The data presented on the current page

Use steps :
First step ： stay pom.xml Introduce dependency in

<dependency>
            <groupId>repMaven.com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>5.3.0</version>
</dependency>

The second step : stay conf.xml Set in PageHelper Interceptor

<plugins>
        <plugin interceptor="com.github.pagehelper.PageInterceptor"></plugin>
</plugins>

Be careful ：

The third step : Testing class ( unit testing ) Medium test :

    @Test
    public void testFindAll() throws Exception{
    
        Reader rd = Resources.getResourceAsReader("conf.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(rd);
        SqlSession session = factory.openSession();
        UserDao userDao = session.getMapper(UserDao.class);
        //pageNum: The current page  pageSize: How many pieces of data are displayed per page 
        PageHelper.startPage(1,2);
        List<User> user = userDao.findAll();
        PageInfo<User> pageInfo = new PageInfo<User>(user);
        System.out.println(" Total number of articles :"+pageInfo.getTotal());
        System.out.println(" Total number of pages :"+pageInfo.getPages());
        System.out.println(" Data corresponding to the current page number :"+pageInfo.getList());
        session.close();
    }

The database for :

/*
 Navicat Premium Data Transfer

 Source Server         : Michinaish
 Source Server Type    : MySQL
 Source Server Version : 80011
 Source Host           : localhost:3306
 Source Schema         : mybatis

 Target Server Type    : MySQL
 Target Server Version : 80011
 File Encoding         : 65001

 Date: 06/06/2022 19:16:07
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for tbl_user02
-- ----------------------------
DROP TABLE IF EXISTS `tbl_user02`;
CREATE TABLE `tbl_user02`  (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT ' Primary key ID',
  `name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ' full name ',
  `pwd` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ' password ',
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ' mailbox ',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 8 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of tbl_user02
-- ----------------------------
INSERT INTO `tbl_user02` VALUES (6, ' Zhang San ', '123', '[email protected]');
INSERT INTO `tbl_user02` VALUES (7, ' Li Si ', '123', '[email protected]');
INSERT INTO `tbl_user02` VALUES (9, 'ac', '123', '[email protected]');
INSERT INTO `tbl_user02` VALUES (10, 'bc', '123', '[email protected]');
INSERT INTO `tbl_user02` VALUES (11, 'cc', '123', '[email protected]');
INSERT INTO `tbl_user02` VALUES (12, 'dc', '123', '[email protected]');

SET FOREIGN_KEY_CHECKS = 1;