分页插件--PageHelper

mybatis的分页查询可以通过PageHelper插件实现

在数据库中我们使用分页查询的sql语句为：
select * from 表名 [where 条件] limit (page-1)*pageSize, pageSize;
page: 当前页码
pageSize: 每页显示的条数。

但是当我们使用PageHelper插件后页码什么的都不用我们计算 我们可以通过直接使用它里面的函数得到我们想要的。如：总条数 总页数 当前页面呈现的数据

使用步骤:
第一步：在pom.xml中引入依赖

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

第二步:在conf.xml中设置PageHelper拦截器

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

注意：

第三步:在测试类(单元测试)中测试:

    @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:当前页 pageSize:每页显示几条数据
        PageHelper.startPage(1,2);
        List<User> user = userDao.findAll();
        PageInfo<User> pageInfo = new PageInfo<User>(user);
        System.out.println("总条数:"+pageInfo.getTotal());
        System.out.println("总页数:"+pageInfo.getPages());
        System.out.println("当前页码对应的数据:"+pageInfo.getList());
        session.close();
    }

数据库为:

/*
 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 '主键ID',
  `name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名',
  `pwd` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '密码',
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '邮箱',
  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, '张三', '123', '[email protected]');
INSERT INTO `tbl_user02` VALUES (7, '李四', '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;