mybaits-plus自定义分页查询

1. 引入依赖

在 pom.xml 文件中添加必要的依赖：

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.4.1</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

2. 配置文件

在 application.yml 文件中配置数据库连接信息：

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/your_database?useSSL=false&serverTimezone=UTC
    username: root
    password: your_password
    driver-class-name: com.mysql.cj.jdbc.Driver

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

3. 实体类

在 com.example.entity 包下创建 User.java：

package com.example.entity;

import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@Data
@TableName("user")
public class User {
    @TableId
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

4. Mapper 接口

在 com.example.mapper 包下创建 UserMapper.java：

package com.example.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.entity.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

public interface UserMapper extends BaseMapper<User> {
    IPage<User> selectPageVo(Page<?> page, @Param("age") Integer age);
}

5. XML 配置

在 resources/mapper 目录下创建 UserMapper.xml：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.example.mapper.UserMapper">
    <select id="selectPageVo" resultType="com.example.entity.User">
        SELECT *
        FROM user
        WHERE age = #{age}
    </select>
</mapper>

6. 服务接口

在 com.example.service 包下创建 IUserService.java：

package com.example.service;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.entity.User;

public interface IUserService {
    IPage<User> selectUserPage(Page<User> page, Integer age);
}

7. 服务实现类

在 com.example.service.impl 包下创建 UserServiceImpl.java：

package com.example.service.impl;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.entity.User;
import com.example.mapper.UserMapper;
import com.example.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements IUserService {
    @Autowired
    private UserMapper userMapper;

    @Override
    public IPage<User> selectUserPage(Page<User> page, Integer age) {
        return userMapper.selectPageVo(page, age);
    }
}

8. 控制器

在 com.example.controller 包下创建 UserController.java：

package com.example.controller;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.entity.User;
import com.example.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {
    @Autowired
    private IUserService userService;

    @GetMapping("/users")
    public IPage<User> getUsers(
            @RequestParam(name = "page", defaultValue = "1") int page,
            @RequestParam(name = "size", defaultValue = "10") int size,
            @RequestParam(name = "age", required = false) Integer age) {
        Page<User> userPage = new Page<>(page, size);
        return userService.selectUserPage(userPage, age);
    }
}

9. 应用程序启动类

在 com.example 包下创建 MyApplication.java：

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

10. 启动和测试

启动 Spring Boot 应用程序，访问 http://localhost:8080/users?page=1&size=10&age=25 以测试分页查询功能。