SpringBoot+Mybatis实现分页查询[通俗易懂]

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文章目录

前言

分页查询是在web开发中常用的一种技术，当某个页面查询返回的数据量较大时，为了提高性能和用户体验不能将所有数据一次性返回给过前端，这时候就需要用到分页查询了

PageHelper是一款开源的Mybatis第三方物理分页插件，spring boot项目中集成PageHelper插件非常简单，下面将为大家详细介绍；

插件地址：https://github.com/pagehelper/Mybatis-PageHelper/blob/master/wikis/zh/HowToUse.md

1.引入依赖

在上一篇文章Mybatis 实现基本的增删改查 (基于Mybatis-generator插件方式)的基础上,在pom.xml中添加如下依赖：

        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
        </dependency>

2.Mapper中接口

在EmployeeMapper.java中新增findByPaging接口，接口返回类型为Page

public interface EmployeeMapper { 
   
    int deleteByPrimaryKey(Long id);

    int insert(Employee record);

    int insertSelective(Employee record);

    Employee selectByPrimaryKey(Long id);

    int updateByPrimaryKeySelective(Employee record);

    int updateByPrimaryKey(Employee record);

    Page<Employee> findByPaging(Map param);
}

3.修改XML文件

在EmployeeMapper.xml中添加上面接口对应Sql查询语句，可以看到使用插件的方式查询时，这里入参的类型为com.github.pagehelper.Page

  <select id="findByPaging" resultMap="BaseResultMap" parameterType="map">
    select
    *
    from employee
    where 1=1
    <if test="age != null">
      and age = #{age}
    </if>
  </select>

4.controller层调用接口

EmployeeController.java中新增findBypaging方法

   @ApiOperation(value = "分页查询")
    @GetMapping("findBypaging")
    public ResultMsg findByPaging(Integer age,Integer pageNum, Integer pageSize){ 
   
        PageHelper.startPage(pageNum,pageSize);
        Map param = new HashMap();
        param.put("age",age);
        Page<Employee> data = employeeMapper.findByPaging(param);
        JSONObject result = new JSONObject();
        result.put("employees",data);
        result.put("pages",data.getPages());
        result.put("total",data.getTotal());
        return ResultMsg.getMsg(result);
    }

ps:这里分页查询参数的传递方式和普通的查询是一样的，map的方式添加就可以了

5.测试

编写一个测试用例，向数据库中批量插入200个员工数据

@RunWith(SpringRunner.class)
@SpringBootTest
public class HrefApplicationTests { 
   
    @Autowired
    private EmployeeMapper employeeMapper;
    @Autowired
    private IdWorker idWorker;
    public static String getRandomStr(int length) { 
   
        String base = "abcdefghijklmnopqrstuvwxyz0123456789";
        int randomNum;
        char randomChar;
        Random random = new Random();
        // StringBuffer类型的可以append增加字符
        StringBuffer str = new StringBuffer();
        for (int i = 0; i < length; i++) { 
   
            // 可生成[0,n)之间的整数，获得随机位置
            randomNum = random.nextInt(base.length());
            // 获得随机位置对应的字符
            randomChar = base.charAt(randomNum);
            // 组成一个随机字符串
            str.append(randomChar);
        }
        return str.toString();
    }
    Employee createRadomEmployee()
    { 
   
        Employee employee = new Employee();
        employee.setAddress("北新街" + getRandomStr(5));
        employee.setAge("22");
        employee.setGender(new Short("1"));
        employee.setCreateTime(new Date());
        employee.setName(getRandomStr(10));
        employee.setId(idWorker.nextId());
        return employee;
    }
    @Test
    public void insertEmployees() { 
   
        for(int i=0;i<402;i++)
        { 
   
            employeeMapper.insert(createRadomEmployee());
        }
    }
}

执行后，看到测试数据已经建好

SpringBoot+Mybatis实现分页查询[通俗易懂]

打开swagger，输入pageNum和pageSize,点击Try it out

SpringBoot+Mybatis实现分页查询[通俗易懂]

返回结果如下：可以看到总数据为402，总页数为134,一共返回了3条数据

{ 
   
  "data": { 
   
    "total": "402",
    "pages": 134,
    "employees": [
      { 
   
        "address": "北新街4wf91",
        "age": "22",
        "createTime": 1558951333000,
        "deptId": 0,
        "gender": 0,
        "id": "317724116919799808",
        "name": "69wcpvii46"
      },
      { 
   
        "address": "北新街8voe8",
        "age": "22",
        "createTime": 1558951333000,
        "deptId": 0,
        "gender": 0,
        "id": "317724117007880192",
        "name": "9sicl9xer4"
      },
      { 
   
        "address": "北新街tbq90",
        "age": "22",
        "createTime": 1558951333000,
        "deptId": 0,
        "gender": 0,
        "id": "317724117309870080",
        "name": "u9zxm84sqo"
      }
    ]
  },
  "result": "SUCCESS",
  "resultCode": 200,
  "resultMsg": ""
}