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
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>
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();
}
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="com.github.pagehelper.Page">
select * from employee
</select>
EmployeeController.java中新增findBypaging方法
@GetMapping("findBypaging")
public ResultMsg findByPaging(Integer pageNum, Integer pageSize){
PageHelper.startPage(pageNum,pageSize);
Page<Employee> data = employeeMapper.findByPaging();
JSONObject result = new JSONObject();
result.put("employees",data);
//获取页面总数
result.put("pages",data.getPages());
//获取数据总数
result.put("total",data.getTotal());
return ResultMsg.getMsg(result);
}
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
打开swagger,输入pageNum和pageSize,点击Try it out
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": ""
}
可以看到在spring boot中使用pageHealper插件进行分页查询很简单,包括如下3步:
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