当请求的数据总量很大时,这时候前端往往都会要求后端将数据分页返回。本文介绍SpringBoot下后端数据层使用JPA+MySQL时,如何分页返回数据(除了当前页面的数据,往往还要返回总页数这项数据)。
Controller层:使用@RequestParam绑定page和pageSize参数,调用Service
Service层:
DAO层:
可以看到,自己实现分页还是比较麻烦的,不详细写具体代码了,重点介绍下一种方法:
Controller层:使用Pageable接收参数
@GetMapping("/byEnterprise")
public Response<PageVO<QuestionBankVO>> getQuestionBanksByEnterpriseId(@PageableDefault(page = 0, value = 6, sort = {"createdTime"}, direction = Sort.Direction.DESC) Pageable pageable) {
return ResponseFactory.okResponse(questionBankService.getQuestionBanksByEnterpriseId(pageable, 1));
}
Service层:利用DAO层获得的Page对象,可以获得当前页数据、总页数等信息
@Override
public PageVO<QuestionBankVO> getQuestionBanksByEnterpriseId(Pageable pageable, int enterpriseId) {
Page<QuestionBank> result = questionBankDao.findByEnterpriseIdAndDisabledFalse(pageable, enterpriseId);
List<QuestionBankVO> bankVOs = result.stream().map(b -> (QuestionBankVO) Converter.map(b, QuestionBankVO.class)).collect(Collectors.toList());
return new PageVO<>(pageable.getPageNumber(), result.getTotalPages(), bankVOs);
}
DAO层:传入Pageable,返回Page
public interface QuestionBankDao extends JpaRepository<QuestionBank, Integer> {
Page<QuestionBank> findByEnterpriseIdAndDisabledFalse(Pageable pageable, int enterpriseId);
}
自定义PageVO:
package com.yuantu.education.vo;
import lombok.Data;
import java.util.List;
/**
* @author deng
* @date 2018/12/13
*/
@Data
public class PageVO<T> {
private int currentPage;
private int totalPage;
private List<T> data;
public PageVO(){
super();
}
public PageVO(int currentPage, int totalPage, List<T> data) {
this.currentPage = currentPage;
this.totalPage = totalPage;
this.data = data;
}
}
如果使用Swagger2.8.0,此时Swagger不会自动显示出Pageable参数。
想要让Swagger2能够针对Pageable参数显示接口参数,增加如下配置即可:
package com.yuantu.education.config;
import com.fasterxml.classmate.TypeResolver;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.data.domain.Pageable;
import springfox.documentation.schema.AlternateTypeRule;
import springfox.documentation.schema.AlternateTypeRuleConvention;
import java.util.List;
import static com.google.common.collect.Lists.newArrayList;
import static springfox.documentation.schema.AlternateTypeRules.newRule;
@Configuration
@SuppressWarnings("SpringJavaAutowiringInspection")
public class PageableParamConfig {
@Bean
public AlternateTypeRuleConvention pageableConvention(final TypeResolver resolver) {
return new AlternateTypeRuleConvention() {
@Override
public int getOrder() {
return Ordered.LOWEST_PRECEDENCE;
}
@Override
public List<AlternateTypeRule> rules() {
return newArrayList(newRule(resolver.resolve(Pageable.class), resolver.resolve(Page.class)));
}
};
}
@ApiModel
@Data
static class Page {
@ApiModelProperty("第page页,从0开始计数")
private Integer page;
@ApiModelProperty("每页数据数量")
private Integer size;
@ApiModelProperty("按属性排序,格式:属性(,asc|desc)")
private List<String> sort;
}
}
Ps: Swagger2的配置学习自:http://blog.51cto.com/7308310/2082742
后话:方法二对JPA框架的依赖性很强(从Controller到Service到DAO都依赖JPA框架);而方法一仅仅在DAO层依赖JPA。比如以后如果因为需求变更而想将框架从JPA迁移至MyBatis的话,方法一只需要修改DAO层代码,而方法二则从头到尾全要改。