spring-cloud传递分页查询

服务提供者使用Pageable传递分页请求, 使用Page<T>传递分页结果
在接口中加入Pageable对象, mvc会接收如下参数: (所有参数均为可选项)

• Integer page
  页码, 第一页为0
• Integer size
  每页数据量
• List<String> sort
  排序规则,字符串格式是 property[, direction], 例如 "datetime, DESC", 可以使用多值参数传递多个排序

可以使用@PageableDefault表明默认参数

@GetMapping("/countries")
public Page<Country> listCountry(@RequestParam(required = false) String continent,
                                 @PageableDefault(page = 0, size = 10) Pageable pageable) {

如果想让swagger识别Pageable对象, 需要加入以下配置:

/**
 * swagger不会自动解析Pageable, 需要加入以下配置
 */
@Configuration
public static class SpringDataConfiguration {
    @Bean
    public AlternateTypeRuleConvention pageableConvention(final TypeResolver resolver) {
        return new AlternateTypeRuleConvention() {
            @Override
            public int getOrder() {
                return Ordered.HIGHEST_PRECEDENCE;
            }

            @Override
            public List<AlternateTypeRule> rules() {
                return newArrayList(AlternateTypeRules.newRule(resolver.resolve(Pageable.class), resolver.resolve(Page.class)));
            }
        };
    }

    @ApiModel
    @Data
    static class Page {
        @ApiModelProperty(position = 0, value = "页码,第一页为0")
        private Integer page;

        @ApiModelProperty(position = 1, value = "每页的数据量")
        private Integer size;

        @ApiModelProperty(position = 2, value = "排序字段,可以是多个, 格式为\"{属性}[,{方向}]\"", example = "createDatetime, DESC")
        private List<String> sort;
    }
}

使用RestTemplate访问的时候, 无法解析Page或者PageImpl对象, 报错:

Can not construct instance of org.springframework.data.domain.Page: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information

一个解决方法是继承一个带默认构造函数的具体类:

public class RestPageImpl<T> extends PageImpl<T> {

    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
    public RestPageImpl(@JsonProperty("content") List<T> content,
                        @JsonProperty("number") int page,
                        @JsonProperty("size") int size,
                        @JsonProperty("totalElements") long total) {
        super(content, new PageRequest(page, size), total);
    }

    public RestPageImpl(List<T> content, Pageable pageable, long total) {
        super(content, pageable, total);
    }

    public RestPageImpl(List<T> content) {
        super(content);
    }

    public RestPageImpl() {
        super(new ArrayList<T>());
    }
}

并使用这个具体类来解析:

ResponseEntity<RestPageImpl<Country>> response = restTemplate.exchange(searchCountries, new ParameterizedTypeReference<RestPageImpl<Country>>() {
        });

通过FeignClient传递Pageable还没有找到特别好的办法 ,选择直接传递刚才提到的几个参数(page,size, sort):

@GetMapping("/countries")
public RestPageImpl<Country> searchCountries(@RequestParam(required = false, name = "continent") String continent,
                                             @RequestParam(required = false, name = "page") Integer page,
                                             @RequestParam(required = false, name = "size") Integer size,
                                             @RequestParam(required = false, name = "sort") List<String> sort

另外FeignClient也是不能解析Page接口, 也是继承一个具体类

调用端拆包Pageable:

@GetMapping("/search")
public Page<Country> listCountry(@RequestParam(required = false) String continent,
                                 @PageableDefault(page = 0, size = 10) Pageable pageable) {

    Page<Country> asia = countryService.searchCountries(continent, pageable.getPageNumber(), pageable.getPageSize(), convert(pageable.getSort()));
    return asia;
}

default List<String> convert(Sort sort) {
    if (sort == null) {
        return null;
    }

    Iterator<Sort.Order> iterator = sort.iterator();

    List<String> sortList = Stream.generate(sort.iterator()::next)
            .map(order -> order.getProperty() + "," + order.getDirection())
            .collect(Collectors.toList());

    return sortList;
}

测试代码项目见 https://gitee.com/liuxy9999/mytest-spring-cloud