在rest api中使用 org.springframework.data.domain.PageImpl  返回分页数据，有出现一些问题，问题以及解决方式如下：

(1) 返回的结果在springboot 1.x 和 springboot 2.x中不一致

例如以下API

@RestController
public class SomeController {

  @GetMapping
  public PageImpl listAll() {
    ...
  }
}

在springboot 1.x中的结果：

{
  "content": [
    {...},
    {...},
    ....
  ],
  "totalElements": 50,
  "totalPages": 3,
  "last": false,
  "size": 20,
  "number": 0,
  "numberOfElements": 1,
  "first": true,
  "sort": [
    {
      "direction": "DESC",
      "property": "date",
      "ignoreCase": false,
      "nullHandling": "NATIVE",
      "ascending": false,
      "descending": true
    }
  ]
}

然而在springboot 2.x中的结果除了content的内容相同，其他的内容都有很大的差别：

{
  "content": [
    {...},
    {...},
    ....
  ],
  "pageable": {
    "sort": {
      "sorted": true,
      "unsorted": false
    },
    "offset": 0,
    "pageNumber": 0,
    "pageSize": 20,
    "paged": true,
    "unpaged": false
  },
  "totalPages": 3,
  "last": false,
  "totalElements": 50,
  "size": 20,
  "number": 0,
  "numberOfElements": 1,
  "sort": {
    "sorted": true,
    "unsorted": false
  },
  "first": true
}

怎么样才能在springboot2的结果和springboot1的一致呢？下面通过jackson自定义反序列实现

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.boot.jackson.JsonComponent;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Sort;

import java.io.IOException;

@JsonComponent
public class PageImplJacksonSerializer extends JsonSerializer {
    @Override
    public void serialize(PageImpl page, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        jsonGenerator.writeStartObject();
        jsonGenerator.writeObjectField("content", page.getContent());
        jsonGenerator.writeBooleanField("first", page.isFirst());
        jsonGenerator.writeBooleanField("last", page.isLast());
        jsonGenerator.writeNumberField("totalPages", page.getTotalPages());
        jsonGenerator.writeNumberField("totalElements", page.getTotalElements());
        jsonGenerator.writeNumberField("numberOfElements", page.getNumberOfElements());
        jsonGenerator.writeNumberField("size", page.getSize());
        jsonGenerator.writeNumberField("number", page.getNumber());
        Sort sort = page.getSort();
        jsonGenerator.writeArrayFieldStart("sort");
        for (Sort.Order order : sort) {
            jsonGenerator.writeStartObject();
            jsonGenerator.writeStringField("property", order.getProperty());
            jsonGenerator.writeStringField("direction", order.getDirection().name());
            jsonGenerator.writeBooleanField("ignoreCase", order.isIgnoreCase());
            jsonGenerator.writeStringField("nullHandling", order.getNullHandling().name());
            jsonGenerator.writeEndObject();
        }
        jsonGenerator.writeEndArray();
        jsonGenerator.writeEndObject();
    }
}