jackson数据绑定不在自定义类中工作

Question

我收到来自服务器的以下回复

{
"count":2,
"data":[
  {
     "promotionId":"5460d40e3956e9b365e24864",
     "promotionName":"happy diwali",
     "description":"happy diwali",
     "startDate":null,
     "endDate":null,
     "createdDate":null,
     "modifiedDate":null,
     "creatorUserId":null,
     "brandId":"545a07e1eb013d0eeb8ad282"
  },
  {
     "promotionId":"5460d45d3956e9b365e24865",
     "promotionName":"happy new YEAR",
     "description":"happy new YEAR",
     "startDate":null,
     "endDate":null,
     "createdDate":null,
     "modifiedDate":null,
     "creatorUserId":null,
     "brandId":"545a07e1eb013d0eeb8ad282"
  }
 ]
}

所以我想将这个响应绑定到一个常见的util类，然后绑定到实际的 Promotion 类。

我有PaginationUtil类，如下所示

import java.util.List;

import com.fasterxml.jackson.annotation.JsonProperty;

public class PaginationUtil {

   private List<Object> Data;
   private int count;
   @JsonProperty("data")
   public List<Object> getData() {
        return Data;
   }
   public void setData(List<Object> data) {
        Data = data;
   }
   @JsonProperty("count")
   public int getCount() {
        return count;
   }
   public void setCount(int count) {
        this.count = count;
   }

}

促销课

import java.util.Date;

public class Promotion {

private String promotionId;
private String promotionName;
private String description;
private Date startDate;
private Date endDate;
private Date createdDate;
private Date modifiedDate;
private String creatorUserId;
private String brandId;

public String getPromotionId() {
    return promotionId;
}

public void setPromotionId(String promotionId) {
    this.promotionId = promotionId;
}

public String getPromotionName() {
    return promotionName;
}

public void setPromotionName(String promotionName) {
    this.promotionName = promotionName;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public Date getStartDate() {
    return startDate;
}

public void setStartDate(Date startDate) {
    this.startDate = startDate;
}

public Date getEndDate() {
    return endDate;
}

public void setEndDate(Date endDate) {
    this.endDate = endDate;
}

public Date getCreatedDate() {
    return createdDate;
}

public void setCreatedDate(Date createdDate) {
    this.createdDate = createdDate;
}

public Date getModifiedDate() {
    return modifiedDate;
}

public void setModifiedDate(Date modifiedDate) {
    this.modifiedDate = modifiedDate;
}

public String getCreatorUserId() {
    return creatorUserId;
}

public void setCreatorUserId(String creatorUserId) {
    this.creatorUserId = creatorUserId;
}

public String getBrandId() {
    return brandId;
}

public void setBrandId(String brandId) {
    this.brandId = brandId;
}
}

我的通话类是

import java.io.IOException;
import java.util.List;

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.test.rest.model.Promotion;
import com.test.rest.utility.PaginationUtil;


public class Test2 {
   public static void main(String[] args) throws JsonParseException,  IOException{
    RestTemplate restTemplate = new RestTemplate();
    String url = url here
    HttpHeaders headers = new HttpHeaders();
    HttpEntity<String> request1 = new HttpEntity<String>(headers);
    ResponseEntity<String> response1 = restTemplate.exchange(url,HttpMethod.GET, request1, String.class);
    String account = response1.getBody();
    System.out.println(account);

    ObjectMapper objectMapper = new ObjectMapper();
    PaginationUtil paginationUtil = objectMapper.readValue(
            account,PaginationUtil.class);
    System.out.println(paginationUtil.getCount());
    for(Promotion p : paginationUtil.getData()){
        System.out.println(p.getPromotionId());
        System.out.println(p.getPromotionName());;
    }


   }
}

我得到了以下json和错误

{"count":2,"data":[{"promotionId":"5460d40e3956e9b365e24864","promotionName":
"happy diwali","description":"happy diwali","startDate":null,"endDate":null,
"createdDate":null,"modifiedDate":null,"creatorUserId":null,
"brandId":"545a07e1eb013d0eeb8ad282"},      
{"promotionId":"5460d45d3956e9b365e24865","promotionName":"happy new YEAR",
"description":"happy new YEAR","startDate":null,"endDate":null,
"createdDate":null,"modifiedDate":null,"creatorUserId":null,
"brandId":"545a07e1eb013d0eeb8ad282"}]}

Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: 
 Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
at [Source: {"count":2,"data":  [{"promotionId":"5460d40e3956e9b365e24864",
"promotionName":"happy diwali","description":"happy diwali","startDate":null,
"endDate":null,"createdDate":null,"modifiedDate":null,
"creatorUserId":null,"brandId":"545a07e1eb013d0eeb8ad282"},
 {"promotionId":"5460d45d3956e9b365e24865","promotionName":"happy new YEAR",
 "description":"happy new YEAR","startDate":null,"endDate":null,"createdDate":null,
 "modifiedDate":null,"creatorUserId":null,"brandId":"545a07e1eb013d0eeb8ad282"}]}; 
line: 1, column: 1]
at com.fasterxml.jackson.databind.JsonMappingException.from
(JsonMappingException.java:148)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException
(DeserializationContext.java:749)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException
(DeserializationContext.java:745)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.handleNonArray
(CollectionDeserializer.java:275)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize
(CollectionDeserializer.java:216)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize
(CollectionDeserializer.java:206)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize
(CollectionDeserializer.java:25)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3051)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2153)
at Test2.main(Test2.java:31)

有人能说出问题是什么吗？