java - 使用Jackson在Java中无法序列化为JSON

早上好家伙!

我有一个JSON字符串，看起来像:

{
   "StatusCode":0,
   "Message":null,
   "ExecutionTime":0,
   "ResponseData":[
        {"Name":"name1","SiteId":"1234","Type":"Type1","X":"1234567","Y":"123456"},
        {"Name":"Name2","SiteId":"2134","Type":"Type2","X":"1234567","Y":"1234567"},
        {"Name":"Name3","SiteId":"3241","Type":"Type3","X":"1234567","Y":"1234567"},
        {"Name":"Name4","SiteId":"4123","Type":"Type4","X":"123456","Y":"123456"}
    ]
}

我想创建一个对象，可以在其中检索X和Y值。

我一直在尝试使用Jackson来序列化JSON字符串，但没有成功。我创建了两个额外的类供Jackson使用。顶层的一类StatusCode，Message，ExecutionTime和ResponseData看起来像

public class PL {
private Long statusCode;
private String executionTime;
private String message;
private ResponseData responseData;
public PL(){
}

public void setStatusCode(Long statusCode){
  this.statusCode = statusCode;
}

public Long getStatusCode(){
  return this.statusCode;
}

public void setExecutionTime(String executionTime){
  this.executionTime = executionTime;
}
public String getExecutionTime(){
  return this.executionTime;
}

public void setMessage(String message){
  this.message = message;
}
public String getMessage(){
  return this.message;
}

public void setResponseData(ResponseData responseData){
  this.responseData = responseData;
}
public ResponseData getResponseData(){
  return this.responseData;
}
}

其中ReponseData作为对象返回，然后我有另一个类用于序列化ResponseData，如下所示

public class ResponseData {

private String name;
private String siteId;
private String type;
private String x;
private String y;

public ResponseData(){
}

public void setName(String name){
  this.name = name;
}
public String getName(){
  return this.name;
}

public void setSiteId(String siteId){
  this.siteId = siteId;
}
public String getSiteId(){
  return this.siteId;
}

public void setType(String type){
  this.type = type;
}
public String setType(){
  return this.type;
}

public void setX(String x){
  this.x = x;
}
public String getX(){
  return this.x;
}

public void setY(String y){
  this.y = y;
}
public String getY(){
  return this.y;
}
}

然后我用创建一个ObjectMapper

private final static ObjectMapper mapper = new ObjectMapper();

并尝试这样读取值

ResponseData e = mapper.readValue(result.toString(), ResponseData.class);

并以例外结束

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException:无法识别的字段“StatusCode”(类MyClass.ResponseData)，未标记为可忽略(5个已知属性:“x”，“y”，“siteId”，“name”，“类型”])

好像它无法解析第一个条目StatusMessage。即使我删除第二个类并仅尝试解析前四个条目，在这些条目中我将ResponseData作为String返回，我仍然会遇到相同的异常。

最佳答案

首先，在PL中，您应该拥有List<ResponseData>，而不是简单的ResponseData属性。如您所见，在JSON中，ResponseData是一个"ResponseData":[...]数组，因此它将被反序列化为List。列表中的每个元素都是您定义的ResponseData对象。

然后遇到一个大小写问题，您的JSON中有大写字母，而类属性中没有。您可以使用@JsonProperty(See API)注释来克服此问题，方法是:

class PL {
    @JsonProperty("StatusCode")
    private Long statusCode;
    @JsonProperty("ExecutionTime")
    private String executionTime;
    @JsonProperty("Message")
    private String message;
    @JsonProperty("ResponseData")
    private List<ResponseData> responseDatas;

    public PL(){
    }

    // getters/Setters

}


class ResponseData {

    @JsonProperty("Name")
    private String name;
    @JsonProperty("SiteId")
    private String siteId;
    @JsonProperty("Type")
    private String type;
    @JsonProperty("X")
    private String x;
    @JsonProperty("Y")
    private String y;

    public ResponseData(){
    }

    // getters/Setters

}

然后将您的JSON作为PL对象读取，如下所示:

ObjectMapper mapper = new ObjectMapper();
PL pl = mapper.readValue(json, PL.class);
for(ResponseData rd : pl.getResponseDatas()) {
    System.out.println(rd.getX());
    System.out.println(rd.getY());
}

输出:

关于java - 使用Jackson在Java中无法序列化为JSON，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/50386188/