如何解决使用GSON的JSON异常
我正在使用get API，该API发送JSON响应。我正在尝试使用Gson库将收到的JSON响应转换为Java POJO，但由于IllegalStateException而失败。以下是带有代码的示例JSON响应。 数据是保存StarEntity对象列表的列表。
示例响应JSON
{ "signature":{"version":"1.0","source":"NASA/JPL Fireball Data API"},"count":3,"fields":["date","lat","lat-dir","lon","lon-dir","alt","vel","energy","impact-e"],"data":[
["2015-10-13 12:23:08","8.0","S","52.5","W","38.9",null,"2.3","0.082"],["2015-10-11 00:07:46","55.4","18.8","3.0","0.1"],["2015-10-10 09:57:51","51.0","21.1","51.8","3.6","0.12"]
]
}
StarResponse对象
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({ "signature","count","fields","data" })
public class StarResponse implements Serializable {
private static final long serialVersionUID = 1L;
Signature signatureObject;
private float count;
ArrayList < String > fields = new ArrayList < String > ();
ArrayList <ArrayList< StarEntity >> data = new ArrayList <ArrayList< StarEntity >>();
// Getter Methods
public Signature getSignature() {
return signatureObject;
}
public float getCount() {
return count;
}
// Setter Methods
public void setSignature(Signature signatureObject) {
this.signatureObject = signatureObject;
}
public void setCount(float count) {
this.count = count;
}
@Override
public String toString() {
return new ToStringBuilder(this).append("signature",signatureObject).append("count",count).append("fields",fields)
.append("data",data).toString();
}
}
明星实体
public class StarEntity {
String date;
String latitude;
String latitudeDirection;
String longitude;
String longitudeDirection;
String altitude;
String velocity;
String energy;
String impact;
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public String getLatitude() {
return latitude;
}
public void setLatitude(String latitude) {
this.latitude = latitude;
}
public String getLatitudeDirection() {
return latitudeDirection;
}
public void setLatitudeDirection(String latitudeDirection) {
this.latitudeDirection = latitudeDirection;
}
public String getLongitude() {
return longitude;
}
public void setLongitude(String longitude) {
this.longitude = longitude;
}
public String getLongitudeDirection() {
return longitudeDirection;
}
public void setLongitudeDirection(String longitudeDirection) {
this.longitudeDirection = longitudeDirection;
}
public String getAltitude() {
return altitude;
}
public void setAltitude(String altitude) {
this.altitude = altitude;
}
public String getVelocity() {
return velocity;
}
public void setVelocity(String velocity) {
this.velocity = velocity;
}
public String getEnergy() {
return energy;
}
public void setEnergy(String energy) {
this.energy = energy;
}
public String getImpact() {
return impact;
}
public void setImpact(String impact) {
this.impact = impact;
}
@Override public String toString() { return
date+" "+latitude+" "+latitudeDirection+" "+longitude+" "+longitudeDirection;
}
HTTP呼叫
public class HttpCall {
static RestTemplate restTemplate = new RestTemplate();
static String NasaResourceUrl = "https://ssd-api.jpl.nasa.gov/fireball.api?req-loc=true";
public static void main(String []a) throws JsonMappingException,JsonProcessingException {
ResponseEntity<String> response = restTemplate.getForEntity(NasaResourceUrl,String.class);
ObjectMapper mapper = new ObjectMapper();
mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
mapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE,true);
mapper.setVisibility(PropertyAccessor.FIELD,Visibility.ANY);
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,false);
mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS,false);
mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS,false);
//String json = mapper.writeValueAsString(response.getBody());
Gson gson = new Gson();
System.out.println("Response Entity: "+response.getBody().toString()+"\n\n");
//StarResponse starresponse = mapper.readValue(response.getBody(),StarResponse.class);
gson.fromJson(response.getBody(),StarResponse.class);
//System.out.println(starresponse.toString());
}
}
例外
Exception in thread "main" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 176 path $.data[0][0]
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:200)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:81)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:81)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:103)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:196)
at com.google.gson.Gson.fromJson(Gson.java:810)
at com.google.gson.Gson.fromJson(Gson.java:775)
at com.google.gson.Gson.fromJson(Gson.java:724)
at com.google.gson.Gson.fromJson(Gson.java:696)
at com.nasa.star.http.call.HttpCall.main(HttpCall.java:34)
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 176 path $.data[0][0]
at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:387)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:189)
... 13 more
解决方法
您的JSON格式和POJO格式不匹配。根据您提供的POJO，JSON如下所示：
{
"signature": {
"version": "1.0","source": "NASA/JPL Fireball Data API"
},"count": 3,"fields": [
"date","lat","lat-dir","lon","lon-dir","alt","vel","energy","impact-e"
],"data": [
[
{
"date": "2015-10-13 12:23:08","latitude": "8.0","latitudeDirection": "S","longitude": "52.5","longitudeDirection": "W","altitude": "38.9","velocity": null,"energy": "2.3","impact": "0.082"
}
]
]
}
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