我为android.net.Uri编写了一个自定义GSON类型的适配器：
public class UriAdpter extends TypeAdapter<Uri> {
@Override
public void write(JsonWriter out, Uri value) throws IOException {
out.value(value.toString());
}
@Override
public Uri read(JsonReader in) throws IOException {
return Uri.parse(in.nextString());
}
}
它工作得很好，直到我解析的JSON提要为URI提供了null值。然后它扔了一个JsonSyntaxException：
03-30 08:40:00.799 16340-16340/com.example.app D/NewsFragment: Failed to retrieve articles
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected a string but was NULL at line 1 column 23588 path $.data[5].thumbnail
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:116)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:216)
at retrofit2.converter.gson.GsonResponseBodyConverter.convert(GsonResponseBodyConverter.java:37)
at retrofit2.converter.gson.GsonResponseBodyConverter.convert(GsonResponseBodyConverter.java:25)
at retrofit2.ServiceMethod.toResponse(ServiceMethod.java:116)
at retrofit2.OkHttpCall.parseResponse(OkHttpCall.java:211)
at retrofit2.OkHttpCall.execute(OkHttpCall.java:174)
at retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call(RxJavaCallAdapterFactory.java:144)
at retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call(RxJavaCallAdapterFactory.java:125)
at rx.Observable$2.call(Observable.java:162)
at rx.Observable$2.call(Observable.java:154)
at rx.Observable$2.call(Observable.java:162)
at rx.Observable$2.call(Observable.java:154)
at rx.Observable.unsafeSubscribe(Observable.java:8314)
at rx.internal.operators.OperatorSubscribeOn$1.call(OperatorSubscribeOn.java:94)
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:423)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:269)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.lang.IllegalStateException: Expected a string but was NULL at line 1 column 23588 path $.data[5].thumbnail
at com.google.gson.stream.JsonReader.nextString(JsonReader.java:830)
at com.example.app.data.rest.adapter.UriAdapter.read(UriAdapter.java:26)
at com.example.app.data.rest.adapter.UriAdapter.read(UriAdapter.java:16)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:116)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:216)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:116)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:216)
at retrofit2.converter.gson.GsonResponseBodyConverter.convert(GsonResponseBodyConverter.java:37)
at retrofit2.converter.gson.GsonResponseBodyConverter.convert(GsonResponseBodyConverter.java:25)
at retrofit2.ServiceMethod.toResponse(ServiceMethod.java:116)
at retrofit2.OkHttpCall.parseResponse(OkHttpCall.java:211)
at retrofit2.OkHttpCall.execute(OkHttpCall.java:174)
at retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call(RxJavaCallAdapterFactory.java:144)
at retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call(RxJavaCallAdapterFactory.java:125)
at rx.Observable$2.call(Observable.java:162)
at rx.Observable$2.call(Observable.java:154)
at rx.Observable$2.call(Observable.java:162)
at rx.Observable$2.call(Observable.java:154)
at rx.Observable.unsafeSubscribe(Observable.java:8314)
at rx.internal.operators.OperatorSubscribeOn$1.call(OperatorSubscribeOn.java:94)
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:423)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:269)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
我在解析之前尝试检查in.nextString()是否为null，但这不起作用，因为in.nextString()会引发异常，而不是Uri.parse()。如何在使用GSON进行反序列化时检查null个对象？
答案 0 :(得分：6)
您是否尝试过使用JsonToken？
curl -XGET 'http://localhost:9200/events/event/_search' -d '
{
"query" : {
"filtered" : {
"filter" : {
"term" : {
"audiences": "Public"
}
},
"query" : {
"match" : {
"title" : "[searchterm]"
}
}
}
}
}'