我正在使用Youtube API。我可以将java Object转换为json字符串。但是当我尝试将其反转（json字符串到java对象）时，它会引发异常：Can not set com.google.api.services.youtube.model.CommentThreadSnippet field com.google.api.services.youtube.model.CommentThread.snippet to java.util.LinkedHashMap。为什么我会收到此错误以及如何解决此问题？
这有效：
CommentThread commentThread = getItSomehow()
Gson gson = new Gson();
String jsonStr = gson.toJson( commentThread );
反向抛出异常：
CommentThread fromJson = gson.fromJson( jsonStr, CommentThread.class );
这是CommentThread类：
@SuppressWarnings("javadoc")
public final class CommentThread extends com.google.api.client.json.GenericJson {
/**
* Etag of this resource.
* The value may be {@code null}.
*/
@com.google.api.client.util.Key
private java.lang.String etag;
/**
* The ID that YouTube uses to uniquely identify the comment thread.
* The value may be {@code null}.
*/
@com.google.api.client.util.Key
private java.lang.String id;
/**
* Identifies what kind of resource this is. Value: the fixed string "youtube#commentThread".
* The value may be {@code null}.
*/
@com.google.api.client.util.Key
private java.lang.String kind;
/**
* The replies object contains a limited number of replies (if any) to the top level comment found
* in the snippet.
* The value may be {@code null}.
*/
@com.google.api.client.util.Key
private CommentThreadReplies replies;
/**
* The snippet object contains basic details about the comment thread and also the top level
* comment.
* The value may be {@code null}.
*/
@com.google.api.client.util.Key
private CommentThreadSnippet snippet;
/**
* Etag of this resource.
* @return value or {@code null} for none
*/
public java.lang.String getEtag() {
return etag;
}
/**
* Etag of this resource.
* @param etag etag or {@code null} for none
*/
public CommentThread setEtag(java.lang.String etag) {
this.etag = etag;
return this;
}
/**
* The ID that YouTube uses to uniquely identify the comment thread.
* @return value or {@code null} for none
*/
public java.lang.String getId() {
return id;
}
/**
* The ID that YouTube uses to uniquely identify the comment thread.
* @param id id or {@code null} for none
*/
public CommentThread setId(java.lang.String id) {
this.id = id;
return this;
}
/**
* Identifies what kind of resource this is. Value: the fixed string "youtube#commentThread".
* @return value or {@code null} for none
*/
public java.lang.String getKind() {
return kind;
}
/**
* Identifies what kind of resource this is. Value: the fixed string "youtube#commentThread".
* @param kind kind or {@code null} for none
*/
public CommentThread setKind(java.lang.String kind) {
this.kind = kind;
return this;
}
/**
* The replies object contains a limited number of replies (if any) to the top level comment found
* in the snippet.
* @return value or {@code null} for none
*/
public CommentThreadReplies getReplies() {
return replies;
}
/**
* The replies object contains a limited number of replies (if any) to the top level comment found
* in the snippet.
* @param replies replies or {@code null} for none
*/
public CommentThread setReplies(CommentThreadReplies replies) {
this.replies = replies;
return this;
}
/**
* The snippet object contains basic details about the comment thread and also the top level
* comment.
* @return value or {@code null} for none
*/
public CommentThreadSnippet getSnippet() {
return snippet;
}
/**
* The snippet object contains basic details about the comment thread and also the top level
* comment.
* @param snippet snippet or {@code null} for none
*/
public CommentThread setSnippet(CommentThreadSnippet snippet) {
this.snippet = snippet;
return this;
}
@Override
public CommentThread set(String fieldName, Object value) {
return (CommentThread) super.set(fieldName, value);
}
@Override
public CommentThread clone() {
return (CommentThread) super.clone();
}
}
以下是例外的详细信息。
Throwable: Can not set com.google.api.services.youtube.model.CommentThreadSnippet field com.google.api.services.youtube.model.CommentThread.snippet to java.util.LinkedHashMap
java.lang.IllegalArgumentException: Can not set com.google.api.services.youtube.model.CommentThreadSnippet field com.google.api.services.youtube.model.CommentThread.snippet to java.util.LinkedHashMap
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81)
at java.lang.reflect.Field.set(Field.java:764)
at com.google.api.client.util.FieldInfo.setFieldValue(FieldInfo.java:245)
at com.google.api.client.util.FieldInfo.setValue(FieldInfo.java:206)
at com.google.api.client.util.GenericData.put(GenericData.java:103)
at com.google.api.client.util.GenericData.put(GenericData.java:47)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:189)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:146)
at com.google.gson.Gson.fromJson(Gson.java:755)
at com.google.gson.Gson.fromJson(Gson.java:721)
at com.google.gson.Gson.fromJson(Gson.java:670)
at com.google.gson.Gson.fromJson(Gson.java:642)
at sam.ut.CommentThreads.handleCommentsThreads(CommentThreads.java:157)
at sam.ut.CommentThreads.DownloadCommentsForThisVideo(CommentThreads.java:84)
at sam.ut.CommentThreads.main(CommentThreads.java:66)
编辑：这是JSON：
{
"etag": "\"0Fu6lI6VPLdRMlQU3wwNcowdAUs/F7bYskj8z3daRWhUSU5zInnZkqw\"",
"id": "z12wxpxozzy1tdxop04cjd1rjzq4cp2jgfw",
"kind": "youtube#commentThread",
"snippet": {
"canReply": true,
"isPublic": true,
"topLevelComment": {
"etag": "\"0Fu6lI6VPLdRMlQU3wwNcowdAUs/PzVv_VFrN7CZoVSIIlPnVsEIwE0\"",
"id": "z12wxpxozzy1tdxop04cjd1rjzq4cp2jgfw",
"kind": "youtube#comment",
"snippet": {
"authorChannelId": {
"value": "UCOjTszsvhfAKFQprwN3ETLQ"
},
"authorChannelUrl": "http://www.youtube.com/channel/UCOjTszsvhfAKFQprwN3ETLQ",
"authorDisplayName": "Spruce Moose Arts",
"authorGoogleplusProfileUrl": "https://plus.google.com/102869292172467105853",
"authorProfileImageUrl": "https://lh6.googleusercontent.com/-eJGw19enrkQ/AAAAAAAAAAI/AAAAAAAAAyg/khd3HglROx4/photo.jpg?sz=50",
"canRate": true,
"likeCount": 0,
"publishedAt": "2016-06-13T22:49:52.000Z",
"textDisplay": "The man behind the camera which recorded this, must be very shaky, \ncondsidering the amount of warp stabilization on this video :P Also, i \nthink this is a matter of personal taste. I personally think the car WITH \npol filter looked much better.",
"updatedAt": "2016-06-13T22:49:52.000Z",
"videoId": "YcZkCnPs45s",
"viewerRating": "none"
}
},
"totalReplyCount": 0,
"videoId": "YcZkCnPs45s"
}
}