GSON 和 Flickr API 问题：反序列化 json 时出现 JsonParseException

Question

我对 java 和 android 开发比较陌生，如果这是一个愚蠢的问题，我很抱歉。我正在构建简单的应用程序，只是为了学习 android 绳索，它将显示上传到 flickr 的最新照片列表。该应用程序已构建，但当它尝试反序列化我从 flickr 返回的 json 时，它就崩溃了。这是我的错误：

06-23 21:11:25.560: WARN/System.err(298): com.google.gson.JsonParseException: The JsonDeserializer com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter@43e28168 failed to deserialized json object {"page":1,"pages":100,"perpage":10,"total":1000,"photo":[{"id":"4728507833","owner":"59492791@N00","secret":"496b96968d","server":"1407","farm":2,"title":"DSCN2733","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1407/4728507833_496b96968d_s.jpg","height_sq":75,"width_sq":75},{"id":"4728507883","owner":"30728507@N07","secret":"ab80a5bdf4","server":"1194","farm":2,"title":"Sultan","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1194/4728507883_ab80a5bdf4_s.jpg","height_sq":75,"width_sq":75},{"id":"4728507955","owner":"30311414@N00","secret":"7d6ea1cd08","server":"1377","farm":2,"title":"DSC04455","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1377/4728507955_7d6ea1cd08_s.jpg","height_sq":75,"width_sq":75},{"id":"4728507979","owner":"24737003@N04","secret":"c76cfe4afb","server":"1162","farm":2,"title":"IMGP1429","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1162/4728507979_c76cfe4afb_s.jpg","height_sq":75,"width_sq":75},{"id":"4728508009","owner":"62084706@N00","secret":"76b858efe7","server":"1366","farm":2,"title":"DSC_2459.JPG","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1366/4728508009_76b858efe7_s.jpg","height_sq":75,"width_sq":75},{"id":"4729153856","owner":"50879555@N02","secret":"843d4f56ec","server":"1129","farm":2,"title":"IMG_1585","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1129/4729153856_843d4f56ec_s.jpg","height_sq":75,"width_sq":75},{"id":"4729153942","owner":"43941986@N08","secret":"f7ea2d3037","server":"1257","farm":2,"title":"IMG_1126","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1257/4729153942_f7ea2d3037_s.jpg","height_sq":75,"width_sq":75},{"id":"4729153952","owner":"50634775@N07","secret":"af6d937dcd","server":"1129","farm":2,"title":"069_69","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1129/4729153952_af6d937dcd_s.jpg","height_sq":75,"width_sq":75},{"id":"4729153962","owner":"34771042@N07","secret":"71f6c321eb","server":"1014","farm":2,"title":"Snapshot_010","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1014/4729153962_71f6c321eb_s.jpg","height_sq":75,"width_sq":75},{"id":"4729153964","owner":"14318596@N08","secret":"6ab627b565","server":"1364","farm":2,"title":"DSC_0679","ispublic":1,"isfriend":0,"isfamily":0,"url_sq":"http://farm2.static.flickr.com/1364/4729153964_6ab627b565_s.jpg","height_sq":75,"width_sq":75}]} given the type com.google.gson.ParameterizedTypeImpl@3dd03b7
06-23 21:11:25.580: WARN/System.err(298):     at com.google.gson.JsonDeserializerExceptionWrapper.deserialize(JsonDeserializerExceptionWrapper.java:63)
06-23 21:11:25.580: WARN/System.err(298):     at com.google.gson.JsonDeserializationVisitor.invokeCustomDeserializer(JsonDeserializationVisitor.java:88)
06-23 21:11:25.600: WARN/System.err(298):     at com.google.gson.JsonObjectDeserializationVisitor.visitFieldUsingCustomHandler(JsonObjectDeserializationVisitor.java:117)
06-23 21:11:25.600: WARN/System.err(298):     at com.google.gson.ObjectNavigator.navigateClassFields(ObjectNavigator.java:150)
06-23 21:11:25.610: WARN/System.err(298):     at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:123)
...
06-23 21:11:25.851: WARN/System.err(298): Caused by: java.lang.IllegalStateException: This is not a JSON Array.
06-23 21:11:25.901: WARN/System.err(298):     at com.google.gson.JsonElement.getAsJsonArray(JsonElement.java:100)
06-23 21:11:25.911: WARN/System.err(298):     at com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter.deserialize(DefaultTypeAdapters.java:468)
06-23 21:11:25.921: WARN/System.err(298):     at com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter.deserialize(DefaultTypeAdapters.java:435)
06-23 21:11:25.921: WARN/System.err(298):     at com.google.gson.JsonDeserializerExceptionWrapper.deserialize(JsonDeserializerExceptionWrapper.java:50)
06-23 21:11:25.931: WARN/System.err(298):     ... 26 more

From，我假设它有一些 GSON 不喜欢返回的 json 的东西，但我对 java 在整个操作过程中如何转换对象和其他类型的变量了解不够。

我不确定您是否需要这个，但这里是该项目的一些代码：

String response = client.getResponse();
response = response.replace("jsonFlickrApi(", "");
response = response.substring(0,response.length()-2);
Gson gson = new Gson();

FlickrPhotos flickrphotos = new FlickrPhotos();
try {
    flickrphotos = gson.fromJson(response, FlickrPhotos.class);
} catch(Exception e) {
    e.printStackTrace();
}

这是 FlickrPhotos：

public class FlickrPhotos {
    private String page, pages, perpage, total;
    private List<FlickrPhoto> photos;

    public List<FlickrPhoto> getPhotos() {
        return photos;
    }
    // More getters
}

这是 FlickrPhoto：

public class FlickrPhoto {
    private String id, owner, secret, server, title, width_sq, url_sq;
    // getters
}

有什么想法吗？非常感谢您的时间和耐心......（如果我不介意的话！）

Answer 1

仅通过查看就让我印象深刻的一件事是 photo 与 photos 之间的差异：

... "total":1000,"photo":[{ ...

vs

private List<FlickrPhoto> photos;

public List<FlickrPhoto> getPhotos() {
    return photos;
}

如果您还没有这样做，也许可以尝试重命名您的 List 改为仅照片？

此外，许多属性（page、pages、perpage、width_sq 等）不是 JSON 中的字符串。我认为有一个自动类型转换器可以处理这个问题，但您也可以将它们声明为 int 。