GSON conversion error when a null field contains subfields

Question

I am trying to parse the JSON result from the Wordpress plugins API using Retrofit2 and GSON. I have generated my POJO using the well known website and modified it into the following model:

PluginsApiResponse.java

public class PluginsApiResponse {

    @SerializedName("plugins")
    @Expose
    private List<Plugin> plugins = null;

    public List<Plugin> getPlugins() {
        return plugins;
    }

    public void setPlugins(List<Plugin> plugins) {
        this.plugins = plugins;
    }
}

Plugin.java

public class Plugin {

    @SerializedName("name")
    @Expose
    private String name;
    @SerializedName("homepage")
    @Expose
    private String homepage;
    @SerializedName("screenshots")
    @Expose
    private Screenshots screenshots;

    public String getName() {
        return name;
    }

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

    public String getHomepage() {
        return homepage;
    }

    public void setHomepage(String homepage) {
        this.homepage = homepage;
    }

    public Screenshots getScreenshots() {
        return screenshots;
    }

    public void setScreenshots(Screenshots screenshots) {
        this.screenshots = screenshots;
    }

}

Screenshots.java

public class Screenshots {

    @SerializedName("1")
    @Expose
    private com.dkalsan.retrofitwordpress._1 _1;
    @SerializedName("2")
    @Expose
    private com.dkalsan.retrofitwordpress._2 _2;
    @SerializedName("3")
    @Expose
    private com.dkalsan.retrofitwordpress._3 _3;

    public com.dkalsan.retrofitwordpress._1 get1() {
        return _1;
    }

    public void set1(com.dkalsan.retrofitwordpress._1 _1) {
        this._1 = _1;
    }

    public com.dkalsan.retrofitwordpress._2 get2() {
        return _2;
    }

    public void set2(com.dkalsan.retrofitwordpress._2 _2) {
        this._2 = _2;
    }

    public com.dkalsan.retrofitwordpress._3 get3() {
        return _3;
    }

    public void set3(com.dkalsan.retrofitwordpress._3 _3) {
        this._3 = _3;
    }

}

_1.java (_2.java and _3.java are identical)

public class _1 {

    @SerializedName("src")
    @Expose
    private String src;
    @SerializedName("caption")
    @Expose
    private String caption;

    public String getSrc() {
        return src;
    }

    public void setSrc(String src) {
        this.src = src;
    }

    public String getCaption() {
        return caption;
    }

    public void setCaption(String caption) {
        this.caption = caption;
    }

}

The problem occurs in case the screenshots field contains no entries. I've set up the HttpLoggingInterceptor, which logs the response code 200 and the json in its entirety. I've also excluded the possibility of it being the internet connectivity issue according to the following article. If I remove the screenshots field from the model there is no trouble parsing. Is it possible that the error persists due to GSON trying to deserialize the nonexistent fields 1, 2, and 3 and if so, how to deal with it?

score 0 · Accepted Answer · answered Apr 27 '18 at 08:25

Turn out the problem was in the JSON response formatting. If there were no screenshots it was formatted as a JSON array, otherwise it was formatted as a JSON object containing objects 1, 2, 3, etc. I've managed to fix it by following the answer on this stackoverflow question.

GSON conversion error when a null field contains subfields

1 Answers1