gson error: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 166

Question

I have following class SolrFBLocationDoc :

public class SolrFBLocationDoc{

    @Field
    private String name;
    @Field
    private String id;
    @Field
    private Location location = new Location();

    //and some more class members
}

where, Location is a class from restfb: com.restfb.types.Location .

I'm trying to convert a solrDocument to an object of class SolrFBLocationDoc as given below:

SolrFBLocationDoc doc = gson.fromJson(gson.toJson(solrDoc), SolrFBLocationDoc.class);

where, solrDoc is:

SolrDocument[{id=106377336067638, location=Location[city=null country=null latitude=null longitude=null state=null street=null zip=null]}]

and gson.toJson(solrDoc) returns,

{"id":"106377336067638","location":"Location[city\u003dnull country\u003dnull latitude\u003dnull longitude\u003dnull state\u003dnull street\u003dnull zip\u003dnull]"}

But, it's resulting into the error:

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 166

I can see the problem is occuring due to conversion of Location class object to String by gson.toJson(solrDoc) .

Then without using gson.toJson(solrDoc) , how can I convert SolrDocument to SolrFBLocationDoc ?

How can I get rid of this problem?

Answer 1

In your SolrFBLocationDoc class, location ivar is of kind com.restfb.types.Location but into your JSON string:

"location":"Location[city\u003dnull country\u003dnull latitude\u003dnull longitude\u003dnull state\u003dnull street\u003dnull zip\u003dnull]" 

means that location is a string. Due to SolrFBLocationDoc definition, indeed, after semicolon, Gson expects a "{" (that is a BEGIN_OBJECT ). But it finds "Location.. , that is a string, so it won't parse.

Right string would be like:

{"id":"106377336067638","location":{"city":null, "country":null, "latitude":null, "longitude":null, "state":null, "street":null, "zip":null}}

So this means that gson.toJson(solrDoc) returns you a escaped string for location key. This could depends on how SolrDocument is defined. Probably in that class location field is a string. If you could put definition of SolrDocument , this answer can be refined and hypothesis confirmed/rejected.