Getting error not a JSON array when using gson

Question

My json string is:

{
    "sigTemplateId": 1,
    "name": "Test Ticket Template",
    "groups": "[{\"sigTemplateId\": 1, \"sigTemplateGroupId\": 1, \"name\": \"Group 1\", \"ordinal\": 1}]"
}

This gets sent from my jsp to the servlet. Servlet code is:

Gson gson = new Gson();

if (jsonData != null) {
    Type objType = new TypeToken<SigTemplateObj>() {}.getType();
    SigTemplateObj sigTemplateToSave = gson.fromJson(jsonData, objType);
    //SigTemplateObj sigTemplateToSave = gson.fromJson(jsonData, SigTemplateObj.class);
}

I get by: java.lang.IllegalStateException: This is not a JSON Array. gson trying to parse the groups array: The JsonDeserializer com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter@1f4db697 failed to deserialize json object "[{\"sigTemplateId\": 1, \"sigTemplateGroupId\": 1, \"name\": \"Group 1\", \"ordinal\": 1}]" given the type java.util.ArrayList

My object code is:

public class SigTemplateObj {

    int sigTemplateId;
    String dyninkName;
    int dyninkFormId;
    String name;

    //children collections
    ArrayList<SigTemplateFieldObj> fields;
    ArrayList<SigTemplateGroupObj> groups;
...
}

public class SigTemplateGroupObj {
    int sigTemplateGroupId;
    int sigTemplateId;
    int ordinal;
    String name;
...
}

I have tried both the code above and this line as well and got the same results both times.

SigTemplateObj sigTemplateToSave = gson.fromJson(jsonData, SigTemplateObj.class);

Any help would be appreciated. Thanks, Eric

Now I just have to fix my javascript to treat the groups array as an array and not a string:

var testObject = new Object();
        testObject.sigTemplateId = 1;
        testObject.name = 'Test Ticket Template';
        testObject['groups'] = [];
        var testGroup = new Object();
        testGroup.sigTemplateId = 1;
        testGroup.sigTemplateGroupId = 1;
        testGroup.name = 'Group 1';
        testGroup.ordinal = 1;
        testObject.groups.push(testGroup);

        var json = JSON.stringify(testObject);

Your JS code produces valid JSON for me. I pasted it to Chrome's console, and took a console.log(json). — user462963
– user462963, Commented Jan 16, 2013 at 19:09

user462963 · Accepted Answer · 2013-01-16 18:45:15Z

3

The groups array is not an array, but a string:

"groups": "..."

Try this JSON instead:

{
    "sigTemplateId": 1,
    "name": "Test Ticket Template",
    "groups": [{"sigTemplateId": 1, "sigTemplateGroupId": 1, "name": "Group 1", "ordinal": 1}]
}

answered Jan 16, 2013 at 18:45

user462963

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4 Comments

Eric Over a year ago

I changed my string and that worked, but how would I change my javascript so that it doesn't treat it as a string, but as an array?

Eric Over a year ago

Javascript: var testObject = new Object(); testObject.sigTemplateId = 1; testObject.name = 'Test Ticket Template'; testObject['groups'] = []; var testGroup = new Object(); testGroup.sigTemplateId = 1; testGroup.sigTemplateGroupId = 1; testGroup.name = 'Group 1'; testGroup.ordinal = 1; testObject.groups.push(testGroup); var json = JSON.stringify(testObject);

user462963 Over a year ago

Please update your question and insert your JS code there. And add the javascript tag to your question.

Eric Over a year ago

I found that my question was already answered with a compatibility issue between prototype and JSON libraries. The fix is to delete Array.prototype.toJSON;

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