Json string to Java object Gson

Question

I have a json string in this format :

 [
   {
     "key1": { "key1":"val1","key2":"val2" },
     "key2": { "key1":"val1","key2":"val2" }
   }
]

To parse it I created a java class :

class data {
     String key;
     List <content> listdata;
     /* getter and setter for the attribute above */
     ...
   }

Now I followed Gson documentation, and try to exract data :

Gson gson =new Gson();
data[] ints = gson.fromJson(MyjsonString, data[].class);

I get parsing error from Gson API, what I done wrong ?

java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1 path

Are you sure, your data should not look like this? [ { "key": [ "key1":"val1","key2":"val2" ]}, { "key": [ "key1":"val1","key2":"val2" ]}] — Gábor Bakos
– Gábor Bakos, Commented Dec 22, 2015 at 12:07

Muhammad Suleman · Accepted Answer · 2015-12-22 12:43:09Z

1

For parsing json like following class

class data {
String key;
List <content> listdata;
/* getter and setter for the attribute above */
...
}

you need a json like as follows

"data" : {
 "key": "value",
 "listdata": [{ content object key attributes here }]
}

As your exception clearly saying BEGIN_ARRAY but was STRING so you have to use array in json for parsing.

In Reply of your comment

If you want a class which parse following json

{
 "key1": { "key1":"val1","key2":"val2" },
 "key2": { "key1":"val1","key2":"val2" }
}

Then you would have classes structure as follows

class Data {
 Map<String, String> key1;
 Map<String, String> key2;
 /* getter and setter for the attribute above */
}

edited Dec 22, 2015 at 12:43

answered Dec 22, 2015 at 11:53

Muhammad Suleman

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5 Comments

Lhoussaine Over a year ago

Thank you for the answer, i know that i have to change my class structure but, can you suggest me a new one ?

Lhoussaine Over a year ago

I can't so change my Json String, but i can change my java class to suite the requirement.

Lhoussaine Over a year ago

You have changed the message structure with this { key:{ content }, key2: {conetent }}, but how we can do it without omit [], i mean to save the message like this [{{},{}}] ?

Muhammad Suleman Over a year ago

well, then you can use Map<String, String> key1 and Map<String, String> key2 in Data class this is very easy to use. also see my updated answer!

Lhoussaine Over a year ago

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

Sandeep Kaul · Accepted Answer · 2015-12-22 12:03:05Z

0

As per the Json, this class structure works:

class data {
 List <Map<String,Content> data;
 /* getter and setter for the attribute above */
 ...

}

answered Dec 22, 2015 at 12:03

Sandeep Kaul

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3 Comments

Lhoussaine Over a year ago

com.google.gson.stream.MalformedJsonException: Expected ':' at line 1 column 9 path

Sandeep Kaul Over a year ago

something is wrong with the json, check your json, you could use jsonlint.com

Lhoussaine Over a year ago

i tested it in this link its a valid json

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