Getting java.lang.NoClassDefFoundError while using Google Gson library

Question

I am using Gson library to convert objects to Json and vice versa. I have copied the jars of that library into a new folder lib and added it to the build path for the project in my Eclipse IDE.

I have one main class where I convert an object into Json using toJson() shown below and send it to a servlet using Apache HttpClient's HttpPost().

Gson gson= new Gson();
String json = gson.toJson(names);

But in the servlet I am not able to convert the Json into Object using fromJson() when I execute the following code.

Gson gson = new Gson();
Names names = gson.fromJson(s, Names.class);

It is throwing the following exception:

java.lang.NoClassDefFoundError: com/google/gson/Gson

Any idea why that could be happening? Should I have copied the jars into the WebContent/WEB-INF/lib folder instead of a new folder called lib?

[See the link here](http://stackoverflow.com/questions/3080454/android-eclipse-error-gson-cannot-be-resolved-to-a-type) it's relevant to your error type — thar45, Oct 09 '12 at 03:57
I have added `gson-2.2.2.jar`. What is puzzling me is `Gson` is resolved in one class but not in the other class(Servlet). — Rajath, Oct 09 '12 at 04:11
What is `s` in `fromJson` call. I doubt its because of it. Check if its not NULL — Hardik Mishra, Oct 09 '12 at 05:08
It is not NULL and the error is not because of that. `s` is perfectly fine. The error is at the line `Gson gson = new Gson()`. — Rajath, Oct 09 '12 at 05:21
You should have posted complete error stack trace as well as necessary code in the first place. Read more on FAQ — Hardik Mishra, Oct 09 '12 at 05:42
@HardikMishra Thanks for the suggestion, will do it more onwards. — Rajath, Oct 09 '12 at 05:44

score 5 · Accepted Answer · edited May 23 '17 at 10:26

5

Okay, I figured out the answer using this post. Please read the comments in the first answer.

I am getting "java.lang.ClassNotFoundException: com.google.gson.Gson" error even though it is defined in my classpath

I just had to place the external jars into my WebContent/WEB-INF/lib folder and Eclipse would take care of the build path itself.

edited May 23 '17 at 10:26

Community

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answered Oct 09 '12 at 05:41

Rajath

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Its good that you found solution but Just FYI `java.lang.NoClassDefFoundError` and `java.lang.ClassNotFoundException` are different things. – Hardik Mishra Oct 09 '12 at 05:44
I got both the type of exceptions when I executed different Dynamic Web Projects with the same code. But thanks! Will take into note. – Rajath Oct 09 '12 at 05:52

Getting java.lang.NoClassDefFoundError while using Google Gson library

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