Grouping with Sentry

I want to group exception with Sentry, the exception comes from different servers, but I want all exception by type together, for example, all NPE be grouped. I know you can extend EventBuilderHelper and this is how sentry group things, but I don’t know how to get the exception type.

package com.test;

import io.sentry.SentryClient;
import io.sentry.event.EventBuilder;
import io.sentry.event.helper.ContextBuilderHelper;

public class FingerprintEventBuilderHelper extends ContextBuilderHelper {

    private static final String EXCEPTION_TYPE = "exception_type";

    public FingerprintEventBuilderHelper(SentryClient sentryClient) {

    public void helpBuildingEvent(EventBuilder eventBuilder) {
        //Get the exception type
        String exceptionType =
        if (exceptionType != null) {
            eventBuilder.withTag(EXCEPTION_TYPE, exceptionType);

the json send to the server has some information about the exception, but I dont know hoy to get it

    "release": null,
    "dist": null,
    "platform": "java",
    "culprit": "com.sun.ejb.containers.BaseContainer in checkExceptionClientTx",
    "message": "Task execution failed",
    "datetime": "2019-06-26T14:13:29.000000Z",
    "time_spent": null,
    "tags": [
        ["logger", "com.test.TestService"],
        ["server_name", "localhost"],
        ["level", "error"]
    "errors": [],
    "extra": {
        "Sentry-Threadname": "MainThread",
        "rid": "5ff37e943-f4b4-4hc9-870b-4f8c4d18cf84"
    "fingerprint": ["{{ default }}"],
    "key_id": 3,
    "metadata": {
        "type": "NullPointerException",
        "value": ""