[jira] [Created] (FLINK-18961) In the case of FlatMap linking map, if map returns null, an exception will be thrown in FlatMap

["Ryan (Jira)" <ji...@apache.org>]

Ryan created FLINK-18961:
----------------------------

             Summary:  In the case of FlatMap linking map, if map returns null, an exception will be thrown in FlatMap
                 Key: FLINK-18961
                 URL: https://issues.apache.org/jira/browse/FLINK-18961
             Project: Flink
          Issue Type: Bug
          Components: API / DataSet
    Affects Versions: 1.11.0
         Environment: Mac OS 10.13.6

Kubernetes 1.16.8

Flink 1.11.0
            Reporter: Ryan
         Attachments: Lark20200814-173817.png, Lark20200814-173821.png, Lark20200814-173824.png

I found a DateSet problem.  In the case of FlatMap linking map, if map returns null, an exception will be thrown in FlatMap.I think it's a problem with the operator chain.I will post a screenshot of the corresponding stack call in the attachment.
{code:java}
text.filter(value -> value.f0.contains("any")).flatMap(new FlatMapFunction<Tuple2<String, String>, String>() {
              @Override
              public void flatMap(Tuple2<String, String> value, Collector<String> out) throws Exception {
                  Pattern pattern = Pattern.compile("\".*\"");
                  Matcher matcher = pattern.matcher(value.f0);
                  if(matcher.find()){
                      String match = matcher.group(0);
                      out.collect(match); // here throw Exception
                  }
              }
        }).map(value -> {
            try {
                String jsonS = value.replace("\"\"","\"");
                jsonS = jsonS.substring(1,jsonS.length()-1);
                JSONObject json = JSONObject.parseObject(jsonS);
                String result = json.getJSONObject("body").getJSONObject("message").getString("data");
                return result; // this is null 
            }catch (Exception e){
                return value;
            }
        }).print();{code}



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