CODEWITHSUNDEEP
javajsonarraylistjackson
Harleen
Harleen

Reputation: 803

Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token

I have looked for other post in stack overflow but none of them work for me. Here is the piece of code:

 public class Forward implements Serializable {
  private List<String> freq;
  public List<String> getFreq() {
    System.out.println("Print Freq::: -->  " + freq);
    return freq;
  }

  public void setFreq(List<String> freq) {
    this.freq = freq;
 }
}

The JSON string is:

{"forward":[{"freq":"78000000"}]}

My mapper is:

ObjectMapper mapper = new ObjectMapper();            
mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
String jsonString = mapper.writeValueAsString(result);

If I remove List freq and change to String freq it works but my JSON can contain one or more freq so I need to create a List.I get exception as:

  Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token at [Source: org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream

Upvotes: 1

Views: 22126

Answers (1)

Andremoniy
Andremoniy

Reputation: 34920

DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY works fine in order to deserialize "freq":"78000000" fragment as value of List<String> freq list.

But you have another problem: your json contains explicit array of forward. In order to deserialize this entire json you need to have some kind of wrapper class, say:

  public class ForwardWrapper {
        private List<Forward> forward;

        public List<Forward> getForward() {
            return forward;
        }

        public void setForward(List<Forward> forward) {
            this.forward = forward;
        }
    }

In this case

    ForwardWrapper fw = mapper.readValue("{\"forward\":[{\"freq\":\"78000000\"}]}", ForwardWrapper.class);

will deserialize it perfectly.

Upvotes: 2

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