CODEWITHSUNDEEP
javaarraysjsonjackson
rkwright
rkwright

Reputation: 457

Reading JSON data into an array/list with Jackson

I have seen and read several questions on this subject, but none seem to address my problem. In all likelihood, I am making one (or two) minor but critical mistakes, but I don't see them.

My JSON looks like this (the real example is much more complex but this is what I have whittled it down to):

[
  {
    "atcID": "AL011851"
  },
  {
   "atcID": "AL021851"
  }
]

The code I used to read it is:

StormData.java:

public class StormData {

@JsonCreator
StormData ( String atcID, String name ) {
    this.atcID = atcID;
    this.name = name;
};

public String getAtcID()    {
    return atcID;
}

public void setAtcID( String atcID )    {
    this.atcID = atcID;
}

String      atcID;
String      name;

}

Main file:

byte[] jsonData = Files.readAllBytes(Paths.get(fileName));

ObjectMapper objectMapper = new ObjectMapper();

List<StormData> myObjects = objectMapper.readValue(jsonData , new TypeReference<List<StormData>>(){});

But the error I get is:

Cannot construct instance of `StormData` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)

So what am I missing? TIA.

Upvotes: 1

Views: 4022

Answers (1)

Eien
Eien

Reputation: 1167

You need to use both annotations: @JsonCreator on constructor and @JsonProperty on each argument:

@JsonCreator
StormData (@JsonProperty("atcID") String atcID, @JsonProperty("name") String name) {
    this.atcID = atcID;
    this.name = name;
}

See the official documentation.

Since JDK 8 you can also register Jackson ParameterNamesModule and compile your code with -parameters option. See the details in the documentation.

Upvotes: 2

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