Mapping Json string to map or hashmap field in java

Question

Say I have the following JSON string returned from server:

{
    "response":{
        "imageInstances":{
            "one":{
                "id":"1",
                "url":"ONE"
            },         
            "two":{
                "id":"2",
                "url":"TWO"
            }
        }
    }  
}

in codehaus Jackson @JsonProperty, how can I get a HashMap object out of it?

import org.codehaus.jackson.annotate.JsonAnySetter;
import org.codehaus.jackson.annotate.JsonProperty;

import java.util.HashMap;
import java.util.List;

public class MSShow {
  @JsonProperty("imageInstances") private HashMap<String, Temp> images;//// HOW DO YOU CONVERT IT TO HASH MAP??????
  @JsonAnySetter public void ignoredField(String key, Object value) { }

  private class Temp {
    @JsonProperty("id") private String id;
    @JsonProperty("url") private String url;
    @JsonAnySetter public void ignoredField(String key, Object value) { }
    }
}

At the end of the day, I want the hash map generated based on the returned JSON string to be (written in java pseudo)

should return me a Temp object with fields id=1 and url=ONE if I call

images.get("one")

should return me a Temp object with fields id=2 and url=TWO if I call

images.get("two")

Haven't done any serious delving or testing, but, for one, I'd say Jackson might have a problem with your nested class Temp being a) private, and b) an inner class (non-static, hence bound to the instance of the containing MediaSlideShow). So I'd start with making Temp public static. — Alistair A. Israel
– Alistair A. Israel, Commented Feb 15, 2012 at 3:47
And do you specifically need a HashMap? If not, consider a Map<String, Temp> instead and let Jackson worry about what implementation to use. — Alistair A. Israel
– Alistair A. Israel, Commented Feb 15, 2012 at 3:49

StaxMan · Accepted Answer · 2012-02-15 17:16:03Z

3

That should work as is, with one small modification: you are using extra "response" entry. So typically you would either use a wrapper POJO like:

class Wrapper {
  public MSShow response;
}

to map structure properly. Or you can use UNWRAP_ROOT_VALUE Feature (from DeserializationConfig) to do this automatically, although name of the class needs to match if so.

Result will indeed be a HashMap if the field type is that (which it is). If it wasn't you could also use:

@JsonDeserialize(as=HashMap.class)

to force specific subtype to be used.

answered Feb 15, 2012 at 17:16

StaxMan

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