How to deserialize this JSON in an elegant way using flexjson

Question

I am working with Oracle OPAM and it has a REST API that has methods like this

{
   "Target Collection":[
      {
     "target":{
        "uri":"https:\/\/opam_server_host:opam_ssl_port\/opam\/target\

           /9bbcbbb087174ad1900ea691a2573b61",
        "type":"ldap",
        "name":"person1-ldap",
        "host":"opam_server_host",
        "domain":"berkeley"
        "description" : "Ldap target"
     }
      },
      {
     "target":{
        "uri":"https:\/\/opam_server_host:opam_ssl_port\/opam\/target\

           /ac246a162ce948c7b1cdcc17dfc92c15",
        "type":"ldap",
        "name":"person1-ldap2",
        "host":"opam_server_host:opam_ssl_port",
        "domain":"berkeley"
        "description" : "Ldap target"
     }
      }
   ]
}

I am using FlexJSON to deserialize these entities. If I could, I'd use Apache CXF to generate the beans for me, but the problem is that the WADL is under an invalid https certificate + basic authentication, and getting wadl2java to work under these conditions are taking more time than I'd like to spend (too bad it isn't WSDL, so I could just create the stubs from inside eclipse fast and easy).

So I am using this cumbersome approach with flexjson to parse this REST API

JSONDeserializer<Map<String,List<Map<String,Map<String,String>>>>> json = new JSONDeserializer<>();
Map<String,List<Map<String,Map<String,String>>>> targetCollection = json.deserialize(new InputStreamReader(content));
List<Map<String,Map<String,String>>> col = targetCollection.get("Target Collection");             Map<String,Map<String,String>> keyVal = col.get(0);
Map<String,String> targetVal = keyVal.get("target");
System.out.println(targetVal);

This obviously works, but it has so many brackets that reminds me LISP.

It would be so much better if we could just use POJOs instead (even better if I could have then generated automatically by some GUI tool, but I know I am asking too much, we're living in 2014).

I know there is some documentation about how to map attributes here : http://flexjson.sourceforge.net/#Deserialization but I really wish they have some real complex sample (including the JSON - what's the use of explaining how to deserialize without any JSON example in the documentation?)

This question is obviously not new, but it seems that related questions like 1, 2 or 3 are also waiting for an answer.

(P.S. except this one seems to have some info I can use)

So my question is: how do I parse this JSON with FlexJSON into a structure not only made of Maps?

It wouldn't be only maps --- there's at least one array in there. — Hot Licks, Feb 18 '14 at 19:33
@HotLicks true :-) but I think if we could just replace maps with POJOs, a List won't bother — Leo, Feb 18 '14 at 19:34

score 4 · Accepted Answer · answered Mar 06 '14 at 18:58

Working solution without any Map:

Let's define the classes bottom-up:

1. Target:

public class Target {

private String uri;
private String type;
private String name;
private String host;
private String domain;
private String description;

public String getUri() {
    return uri;
}

public void setUri(String uri) {
    this.uri = uri;
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getHost() {
    return host;
}

public void setHost(String host) {
    this.host = host;
}

public String getDomain() {
    return domain;
}

public void setDomain(String domain) {
    this.domain = domain;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}
}

This class represents the following JSON:

 "target": {
        "uri": "https://opam_server_host:opam_ssl_port/opam/target/9bbcbbb087174ad1900ea691a2573b61",
        "type": "ldap",
        "name": "person1-ldap",
        "host": "opam_server_host",
        "domain": "berkeley",
        "description": "Ldap target"
      }

2. TargetWrapper:

Note that target it is inside braces. This class simply wraps it.

public class TargetWrapper {

    private Target target;

    public Target getTarget() {
        return target;
    }

    public void setTarget(Target target) {
        this.target = target;
    }
 }

This class represents the following JSON:

{
      "target": {
        "uri": "https://opam_server_host:opam_ssl_port/opam/target/9bbcbbb087174ad1900ea691a2573b61",
        "type": "ldap",
        "name": "person1-ldap",
        "host": "opam_server_host",
        "domain": "berkeley",
        "description": "Ldap target"
      }
    }

3. RestApiResponse

This class represents the whole JSON returned by your api

public class RestApiResponse {

    @JSON(name="Target Collection")
    private List<TargetWrapper> targetCollection = new ArrayList<TargetWrapper>();

    @JSON(name="Target Collection")
    public List<TargetWrapper> getTarget_Collection() {
        return targetCollection;
    }
    @JSON(name="Target Collection")
    public void setTarget_Collection(List<TargetWrapper> tc) {
        this.targetCollection = tc;
    }

}

4. Let's test it!

public static void main(String[] args) {


        JSONDeserializer<RestApiResponse> js = new JSONDeserializer<RestApiResponse>();


        String input="{\"Target Collection\":[{\"target\":{\"uri\":\"https://opam_server_host:opam_ssl_port/opam/target/9bbcbbb087174ad1900ea691a2573b61\",\"type\":\"ldap\",\"name\":\"person1-ldap\",\"host\":\"opam_server_host\",\"domain\":\"berkeley\",\"description\":\"Ldap target\"}},{\"target\":{\"uri\":\"https://opam_server_host:opam_ssl_port/opam/target/ac246a162ce948c7b1cdcc17dfc92c15\",\"type\":\"ldap\",\"name\":\"person1-ldap2\",\"host\":\"opam_server_host:opam_ssl_port\",\"domain\":\"berkeley\",\"description\":\"Ldap target\"}}]}";

        RestApiResponse restApiResponse=js.deserialize(input,RestApiResponse.class);

        System.out.println(new JSONSerializer()
        .exclude("*.class").deepSerialize(restApiResponse));


    }

Output:

{
  "Target Collection": [
    {
      "target": {
        "description": "Ldap target",
        "domain": "berkeley",
        "host": "opam_server_host",
        "name": "person1-ldap",
        "type": "ldap",
        "uri": "https://opam_server_host:opam_ssl_port/opam/target/9bbcbbb087174ad1900ea691a2573b61"
      }
    },
    {
      "target": {
        "description": "Ldap target",
        "domain": "berkeley",
        "host": "opam_server_host:opam_ssl_port",
        "name": "person1-ldap2",
        "type": "ldap",
        "uri": "https://opam_server_host:opam_ssl_port/opam/target/ac246a162ce948c7b1cdcc17dfc92c15"
      }
    }
  ]
}

I hope it helps.

@Leo I didn't notice the version. can't you do it with that version? — rpax, Mar 06 '14 at 19:24

score 0 · Answer 2 · answered Feb 18 '14 at 20:11

Oh, look at this

    JSONDeserializer<Map<String,List<MetaTarget>>> j = new JSONDeserializer<>();
    List<MetaTarget> l = j.use("values.values", MetaTarget.class) //magic that means that the item inside a list (values #1) inside a map (values #2) is a MetaTarget
    .deserialize(new InputStreamReader(JSONParser.class.getResourceAsStream("sample.json")),Map.class) //have no idea what Map does here
    .get("Target Collection"); //since deserializer returns a map, use this get to return a map value, in this case, a List

    for(MetaTarget mt : l){
        System.out.println(mt.getTarget());
        mt.getTarget().getHostname(); //I can access the attribute... thanks god
    }

where

public class MetaTarget {
    private Target target;

    public Target getTarget() {
        return target;
    }

    public void setTarget(Target target) {
        this.target = target;
    }
}

and

public class Target {

    /**
     * uri is the target resource URI.
     */
    private String  uri;

    /**
     * type is the target type.
     */
    private String  type;

    /**
     * hostname is the target's host name.
     */
    private String  hostname;

    /**
     * name is the target name.
     */
    private String  name;

    /**
     * org is the target's organization.
     */
    private String  org;

    /**
     * domain is the target's domain.
     */
    private String  domain;

    /**
     * description is a description of the target system.
     */
    private String  description;

    public String getUri() {
        return uri;
    }

    public void setUri(String uri) {
        this.uri = uri;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getHostname() {
        return hostname;
    }

    public void setHostname(String hostname) {
        this.hostname = hostname;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getOrg() {
        return org;
    }

    public void setOrg(String org) {
        this.org = org;
    }

    public String getDomain() {
        return domain;
    }

    public void setDomain(String domain) {
        this.domain = domain;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public String toString() {
        return "Target [uri=" + uri + ", type=" + type + ", hostname=" + hostname + ", name=" + name + ", org=" + org + ", domain=" + domain + ", description=" + description + "]";
    }

}

less maps!

How to deserialize this JSON in an elegant way using flexjson

2 Answers2