Parsing JSON with a value with dynamic type (either string or object) with Jackson's ObjectMapper

Question

I am new to Jackson and I am having some problems determining the best way to deal with processing JSON files that are dynamic in nature. I know I could solve the issue with the streaming or tree API, but this would involve a lot of code which will not be easily maintained. For example, take the following two json files:

{
   something: "somethingValue"
   somethingelse: "anotherValue"
   url: "http://something.com"
}

and

{
   something: "somethingValue"
   somethingelse: "anotherValue"
   url: {
           service1: [
              "http://something.com",
              "https://something.com" ],
           service2: [
              "http://something2.com",
              "https://something2.com" ],
        }
}

the default behaviour of the first json object after being parsed, should add the URL to both service1 and service2 url lists in the subclass "URL". where the second allow specifying very specific urls to each. The data object for url class I was planning on use is as follows:

public class url {

   // ideally, I would use the java.net.URL instead of String
   public List<String> service1;    
   public List<String> service2;

   // also includes getter/setters using a fluent style
   ...
}

There would also be some other parent class which would have a parameter for URL and other first level json parameters.

What is the best way to handle this in jackson?

libik · Accepted Answer · 2015-04-23 14:56:47Z

1

The second one is not valid JSON, this is :

{
   "something": "somethingValue",
   "somethingelse": "anotherValue",
   "url": {
           "service1" : [
              "http://something.com",
              "https://something.com" ],
           "service2" : [
              "http://something2.com",
              "https://something2.com" ]
        }
}

You can create it/consume it with class A which looks like following

class A{
 String something;
 String somethingElse;
 B url;
}

class B{
 Str service1;
 List<String> service2;
}

To achieve anything dynamically no matter what, you have to put it in Lists, therefore instead of solution above, you can do this

class A{
 String something;
 String somethingElse;
 B url;
}

class B{
 List<C> services;
}    

class C{
  List<String> service;
}

edited Apr 23, 2015 at 14:56

answered Apr 23, 2015 at 14:38

libik

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2 Comments

user1187957 Over a year ago

you are right about my second json code. I will update - forgot the colons. :) and how would this class structure be wired up using (i assume) the jackson mapper?

oberlies Over a year ago

And how would you propose to solve the problem that url may either be a String or an instance of B?

Matthew Moisen · Accepted Answer · 2017-01-27 21:23:06Z

I ended up mixing JsonNode to get this working.

public class Foo {
    @JsonProperty("something")
    private String something;

    @JsonProperty("somethingelse")
    private String somethingelse;

    @JsonProperty("url") 
    JsonNode url;

    // getters setters

    public static Foo parse(String jsonString) {
        ObjectMapper mapper = new ObjectMapper();
        Foo foo = mapper.readValue(jsonString, Foo.class);
        return foo;
    }

    public static boolean validate(Foo foo) {
        JsonNode url = foo.path("url");
        if (url.isTextual()) {
            // this is the first case {"url": "http://something.com"}
            System.out.println(url.getTextValue());
        } else {
            // This is the second case

        }
    }
}

user1187957 · Accepted Answer · 2015-04-27 13:53:50Z

-1

Answer:

After struggling with Jackson to do what I want in a simple and elegant way, I ended up switching to Gson library for JSON parsing. it allowed me to create a custom deserializer for my class that was extremely easy.

An example of something similar that I did can be found here:

http://www.baeldung.com/gson-deserialization-guide

I appreciate the help and guidance with Jackson, however it just made me realize that Jackson was just not going to meet my needs.

-Stewart

answered Apr 27, 2015 at 13:53

user1187957

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1 Comment

oberlies Over a year ago

Link-only answers are discouraged on StackOverflow. It is okay to provide a link, but the post here shall still contain a summary of the solution.

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