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given a JSON-annotated Java class, I am looking for some utility to get its type information.

For example having below class structure:

class A extends B {
  @JsonIgnore
  int _some_internal_field;
  int f1;
  C f2;
}
class B {
  boolean f3;
  String f4;
}
class C {
  float f5;
}

I would like to call

System.out.println(
  jsonTypeInfoFrom(A.class)
 .toString());

and get:

{
  "f1": "int",
  "f2": {
    "f5": "float"
  },
  "f3": "boolean",
  "f4": "string"
}

Where I can find such a jsonTypeInfoFrom(Class) method? Looked into Jackson itself, but could not find one (yet).

Please help :)

Adrian.

Adrian Herscu
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  • This might answer your need : https://stackoverflow.com/questions/26199716/generate-json-schema-from-java-class – Aaron Oct 29 '18 at 10:40
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    The answer from the question I linked seems to be deprecated, looks like you should use [this](https://github.com/FasterXML/jackson-module-jsonSchema) jackson module (no idea whether it is included in a standard jackson install). Both produce a json-schema which isn't the format you asked for but includes the same data – Aaron Oct 29 '18 at 10:59

2 Answers2

1

You can use jacksin-module-jsonSchema library. you can add the library using the folowing dependency:

>       <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-jsonSchema</artifactId>
            <version>2.9.5</version>
        </dependency>

and here is a sample code for generating json schema from java class:

  SchemaFactoryWrapper schemaFactory = new SchemaFactoryWrapper();
  ObjectMapper mapper = new ObjectMapper();
  mapper.acceptJsonFormatVisitor(Entity.class, schemaFactory);
  JsonSchema resultSchema = schemaFactory.finalSchema();
  System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(resultSchema));
Amir
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//Use refelcting Api to get the declared fields and create the json schema using HashMap
public static String getJsonSchema(Class clazz) throws IOException {
         Field[] fields = clazz.getDeclaredFields();

         List<Map<String,String>> map=new ArrayList<Map<String,String>>();
         for (Field field : fields) {
             HashMap<String, String> objMap=new  HashMap<String, String>();
             objMap.put("name", field.getName());
             objMap.put("type", field.getType().getSimpleName());
             objMap.put("format", "");
             map.add(objMap);
         }
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(map);

       return json;
    }
P Rajesh
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