How to convert hashmap to JSON object in Java

Question

How to convert or cast hashmap to JSON object in Java, and again convert JSON object to JSON string?

Answer 1

I faced a similar problem when deserializing the Response from custom commands in selenium. The response was json, but selenium internally translates that into a java.util.HashMap[String, Object]

If you are familiar with scala and use the play-API for JSON, you might benefit from this:

import play.api.libs.json.{JsValue, Json}
import scala.collection.JavaConversions.mapAsScalaMap


object JsonParser {

  def parse(map: Map[String, Any]): JsValue = {
    val values = for((key, value) <- map) yield {
      value match {
        case m: java.util.Map[String, _] @unchecked => Json.obj(key -> parse(m.toMap))
        case m: Map[String, _] @unchecked => Json.obj(key -> parse(m))
        case int: Int => Json.obj(key -> int)
        case str: String => Json.obj(key -> str)
        case bool: Boolean => Json.obj(key -> bool)
      }
    }

    values.foldLeft(Json.obj())((temp, obj) => {
      temp.deepMerge(obj)
    })
  }
}

Small code description:

The code recursively traverses through the HashMap until basic types (String, Integer, Boolean) are found. These basic types can be directly wrapped into a JsObject. When the recursion is unfolded, the deepmerge concatenates the created objects.

'@unchecked' takes care of type erasure warnings.