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Convert JSON to/from Map using Jackson library in Java?
The JSON Jackson is a library for Java and it has very powerful data binding capabilities and provides a framework to serialize custom java objects to JSON and deserialize JSON back to Java object. We can convert JSON to/from Map using readValue() and writeValueAsString() methods of com.fasterxml.jackson.databind.ObjectMapper class.
JSON to Map
Syntax
public <T> T readValue(String content, TypeReference valueTypeRef) throws IOException, JsonParseException, JsonMappingException
Example
import java.io.*; import java.util.*; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.core.type.TypeReference; public class ConvertJSONToMapTest { public static void main(String args[]) { try { ObjectMapper mapper = new ObjectMapper(); String jsonString = "{\"Name\":\"Raja\", \"Technology\":\"Java\"}"; Map<String, Object> jsonMap = new HashMap<String, Object>(); jsonMap = mapper.readValue(jsonString, new TypeReference<Map<String, String>>(){}); // converts JSON to Map System.out.println(jsonMap); } catch(IOException ie) { ie.printStackTrace(); } } }
Output
{Name=Raja, Technology=Java}
Map to JSON
Syntax
public String writeValueAsString(Object value) throws JsonProcessingException
Example
import java.io.*; import java.util.*; import com.fasterxml.jackson.core.*; import com.fasterxml.jackson.databind.ObjectMapper; public class ConvertMapToJSONTest { public static void main(String args[]) throws IOException { ObjectMapper mapper = new ObjectMapper(); String jsonString = ""; Map<String, Object> map = new HashMap<String, Object>(); map.put("Raja", "Java Technology"); map.put("Ravi", "Python Technology"); map.put("Adithya", "Spark Technology"); map.put("Vamsi", "Web Technology"); jsonString = mapper.writeValueAsString(map); // converts Map to JSON System.out.println(map); } }
Output
{"Raja":"Java Technology", "Vamsi":"Web Technology", "Ravi":"Python Technology", "Adithya":"Spark Technology"}
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