Jackson - Tree to JSON
In this example, we've created a Tree using JsonNode and write it to a json file and read back.
Create a java class file named JacksonTester in C:\>Jackson_WORKSPACE.
File: JacksonTester.java
import java.io.File; import java.io.IOException; import java.util.Iterator; import com.fasterxml.jackson.core.JsonParseException; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.node.ArrayNode; import com.fasterxml.jackson.databind.node.ObjectNode; public class JacksonTester { public static void main(String args[]){ JacksonTester tester = new JacksonTester(); try { ObjectMapper mapper = new ObjectMapper(); JsonNode rootNode = mapper.createObjectNode(); JsonNode marksNode = mapper.createArrayNode(); ((ArrayNode)marksNode).add(100); ((ArrayNode)marksNode).add(90); ((ArrayNode)marksNode).add(85); ((ObjectNode) rootNode).put("name", "Mahesh Kumar"); ((ObjectNode) rootNode).put("age", 21); ((ObjectNode) rootNode).put("verified", false); ((ObjectNode) rootNode).put("marks",marksNode); mapper.writeValue(new File("student.json"), rootNode); rootNode = mapper.readTree(new File("student.json")); JsonNode nameNode = rootNode.path("name"); System.out.println("Name: "+ nameNode.textValue()); JsonNode ageNode = rootNode.path("age"); System.out.println("Age: " + ageNode.intValue()); JsonNode verifiedNode = rootNode.path("verified"); System.out.println("Verified: " + (verifiedNode.booleanValue() ? "Yes":"No")); JsonNode marksNode1 = rootNode.path("marks"); Iterator<JsonNode> iterator = marksNode1.elements(); System.out.print("Marks: [ "); while (iterator.hasNext()) { JsonNode marks = iterator.next(); System.out.print(marks.intValue() + " "); } System.out.println("]"); } catch (JsonParseException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }
Verify the result
Compile the classes using javac compiler as follows:
C:\Jackson_WORKSPACE>javac JacksonTester.java
Now run the jacksonTester to see the result:
C:\Jackson_WORKSPACE>java JacksonTester
Verify the Output
Name: Mahesh Kumar Age: 21 Verified: No Marks: [ 100 90 85 ]
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