Iterating a JSON using Jackson-Databind Library like JDOM for XML
I recently came across a situation that required me to be able to iterate over a JSON message payload similar to what can be done with JDOM in regards to XML similar to what I do within my Stax XML Mapreduce InputFormat. So basically in this case you need to treat JSONArray’s similar to XML ChildElements and JSONObjects as an Element or Attribute. Jackson-databind javadoc and Jackson-databind maven package.
See Example code on how to iterate a JSONObject or a JSONArray:
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import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.util.Iterator; import java.util.Map; import org.apache.commons.io.IOUtils; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.node.ObjectNode; public class JsonTester { public static void main(String[] args) throws IOException { ObjectMapper mapper = new ObjectMapper(); JsonNode rootNodeOrig = mapper.readTree(readJsonFile(“/tmp/json2.txt”)); JsonNode rootNode = mapper.readTree(readJsonFile(“/tmp/json2.txt”)); if (rootNode.isArray()) { iterateArrElements(rootNode); } else if (rootNode.isObject()) { iterateObjFields(rootNode); } System.out.println(“rootNodeNew: “+rootNode.toString()); System.out.println(“RootNodeOrig: “+rootNodeOrig.toString()); } public static void iterateObjFields(JsonNode jsonNode) { Iterator<Map.Entry<String, JsonNode>> fieldIter = jsonNode.fields(); ObjectNode parentObjectNode = (ObjectNode) jsonNode; while (fieldIter.hasNext()) { Map.Entry<String, JsonNode> field = fieldIter.next(); System.out.println(“Object/field.getKey(): ” + field.getKey()); if (field.getValue().isContainerNode()) { if (field.getValue().isArray()) { iterateArrElements(field.getValue()); } else if (field.getValue().isObject()) { iterateObjFields(field.getValue()); } } else { if (field.getKey().equalsIgnoreCase(“type”)) { parentObjectNode.put(field.getKey(), field.getValue().asText()+”_trash”); } System.out.println(“Object/field.getValue(): ” + field.getValue()); } } } public static void iterateArrElements(JsonNode jsonNode) { Iterator<JsonNode> elementsIter = jsonNode.elements(); while (elementsIter.hasNext()) { JsonNode element = elementsIter.next(); System.out.println(“ElementArray”); if (element.isContainerNode()) { if (element.isArray()) { iterateArrElements(element); } else if (element.isObject()) { iterateObjFields(element); } } } } public static String readJsonFile(String file) { File f = new File(file); if (f.exists()) { InputStream is = null; try { is = new FileInputStream(file); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } String jsonTxt = null; try { jsonTxt = IOUtils.toString(is); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return jsonTxt; } return null; } |
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