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Inner object(ArrayList) is not converting to JSON String?

I am facing issue in converting the nested list object to JSON.I am using object mapper and it is only converting the starting values and after that there is one arraylist inside it and it is not going through that list.
I have tried some basic iteration using JsonNode root = mapper.valueToTree(obj)so that i can iterate through the inner arraylist but i am not getting the result.I am new to this parsing conversion.
code snippet--
public class JsonUtils {
public static <T> String toJsonString(final T obj) throws IOException {
final ObjectMapper mapper = new ObjectMapper();
String jsonString = null;
try {
//JsonNode root = mapper.valueToTree(obj);
jsonString = mapper.writeValueAsString(obj);
} catch (final JsonProcessingException e) {
throw e;
} catch (IOException e) {
throw e;
}
return jsonString;
}
public static <T> String toJsonString(final List<T> lstObject) throws JSONException, IOException {
final JSONArray jsonArray = new JSONArray();
for (final T object : lstObject) {
final String json = JsonUtils.toJsonString(object);
final JSONObject jsonObj = new JSONObject(json);
jsonArray.put(jsonObj);
}
return jsonArray.toString();
}
}
So here is the result which i am getting -
[2, [{"geoMarketId":1,"geoname":"AP","geoId":1,"checked":false},
{"geoMarketId":7,"geoname":"EP","geoId":2,"checked":false},
{"geoMarketId":16,"geoname":"Japan","geoId":3,"checked":true},
{"geoMarketId":18,"geoname":"LA","geoId":4,"checked":true},
{"geoMarketId":22,"geoname":"MEA","geoId":5,"checked":true},
{"geoMarketId":24,"geoname":"NA","geoId":6,"checked":false}]]
Actual Result which should come-
{"geoMarketId":1,"geoname":"AP","geoId":1,"checked":false,
marketName:{"marketname":JP,"marketname":"AP","marketname":MP}}
My json conversion is ignoring this inner list in the same index.
Is there any way my json class can iterate and also convert that innerlist to JSON?

jackson xml lists deserialization recognized as duplicate keys

I'm trying to convert xml into json using jackson-2.5.1 and jackson-dataformat-xml-2.5.1
The xml structure is received from web server and unknown, therefore I can't have java class to represent the object, and I'm trying to convert directly into TreeNode using ObjectMapper.readTree.
My problem is jackson failing to parse lists. It is takes only the last item of the list.
code:
String xml = "<root><name>john</name><list><item>val1</item>val2<item>val3</item></list></root>";
XmlMapper xmlMapper = new XmlMapper();
JsonNode jsonResult = xmlMapper.readTree(xml);
The json result:
{"name":"john","list":{"item":"val3"}}
If I enable failure on duplicate keys xmlMapper.enable(DeserializationFeature.FAIL_ON_READING_DUP_TREE_KEY), exception is thrown:
com.fasterxml.jackson.databind.JsonMappingException: Duplicate field 'item' for ObjectNode: not allowed when FAIL_ON_READING_DUP_TREE_KEY enabled
Is there any feature which fixes this problem? Is there a way for me to write custom deserializer which in event of duplicate keys turn them into array?

I use this approach:
Plugin a serializer into XmlMapper using a guava multimap. This puts everything into lists.
Write out the json using SerializationFeature.WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED. This unwrapps all lists with size==1.
Here is my code:
#Test
public void xmlToJson() {
String xml = "<root><name>john</name><list><item>val1</item>val2<item>val3</item></list></root>";
Map<String, Object> jsonResult = readXmlToMap(xml);
String jsonString = toString(jsonResult);
System.out.println(jsonString);
}
private Map<String, Object> readXmlToMap(String xml) {
try {
ObjectMapper xmlMapper = new XmlMapper();
xmlMapper.registerModule(new SimpleModule().addDeserializer(Object.class, new UntypedObjectDeserializer() {
#SuppressWarnings({ "unchecked", "rawtypes" })
#Override
protected Map<String, Object> mapObject(JsonParser jp, DeserializationContext ctxt) throws IOException {
JsonToken t = jp.getCurrentToken();
Multimap<String, Object> result = ArrayListMultimap.create();
if (t == JsonToken.START_OBJECT) {
t = jp.nextToken();
}
if (t == JsonToken.END_OBJECT) {
return (Map) result.asMap();
}
do {
String fieldName = jp.getCurrentName();
jp.nextToken();
result.put(fieldName, deserialize(jp, ctxt));
} while (jp.nextToken() != JsonToken.END_OBJECT);
return (Map) result.asMap();
}
}));
return (Map) xmlMapper.readValue(xml, Object.class);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
static public String toString(Object obj) {
try {
ObjectMapper jsonMapper = new ObjectMapper().configure(SerializationFeature.INDENT_OUTPUT, true)
.configure(SerializationFeature.WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED, true);
StringWriter w = new StringWriter();
jsonMapper.writeValue(w, obj);
return w.toString();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
It prints
{
"list" : {
"item" : [ "val1", "val3" ]
},
"name" : "john"
}
Altogether it is a variante of this approach, which comes out without guava multimap:
https://github.com/DinoChiesa/deserialize-xml-arrays-jackson
Same approach is used here:
Jackson: XML to Map with List deserialization

I ran into the same problem and decided to roll my own using straightforward DOM. The main problem is that XML does not really lends itself to a Map-List-Object type mapping like JSon does. However, with some assumptions, it is still possible:
Text are stored in null keys either as a single String or a List.
Empty elements, i.e. are modeled with an empty map.
Here's the class in the hope that it might just help someone else:
public class DeXML {
public DeXML() {}
public Map<String, Object> toMap(InputStream is) {
return toMap(new InputSource(is));
}
public Map<String, Object> toMap(String xml) {
return toMap(new InputSource(new StringReader(xml)));
}
private Map<String, Object> toMap(InputSource input) {
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(input);
document.getDocumentElement().normalize();
Element root = document.getDocumentElement();
return visitChildNode(root);
} catch (ParserConfigurationException | SAXException | IOException e) {
throw new RuntimeException(e);
}
}
// Check if node type is TEXT or CDATA and contains actual text (i.e. ignore
// white space).
private boolean isText(Node node) {
return ((node.getNodeType() == Element.TEXT_NODE || node.getNodeType() == Element.CDATA_SECTION_NODE)
&& node.getNodeValue() != null && !node.getNodeValue().trim().isEmpty());
}
private Map<String, Object> visitChildNode(Node node) {
Map<String, Object> map = new HashMap<>();
// Add the plain attributes to the map - fortunately, no duplicate attributes are allowed.
if (node.hasAttributes()) {
NamedNodeMap nodeMap = node.getAttributes();
for (int j = 0; j < nodeMap.getLength(); j++) {
Node attribute = nodeMap.item(j);
map.put(attribute.getNodeName(), attribute.getNodeValue());
}
}
NodeList nodeList = node.getChildNodes();
// Any text children to add to the map?
List<Object> list = new ArrayList<>();
for (int i = 0; i < node.getChildNodes().getLength(); i++) {
Node child = node.getChildNodes().item(i);
if (isText(child)) {
list.add(child.getNodeValue());
}
}
if (!list.isEmpty()) {
if (list.size() > 1) {
map.put(null, list);
} else {
map.put(null, list.get(0));
}
}
// Process the element children.
for (int i = 0; i < node.getChildNodes().getLength(); i++) {
// Ignore anything but element nodes.
Node child = nodeList.item(i);
if (child.getNodeType() != Element.ELEMENT_NODE) {
continue;
}
// Get the subtree.
Map<String, Object> childsMap = visitChildNode(child);
// Now, check if this is key already exists in the map. If it does
// and is not a List yet (if it is already a List, simply add the
// new structure to it), create a new List, add it to the map and
// put both elements in it.
if (map.containsKey(child.getNodeName())) {
Object value = map.get(child.getNodeName());
List<Object> multiple = null;
if (value instanceof List) {
multiple = (List<Object>)value;
} else {
map.put(child.getNodeName(), multiple = new ArrayList<>());
multiple.add(value);
}
multiple.add(childsMap);
} else {
map.put(child.getNodeName(), childsMap);
}
}
return map;
}
}

You can catch that exception and do something like :
List<MyClass> myObjects = mapper.readValue(input, new TypeReference<List<MyClass>>(){});
(got it from here How to use Jackson to deserialise an array of objects)
It's a hackish approach and you will have to figure out how to resume from there.

Underscore-java library supports this XML.
String xml = "<root><name>john</name><list><item>val1</item>val2<item>val3</item></list></root>";
String json = U.xmlToJson(xml);
System.out.println(json);
Output JSON:
{
"root": {
"name": "john",
"list": {
"item": [
"val1",
{
"#item": {
"#text": "val2"
}
},
"val3"
]
}
},
"#omit-xml-declaration": "yes"
}

Converting POJO to JsonNode using a JsonView

I'm writing a typical Play Framework app where I want to return a JsonNode from my Controller's methods, using Jackson.
This is how I'm doing it right now:
public static Result foo() {
MyPojoType myPojo = new myPojo();
String tmp = new ObjectMapper().writerWithView(JSONViews.Public.class).writeValueAsString(myPojo);
JsonNode jsonNode = Json.parse(tmp);
return ok(jsonNode);
}
Is it possible to avoid the "String tmp" copy and convert directly from MyPojoType to JsonNode using a view?
Maybe I can use ObjectMapper.valueToTree, but I don't know how to specify a JSonView to it.

Interesting question: off-hand, I don't think there is a specific method, and your code is the most straight-forward way to do it: valueToTree method does not apply any views.
So code is fine as is.

After more investigation, this is what I did in the end to avoid the redundant work:
public Result toResult() {
Content ret = null;
try {
final String jsonpayload = new ObjectMapper().writerWithView(JsonViews.Public.class).writeValueAsString(payload);
ret = new Content() {
#Override public String body() { return jsonpayload; }
#Override public String contentType() { return "application/json"; }
};
} catch (JsonProcessingException exc) {
Logger.error("toResult: ", exc);
}
if (ret == null)
return Results.badRequest();
return Results.ok(ret);
}
In summary: The methods ok, badRequest, etc accept a play.mvc.Content class. Then, simply use it to wrap your serialized json object.

As i know, with jax-rs, you can do this :
public Response toResult() throws JsonProcessingException {
final ObjectWriter writer = new ObjectMapper()
.writerWithView(JSONViews.Public.class);
return Response.ok(new StreamingOutput() {
#Override
public void write(OutputStream outputStream) throws IOException, WebApplicationException {
writer.writeValue(outputStream, /*Pojo*/ payload);
}
}).build();
}
So you have to find a class in the Play framework which able to stream the result (through an OutputStream)

I think this is more efficient way
public Result toResult() {
MyPojo result = new MyPojo();
JsonNode node = objectMapper.valueToTree(result);
return ok(node);
}

RestTemplate & Jackson - Custom JSON deserializing?

The webservice returns an empty string instead of NULL which causes Jackson to crash.
So I created a custom parser, and I'm trying to parse it manually? Any idea How I could achieve this?
What Am I doing wrong here? All I'm trying to do is to parse JSON to object as I normally would. The field names are added to my properties using #JsonProperty so the parser should know how to convert it.
public class InsertReplyDeserializer extends JsonDeserializer<ListingReply> {
#Override
public ListingReply deserialize(JsonParser jsonParser, DeserializationContext arg1)
throws IOException, JsonProcessingException {
ObjectCodec oc = jsonParser.getCodec();
JsonNode node = oc.readTree(jsonParser);
// If service returns "" instead of null return a NULL object and don't try to parse
if (node.getValueAsText() == "")
return null;
ObjectMapper objectMapper = new ObjectMapper();
ListingReply listingReply = objectMapper.readValue(node, ListingReply.class);
return listingReply;
}
}

Here is how I resolved it
#Override
public MyObject deserialize(JsonParser jsonParser, DeserializationContext arg1)
throws IOException, JsonProcessingException {
ObjectCodec oc = jsonParser.getCodec();
JsonNode node = oc.readTree(jsonParser);
if (node.getValueAsText() == "")
return null;
MyObject myObject = new MyObject();
myObject.setMyStirng(node.get("myString").getTextValue());
JsonNode childNode = node.get("childObject");
ObjectMapper objectMapper = new ObjectMapper();
ChildObject childObject = objectMapper.readValue(childNode,
ChildObject.class);
myObject.setChildObject(childObject);
return myObject;
}

I am not sure you need to manually parse response. You solution would work but seems sub-optimal in my opinion. Since it looks like that you are using RestTemplate, you should rather write (or move your parser code to) your own message converter. Then add this converter to your rest template object which will internally deserialize the value for you. Something along the lines,
public class CustomHttpmsgConverter extends AbstractHttpMessageConverter<Object> {
private ObjectMapper objectMapper = new ObjectMapper();
#Override
protected Object readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
InputStream istream = inputMessage.getBody();
String responseString = IOUtils.toString(istream);
if(responseString.isEmpty()) //if your response is empty
return null;
JavaType javaType = getJavaType(clazz);
try {
return this.objectMapper.readValue(responseString, javaType);
} catch (Exception ex) {
throw new HttpMessageNotReadableException(responseString);
}
}
//add this converter to your resttemplate
RestTemplate template = new RestTemplate();
List<HttpMessageConverter<?>> converters = new ArrayList<HttpMessageConverter<?>>();
converters.add(new CustomHttpmsgConverter());
template.setMessageConverters(converters);

Jackson custom deserializers creating empty pojo when reading list

I have the following json
{
"id":null,
"name":"Myapp",
"description":"application",
"myListA":["java.util.ArrayList",[{
"id":50,
"name":"nameA1",
"myListB":{
"id":48,
"name":"nameB1",
"myListC":["java.util.ArrayList",[{
"id":1250,
"name":"nameC1",
"description":"nameC1_desc",
"myReferenceObject":{
"code":"someCodeA"
}
},{
"id":1251,
"name":"nameC2",
"description":"nameC1_desc",
"myReferenceObject":{
"code":"someCodeB"
}
and so on.
I i wish to replace myReferenceObject with an item from persistence layer.
I followed JacksonHowToCustomDeserializers
My deserializer is as follows:
public class MyReferenceObjectCodeDeserializer extends JsonDeserializer<MyReferenceObjectBean> {
#Override
public ColumnReferenceBean deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
while (jp.nextToken() != JsonToken.END_OBJECT) {
String fieldname = jp.getCurrentName();
jp.nextToken();
if ("code".equalsIgnoreCase(fieldname)) {
MyReferenceObjectBean b = MyReferenceObjectServiceImpl.retrieveByCode(jp.getText());
logger.info("returning " +b.toString());
return b;
}
}
logger.info("returning null");
return null;
}
}
And I attache the module like so:
ObjectMapper mapper = new ObjectMapper();
mapper.enableDefaultTyping();
SimpleModule module = new SimpleModule("myModule", new Version(1, 0, 0, null));
module.addDeserializer(MyReferenceObjectBean.class, new MyReferenceObjectCodeDeserializer());
mapper.registerModule(module);
try {
return mapper.readValue(serializedJsonString, MyMainObjectBean.class);
} catch (IOException e) {
logger.error("Unable to parse=" + serializedJsonString, e);
}
everything debugs correctly however the resulting myListC list has double the amount of objects with even numbers holding the correct objects along with the correct myReferenceObject out of persistence (deserialized correctly using my module) and the odd elements holding empty Pojos, that is an object with null values for all variables.
Through debug, It never reaches return null in my custom deserializer, for it works properly each time its executed. The issue seems to be further up stream where it inserts blank myListC objects.
Any help would greeatly be appreciated.
Thanks!

There is a logic problem in your code.
You want to loop until you reach the end of the object but break your loop with return b (if block). This means that you will not read the object stream until its end.
Try something like this (didn't try it but should work).
public class MyReferenceObjectCodeDeserializer extends JsonDeserializer<MyReferenceObjectBean> {
#Override
public ColumnReferenceBean deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
MyReferenceObjectBean b = null;
while (jp.nextToken() != JsonToken.END_OBJECT) {
String fieldname = jp.getCurrentName();
jp.nextToken();
if ("code".equalsIgnoreCase(fieldname)) {
b = MyReferenceObjectServiceImpl.retrieveByCode(jp.getText());
logger.info("returning " +b.toString());
}
}
if (b==null) logger.info("returning null");
return b;
}
}
You can also have a look at Genson http://code.google.com/p/genson/ if you can change from jackson. In addition of some other features it is supposed to be easier to use. Here is how you can solve your problem with genson (for this example it is quite similar to jackson):
public class MyReferenceObjectCodeDeserializer implements Deserializer<MyReferenceObjectBean> {
public MyReferenceObjectBeandeserialize(ObjectReader reader, Context ctx) throws TransformationException, IOException {
MyReferenceObjectBean b = null;
reader.beginObject();
while (reader.hasNext()) {
reader.next();
if ("code".equalsIgnoreCase(reader.name()))
b = MyReferenceObjectServiceImpl.retrieveByCode(reader.valueAsString());
}
reader.endObject();
return b;
}
}
// register it
Genson genson = new Genson.Builder().withDeserializers(new MyReferenceObjectCodeDeserializer()).create();
MyClass myClass = genson.deserialize(json, MyClass.class);