Develop Reference

Can I tell Jackson to conditionally serialize a private instance variable based on differently-typed method?

To the best of my understanding, Jackson will
serialize a public instance variable to the variable name
public List<String> myStrings = new ArrayList<>();
serializes to
{ 'myStrings' : [ ... ] }
serialize a private instance variable to the variable name if it has a public getter named getVariable():
private List<String> myStrings = new ArrayList<>();
public List<String> getMyStrings() { return myStrings; }
serializes similar to
{ 'myStrings' : [ ... ] }
However, what I am trying to achieve is to serialize it to a String (instead of array of Strings) based on another method, but keep the JSON key (based on #JsonInclude(JsonInclude.Include.NON_NULL) suppressing the original accessor in some cases
#JsonInclude(JsonInclude.Include.NON_NULL)
private boolean firstStringOnly = true;
private List<String> myStrings = new ArrayList<>();
public List<String> getMyStrings() { return firstStringOnly ? null: myStrings; }
public String getFirstString() { return firstStringOnly ? myStrings.get(0) : null; }
Desired JSON serialization:
For firstStringOnly==true: { 'myStrings' : 'first_String' } (using getFirstString())
For firstStringOnly==false: { 'myStrings' : [ ... ] } (using getMyStrings())
Is this possible to do? I'm specifically looking to avoid using custom serializers, and do this via annotations only.
You can assume a reasonably recent version of Jackson and Java 8.
Just to re-iterate, the question constraints are:
* NO custom serializer
* Both use cases produce the same JSON key

You can generalize getMyStrings() method and make it return Object. And inside check the flag and return first value or all values. Here is my sample
public class tst {
private static class YourObject {
private boolean firstStringOnly;
private List<String> myStrings = new ArrayList<>();
public YourObject(boolean firstStringOnly) {
this.firstStringOnly = firstStringOnly;
this.myStrings.add("str1");
this.myStrings.add("str2");
}
public Object getMyStrings(){
return firstStringOnly ? myStrings.get(0) : myStrings;
}
}
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(new YourObject(true)));
System.out.println(mapper.writeValueAsString(new YourObject(false)));
}
}
The output is
{"myStrings":"str1"}
{"myStrings":["str1","str2"]}

EDIT: Sorry, i have misread your initial question. I assume you want to keep both of the typed getters. Would this work for you?
public class TestClass {
private boolean firstStringOnly = true;
private List<String> myStrings = new ArrayList<>();
#JsonIgnore
public boolean isFirstStringOnly() {
return firstStringOnly;
}
public void setFirstStringOnly(boolean firstStringOnly) {
this.firstStringOnly = firstStringOnly;
}
#JsonIgnore
public List<String> getMyStrings() {
return firstStringOnly ? null : myStrings;
}
#JsonIgnore
public String getFirstString() { return firstStringOnly ? myStrings.get(0) : null; }
#JsonProperty("myStrings")
public Object getMyStringsForSerialization() {
return firstStringOnly ? getFirstString() : getMyStrings();
}
public void setMyStrings(List<String> myStrings) {
this.myStrings = myStrings;
}

Gson- Parsing a JSON array of JSON objects to ArrayList<org.json.JSONObject>

I have a JSON string like this:
{
"r": [
{
"pic": "1.jpg",
"name": "Name1"
},
{
"pic": "2.jpg",
"name": "Name2"
},
{
"pic": "3.jpg",
"name": "Name3"
}
]
}
I want to parse to this POJO model:
public class Catalog {
#SerializedName("r")
#Expose
private List<JSONObject> r = new ArrayList<JSONObject>();
public List<JSONObject> getR() {
return r;
}
public void setR(List<JSONObject> r) {
this.r = r;
}
}
I am parsing this way:
Catalog cat = new Gson().fromJson(jsonString,Catalog.class);
But finally am getting this json
{
"r": [
{
"nameValuePairs": {}
},
{
"nameValuePairs": {}
},
{
"nameValuePairs": {}
}
]
}
Please note that I don't want to use com.google.gson.JsonObject.
I want to use org.json.JSONObject. How to achieve this because almost all of my code uses it?

As it was already mentioned in other answer and comments, you probably might not really want to use org.json.JSONObject for several reasons. But if it's a must for you, you just have to create your org.json.JSONObject-aware Gson instance.
final class JSONObjectJsonDeserializer
implements JsonDeserializer<JSONObject> {
// The implementation is fully thread-safe and can be instantiated once
private static final JsonDeserializer<JSONObject> jsonObjectJsonDeserializer = new JSONObjectJsonDeserializer();
// Type tokens are immutable values and therefore can be considered constants (and final) and thread-safe as well
private static final TypeToken<Map<String, Object>> mapStringToObjectTypeToken = new TypeToken<Map<String, Object>>() {
};
private JSONObjectJsonDeserializer() {
}
static JsonDeserializer<JSONObject> getJsonObjectJsonDeserializer() {
return jsonObjectJsonDeserializer;
}
#Override
public JSONObject deserialize(final JsonElement jsonElement, final Type type, final JsonDeserializationContext context) {
// Convert the input jsonElement as if it were a Map<String, Object> (a generic representation for JSON objectS)
final Map<String, Object> map = context.deserialize(jsonElement, mapStringToObjectTypeToken.getType());
// And forward the map to the JSONObject constructor - it seems to accept it nice
return new JSONObject(map);
}
}
Gson is designed thread-safe and does not need to be instantiated every time serialization or deserialization is necessary:
private static final Gson gson = new GsonBuilder()
.registerTypeAdapter(JSONObject.class, getJsonObjectJsonDeserializer())
.create();
And finally:
final Catalog catalog = gson.fromJson(jsonString, Catalog.class);
out.println(catalog.getR());
with the following result:
[{"name":"Name1","pic":"1.jpg"}, {"name":"Name2","pic":"2.jpg"}, {"name":"Name3","pic":"3.jpg"}]
Anyway, I would suggest you to redesign your mappings model.

I think you don't need JSONObject.
Try this
// is wrapped class for serialized json.
public class JsonExample
{
List<Catalog> r;
}
public class Catalog {
private String pic;
private String name;
public String getPic() {
return pic;
}
public String getName() {
return name;
}
}
JsonExample example = new Gson().fromJson(json, JsonExample.class);
Additional - using JSONObject
JSONObject obj = new JSONObject(json);
JSONArray arr = obj.getJSONArray("r");
List<Catalog> cataList = new ArrayList<>();
for(int i = 0 ; i < arr.length() ; ++i)
{
cataList.add(new Catalog(arr.getJSONObject(i)));
}
public class Catalog {
private String pic;
private String name;
public Catalog(JSONObject obj) throws JSONException
{
pic = obj.getString("pic");
name = obj.getString("name");
}
public String getPic() {
return pic;
}
public String getName() {
return name;
}
}

I think in your case, usage of gson library is not required at all.
Only org.json can solve the entire problem.
E.g.:
JSONObject json = new JSONObject(jsonString);
JSONArray jsonArray = json.getJSONArray("r");
List<JSONObject> jsonList = new ArrayList<>();
for (int i = 0; i < jsonArray.length(); i++) {
jsonList.add(jsonArray.getJSONObject(i));
}
Catalog catalog = new Catalog();
catalog.setR(jsonList);

Convert ArrayList of custom objects to JSON

I have an ArrayList of custom Objects. Each of these objects have an arraylist of another custom object. Then these second level of custom objects have an arraylist of another custom object.
This is how the class hierarchy looks like
public class Undle {
private String undleStatus;
private ArrayList<ArcelFolder> arcelFolders;
public ArrayList<ArcelFolder> getArcelFolders() {
return arcelFolders;
}
public void setArcelFolders(ArrayList<ArcelFolder> arcelFolders) {
this.arcelFolders = arcelFolders;
}
//Other getter and setters
}
public class ArcelFolder {
private ArrayList<ArcelDocument> arcelDocuments;
private String arcelStatus;
public String getArcelStatus() {
return arcelStatus;
}
public void setArcelStatus(String arcelStatus) {
this.arcelStatus = arcelStatus;
}
public ArrayList<ArcelDocument> getArcelDocuments() {
return arcelDocuments;
}
public void setArcelDocuments(ArrayList<ArcelDocument> arcelDocuments) {
this.arcelDocuments = arcelDocuments;
}
}
public class ArcelDocument {
private String gain;
public String getGain() {
return gain;
}
public void setGain(String gain) {
this.gain = gain;
}
}
I have an arraylist of Undle objects
ArrayList<Undle> undleList = new ArrayList<Undle>();
// Create objects of ArcelFolder and ArcelDocument
// Add ArcelDocument list to ArcelFolder
// Add ArcelFolder list to Undle arraylist
I would like to convert Undle ArrayList to a JSON. How can I flatten this hierarcical structure of beans and put it in a JSON?
I tried doing something like
org.json.simple.JSONObject resultObj = new JSONObject(undleList);
and
org.json.simple.JSONArray arr = new JSONArray(undleList);
But it seems that they work only if a String ArrayList is passed.

Gson gson = new Gson();
Type type = new TypeToken<List<Bundle>>() {}.getType();
String json = gson.toJson(bundleList, type);
System.out.println(json);
List<Bundle> fromJson = gson.fromJson(json, type);
for (Bundle bundle : fromJson) {
System.out.println(bundle);
}

How to generate Json with Java

I am working on an application where i have to generate a json like this:
[
{"title":"Culture","start":"Salary","end":"Work"},
{"title":"Work","start":"Salary","end":"Work"}
]
But my code generates json like this:
{{"name":"Culture"},[{"name":"Salary"},{"name":"Work"}],}
My code:
public class ParseJson {
public static class EntryListContainer {
public List<Entry> children = new ArrayList<Entry>();
public Entry name;
}
public static class Entry {
private String name;
public Entry(String name) {
this.name = name;
}
}
public static void main(String[] args) {
EntryListContainer elc1 = new EntryListContainer();
elc1.name = new Entry("Culture");
elc1.children.add(new Entry("Salary"));
elc1.children.add(new Entry("Work"));
ArrayList<EntryListContainer> al = new ArrayList<EntryListContainer>();
Gson g = new Gson();
al.add(elc1);
StringBuilder sb = new StringBuilder("{");
for (EntryListContainer elc : al) {
sb.append(g.toJson(elc.name));
sb.append(",");
sb.append(g.toJson(elc.children));
sb.append(",");
}
String partialJson = sb.toString();
if (al.size() > 1) {
int c = partialJson.lastIndexOf(",");
partialJson = partialJson.substring(0, c);
}
String finalJson = partialJson + "}";
System.out.println(finalJson);
}
}
Can anyone help me to generate this json in my required format ?? please thanks in advance

Try this
public class Entry {
public String title;
public String start;
public String end;
}
And in another part of your code
private ArrayList<Entry> entries = new ArrayList<>();
// Fill the entries...
String the_json = new Gson().toJson(entries);

1) First Create your POJO
public class MyJSONObject {
private String title;
private String start;
private String end;
//getter and setter methods
[...]
#Override
public String toString() {
}
}
2) Use com.google.code.gson library
public static void main(String[] args) {
{
ArrayList<MyJSONObject> myJSONArray = new ArrayList<>();
MyJSONObject obj = new MyJSONObject();
obj.setTitle="Culture";
obj.set[...]
myJSONArray.add(obj);
Gson gson = new Gson();
// convert java object to JSON format,
// and returned as JSON formatted string
String json = gson.toJson(myJSONArray);
System.out.println(json);
}
Output : [{"title":"Culture","start":"Salary","end":"Work"}, ...]

I recommend you to use some JSON Java API, like Gson. It's very simple to generate a string json from a POJO object or to create a POJO object from a string json.
The code for generating a string json from a POJO object is like this:
Gson gson = new Gson();
String stringJson = gson.toJson(somePojoObject);
The code for creating a POJO object from a string json is like this:
Gson gson = new Gson();
SomePojoClass object = gson.fromJson(stringJson, SomePojoClass.class);
Note that you can not serialize objects with circular references. This causes infinite recursion.

Converting the Database details to JSON object

I have a table with has the columns namely
recordID, recordName , titleFeild, titleIDMap, titleId, titleStartDate, titleEndDate, languageId
Now I have convert the data from above columns to the JSON object data which looks like below
{
"recordId" :10,
"recordName" : "RECORDS",
"records" : [ {
"titleField" : 1,
"titleIDMap" : null,
"titleId" : 500,
"titleStartDate" : "2013-12-22T00:00:00.000+0000",
"titleEndDate" : "2013-12-03T00:00:00.000+0000",
"languageId" : 20
}]
}
Please note that records is an array of columns ( titleFeild,titleIDMap,titleId,titleStartDate,titleEndDate,languageId)
The code so far I have developed is
List<Object[]> objList = dao.getStatus();
Integer result = null;
JSONObject jsonData = new JSONObject();
JSONArray jsonDataArray = new JSONArray();
if(objList!=null && objList.size()>10000)
{
for (Object[] nameObj : objList) {
jsonData.put("", nameObj.get(arg0) );
}
}
How do I construct the JSON Object from the columns data ?

You can easily achieve this with google-gson library. In simple terms you would have to create a couple of Pojos (with reference to another containin a list of references).
Consider RecordID and RecordName as Meta Data.
Create a pojo representing this information:
public class DbMetaPojo {
private int recordID;
private String recordName;
private List<Record> records;
public List<Record> getRecords() {
return records;
}
public void setRecords(List<Record> records) {
this.records = records;
}
public String getRecordName() {
return recordName;
}
public void setRecordName(String recordName) {
this.recordName = recordName;
}
public int getRecordID() {
return recordID;
}
public void setRecordID(int recordID) {
this.recordID = recordID;
}
}
Create another pojo with the actual Record fields:
public class Record {
public int getTitleFeild() {
return titleFeild;
}
public void setTitleFeild(int i) {
this.titleFeild = i;
}
public String getTitleIDMap() {
return titleIDMap;
}
public void setTitleIDMap(String titleIDMap) {
this.titleIDMap = titleIDMap;
}
public int getTitleId() {
return titleId;
}
public void setTitleId(int titleId) {
this.titleId = titleId;
}
public String getTitleStartDate() {
return titleStartDate;
}
public void setTitleStartDate(String titleStartDate) {
this.titleStartDate = titleStartDate;
}
public String getTitleEndDate() {
return titleEndDate;
}
public void setTitleEndDate(String titleEndDate) {
this.titleEndDate = titleEndDate;
}
public int getLanguageId() {
return languageId;
}
public void setLanguageId(int languageId) {
this.languageId = languageId;
}
private int titleFeild;
private String titleIDMap;
private int titleId;
private String titleStartDate;
private String titleEndDate;
private int languageId;
}
Now just a method to populate your POJOs with the relevant data (replace the hardcoding logic with your data retrieve):
public static void main(String... main) {
DbMetaPojo obj = new DbMetaPojo();
obj.setRecordID(10);
obj.setRecordName("RECORDS");
Record record = new Record();
record.setLanguageId(20);
record.setTitleEndDate("2013-12-22T00:00:00.000+0000");
record.setTitleFeild(1);
record.setTitleId(500);
record.setTitleIDMap("SOME NULL");
record.setTitleStartDate("2013-12-22T00:00:00.000+0000");
List<Record> list = new ArrayList<Record>();
list.add(record);
obj.setRecords(list);
Gson gson = new Gson();
String json = gson.toJson(obj);
System.out.println(json);
}
Output is your formed JSON:
{
"recordID": 10,
"recordName": "RECORDS",
"records": [
{
"titleFeild": 1,
"titleIDMap": "SOME NULL",
"titleId": 500,
"titleStartDate": "2013-12-22T00:00:00.000+0000",
"titleEndDate": "2013-12-22T00:00:00.000+0000",
"languageId": 20
}
]
}
EDIT:
To align to your code, you might want to do something like:
List<Object> objList = dao.getStatus();
List<DbMetaPojo> metaList = new ArrayList<DbMetaPojo> ();
if (objList != null && objList.size() > 10000) {
for (Object nameObj : objList) {
DbMetaPojo meta = new DbMetaPojo();
meta.setRecordID(nameObj[0]);
meta.setRecordName(nameObj[0]);
...
...
...
metaList.add(meta);
}
}

First of all what you have to do is retrieve the data from the columns of the table using your DAO and calling a Function from DAOIMPL which in turn will return the list of data(POJO probably).
Create a map like this which will contain your key value pair for example recordid and value,
recordname and value
Map<String,Object> objMap = new HashMap<String,Object>();
objMap.put("recordId", Record.getId());
objMap.put("recordName",Record.getName());
// Now here is the deal create another hashmap here whose key will be records "the key for your second array"
//Put the values in this second hashmap as instructed above and put it as a key value pair.
........
.......
.......
JSONObject JsonObject = JSONObject.fromObject(objMap);//This will create JSON object out of your hashmap.
objJSONList.add(JsonObject);
}
StringBuffer jsonBuffer = new StringBuffer();
jsonBuffer.append("{\"data\": {");
jsonBuffer.append(objJSONList.tostring());
jsonBuffer.append("}");
//jsonBuffer.append(",\"total\":"+ objJSONList.size());// TOTAL Optional
//jsonBuffer.append(",\"success\":true}");//SUCCESS message if using in callback Optional

Create an object which has your attribues. (recordID, recordName , titleFeild, titleIDMap, titleId, titleStartDate, titleEndDate, languageId)
Get data from dao and convert it to json. It will looks like what you want.
Gson gson = new Gson();
// convert java object to JSON format,
// and returned as JSON formatted string
String json = gson.toJson(obj);

I think your dao.getStatus() should return a List with Map keys and values. Your key would be column name and value would be content.
List<Map<String,Object>> objList = dao.getStatus();
if(objList!=null && objList.size()>10000){
for(Map<String,Object> row : objList) {
Iterator<String> keyList = row.keySet().iterator();
while(keyList.hasNext()){
String key = keyList.next();
jsonData.put(key, row.get(key));
}
}
}
For the records array you need to build it while iterating table columns.
Combining above code with building records array would be something like this..
String[] group = {"titleField","titleIDMap","titleId","titleStartDate","titleEndDate","languageId"};
List<String> recordGroup = Arrays.asList(group);
Map<Object, JSONArray> records = new HashMap<Object,JSONArray>();
List<Map<String,Object>> objList = dao.getStatus();
JSONObject jsonData = new JSONObject();
if(objList!=null && objList.size()>10000){
for(Map<String,Object> row : objList) {
int columnCount = 0;
Iterator<String> keyList = row.keySet().iterator();
while(keyList.hasNext()){
String key = keyList.next();
if(recordGroup.contains(key)){
Object recordId = row.get("recordId");
JSONArray recordArray = new JSONArray();
if(records.containsKey(recordId)){
recordArray = records.get(recordId);
JSONObject jsonObj = null;
if(columnCount >= recordGroup.size()){
jsonObj = new JSONObject();
recordarray.add(jsonObj);
columnCount = 0;
}
else {
jsonObj = (JSONObject) recordArray.get(recordArray.size()-1);
}
jsonObj.put(key, row.get(key));
columnCount++;
}
else {
JSONObject jsonObj = new JSONObject();
jsonObj.put(key, row.get(key));
recordArray.add(jsonObj);
records.put(recordId, recordArray);
}
jsonData.put("records", records.get(recordId));
}
else {
jsonData.put(key, row.get(key));
}
}
}
}