We Keep Coding

While converting json string to object \u003c is getting converted to < How to stop this conversion?

{"userName":"1_jan_\u003cscript>alert(1)\u003c/script>
I have used
ObjectMapper mapper = new ObjectMapper();
User user = mapper.readValue(input, User.class);
and
Gson g = new GsonBuilder().create();
I doesn't want \u003c to get converted to <.
Please help me in doing it.

Try that
Gson g= new GsonBuilder().disableHtmlEscaping().create();

how to print Original request body JSON without any modification in java?

Normally to print out request body i using ObjectMapper, but this way removing space and printing object to string in one line, example :
if i send request body like this :
{
"Header" : "value"
}
and i using objectMapper to print that object
ObjectMapper mapper = new ObjectMapper();
mapper.writeValueAsString(requestBody)
the out put is like this :
{"Header":"value"}
how to print Original request body without any modification ?

I'm not sure if you can print it in it's original form but you can pretty print it.
With Jackson's Object Mapper, you can do something like:
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(body);
System.out.println(json);
or
ObjectMapper mapper = new ObjectMapper().enable(SerializationFeature.INDENT_OUTPUT);
String json = mapper.writeValueAsString(body);
System.out.println(json);

I don't think you can do this without using any framework.
But you can use the gson for this if you enable the prettyPrinting option. Example:
Gson gson = new GsonBuilder()
.setPrettyPrinting()
.create();
prettyPrintedString = gson.toJson(requestBody, Object.class);

Parsing unquoted JSON keys using org.json.simple in Java

I have a JSON stored in a string.
String data = "{code: '0', distCode: '123'}";
I need to get the values of code, distCode. But when I try to parse it as below
JSONParser parser = new JSONParser();
JSONObject Details = (JSONObject) parser.parse(data);
Unexpected character (c) at position 2 exception is thrown.
I am sure it is because of unquoted keys in the string. How to parse the string into an JSON object using org.json.simple library?

Could not find way to achieve it using org.json.simple library. Finally done it using jackson libraries.
String data = "{code: '0', distCode: '123'}";
ObjectMapper mapper = new ObjectMapper();
mapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
mapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
Map<String, String> Shop_Details = mapper.readValue(data), Map.class);

Jackson: How to parse comma-separated String values to String[]

Is there a way to tell Jackson-Objectmapper to parse a comma-separated String to a String[]?

Jackson has module jackson-dataformat-csv for parsing CSV data.
Just use its CsvMapper instead of plain ObjectMapper. For example:
String s = "aa,bbb,c,dd";
ObjectMapper objectMapper = new CsvMapper();
String[] array = objectMapper.readValue(s, String[].class);

Convert JsonNode into POJO

This may seem a little unusual, but I am looking for an efficient way to transform/map a JsonNode into a POJO.
I store some of my Model's information in json files and I have to support a couple of version of my model.
What I do is load the json file in memory in a JsonNode, apply a couple of versioning strategies to make it match the latest version of my Model.
ObjectMapper mapper = new ObjectMapper();
BufferedReader fileReader = new BufferedReader(new FileReader(projPath));
JsonNode rootNode = mapper.readTree(fileReader);
//Upgrade our file in memory
applyVersioningStrategy(rootNode);
ProjectModel project = mapJsonNodeToProject(rootNode);
Unless there's a faster way to do it, I will probably end up simply manually applying the JsonNodes to my Model

In Jackson 2.4, you can convert as follows:
MyClass newJsonNode = jsonObjectMapper.treeToValue(someJsonNode, MyClass.class);
where jsonObjectMapper is a Jackson ObjectMapper.
In older versions of Jackson, it would be
MyClass newJsonNode = jsonObjectMapper.readValue(someJsonNode, MyClass.class);

This should do the trick:
mapper.readValue(fileReader, MyClass.class);
I say should because I'm using that with a String, not a BufferedReader but it should still work.
Here's my code:
String inputString = // I grab my string here
MySessionClass sessionObject;
try {
ObjectMapper objectMapper = new ObjectMapper();
sessionObject = objectMapper.readValue(inputString, MySessionClass.class);
Here's the official documentation for that call: http://jackson.codehaus.org/1.7.9/javadoc/org/codehaus/jackson/map/ObjectMapper.html#readValue(java.lang.String, java.lang.Class)
You can also define a custom deserializer when you instantiate the ObjectMapper:
http://wiki.fasterxml.com/JacksonHowToCustomDeserializers
Edit:
I just remembered something else. If your object coming in has more properties than the POJO has and you just want to ignore the extras you'll want to set this:
objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
Or you'll get an error that it can't find the property to set into.

If you're using org.codehaus.jackson, this has been possible since 1.6. You can convert a JsonNode to a POJO with ObjectMapper#readValue: http://jackson.codehaus.org/1.9.4/javadoc/org/codehaus/jackson/map/ObjectMapper.html#readValue(org.codehaus.jackson.JsonNode, java.lang.Class)
ObjectMapper mapper = new ObjectMapper();
JsonParser jsonParser = mapper.getJsonFactory().createJsonParser("{\"foo\":\"bar\"}");
JsonNode tree = jsonParser.readValueAsTree();
// Do stuff to the tree
mapper.readValue(tree, Foo.class);

String jsonInput = "{ \"hi\": \"Assume this is the JSON\"} ";
com.fasterxml.jackson.databind.ObjectMapper mapper =
new com.fasterxml.jackson.databind.ObjectMapper();
MyClass myObject = objectMapper.readValue(jsonInput, MyClass.class);
If your JSON input in has more properties than your POJO has and you just want to ignore the extras in Jackson 2.4, you can configure your ObjectMapper as follows. This syntax is different from older Jackson versions. (If you use the wrong syntax, it will silently do nothing.)
mapper.disable(com.fasterxml.jackson.databind.DeserializationFeature.FAIL_ON_UNK‌​NOWN_PROPERTIES);

This is also a different way and can be used for an array of objects
ObjectReader reader = mapper.readerFor(new TypeReference<List<SomeClass>>() {
});
assert someJsonNode.isArray()
List<SomeClass> list = reader.readValue(someJsonNode);