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Parsing Nested JSON in java without know structure of JSON

I have a use case where i get a random jsonstring and variable name. I need to verify if that particular variable is present in that json, and if present fetch its value. For example, let us the json is as follows
{
"a" : {
"b":1,
"c":2
}
}
Along with above jsonString, say i get an input "a.b" . Now I need to return 1.
Is there any library to achieve this in java directly?

JsonPath is a library that provides the functionality you're after.
You will have to do some conversion between your input and the library's input.
As per your example, if your input is "a.b":
String convertedInput = ".." + input
JsonPath.read(json, convertedInput)

Jackson not escaping quotes in JSON

I'm trying to put a json in a javascript file in java, but when I write the json to a string, the string doesn't appear to be a valid json for javascript; it is missing some escapes. (This is happening in a string in the json which I formatted as a faux json.)
For example, this would be a valid json in my javascript file:
{
"message":
"the following books failed: [{\"book\": \"The Horse and his Boy\",\"author\": \"C.S. Lewis\"}, {\"book\": \"The Left Hand of Darkness\",\"author\": \"Ursula K. le Guin\"}, ]"
}
Here's what I get, though, where the double quotes aren't escaped:
{
"message":
"The following books failed: [{"book": "The Horse and his Boy","author": "C.S. Lewis"}, {"book": "The Left Hand of Darkness","author": "Ursula K. le Guin"}, ]"
}
I get the second result when I do this:
new ObjectMapper().writer().writeValueAsString(booksMessage);
But when I write it directly to a file with jackson, I get the first, good result:
new ObjectMapper().writer().writeValue(fileToWriteTo, booksMessage);
So why does jackson escape differently when writing to a file, and how do I get it to escape like that for me when writing to a string?

The writeValue() methods of the ObjectWriter class encode the input text.
You don't need to write to a file. An alternative approach for getting the same string could be:
StringWriter sw = new StringWriter();
new ObjectMapper().writer().writeValue(sw, booksMessage);
String result = sw.toString();

I added
booksJson = Pattern.compile("\\\\").matcher(booksJson).replaceAll("\\\\\\\\");
which escapes all the escape characters. That way when I write it to file and it removes the escapes, I still have the escapes I need. So turns out my real question was how to write to file without Java escapes being removed.

I'm very late to the party but I faced a similar problem and I realized it was not a problem with Jackson or my data. It was Java. I was reading from a JSON file and then trying to write it into a template HTML file.
I had a line my original JSON like yours, something like:
{"field" : "This field contains what looks like another JSON field: {\"abc\": \"value\"}"}
And when I wrote the above to a string, the backslash before the quotes in abc and value disappeared. I noticed that the contextual help for String.replaceAll mentioned something about Matcher.quoteReplacement. I went from this:
template = template.replaceAll("%template%", jsonDataString);
to this:
Pattern pattern = Pattern.compile("%template%");
Matcher matcher = Pattern.matcher(template);
matcher.replaceAll(matcher.quoteReplacement(jsonDataString));
Problem solved.
Matcher.quoteReplacement

JSon to CSV with Java using CDL: possible to replace comma-sep. by semi-colum sep. values?

Everything is in the title :)
I'm using org.json.CDL to convert JSONArray into CSV data but it renders a string with ',' as separator.
I'd like to know if it's possible to replace with ';' ?
Here is a simple example of what i'm doing:
public String exportAsCsv() throws Exception {
return CDL.toString(
new JSONArray(
mapper.writeValueAsString(extractAccounts()))
);
}
Thanks in advance for any advice on that question.
Edit: No replacement solution of course, as this could have impact for large data, and of course the library used enable me to specify the field separator.
Edit2: Finally the solution to extract data as JSONArray (and String...) was not very good, especially for large data file.
So i made the following changes:
use a Java CSV library (for example: http://www.csvreader.com/java_csv_samples.php)
refactor code to stream data from json input source to csv output source
This is nicer for large data treatment. If you have comments do not hesitate.

String output = "Hello,This,is,separated,by,a,comma";
// Simple call the replaceAll method.
output = output.replace(',',';');
I found this in the String documentation.
Example
String value = "Hello,tthis,is,a,string";
value = value.replace(',', ';');
System.out.println(value);
// Outputs: Hello;tthis;is;a;string

How to create a JSONArray that contains Javascript code inside Java?

I am creating a JSONArray and parse it to a String, but as it even contains Strings instead of code it doesn't output as I need it.
for(Place place: places){
locations.put("new google.maps.LatLng("+place.getContactData().getLatitude()+","+place.getContactData().getLongitude()+")");
}
return locations.toString();
It outputs as: ["new google.maps.LatLng(53.5608,9.96357)","new google.maps.LatLng(53.5608,9.96357)"] but I need it without quotation marks like [new google.maps.LatLng(53.5608,9.96357),new google.maps.LatLng(53.5608,9.96357)] to be correctly interpreted by javascript.

Another method would be:
create an array with just the coordinates:
for(Place place: places){
JSONObject obj = new JSONObject();
obj.put("lat",place.getContactData().getLatitude());
obj.put("lng",place.getContactData().getLongitude());
locations.put(obj);
}
and then in javascript:
var places = (yourPlacesJson);
var placeObjects = [];
for(var i=0;i<places.length;i++)
{
placeObjects[placeObjects.length] = new google.maps.LatLng(places[i].lat,places[i].lng);
}

JSON only supports plain-old-data. It can't include any executable code (a new is executable code). This is by design - when JSON would be able to include executable code you would have to be much more carefully with importing JSON from an untrusted source.
All you can do is pass javascript code as strings and eval() it on the JS side after parsing the JSON.

Also you could use Regular expressions to remove the ", if you parse the json to another language

i had a similar problem, the way i made this work:
instead of writing the javascript before the json conversion, insert a placeholder.
locations.put("%mapsPlaceholder1%");
then after filling the array with placeholders, do:
locations.toString().replaceFirst("\"%mapsPlaceholder1%\"","yourJsCode");
something like that
you could also just create the array string manually

Java : How to assign Json formated String to Java String?

I have a big json string which i will be getting as a request from the UI , which will be converted to a String and parsed .
I want to simulate the similar environment for testing locally , so for this purpose i captured the JSon format.
Currently i am manually adding "/" to this big json string .
Is there any other way to achieve this ??
For example i got this json
{"age":29,"messages":["msg 1","msg 2","msg 3"],"name":"Preethi"}
and converted that into
String str = "{\"age\":\"29\",\"messages\":[\"msg 1\",\"msg 2\",\"msg 3\"],\"name\":\"mkyong\"}";
Is there any other way to achieve this ??

On the client-side, do a search and regex "replace all" of double-quotes into single quotes on the desired form field before actually sending the request.

Actually, Java doesn't have verbatim string literals.
If you want a Java-like (and Java-VM-based) language that does, however, you might want to look at Groovy which has various forms of string literal.

we have in build method to convert jsonObject to string. Why don't you use that.
JSONObject json = new JSONObject();
json.toString();