JSON Interview Questions and Answers
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Ques 6. Explain JSON Structures.
• A collection of name/value pairs
> In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array
• An ordered list of values
> In most languages, this is realized as an array, vector, list, or sequence
• These are universal data structures supported
• A JSON object is an unordered set of name/value pairs
• A JSON object begins with { (left brace) and ends with } (right brace)
• Each name is followed by : (colon) and the name/value pairs are separated by , (comma)
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Ques 7. Compare JSON with JavaScript.
• JSON is a subset of the object literal notation of JavaScript
> JSON can be used in the JavaScript language with no muss or fuss
Example: JSON Object
var myJSONObject = {"bindings": [ {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"},
{"ircEvent": "PRIVMSG", "method": "deleteURI", "regex": "^delete.*"},
{"ircEvent": "PRIVMSG", "method": "randomURI", "regex": "^random.*"}
]
};
• In this example, a JSON JavaScript object is created
containing a single member "bindings", which contains
an array containing three objects, each containing
"ircEvent", "method", and "regex" members
• Members can be retrieved using dot or subscript
operators myJSONObject.bindings[0].method // "newURI"
Text to Object Conversion in
JavaScript code
var myObject = eval('(' + myJSONtext + ')');
• To convert a JSON text into an JSON object, use
the eval() function > eval() invokes the JavaScript compiler
> Since JSON is a proper subset of JavaScript, the compiler will
correctly parse the text and produce an object structure
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Ques 8. What is the Security and JSON Parser?
Security and JSON Parser to understand by below examples
// Include http://www.json.org/json.js
var myObject = myJSONtext.parseJSON();
• eval() can compile and execute any JavaScript program, so there can be security issues (cross-site scripting)
Use eval() when the source can be trusted
• When security is a concern - the source cannot be trusted -, it is better to use a JSON parser
A JSON parser will only recognize JSON text and so is much safer
Object to Text Conversion
var myJSONText = myObject.toJSONString();
• You can convert JSON object into JSON text
• JSON does not support cyclic data structure
Do not give cyclical structures to the JSON stringifier
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Ques 9. What are the JSON Tools for Java Developer?
Some of JSON tools for java developer is
• Parser
> Parse JSON text files and convert these to a Java model
• Renderer
> Render a Java representation into text
• Serializer
> Serialize plain POJO clusters to a JSON representation
• Validator
> Validate the contents of a JSON file using a JSON schema
JSONObject Java Class
• A JSONObject is an unordered collection of name/value pairs
• The put methods adds a name/value pair to an object
• The texts produced by the toString methods strictly conform to the JSON syntax rules
myString = new JSONObject().put("JSON", "Hello, World!").toString();
// myString is {"JSON": "Hello, World"}
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Ques 10. How to Generate or Send JSON Data at the Server Side?
• Create JSON Java object
• Add name and value pairs using put method
• Convert it to String type using toString method and send it to the client with content-type as "text/xml" or "text/plain"
myString = new JSONObject().put("JSON", "Hello, World!").toString();
// myString is {"JSON": "Hello, World"}
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