JSON Questions et reponses d'entretien
Differences associees
Question 11. How to receive JSON Data at the Client Side?
JSON data is received as a string
Calling eval() will generate JSON object in JavaScript code
var JSONdata = eval(req.responseText);
Once you have JSON object, you can use . notation to access its properties
var name = JSONdata.name;
var address = JSONdata.addresses[3];
var streetname = JSONdata.addresses[3].street;
Question 12. How to Generate/Send JSON Data at the Client Side?
Create JSON JavaScript object
Use "POST" HTTP method in the open method of the XMLHttpRequest object
Pass JSON JavaScript object in the send method of XMLHttpRequest object
var carAsJSON = JSON.stringify(car);
var url = "JSONExample?timeStamp=" + new Date().getTime(); createXMLHttpRequest();
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlHttp.send(carAsJSON);
Question 13. How to receive JSON Data at the Server Side?
Read the JSON data as a String type
Create JSONObject Java object from the string String json = readJSONStringFromRequestBody(request);
//Use the JSON-Java binding library to create a JSON object in Java JSONObject jsonObject = null;
try {
jsonObject = new JSONObject(json);
}
catch(ParseException pe) {
}
Question 14. What is JSON-RPC and JSON-RPC-Java?
JSON-RPC is a simple remote procedure call protocol similar to XML-RPC although it uses the lightweight JSON format instead of XML
JSON-RPC-Java is a Java implementation of the JSON-RPC protocol
Question 15. Why JSON-RPC-Java?
It allows you to transparently call server-side Java code from JavaScript with an included lightweight JSON-RPC JavaScript client.
It is designed to run in a Servlet container such as Tomcat and can be used with J2EE Application servers to allow calling of plain Java or EJB methods from within a JavaScript DHTML web application.
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