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I implemented a servlet that receives a JSON string, converts it into an object and inserts its data into the database. I call that servlet from a HTML page using AJAX and post the JSON string to it. In my case, does it make sense for the servlet to write anything to the response?

urbaindepuce
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3 Answers3

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Since you mention that you had an ajax call to your servlet, you should probably return a JSON status back to calling .ajax() 

response.setContentType("application/json");
// Get the printwriter object from response to write the required json object    to     the output stream      
PrintWriter out = response.getWriter();
// Assuming your database operation insert is successful
JSONObject json = new JSONObject();

// put a success message into the JSON object .
json.put("status", "success");

out.print(jsonObject);
out.flush();

On the client side

success: function(data) {
if(data.status == 'success'){
    alert("Thank you for subscribing!");
}else if(data.status == 'error'){
    alert("Error on query!");
}
}
vijayasundaram
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You need not to return anything. Once the request cycle complete, your browser receives the response object of it as a stream. If you want to add something to it.

response.getWriter().write(somedata);

That somedata you'll receive in your AJAX callback.

For detailed example with codes : How to use Servlets and Ajax?

Community
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Suresh Atta
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  • But is it recommended to just return nothing to the caller? – urbaindepuce Sep 24 '15 at 14:40
  • You need not return anything if you don't want anything on client side. If you want to acknowldgement return your data. For ex : `1` `0`,`true`,`false` etc even a List of objects in json format. – Suresh Atta Sep 24 '15 at 14:50
1

It is good practice to perform the database transaction inside a try catch block, and return a success / failure status flag to the client, in case the transaction failed for whatever reason.

aengus
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