Calling Servlet Post from another Servlet

Question

I need to call a servlets POST method from another servlet and pass a blob in the servlets parameters. Is this posible, if so how can it be done. PS: I cant use Apache HttpClient

Solution 1

You need to create and send a HTTP request yourself. You cannot make use of forward/redirect/include because you want to change the method from GET to POST and you want to send a multipart/form-data request.

As HttpClient (and other 3rd party library?) is apparently not an option, your best bet is to use the standard Java SE API provided java.net.URLConnection. Long story short: Using java.net.URLConnection to fire and handle HTTP requests At the bottom you can find a multipart/form-data example.

Please note that this problem is not specific to servlets. In other words, you must be able to execute this code in a plain vanilla Java application with a main() method. This allows for easier testing and finetuning. Once you get it to work, just let the servlet execute the same piece of code.

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Unrelated to the problem, I have the impression that there's a major design failure somewhere, certainly if the both servlets runs in the same webapplication context. The other servlet where you want to send the POST request to is apparently too tight coupled and should be refactored.

Solution 2

You can get a dispatcher to another servlet in your application and forward it or include it as @Ryan suggests. The code should be something like this inside your first servlet:

ServletContext context = this.getServletContext();
RequestDispatcher dispatcher = context.getRequestDispatcher("/otherurltoservlet");

// change your request and response accordingly

dispatcher.forward(request, response);

Solution 3

Do you mean call from your application to another web service? If so, then something like HttpClient is what you want. If you mean you want to programmatically invoke another servlet in your app, then you're looking to either forward to it or include it.

Comments

[Chris J]

Well Apache HttpClient is open source... copy and paste?

[fernandohur]

I can't use because I use the Google App Engine and It imposes limitations on some classes that can be used

[fernandohur]

Im looking to call another servlet inside my app, but it must be vía the POST method. What I would normally do is response.redirect(...) but that calls the GET method... How can I call the POST?

[fernandohur]

What I need is to call the POST method on another servlet in my app. Will that call "otherurltoservlet"'s POST method?

[Ryan Stewart]

What I said: forward or include, depending on which you're trying to do. See the "Invoking Other Web Resources" in the JEE tutorial for more details.

[Ricardo Marimon]

I believe that if the first servlet was called via post the second will be called via post in the dispatcher.forward chain.

[Ricardo Marimon]

Take a look here for question regarding GET to POST stackoverflow.com/questions/4374548/…