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Servlet 3.1 API / Asynchronous processing / error handling: approach #2
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package fi.markoa.experiment.servlet3; | |
import javax.servlet.AsyncContext; | |
import javax.servlet.ServletException; | |
import javax.servlet.annotation.WebServlet; | |
import javax.servlet.http.HttpServlet; | |
import javax.servlet.http.HttpServletRequest; | |
import javax.servlet.http.HttpServletResponse; | |
import java.io.IOException; | |
/** | |
* Servlet 3.1 API / Asynchronous processing / error handling: approach #2 | |
* | |
* @author marko asplund | |
*/ | |
@WebServlet(urlPatterns={"/error2"}, asyncSupported=true) | |
public class AsyncErrorServlet2 extends HttpServlet { | |
@Override | |
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { | |
final AsyncContext asyncContext = req.startAsync(); | |
asyncContext.start(new Runnable() { | |
@Override | |
public void run() { | |
if(isOperationFailed(asyncContext.getRequest().getParameter("fail"))) { | |
errorDispatch(asyncContext, 503, "hello, erroneous world"); | |
} else { | |
try { | |
asyncContext.getResponse().getWriter().write(generateResponse()); | |
asyncContext.complete(); | |
} catch (IOException e) { | |
e.printStackTrace(); | |
} | |
} | |
} | |
}); | |
} | |
private void errorDispatch(AsyncContext asyncContext, int statusCode, String message) { | |
asyncContext.getRequest().setAttribute("statusCode", statusCode); | |
asyncContext.getRequest().setAttribute("message", message); | |
// dispatch completes AsyncContext. | |
asyncContext.dispatch("/jsp/error.jsp"); // can't be placed in /WEB-INF | |
} | |
private String generateResponse() { | |
return "hello, happy world"; | |
} | |
private boolean isOperationFailed(String fail) { | |
return Boolean.valueOf(fail); | |
} | |
} |
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