AsyncServlet

AsyncServlet

import javax.servlet.AsyncContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(name="AsyncServlet", urlPatterns="/async", asyncSupported=true)
public class AsyncServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	//context를 저장할 List변수를 생성한다.
	private List<AsyncContext> contexts = new LinkedList<>();
       
    public AsyncServlet() {
        super();
     }
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //비동기요청에 대한 준비를 시작한다.
		final AsyncContext context = request.startAsync( request, response );
		context.setTimeout( 10 * 60 * 1000 );
		contexts.add(context);
              System.out.println(“start async”);
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		List<AsyncContext> asyncContexts = new ArrayList<>( this.contexts );
		this.contexts.clear();
		String name = request.getParameter("name");
		String message = request.getParameter("messaege");
		String htmlMessage = "<p><b> " + name + "</b><br/>" + message + "</P>";
		ServletContext sc = request.getServletContext();
		if( sc.getAttribute("messages") == null){
			sc.setAttribute("messages", htmlMessage);
		}else{
			String currentMessages = (String) sc.getAttribute("messages");
			sc.setAttribute("messages", htmlMessage + currentMessages);
		}
		for( AsyncContext asynContext : asyncContexts){
			try	(PrintWriter writer = asynContext.getResponse().getWriter()) {
	                writer.println(htmlMessage);
	                writer.flush();
	                asynContext.complete();
			}catch(Exception e){
		  }
		}
	}
}