platform/tools/studio-web/src/main/java/org/eclipse/sensinact/studio/web/ResourceServlet.java

/*
* Copyright (c) 2020 Kentyou.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
*    Kentyou - initial API and implementation
 */
package org.eclipse.sensinact.studio.web;

import org.eclipse.sensinact.gateway.util.IOUtils;

import javax.servlet.AsyncContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URL;

@WebServlet(asyncSupported = true)
public final class ResourceServlet extends HttpServlet {
    /**
     * @param path the alias of the servlet
     */
    ResourceServlet() {
    }

    /**
     * @inheritDoc
     * @see HttpServlet#doGet(HttpServletRequest, HttpServletResponse)
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        if (response.isCommitted()) {
            return;
        }
        final AsyncContext asyncContext;
        if (request.isAsyncStarted()) {
            asyncContext = request.getAsyncContext();

        } else {
            asyncContext = request.startAsync(request, response);
        }
        ((HttpServletResponse) asyncContext.getResponse()).getOutputStream().setWriteListener(new WriteListener() {
            @Override
            public void onWritePossible() throws IOException {
                String resName = null;
                URL url = null;

                HttpServletRequest request = (HttpServletRequest) asyncContext.getRequest();
                HttpServletResponse response = (HttpServletResponse) asyncContext.getResponse();

                String target = request.getPathInfo();

                if (target == null) {
                    target = "";
                }

                if (!target.startsWith("/")) {
                    target += "/" + target;
                }

                resName = target;

                try {
                    url = ResourceServlet.this.getServletContext().getResource(resName);
                } catch (Exception e) {
                    e.printStackTrace();
                }

                if (url == null) {
                    response.setStatus(HttpServletResponse.SC_NOT_FOUND);
                    return;
                }

                try {
                    String contentType = ResourceServlet.this.getServletContext().getMimeType(resName);

                    if (contentType != null) {
                        response.setContentType(contentType);
                    }

                    ServletOutputStream output = response.getOutputStream();
                    if (output.isReady()) {
                        byte[] resourceBytes = IOUtils.read(url.openStream(), true);
                        int length;

                        if ((length = resourceBytes == null ? 0 : resourceBytes.length) > 0) {
                            response.setContentLength(resourceBytes.length);
                            response.setBufferSize(resourceBytes.length);
                            output.write(resourceBytes, 0, length);
                        }
                        response.setStatus(HttpServletResponse.SC_OK);
                    }
                } catch (Exception e) {
                    response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
                } finally {
                    if (request.isAsyncStarted()) {
                        asyncContext.complete();
                    }
                }
            }

            @Override
            public void onError(Throwable t) {
                t.printStackTrace();
            }
        });
    }
}