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* Copyright (c) 1997-2017 Oracle and/or its affiliates. All rights reserved.
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* or LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
* When distributing the software, include this License Header Notice in each
* file and include the License file at LICENSE.txt.
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
public class TestServlet extends HttpServlet {
protected void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.addHeader("Transfer-encoding", "chunked");
res.addHeader("TE", "trailers");
res.addHeader("Trailer", "bar1, bar2");
StringBuilder sb = new StringBuilder();
final InputStream in = req.getInputStream();
int b;
while ((b = != -1) {
sb.append((char) b);
System.out.println("--> body = " + sb.toString());
if (req.isTrailerFieldsReady()) {
Map<String, String> reqTrailerFields = req.getTrailerFields();
Supplier<Map<String, String>> prevSupplier = res.getTrailerFields();
res.setTrailerFields(new Supplier<Map<String, String>>() {
public Map<String, String> get() {
Map<String, String> map = new HashMap<>();
if (prevSupplier != null) {
map.put("bar2", "B");
System.out.println("--> new supplier return: " + map);
return map;
PrintWriter writer = res.getWriter();
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