webapps/examples/WEB-INF/classes/trailers/ResponseTrailers.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package trailers;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;

import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

/**
 * This example writes some trailer fields to the HTTP response.
 */
public class ResponseTrailers extends HttpServlet {

    private static final long serialVersionUID = 1L;
    private static final Supplier<Map<String,String>> TRAILER_FIELD_SUPPLIER =
            new TrailerFieldSupplier();


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        resp.setTrailerFields(TRAILER_FIELD_SUPPLIER);
        resp.setContentType("text/plain");
        resp.setCharacterEncoding("UTF-8");

        PrintWriter pw  = resp.getWriter();

        pw.print("This response should include trailer fields.");
    }


    private static class TrailerFieldSupplier implements Supplier<Map<String,String>> {

        private static final Map<String,String> trailerFields = new HashMap<>();

        static {
            trailerFields.put("x-trailer-1", "Trailer value one");
            trailerFields.put("x-trailer-2", "Trailer value two");
        }

        @Override
        public Map<String, String> get() {
            return trailerFields;
        }
    }
}