Java example source code file (Http2RequestHandler.java)

This example Java source code file (Http2RequestHandler.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

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Java - Java tags/keywords

bytebuf, channelhandlercontext, defaultfullhttpresponse, exception, fullhttprequest, fullhttpresponse, image_coordinate_x, image_coordinate_y, latency_field_name, max_latency, min_latency, override, string, threading, threads

The Http2RequestHandler.java Java example source code

/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project 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 io.netty.example.http2.tiles;

import static io.netty.buffer.Unpooled.EMPTY_BUFFER;
import static io.netty.example.http2.Http2ExampleUtil.firstValue;
import static io.netty.example.http2.Http2ExampleUtil.toInt;
import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpUtil.setContentLength;
import static io.netty.handler.codec.http.HttpResponseStatus.BAD_REQUEST;
import static io.netty.handler.codec.http.HttpResponseStatus.OK;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
import static java.lang.Integer.parseInt;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.QueryStringDecoder;
import io.netty.handler.codec.http2.HttpConversionUtil;
import io.netty.handler.codec.http2.InboundHttp2ToHttpAdapter;

import java.util.concurrent.TimeUnit;

/**
 * Handles all the requests for data. It receives a {@link FullHttpRequest},
 * which has been converted by a {@link InboundHttp2ToHttpAdapter} before it
 * arrived here. For further details, check {@link Http2OrHttpHandler} where the
 * pipeline is setup.
 */
public class Http2RequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    private static final String LATENCY_FIELD_NAME = "latency";
    private static final int MIN_LATENCY = 0;
    private static final int MAX_LATENCY = 1000;
    private static final String IMAGE_COORDINATE_Y = "y";
    private static final String IMAGE_COORDINATE_X = "x";

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        QueryStringDecoder queryString = new QueryStringDecoder(request.uri());
        String streamId = streamId(request);
        int latency = toInt(firstValue(queryString, LATENCY_FIELD_NAME), 0);
        if (latency < MIN_LATENCY || latency > MAX_LATENCY) {
            sendBadRequest(ctx, streamId);
            return;
        }
        String x = firstValue(queryString, IMAGE_COORDINATE_X);
        String y = firstValue(queryString, IMAGE_COORDINATE_Y);
        if (x == null || y == null) {
            handlePage(ctx, streamId, latency, request);
        } else {
            handleImage(x, y, ctx, streamId, latency, request);
        }
    }

    private void sendBadRequest(ChannelHandlerContext ctx, String streamId) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, BAD_REQUEST, EMPTY_BUFFER);
        streamId(response, streamId);
        ctx.writeAndFlush(response);
    }

    private void handleImage(String x, String y, ChannelHandlerContext ctx, String streamId, int latency,
            FullHttpRequest request) {
        ByteBuf image = ImageCache.INSTANCE.image(parseInt(x), parseInt(y));
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, image.duplicate());
        response.headers().set(CONTENT_TYPE, "image/jpeg");
        sendResponse(ctx, streamId, latency, response, request);
    }

    private void handlePage(ChannelHandlerContext ctx, String streamId, int latency, FullHttpRequest request) {
        byte[] body = Html.body(latency);
        ByteBuf content = ctx.alloc().buffer(Html.HEADER.length + body.length + Html.FOOTER.length);
        content.writeBytes(Html.HEADER);
        content.writeBytes(body);
        content.writeBytes(Html.FOOTER);
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, content);
        response.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");
        sendResponse(ctx, streamId, latency, response, request);
    }

    protected void sendResponse(final ChannelHandlerContext ctx, String streamId, int latency,
            final FullHttpResponse response, final FullHttpRequest request) {
        setContentLength(response, response.content().readableBytes());
        streamId(response, streamId);
        ctx.executor().schedule(new Runnable() {
            @Override
            public void run() {
                ctx.writeAndFlush(response);
            }
        }, latency, TimeUnit.MILLISECONDS);
    }

    private String streamId(FullHttpRequest request) {
        return request.headers().get(HttpConversionUtil.ExtensionHeaderNames.STREAM_ID.text());
    }

    private void streamId(FullHttpResponse response, String streamId) {
        response.headers().set(HttpConversionUtil.ExtensionHeaderNames.STREAM_ID.text(), streamId);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}