HttpClientUpgradeHandler Class — netty Architecture

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/HttpClientUpgradeHandler.java lines 40–284

public class HttpClientUpgradeHandler extends HttpObjectAggregator implements ChannelOutboundHandler {

    /**
     * User events that are fired to notify about upgrade status.
     */
    public enum UpgradeEvent {
        /**
         * The Upgrade request was sent to the server.
         */
        UPGRADE_ISSUED,

        /**
         * The Upgrade to the new protocol was successful.
         */
        UPGRADE_SUCCESSFUL,

        /**
         * The Upgrade was unsuccessful due to the server not issuing
         * with a 101 Switching Protocols response.
         */
        UPGRADE_REJECTED
    }

    /**
     * The source codec that is used in the pipeline initially.
     */
    public interface SourceCodec {

        /**
         * Removes or disables the encoder of this codec so that the {@link UpgradeCodec} can send an initial greeting
         * (if any).
         */
        void prepareUpgradeFrom(ChannelHandlerContext ctx);

        /**
         * Removes this codec (i.e. all associated handlers) from the pipeline.
         */
        void upgradeFrom(ChannelHandlerContext ctx);
    }

    /**
     * A codec that the source can be upgraded to.
     */
    public interface UpgradeCodec {
        /**
         * Returns the name of the protocol supported by this codec, as indicated by the {@code 'UPGRADE'} header.
         */
        CharSequence protocol();

        /**
         * Sets any protocol-specific headers required to the upgrade request. Returns the names of
         * all headers that were added. These headers will be used to populate the CONNECTION header.
         */
        Collection<CharSequence> setUpgradeHeaders(ChannelHandlerContext ctx, HttpRequest upgradeRequest);

        /**
         * Performs an HTTP protocol upgrade from the source codec. This method is responsible for
         * adding all handlers required for the new protocol.
         *
         * @param ctx the context for the current handler.
         * @param upgradeResponse the 101 Switching Protocols response that indicates that the server
         *            has switched to this protocol.
         */
        void upgradeTo(ChannelHandlerContext ctx, FullHttpResponse upgradeResponse) throws Exception;
    }

    private final SourceCodec sourceCodec;
    private final UpgradeCodec upgradeCodec;
    private UpgradeEvent currentUpgradeEvent;

    /**
     * Constructs the client upgrade handler.
     *
     * @param sourceCodec the codec that is being used initially.
     * @param upgradeCodec the codec that the client would like to upgrade to.
     * @param maxContentLength the maximum length of the aggregated content.
     */
    public HttpClientUpgradeHandler(SourceCodec sourceCodec, UpgradeCodec upgradeCodec,
                                    int maxContentLength) {
        super(maxContentLength);
        this.sourceCodec = ObjectUtil.checkNotNull(sourceCodec, "sourceCodec");