Apply Nullable/NotNullByDefault annotations (#289)

Motivation:
`Nullable`/`NotNullByDefault` annotations give an idea of what to expect
from the API. Plus, they provide a better IDE integration. This PR is
based on the work done in netty/netty#12878

Modification:
`Nullable`/`NotNullByDefault` annotations are applied where necessary.

Result:
The change extends the API with nullability expectations. Plus, it
provides a better IDE integration.

---------

Co-authored-by: Norman Maurer <[email protected]>

Author: simonatan

pom.xml

@@ -468,5 +468,17 @@
       <version>1.75</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.jetbrains</groupId>
+      <artifactId>annotations</artifactId>
+      <version>24.1.0</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <version>3.0.2</version>
+      <scope>provided</scope>
+    </dependency>
   </dependencies>
 </project>

src/main/java/io/netty/incubator/codec/http3/DefaultHttp3Headers.java

@@ -19,6 +19,7 @@
 import io.netty.handler.codec.DefaultHeaders;
 import io.netty.util.AsciiString;
 import io.netty.util.ByteProcessor;
+import org.jetbrains.annotations.Nullable;
 
 import static io.netty.incubator.codec.http3.Http3Headers.PseudoHeaderName.hasPseudoHeaderFormat;
 import static io.netty.util.AsciiString.CASE_INSENSITIVE_HASHER;
@@ -35,7 +36,7 @@ public boolean process(byte value) {
     };
     static final NameValidator<CharSequence> HTTP3_NAME_VALIDATOR = new NameValidator<CharSequence>() {
         @Override
-        public void validateName(CharSequence name) {
+        public void validateName(@Nullable CharSequence name) {
             if (name == null || name.length() == 0) {
                 throw new Http3HeadersValidationException(String.format("empty headers are not allowed [%s]", name));
             }

src/main/java/io/netty/incubator/codec/http3/Http3.java

@@ -26,6 +26,7 @@
 import io.netty.incubator.codec.quic.QuicStreamType;
 import io.netty.util.AttributeKey;
 import io.netty.util.concurrent.Future;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * Contains utility methods that help to bootstrap server / clients with HTTP3 support.
@@ -53,6 +54,7 @@ private Http3() {  }
      * @param channel   the channel for the HTTP/3 connection.
      * @return          the control stream.
      */
+    @Nullable
     public static QuicStreamChannel getLocalControlStream(Channel channel) {
         return channel.attr(HTTP3_CONTROL_STREAM_KEY).get();
     }
@@ -78,6 +80,7 @@ static void setLocalControlStream(Channel channel, QuicStreamChannel controlStre
         channel.attr(HTTP3_CONTROL_STREAM_KEY).set(controlStreamChannel);
     }
 
+    @Nullable
     static QpackAttributes getQpackAttributes(Channel channel) {
         return channel.attr(QPACK_ATTRIBUTES_KEY).get();
     }

src/main/java/io/netty/incubator/codec/http3/Http3ClientConnectionHandler.java

@@ -18,6 +18,7 @@
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.incubator.codec.quic.QuicStreamChannel;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.function.LongFunction;
 
@@ -49,10 +50,10 @@ public Http3ClientConnectionHandler() {
      *                                              remote peer or {@code null} if the default settings should be used.
      * @param disableQpackDynamicTable              If QPACK dynamic table should be disabled.
      */
-    public Http3ClientConnectionHandler(ChannelHandler inboundControlStreamHandler,
-                                        LongFunction<ChannelHandler> pushStreamHandlerFactory,
-                                        LongFunction<ChannelHandler> unknownInboundStreamHandlerFactory,
-                                        Http3SettingsFrame localSettings, boolean disableQpackDynamicTable) {
+    public Http3ClientConnectionHandler(@Nullable ChannelHandler inboundControlStreamHandler,
+                                        @Nullable LongFunction<ChannelHandler> pushStreamHandlerFactory,
+                                        @Nullable LongFunction<ChannelHandler> unknownInboundStreamHandlerFactory,
+                                        @Nullable Http3SettingsFrame localSettings, boolean disableQpackDynamicTable) {
         super(false, inboundControlStreamHandler, unknownInboundStreamHandlerFactory, localSettings,
                 disableQpackDynamicTable);
         this.pushStreamHandlerFactory = pushStreamHandlerFactory;

src/main/java/io/netty/incubator/codec/http3/Http3CodecUtils.java

@@ -26,6 +26,7 @@
 import io.netty.util.CharsetUtil;
 import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.StringUtil;
+import org.jetbrains.annotations.Nullable;
 
 import static io.netty.channel.ChannelFutureListener.CLOSE_ON_FAILURE;
 import static io.netty.incubator.codec.http3.Http3ErrorCode.H3_INTERNAL_ERROR;
@@ -243,7 +244,7 @@ static void connectionError(ChannelHandlerContext ctx, Http3Exception exception,
      * @param fireException {@code true} if we should also fire the {@link Http3Exception} through the pipeline.
      */
     static void connectionError(ChannelHandlerContext ctx, Http3ErrorCode errorCode,
-                                String msg, boolean fireException) {
+                                @Nullable String msg, boolean fireException) {
          if (fireException) {
              ctx.fireExceptionCaught(new Http3Exception(errorCode, msg));
          }
@@ -270,7 +271,7 @@ static void closeOnFailure(ChannelFuture future) {
      * @param errorCode     the {@link Http3ErrorCode} that caused the error.
      * @param msg           the message that should be used as reason for the error, may be {@code null}.
      */
-    static void connectionError(Channel channel, Http3ErrorCode errorCode, String msg) {
+    static void connectionError(Channel channel, Http3ErrorCode errorCode, @Nullable String msg) {
         final QuicChannel quicChannel;
 
         if (channel instanceof QuicChannel) {
@@ -306,6 +307,7 @@ static void readIfNoAutoRead(ChannelHandlerContext ctx) {
      * @param ch for which the {@link Http3ConnectionHandler} is to be retrieved.
      * @return {@link Http3ConnectionHandler} if available, else close the connection and return {@code null}.
      */
+    @Nullable
     static Http3ConnectionHandler getConnectionHandlerOrClose(QuicChannel ch) {
         Http3ConnectionHandler connectionHandler = ch.pipeline().get(Http3ConnectionHandler.class);
         if (connectionHandler == null) {

src/main/java/io/netty/incubator/codec/http3/Http3ConnectionHandler.java

@@ -22,6 +22,7 @@
 import io.netty.incubator.codec.quic.QuicChannel;
 import io.netty.incubator.codec.quic.QuicStreamChannel;
 import io.netty.incubator.codec.quic.QuicStreamType;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.function.LongFunction;
 
@@ -58,9 +59,9 @@ public abstract class Http3ConnectionHandler extends ChannelInboundHandlerAdapte
      *                                              remote peer or {@code null} if the default settings should be used.
      * @param disableQpackDynamicTable              If QPACK dynamic table should be disabled.
      */
-    Http3ConnectionHandler(boolean server, ChannelHandler inboundControlStreamHandler,
-                           LongFunction<ChannelHandler> unknownInboundStreamHandlerFactory,
-                           Http3SettingsFrame localSettings, boolean disableQpackDynamicTable) {
+    Http3ConnectionHandler(boolean server, @Nullable ChannelHandler inboundControlStreamHandler,
+                           @Nullable LongFunction<ChannelHandler> unknownInboundStreamHandlerFactory,
+                           @Nullable Http3SettingsFrame localSettings, boolean disableQpackDynamicTable) {
         this.unknownInboundStreamHandlerFactory = unknownInboundStreamHandlerFactory;
         this.disableQpackDynamicTable = disableQpackDynamicTable;
         if (localSettings == null) {

src/main/java/io/netty/incubator/codec/http3/Http3ControlStreamInboundHandler.java

@@ -26,6 +26,7 @@
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.concurrent.Future;
 import io.netty.util.concurrent.GenericFutureListener;
+import org.jetbrains.annotations.Nullable;
 
 import java.nio.channels.ClosedChannelException;
 
@@ -50,7 +51,8 @@ final class Http3ControlStreamInboundHandler extends Http3FrameTypeInboundValida
     private Long receivedGoawayId;
     private Long receivedMaxPushId;
 
-    Http3ControlStreamInboundHandler(boolean server, ChannelHandler controlFrameHandler, QpackEncoder qpackEncoder,
+    Http3ControlStreamInboundHandler(boolean server, @Nullable ChannelHandler controlFrameHandler,
+                                     QpackEncoder qpackEncoder,
                                      Http3ControlStreamOutboundHandler remoteControlStreamHandler) {
         super(Http3ControlStreamFrame.class);
         this.server = server;

src/main/java/io/netty/incubator/codec/http3/Http3ControlStreamOutboundHandler.java

@@ -22,6 +22,7 @@
 import io.netty.channel.socket.ChannelInputShutdownEvent;
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.internal.ObjectUtil;
+import org.jetbrains.annotations.Nullable;
 
 import static io.netty.incubator.codec.http3.Http3CodecUtils.closeOnFailure;
 
@@ -45,6 +46,7 @@ final class Http3ControlStreamOutboundHandler
      *
      * @return the id.
      */
+    @Nullable
     Long sentMaxPushId() {
         return sentMaxPushId;
     }

src/main/java/io/netty/incubator/codec/http3/Http3Exception.java

@@ -16,6 +16,7 @@
 package io.netty.incubator.codec.http3;
 
 import io.netty.util.internal.ObjectUtil;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * An exception related to violate the HTTP3 spec.
@@ -29,7 +30,7 @@ public final class Http3Exception extends Exception {
      * @param errorCode the {@link Http3ErrorCode} that caused this exception.
      * @param message   the message to include.
      */
-    public Http3Exception(Http3ErrorCode errorCode, String message) {
+    public Http3Exception(Http3ErrorCode errorCode, @Nullable String message) {
         super(message);
         this.errorCode = ObjectUtil.checkNotNull(errorCode, "errorCode");
     }
@@ -41,7 +42,7 @@ public Http3Exception(Http3ErrorCode errorCode, String message) {
      * @param message   the message to include.
      * @param cause     the {@link Throwable} to wrap.
      */
-    public Http3Exception(Http3ErrorCode errorCode, String message, Throwable cause) {
+    public Http3Exception(Http3ErrorCode errorCode, String message, @Nullable Throwable cause) {
         super(message, cause);
         this.errorCode = ObjectUtil.checkNotNull(errorCode, "errorCode");
     }

src/main/java/io/netty/incubator/codec/http3/Http3FrameCodec.java

@@ -28,6 +28,7 @@
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.concurrent.Future;
 import io.netty.util.concurrent.GenericFutureListener;
+import org.jetbrains.annotations.Nullable;
 
 import java.net.SocketAddress;
 import java.util.List;
@@ -349,6 +350,7 @@ private boolean enforceMaxPayloadLength(
         return in.readableBytes() >= payLoadLength;
     }
 
+    @Nullable
     private Http3SettingsFrame decodeSettings(ChannelHandlerContext ctx, ByteBuf in, int payLoadLength) {
         Http3SettingsFrame settingsFrame = new DefaultHttp3SettingsFrame();
         while (payLoadLength > 0) {