Fix some low-hanging code quality issue fruits (#1047)

* Fix some low-hanging code quality issue fruits

These include problems such as: use of raw types, unnecessary throw clauses,
unused variables, and more.

proxy/src/main/java/google/registry/proxy/ProxyServer.java

@@ -84,7 +84,7 @@ public class ProxyServer implements Runnable {
    */
   private static class ServerChannelInitializer extends ChannelInitializer<NioSocketChannel> {
     @Override
-    protected void initChannel(NioSocketChannel inboundChannel) throws Exception {
+    protected void initChannel(NioSocketChannel inboundChannel) {
       // Add inbound channel handlers.
       FrontendProtocol inboundProtocol =
           (FrontendProtocol) inboundChannel.parent().attr(PROTOCOL_KEY).get();
@@ -110,8 +110,7 @@ public class ProxyServer implements Runnable {
                 .handler(
                     new ChannelInitializer<NioSocketChannel>() {
                       @Override
-                      protected void initChannel(NioSocketChannel outboundChannel)
-                          throws Exception {
+                      protected void initChannel(NioSocketChannel outboundChannel) {
                         addHandlers(
                             outboundChannel.pipeline(), outboundProtocol.handlerProviders());
                       }
@@ -301,7 +300,7 @@ public class ProxyServer implements Runnable {
     }
   }
 
-  public static void main(String[] args) throws Exception {
+  public static void main(String[] args) {
     // Use JDK logger for Netty's LoggingHandler,
     // which is what Flogger uses under the hood.
     InternalLoggerFactory.setDefaultFactory(JdkLoggerFactory.INSTANCE);

proxy/src/main/java/google/registry/proxy/handler/BackendMetricsHandler.java

@@ -102,8 +102,7 @@ public class BackendMetricsHandler extends ChannelDuplexHandler {
   }
 
   @Override
-  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
-      throws Exception {
+  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
     checkArgument(msg instanceof FullHttpRequest, "Outgoing request must be FullHttpRequest.");
     // For WHOIS, client certificate hash is always set to "none".
     // For EPP, the client hash attribute is set upon handshake completion, before the first HELLO

proxy/src/main/java/google/registry/proxy/handler/FrontendMetricsHandler.java

@@ -88,8 +88,7 @@ public class FrontendMetricsHandler extends ChannelDuplexHandler {
   }
 
   @Override
-  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
-      throws Exception {
+  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
     // Only instrument request metrics when the response is actually sent to client.
     // It is OK to check the queue size preemptively here, not when the front element of the queue
     // is acutally removed after the write to the client is successful,  because responses are

proxy/src/main/java/google/registry/proxy/handler/HealthCheckHandler.java

@@ -33,7 +33,7 @@ public class HealthCheckHandler extends ChannelInboundHandlerAdapter {
   }
 
   @Override
-  public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+  public void channelRead(ChannelHandlerContext ctx, Object msg) {
     ByteBuf buf = (ByteBuf) msg;
     if (buf.equals(checkRequest)) {
       ChannelFuture unusedFuture = ctx.writeAndFlush(checkResponse);

proxy/src/main/java/google/registry/proxy/handler/HttpsRelayServiceHandler.java

@@ -125,8 +125,7 @@ public abstract class HttpsRelayServiceHandler extends ByteToMessageCodec<FullHt
   }
 
   @Override
-  protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuf, List<Object> out)
-      throws Exception {
+  protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuf, List<Object> out) {
     FullHttpRequest request = decodeFullHttpRequest(byteBuf);
     loadCookies(request);
     out.add(request);
@@ -169,7 +168,7 @@ public abstract class HttpsRelayServiceHandler extends ByteToMessageCodec<FullHt
 
   /** Terminates connection upon inbound exception. */
   @Override
-  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
     if (NON_FATAL_INBOUND_EXCEPTIONS.contains(Throwables.getRootCause(cause).getClass())) {
       logger.atWarning().withCause(cause).log(
           "Inbound exception caught for channel %s", ctx.channel());

proxy/src/main/java/google/registry/proxy/handler/ProxyProtocolHandler.java

@@ -133,7 +133,7 @@ public class ProxyProtocolHandler extends ByteToMessageDecoder {
    *     then removed from the pipeline.
    */
   @Override
-  protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
+  protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {
     // Wait until there are more bytes available than the header's length before processing.
     if (in.readableBytes() >= HEADER_PREFIX.length) {
       if (containsHeader(in)) {

proxy/src/main/java/google/registry/proxy/handler/RelayHandler.java

@@ -62,7 +62,7 @@ public class RelayHandler<I> extends SimpleChannelInboundHandler<I> {
 
   /** Read message of type {@code I}, write it as-is into the relay channel. */
   @Override
-  protected void channelRead0(ChannelHandlerContext ctx, I msg) throws Exception {
+  protected void channelRead0(ChannelHandlerContext ctx, I msg) {
     Channel channel = ctx.channel();
     Channel relayChannel = channel.attr(RELAY_CHANNEL_KEY).get();
     if (relayChannel == null) {