Replace all logic that checks Null with the ObjectUtil utility class (#9145)

Motivation:

Clean the code , replace all logic that checks Null with the ObjectUtil utility class in bootstrap package

Modification:
Replace all logic that checks null with the ObjectUtil utility class

Result:

Less verbose code.

transport/src/main/java/io/netty/bootstrap/AbstractBootstrap.java

@@ -26,10 +26,11 @@ import io.netty.channel.DefaultChannelPromise;
 import io.netty.channel.EventLoop;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.ReflectiveChannelFactory;
-import io.netty.util.internal.SocketUtils;
 import io.netty.util.AttributeKey;
 import io.netty.util.concurrent.EventExecutor;
 import io.netty.util.concurrent.GlobalEventExecutor;
+import io.netty.util.internal.ObjectUtil;
+import io.netty.util.internal.SocketUtils;
 import io.netty.util.internal.StringUtil;
 import io.netty.util.internal.logging.InternalLogger;
 
@@ -79,9 +80,7 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      * {@link Channel}
      */
     public B group(EventLoopGroup group) {
-        if (group == null) {
+        ObjectUtil.checkNotNull(group, "group");
-            throw new NullPointerException("group");
-        }
         if (this.group != null) {
             throw new IllegalStateException("group set already");
         }
@@ -100,10 +99,9 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      * {@link Channel} implementation has no no-args constructor.
      */
     public B channel(Class<? extends C> channelClass) {
-        if (channelClass == null) {
+        return channelFactory(new ReflectiveChannelFactory<C>(
-            throw new NullPointerException("channelClass");
+                ObjectUtil.checkNotNull(channelClass, "channelClass")
-        }
+        ));
-        return channelFactory(new ReflectiveChannelFactory<C>(channelClass));
     }
 
     /**
@@ -111,9 +109,7 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      */
     @Deprecated
     public B channelFactory(ChannelFactory<? extends C> channelFactory) {
-        if (channelFactory == null) {
+        ObjectUtil.checkNotNull(channelFactory, "channelFactory");
-            throw new NullPointerException("channelFactory");
-        }
         if (this.channelFactory != null) {
             throw new IllegalStateException("channelFactory set already");
         }
@@ -168,9 +164,7 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      * created. Use a value of {@code null} to remove a previous set {@link ChannelOption}.
      */
     public <T> B option(ChannelOption<T> option, T value) {
-        if (option == null) {
+        ObjectUtil.checkNotNull(option, "option");
-            throw new NullPointerException("option");
-        }
         if (value == null) {
             synchronized (options) {
                 options.remove(option);
@@ -188,9 +182,7 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      * {@code null}, the attribute of the specified {@code key} is removed.
      */
     public <T> B attr(AttributeKey<T> key, T value) {
-        if (key == null) {
+        ObjectUtil.checkNotNull(key, "key");
-            throw new NullPointerException("key");
-        }
         if (value == null) {
             synchronized (attrs) {
                 attrs.remove(key);
@@ -272,10 +264,7 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      */
     public ChannelFuture bind(SocketAddress localAddress) {
         validate();
-        if (localAddress == null) {
+        return doBind(ObjectUtil.checkNotNull(localAddress, "localAddress"));
-            throw new NullPointerException("localAddress");
-        }
-        return doBind(localAddress);
     }
 
     private ChannelFuture doBind(final SocketAddress localAddress) {
@@ -375,10 +364,7 @@ public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C ext
      * the {@link ChannelHandler} to use for serving the requests.
      */
     public B handler(ChannelHandler handler) {
-        if (handler == null) {
+        this.handler = ObjectUtil.checkNotNull(handler, "handler");
-            throw new NullPointerException("handler");
-        }
-        this.handler = handler;
         return self();
     }
 

transport/src/main/java/io/netty/bootstrap/Bootstrap.java

@@ -30,6 +30,7 @@ import io.netty.resolver.AddressResolverGroup;
 import io.netty.util.AttributeKey;
 import io.netty.util.concurrent.Future;
 import io.netty.util.concurrent.FutureListener;
+import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
 
@@ -137,10 +138,7 @@ public class Bootstrap extends AbstractBootstrap<Bootstrap, Channel> {
      * Connect a {@link Channel} to the remote peer.
      */
     public ChannelFuture connect(SocketAddress remoteAddress) {
-        if (remoteAddress == null) {
+        ObjectUtil.checkNotNull(remoteAddress, "remoteAddress");
-            throw new NullPointerException("remoteAddress");
-        }
-
         validate();
         return doResolveAndConnect(remoteAddress, config.localAddress());
     }
@@ -149,9 +147,7 @@ public class Bootstrap extends AbstractBootstrap<Bootstrap, Channel> {
      * Connect a {@link Channel} to the remote peer.
      */
     public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress) {
-        if (remoteAddress == null) {
+        ObjectUtil.checkNotNull(remoteAddress, "remoteAddress");
-            throw new NullPointerException("remoteAddress");
-        }
         validate();
         return doResolveAndConnect(remoteAddress, localAddress);
     }

transport/src/main/java/io/netty/bootstrap/ServerBootstrap.java

@@ -28,6 +28,7 @@ import io.netty.channel.ChannelPipeline;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.ServerChannel;
 import io.netty.util.AttributeKey;
+import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
 
@@ -79,9 +80,7 @@ public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerCh
      */
     public ServerBootstrap group(EventLoopGroup parentGroup, EventLoopGroup childGroup) {
         super.group(parentGroup);
-        if (childGroup == null) {
+        ObjectUtil.checkNotNull(childGroup, "childGroup");
-            throw new NullPointerException("childGroup");
-        }
         if (this.childGroup != null) {
             throw new IllegalStateException("childGroup set already");
         }
@@ -95,9 +94,7 @@ public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerCh
      * {@link ChannelOption}.
      */
     public <T> ServerBootstrap childOption(ChannelOption<T> childOption, T value) {
-        if (childOption == null) {
+        ObjectUtil.checkNotNull(childOption, "childOption");
-            throw new NullPointerException("childOption");
-        }
         if (value == null) {
             synchronized (childOptions) {
                 childOptions.remove(childOption);
@@ -115,9 +112,7 @@ public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerCh
      * {@code null} the {@link AttributeKey} is removed
      */
     public <T> ServerBootstrap childAttr(AttributeKey<T> childKey, T value) {
-        if (childKey == null) {
+        ObjectUtil.checkNotNull(childKey, "childKey");
-            throw new NullPointerException("childKey");
-        }
         if (value == null) {
             childAttrs.remove(childKey);
         } else {
@@ -130,10 +125,7 @@ public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerCh
      * Set the {@link ChannelHandler} which is used to serve the request for the {@link Channel}'s.
      */
     public ServerBootstrap childHandler(ChannelHandler childHandler) {
-        if (childHandler == null) {
+        this.childHandler = ObjectUtil.checkNotNull(childHandler, "childHandler");
-            throw new NullPointerException("childHandler");
-        }
-        this.childHandler = childHandler;
         return this;
     }