Add argument check to ChannelWriter.write

Author: mp911de

src/main/java/com/lambdaworks/redis/cluster/ClusterDistributionChannelWriter.java

@@ -41,6 +41,8 @@ public ClusterDistributionChannelWriter(RedisChannelWriter<K, V> defaultWriter)
     @SuppressWarnings("unchecked")
     public <T, C extends RedisCommand<K, V, T>> C write(C command) {
 
+        checkArgument(command != null, "command must not be null");
+
         if (closed) {
             throw new RedisException("Connection is closed");
         }

src/main/java/com/lambdaworks/redis/protocol/CommandHandler.java

@@ -2,6 +2,8 @@
 
 package com.lambdaworks.redis.protocol;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 import java.nio.channels.ClosedChannelException;
 import java.nio.charset.Charset;
 import java.util.ArrayDeque;
@@ -164,6 +166,8 @@ protected void decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Interrup
     @Override
     public <T, C extends RedisCommand<K, V, T>> C write(C command) {
 
+        checkArgument(command != null, "command must not be null");
+
         if (lifecycleState == LifecycleState.CLOSED) {
             throw new RedisException("Connection is closed");
         }