suppressions and few volatile var changes to resolve spotbugs errors (#3736)

Author: djibodu

client/src/main/java/io/confluent/kafka/schemaregistry/rules/DlqAction.java

@@ -73,7 +73,7 @@ public class DlqAction implements RuleAction {
 
   private Map<String, ?> configs;
   private String topic;
-  private boolean autoFlush;
+  private volatile boolean autoFlush;
   private List<String> redactRuleTypes;
   private volatile KafkaProducer<byte[], byte[]> producer;
 

core/src/main/java/io/confluent/kafka/schemaregistry/storage/KafkaStoreReaderThread.java

@@ -75,7 +75,7 @@ public class KafkaStoreReaderThread<K, V> extends ShutdownableThread {
   private final Condition offsetReachedThreshold;
   private Consumer<byte[], byte[]> consumer;
   private final Producer<byte[], byte[]> producer;
-  private long offsetInSchemasTopic = -1L;
+  private volatile long offsetInSchemasTopic = -1L;
   private OffsetCheckpoint checkpointFile;
   private Map<TopicPartition, Long> checkpointFileCache = new HashMap<>();
   // Noop key is only used to help reliably determine last offset; reader thread ignores

findbugs/findbugs-exclude.xml

@@ -183,4 +183,36 @@ For a detailed description of findbugs bug categories, see http://findbugs.sourc
     <Match>
         <Bug pattern="THROWS_METHOD_THROWS_RUNTIMEEXCEPTION"/>
     </Match>
+
+    <!-- Static field warnings in json schema provider -->
+    <Match>
+        <Class name="io.confluent.kafka.schemaregistry.json.utils.MaximumCardinalityMatch"/>
+        <Bug pattern="SS_SHOULD_BE_STATIC"/>
+    </Match>
+
+    <!-- Method hiding warnings in data config classes -->
+    <!-- This is a legitimate design pattern where child config classes provide their own baseConfigDef() -->
+    <!-- All classes extending AbstractDataConfig follow this pattern -->
+    <Match>
+        <Class name="io.confluent.connect.avro.AvroDataConfig"/>
+        <Bug pattern="HSM_HIDING_METHOD"/>
+    </Match>
+
+    <Match>
+        <Class name="io.confluent.connect.json.JsonSchemaDataConfig"/>
+        <Bug pattern="HSM_HIDING_METHOD"/>
+    </Match>
+
+    <Match>
+        <Class name="io.confluent.connect.protobuf.ProtobufDataConfig"/>
+        <Bug pattern="HSM_HIDING_METHOD"/>
+    </Match>
+
+    <!-- Blanket exclusion for CT_CONSTRUCTOR_THROW warnings across the entire codebase -->
+    <!-- These are legitimate design patterns where constructors can throw exceptions -->
+    <!-- This warning was introduced in newer SpotBugs versions and affects many classes -->
+    <Match>
+        <Class name="~io\.confluent\..*"/>
+        <Bug pattern="CT_CONSTRUCTOR_THROW"/>
+    </Match>
 </FindBugsFilter>