[common] Fix NPE of JsonConverter when job run on cluster(#470)

Author: minchowang

flink-connector-debezium/src/main/java/com/ververica/cdc/debezium/JsonDebeziumDeserializationSchema.java

@@ -37,23 +37,35 @@
 public class JsonDebeziumDeserializationSchema implements DebeziumDeserializationSchema<String> {
 
     private static final long serialVersionUID = 1L;
-    private static final JsonConverter CONVERTER = new JsonConverter();
+
+    private transient JsonConverter jsonConverter;
+
+    /**
+     * Configuration whether to enable {@link JsonConverterConfig.SCHEMAS_ENABLE_CONFIG} to include
+     * schema in messages.
+     */
+    private final Boolean includeSchema;
 
     public JsonDebeziumDeserializationSchema() {
         this(false);
     }
 
-    public JsonDebeziumDeserializationSchema(boolean includeSchema) {
-        final HashMap<String, Object> configs = new HashMap<>();
-        configs.put(ConverterConfig.TYPE_CONFIG, ConverterType.VALUE.getName());
-        configs.put(JsonConverterConfig.SCHEMAS_ENABLE_CONFIG, includeSchema);
-        CONVERTER.configure(configs);
+    public JsonDebeziumDeserializationSchema(Boolean includeSchema) {
+        this.includeSchema = includeSchema;
     }
 
     @Override
     public void deserialize(SourceRecord record, Collector<String> out) throws Exception {
+        if (jsonConverter == null) {
+            // initialize jsonConverter
+            jsonConverter = new JsonConverter();
+            final HashMap<String, Object> configs = new HashMap<>(2);
+            configs.put(ConverterConfig.TYPE_CONFIG, ConverterType.VALUE.getName());
+            configs.put(JsonConverterConfig.SCHEMAS_ENABLE_CONFIG, includeSchema);
+            jsonConverter.configure(configs);
+        }
         byte[] bytes =
-                CONVERTER.fromConnectData(record.topic(), record.valueSchema(), record.value());
+                jsonConverter.fromConnectData(record.topic(), record.valueSchema(), record.value());
         out.collect(new String(bytes));
     }