[cdc-base] Improve Incremental snapshot framework code style. (#1054)

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/config/BaseSourceConfig.java

@@ -61,26 +61,32 @@ public abstract class BaseSourceConfig implements SourceConfig {
         this.dbzConfiguration = dbzConfiguration;
     }
 
+    @Override
     public StartupOptions getStartupOptions() {
         return startupOptions;
     }
 
+    @Override
     public int getSplitSize() {
         return splitSize;
     }
 
+    @Override
     public int getSplitMetaGroupSize() {
         return splitMetaGroupSize;
     }
 
+    @Override
     public double getDistributionFactorUpper() {
         return distributionFactorUpper;
     }
 
+    @Override
     public double getDistributionFactorLower() {
         return distributionFactorLower;
     }
 
+    @Override
     public boolean isIncludeSchemaChanges() {
         return includeSchemaChanges;
     }

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/dialect/DataSourceDialect.java

@@ -61,7 +61,7 @@ public interface DataSourceDialect<ID extends DataCollectionId, S, C extends Sou
      */
     Offset displayCurrentOffset(C sourceConfig);
 
-    /** Check if the CollectionId is case sensitive or not. */
+    /** Check if the CollectionId is case-sensitive or not. */
     boolean isDataCollectionIdCaseSensitive(C sourceConfig);
 
     /** Returns the {@link ChunkSplitter} which used to split collection to splits. */

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/dialect/JdbcDataSourceDialect.java

@@ -41,9 +41,11 @@ public interface JdbcDataSourceDialect
         extends DataSourceDialect<TableId, TableChange, JdbcSourceConfig> {
 
     /** Discovers the list of table to capture. */
+    @Override
     List<TableId> discoverDataCollections(JdbcSourceConfig sourceConfig);
 
     /** Discovers the captured tables' schema by {@link SourceConfig}. */
+    @Override
     Map<TableId, TableChange> discoverDataCollectionSchemas(JdbcSourceConfig sourceConfig);
 
     /**

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/relational/JdbcSourceRecordEmitter.java

@@ -64,7 +64,7 @@ public class JdbcSourceRecordEmitter<T>
     private final SourceReaderMetrics sourceReaderMetrics;
     private final boolean includeSchemaChanges;
     private final OutputCollector<T> outputCollector;
-    private OffsetFactory offsetFactory;
+    private final OffsetFactory offsetFactory;
 
     public JdbcSourceRecordEmitter(
             DebeziumDeserializationSchema<T> debeziumDeserializationSchema,

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/relational/connection/JdbcConnectionPools.java

@@ -39,13 +39,11 @@ public class JdbcConnectionPools implements ConnectionPools<HikariDataSource, Jd
 
     public static synchronized JdbcConnectionPools getInstance(
             JdbcConnectionPoolFactory jdbcConnectionPoolFactory) {
-        if (instance != null) {
-            return instance;
-        } else {
+        if (instance == null) {
             JdbcConnectionPools.jdbcConnectionPoolFactory = jdbcConnectionPoolFactory;
             instance = new JdbcConnectionPools();
-            return instance;
         }
+        return instance;
     }
 
     @Override

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/assigner/SnapshotSplitAssigner.java

@@ -66,7 +66,7 @@ public class SnapshotSplitAssigner implements SplitAssigner {
 
     @Nullable private Long checkpointIdToFinish;
     private final DataSourceDialect dialect;
-    private OffsetFactory offsetFactory;
+    private final OffsetFactory offsetFactory;
 
     public SnapshotSplitAssigner(
             SourceConfig sourceConfig,

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/meta/split/FinishedSnapshotSplitInfo.java

@@ -45,7 +45,7 @@ public class FinishedSnapshotSplitInfo implements OffsetDeserializerSerializer {
     private final Object[] splitEnd;
     private final Offset highWatermark;
 
-    private OffsetFactory offsetFactory;
+    private final OffsetFactory offsetFactory;
 
     public FinishedSnapshotSplitInfo(
             TableId tableId,

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/meta/split/SnapshotSplitState.java

@@ -41,6 +41,7 @@ public class SnapshotSplitState extends SourceSplitState {
         this.highWatermark = highWatermark;
     }
 
+    @Override
     public SnapshotSplit toSourceSplit() {
         final SnapshotSplit snapshotSplit = split.asSnapshotSplit();
         return new SnapshotSplit(

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/meta/split/StreamSplitState.java

@@ -66,6 +66,7 @@ public class StreamSplitState extends SourceSplitState {
         this.tableSchemas.put(tableId, latestTableChange);
     }
 
+    @Override
     public StreamSplit toSourceSplit() {
         final StreamSplit binlogSplit = split.asStreamSplit();
         return new StreamSplit(

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/metrics/SourceReaderMetrics.java

@@ -52,9 +52,14 @@ public class SourceReaderMetrics {
     }
 
     public void registerMetrics() {
-        metricGroup.gauge("currentFetchEventTimeLag", (Gauge<Long>) this::getFetchDelay);
-        metricGroup.gauge("currentEmitEventTimeLag", (Gauge<Long>) this::getEmitDelay);
-        metricGroup.gauge("sourceIdleTime", (Gauge<Long>) this::getIdleTime);
+        metricGroup.gauge(
+                SoureReaderMetricConstants.CURRENT_FETCH_EVENT_TIME_LAG,
+                (Gauge<Long>) this::getFetchDelay);
+        metricGroup.gauge(
+                SoureReaderMetricConstants.CURRENT_EMIT_EVENT_TIME_LAG,
+                (Gauge<Long>) this::getEmitDelay);
+        metricGroup.gauge(
+                SoureReaderMetricConstants.SOURCE_IDLE_TIME, (Gauge<Long>) this::getIdleTime);
     }
 
     public long getFetchDelay() {

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/metrics/SoureReaderMetricConstants.java

@@ -0,0 +1,27 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.ververica.cdc.connectors.base.source.metrics;
+
+/** A collection of Source Reader metrics related constant strings. */
+public class SoureReaderMetricConstants {
+
+    public static final String SOURCE_IDLE_TIME = "sourceIdleTime";
+    public static final String CURRENT_FETCH_EVENT_TIME_LAG = "currentFetchEventTimeLag";
+    public static final String CURRENT_EMIT_EVENT_TIME_LAG = "currentEmitEventTimeLag";
+}

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/reader/JdbcSourceSplitReader.java

@@ -52,7 +52,7 @@ public class JdbcSourceSplitReader implements SplitReader<SourceRecord, SourceSp
 
     @Nullable private Fetcher<SourceRecord, SourceSplitBase> currenFetcher;
     @Nullable private String currentSplitId;
-    private JdbcDataSourceDialect dataSourceDialect;
+    private final JdbcDataSourceDialect dataSourceDialect;
 
     public JdbcSourceSplitReader(int subtaskId, JdbcDataSourceDialect dataSourceDialect) {
         this.subtaskId = subtaskId;

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/reader/external/JdbcSourceStreamFetcher.java

@@ -75,6 +75,7 @@ public class JdbcSourceStreamFetcher implements Fetcher<SourceRecord, SourceSpli
         this.executor = Executors.newSingleThreadExecutor(threadFactory);
     }
 
+    @Override
     public void submitTask(FetchTask<SourceSplitBase> fetchTask) {
         this.streamFetchTask = fetchTask;
         this.currentStreamSplit = fetchTask.getSplit().asStreamSplit();

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/utils/SourceRecordUtils.java

@@ -76,26 +76,17 @@ public class SourceRecordUtils {
 
     public static boolean isLowWatermarkEvent(SourceRecord record) {
         Optional<WatermarkKind> watermarkKind = getWatermarkKind(record);
-        if (watermarkKind.isPresent() && watermarkKind.get() == WatermarkKind.LOW) {
-            return true;
-        }
-        return false;
+        return watermarkKind.isPresent() && watermarkKind.get() == WatermarkKind.LOW;
     }
 
     public static boolean isHighWatermarkEvent(SourceRecord record) {
         Optional<WatermarkKind> watermarkKind = getWatermarkKind(record);
-        if (watermarkKind.isPresent() && watermarkKind.get() == WatermarkKind.HIGH) {
-            return true;
-        }
-        return false;
+        return watermarkKind.isPresent() && watermarkKind.get() == WatermarkKind.HIGH;
     }
 
     public static boolean isEndWatermarkEvent(SourceRecord record) {
         Optional<WatermarkKind> watermarkKind = getWatermarkKind(record);
-        if (watermarkKind.isPresent() && watermarkKind.get() == WatermarkKind.BINLOG_END) {
-            return true;
-        }
-        return false;
+        return watermarkKind.isPresent() && watermarkKind.get() == WatermarkKind.BINLOG_END;
     }
 
     /**
@@ -134,10 +125,7 @@ public class SourceRecordUtils {
 
     public static boolean isSchemaChangeEvent(SourceRecord sourceRecord) {
         Schema keySchema = sourceRecord.keySchema();
-        if (keySchema != null && SCHEMA_CHANGE_EVENT_KEY_NAME.equalsIgnoreCase(keySchema.name())) {
-            return true;
-        }
-        return false;
+        return keySchema != null && SCHEMA_CHANGE_EVENT_KEY_NAME.equalsIgnoreCase(keySchema.name());
     }
 
     public static boolean isDataChangeRecord(SourceRecord record) {

flink-cdc-base/src/test/java/com/ververica/cdc/connectors/base/experimental/config/MySqlSourceConfigFactory.java

@@ -67,8 +67,7 @@ public class MySqlSourceConfigFactory extends JdbcSourceConfigFactory {
         // database history
         props.setProperty(
                 "database.history", EmbeddedFlinkDatabaseHistory.class.getCanonicalName());
-        props.setProperty(
-                "database.history.instance.name", UUID.randomUUID().toString() + "_" + subtaskId);
+        props.setProperty("database.history.instance.name", UUID.randomUUID() + "_" + subtaskId);
         props.setProperty("database.history.skip.unparseable.ddl", String.valueOf(true));
         props.setProperty("database.history.refer.ddl", String.valueOf(true));
         props.setProperty("connect.timeout.ms", String.valueOf(connectTimeout.toMillis()));

flink-cdc-base/src/test/java/com/ververica/cdc/connectors/base/experimental/config/ServerIdRange.java

@@ -62,7 +62,7 @@ public class ServerIdRange implements Serializable {
                                     + "please adjust the server id range to "
                                     + "make the number of server id larger than "
                                     + "the source parallelism.",
-                            subTaskId, this.toString()));
+                            subTaskId, this));
         }
         return startServerId + subTaskId;
     }

flink-cdc-base/src/test/java/com/ververica/cdc/connectors/base/experimental/fetch/MySqlScanFetchTask.java

@@ -150,8 +150,7 @@ public class MySqlScanFetchTask implements FetchTask<SourceSplitBase> {
     private MySqlBinlogSplitReadTask createBackfillBinlogReadTask(
             StreamSplit backfillBinlogSplit, MySqlSourceFetchTaskContext context) {
         final MySqlOffsetContext.Loader loader =
-                new MySqlOffsetContext.Loader(
-                        (MySqlConnectorConfig) context.getSourceConfig().getDbzConnectorConfig());
+                new MySqlOffsetContext.Loader(context.getSourceConfig().getDbzConnectorConfig());
         final MySqlOffsetContext mySqlOffsetContext =
                 (MySqlOffsetContext)
                         loader.load(backfillBinlogSplit.getStartingOffset().getOffset());

flink-cdc-base/src/test/java/com/ververica/cdc/connectors/base/testutils/MySqlVersion.java

@@ -25,7 +25,7 @@ public enum MySqlVersion {
     V5_7("5.7"),
     V8_0("8.0");
 
-    private String version;
+    private final String version;
 
     MySqlVersion(String version) {
         this.version = version;