refactor merger into ShardingResultSet 12th version, refactor MergeEngine

sharding-jdbc-core/src/main/java/com/dangdang/ddframe/rdb/sharding/jdbc/core/statement/ShardingPreparedStatement.java

@@ -84,7 +84,7 @@ public final class ShardingPreparedStatement extends AbstractPreparedStatementAd
             Collection<PreparedStatementUnit> preparedStatementUnits = route();
             List<ResultSet> resultSets = new PreparedStatementExecutor(
                     getShardingConnection().getShardingContext().getExecutorEngine(), getRouteResult().getSqlStatement().getType(), preparedStatementUnits, getParameters()).executeQuery();
-            result = new ShardingResultSet(resultSets, MergeEngine.getResultSet(resultSets, (SelectStatement) getRouteResult().getSqlStatement()));
+            result = new ShardingResultSet(resultSets, new MergeEngine(resultSets, (SelectStatement) getRouteResult().getSqlStatement()).merge());
         } finally {
             clearBatch();
         }

sharding-jdbc-core/src/main/java/com/dangdang/ddframe/rdb/sharding/jdbc/core/statement/ShardingStatement.java

@@ -104,7 +104,7 @@ public class ShardingStatement extends AbstractStatementAdapter {
         ResultSet result;
         try {
             List<ResultSet> resultSets = generateExecutor(sql).executeQuery();
-            result = new ShardingResultSet(resultSets, MergeEngine.getResultSet(resultSets, (SelectStatement) getRouteResult().getSqlStatement()));
+            result = new ShardingResultSet(resultSets, new MergeEngine(resultSets, (SelectStatement) getRouteResult().getSqlStatement()).merge());
         } finally {
             setCurrentResultSet(null);
         }
@@ -248,7 +248,7 @@ public class ShardingStatement extends AbstractStatementAdapter {
         for (Statement each : routedStatements) {
             resultSets.add(each.getResultSet());
         }
-        currentResultSet = new ShardingResultSet(resultSets, MergeEngine.getResultSet(resultSets, (SelectStatement) getRouteResult().getSqlStatement()));
+        currentResultSet = new ShardingResultSet(resultSets, new MergeEngine(resultSets, (SelectStatement) getRouteResult().getSqlStatement()).merge());
         return currentResultSet;
     }
 }

sharding-jdbc-core/src/main/java/com/dangdang/ddframe/rdb/sharding/merger/core/MergeEngine.java

@@ -23,51 +23,55 @@ import com.dangdang.ddframe.rdb.sharding.merger.core.stream.IteratorStreamResult
 import com.dangdang.ddframe.rdb.sharding.merger.core.stream.OrderByStreamResultSetMerger;
 import com.dangdang.ddframe.rdb.sharding.merger.util.ResultSetUtil;
 import com.dangdang.ddframe.rdb.sharding.parsing.parser.statement.select.SelectStatement;
-import lombok.AccessLevel;
-import lombok.RequiredArgsConstructor;
-import lombok.extern.slf4j.Slf4j;
 
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.List;
+import java.util.Map;
 
 /**
  * 分片结果集归并引擎.
  *
  * @author zhangliang
  */
-@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
-@Slf4j
 public final class MergeEngine {
     
+    private final List<ResultSet> resultSets;
+    
+    private final SelectStatement selectStatement;
+    
+    private final Map<String, Integer> columnLabelIndexMap;
+    
+    public MergeEngine(final List<ResultSet> resultSets, final SelectStatement selectStatement) throws SQLException {
+        this.resultSets = resultSets;
+        this.selectStatement = selectStatement;
+        columnLabelIndexMap = ResultSetUtil.getColumnLabelIndexMap(resultSets.get(0));
+    }
+    
     /**
-     * 获取结果集.
+     * 合并结果集.
      *
-     * @param resultSets 结果集列表
-     * @param selectStatement SQL语句对象
-     * @return 结果集包装
+     * @return 归并完毕后的结果集
      * @throws SQLException SQL异常
      */
-    public static ResultSetMerger getResultSet(final List<ResultSet> resultSets, final SelectStatement selectStatement) throws SQLException {
-        selectStatement.setIndexForItems(ResultSetUtil.getColumnLabelIndexMap(resultSets.get(0)));
-        ResultSetMerger result = !selectStatement.getGroupByItems().isEmpty() || !selectStatement.getAggregationSelectItems().isEmpty()
-                ? buildMemoryResultSet(resultSets, selectStatement) : buildStreamResultSet(resultSets, selectStatement);
-        return buildDecorateResultSet(result, selectStatement);
+    public ResultSetMerger merge() throws SQLException {
+        selectStatement.setIndexForItems(columnLabelIndexMap);
+        ResultSetMerger result = !selectStatement.getGroupByItems().isEmpty() || !selectStatement.getAggregationSelectItems().isEmpty() ? buildMemoryResultSet() : buildStreamResultSet();
+        return buildDecorateResultSet(result);
     }
     
-    private static ResultSetMerger buildMemoryResultSet(final List<ResultSet> resultSets, final SelectStatement selectStatement) throws SQLException {
-        return new GroupByMemoryResultSetMerger(
-                ResultSetUtil.getColumnLabelIndexMap(resultSets.get(0)), resultSets, selectStatement.getGroupByItems(), selectStatement.getOrderByItems(), selectStatement.getAggregationSelectItems());
+    private ResultSetMerger buildMemoryResultSet() throws SQLException {
+        return new GroupByMemoryResultSetMerger(columnLabelIndexMap, resultSets, selectStatement.getGroupByItems(), selectStatement.getOrderByItems(), selectStatement.getAggregationSelectItems());
     }
     
-    private static ResultSetMerger buildStreamResultSet(final List<ResultSet> resultSets, final SelectStatement selectStatement) throws SQLException {
+    private ResultSetMerger buildStreamResultSet() throws SQLException {
         if (selectStatement.getGroupByItems().isEmpty() && selectStatement.getOrderByItems().isEmpty()) {
             return new IteratorStreamResultSetMerger(resultSets);
         }
         return new OrderByStreamResultSetMerger(resultSets, selectStatement.getOrderByItems());
     }
     
-    private static ResultSetMerger buildDecorateResultSet(final ResultSetMerger resultSetMerger, final SelectStatement selectStatement) throws SQLException {
+    private ResultSetMerger buildDecorateResultSet(final ResultSetMerger resultSetMerger) throws SQLException {
         ResultSetMerger result = resultSetMerger;
         if (null != selectStatement.getLimit()) {
             result = new LimitDecoratorResultSetMerger(result, selectStatement.getLimit());