Enable mapping of arbitrary SQL results to aggregate entities

doma-core/src/main/java/module-info.java

@@ -57,6 +57,7 @@
   exports org.seasar.doma.internal.expr.node;
   exports org.seasar.doma.internal.jdbc.sql.node;
   exports org.seasar.doma.internal.jdbc.util;
+  exports org.seasar.doma.jdbc.aggregate;
 
   // Requires
   requires transitive java.sql;

doma-core/src/main/java/org/seasar/doma/Association.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright Doma Authors
+ *
+ * Licensed 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
+ *
+ *     https://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 org.seasar.doma;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates an association between entities.
+ *
+ * <p>This annotation is applied to fields that represent a relationship between entities.
+ */
+@Target(ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Association {}

doma-core/src/main/java/org/seasar/doma/AssociationLinker.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright Doma Authors
+ *
+ * Licensed 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
+ *
+ *     https://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 org.seasar.doma;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.function.BiFunction;
+
+/**
+ * Associates a field in an entity class with properties in a related object for the purpose of
+ * creating object relationships when mapping between database tables and entities.
+ *
+ * <p>This class can only be annotated on {@code public static final} fields of type {@link
+ * BiFunction}.
+ */
+@Target(java.lang.annotation.ElementType.FIELD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface AssociationLinker {
+  /**
+   * Specifies the path to the property in the related object.
+   *
+   * @return the property path as a string
+   */
+  String propertyPath();
+
+  /**
+   * Defines the prefix for the column in the database table that is linked to the field.
+   *
+   * @return the column prefix as a string
+   */
+  String columnPrefix();
+}

doma-core/src/main/java/org/seasar/doma/Select.java

@@ -20,6 +20,7 @@
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.sql.Statement;
+import java.util.function.BiFunction;
 import org.seasar.doma.jdbc.Config;
 import org.seasar.doma.jdbc.JdbcException;
 import org.seasar.doma.jdbc.NoResultException;
@@ -163,4 +164,14 @@
    * @return the output format of SQL logs.
    */
   SqlLogType sqlLog() default SqlLogType.FORMATTED;
+
+  /**
+   * Specifies a strategy class used for aggregation operations.
+   *
+   * <p>The class specified here must contain at least one field of type {@link BiFunction}
+   * annotated with {@link AssociationLinker}.
+   *
+   * @return the class representing the aggregation strategy, or {@code Void.class} if not specified
+   */
+  Class<?> aggregateStrategy() default Void.class;
 }

doma-core/src/main/java/org/seasar/doma/jdbc/CommandImplementors.java

@@ -16,9 +16,38 @@
 package org.seasar.doma.jdbc;
 
 import java.lang.reflect.Method;
+import java.util.List;
 import java.util.function.BiFunction;
-import org.seasar.doma.jdbc.command.*;
-import org.seasar.doma.jdbc.query.*;
+import org.seasar.doma.jdbc.aggregate.AggregateCommand;
+import org.seasar.doma.jdbc.aggregate.AssociationLinkerType;
+import org.seasar.doma.jdbc.aggregate.StreamReducer;
+import org.seasar.doma.jdbc.command.BatchDeleteCommand;
+import org.seasar.doma.jdbc.command.BatchInsertCommand;
+import org.seasar.doma.jdbc.command.BatchUpdateCommand;
+import org.seasar.doma.jdbc.command.Command;
+import org.seasar.doma.jdbc.command.CreateCommand;
+import org.seasar.doma.jdbc.command.DeleteCommand;
+import org.seasar.doma.jdbc.command.FunctionCommand;
+import org.seasar.doma.jdbc.command.InsertCommand;
+import org.seasar.doma.jdbc.command.ProcedureCommand;
+import org.seasar.doma.jdbc.command.ResultSetHandler;
+import org.seasar.doma.jdbc.command.ScriptCommand;
+import org.seasar.doma.jdbc.command.SelectCommand;
+import org.seasar.doma.jdbc.command.SqlProcessorCommand;
+import org.seasar.doma.jdbc.command.UpdateCommand;
+import org.seasar.doma.jdbc.entity.EntityType;
+import org.seasar.doma.jdbc.query.BatchDeleteQuery;
+import org.seasar.doma.jdbc.query.BatchInsertQuery;
+import org.seasar.doma.jdbc.query.BatchUpdateQuery;
+import org.seasar.doma.jdbc.query.CreateQuery;
+import org.seasar.doma.jdbc.query.DeleteQuery;
+import org.seasar.doma.jdbc.query.FunctionQuery;
+import org.seasar.doma.jdbc.query.InsertQuery;
+import org.seasar.doma.jdbc.query.ProcedureQuery;
+import org.seasar.doma.jdbc.query.ScriptQuery;
+import org.seasar.doma.jdbc.query.SelectQuery;
+import org.seasar.doma.jdbc.query.SqlProcessorQuery;
+import org.seasar.doma.jdbc.query.UpdateQuery;
 
 /** A factory for the {@link Command} implementation classes. */
 public interface CommandImplementors {
@@ -37,6 +66,15 @@ default <RESULT> SelectCommand<RESULT> createSelectCommand(
     return new SelectCommand<>(query, resultSetHandler);
   }
 
+  default <RESULT, ENTITY> AggregateCommand<RESULT, ENTITY> createAggregateCommand(
+      Method method,
+      SelectQuery query,
+      EntityType<ENTITY> entityType,
+      StreamReducer<RESULT, ENTITY> resultReducer,
+      List<AssociationLinkerType<?, ?>> associationLinkerTypes) {
+    return new AggregateCommand<>(query, entityType, resultReducer, associationLinkerTypes);
+  }
+
   /**
    * Creates a {@link DeleteCommand} object.
    *

doma-core/src/main/java/org/seasar/doma/jdbc/aggregate/AggregateCommand.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright Doma Authors
+ *
+ * Licensed 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
+ *
+ *     https://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 org.seasar.doma.jdbc.aggregate;
+
+import java.util.Comparator;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.BiFunction;
+import java.util.stream.Stream;
+import org.seasar.doma.internal.util.Combinations;
+import org.seasar.doma.internal.util.Pair;
+import org.seasar.doma.jdbc.command.Command;
+import org.seasar.doma.jdbc.command.SelectCommand;
+import org.seasar.doma.jdbc.entity.EntityType;
+import org.seasar.doma.jdbc.query.Query;
+import org.seasar.doma.jdbc.query.SelectQuery;
+
+public class AggregateCommand<RESULT, ENTITY> implements Command<RESULT> {
+  private final SelectQuery query;
+  private final EntityType<ENTITY> entityType;
+  private final StreamReducer<RESULT, ENTITY> streamReducer;
+  private final List<AssociationLinkerType<?, ?>> associationLinkerTypes;
+
+  public AggregateCommand(
+      SelectQuery query,
+      EntityType<ENTITY> entityType,
+      StreamReducer<RESULT, ENTITY> streamReducer,
+      List<AssociationLinkerType<?, ?>> associationLinkerTypes) {
+    this.query = Objects.requireNonNull(query);
+    this.entityType = Objects.requireNonNull(entityType);
+    this.streamReducer = Objects.requireNonNull(streamReducer);
+    Objects.requireNonNull(associationLinkerTypes);
+    this.associationLinkerTypes = sortAssociationLinkerTypes(associationLinkerTypes);
+  }
+
+  private static List<AssociationLinkerType<?, ?>> sortAssociationLinkerTypes(
+      List<AssociationLinkerType<?, ?>> associationLinkerTypes) {
+    Comparator<AssociationLinkerType<?, ?>> reversedComparator =
+        Comparator.<AssociationLinkerType<?, ?>>comparingInt(AssociationLinkerType::getDepth)
+            .reversed();
+    return associationLinkerTypes.stream().sorted(reversedComparator).toList();
+  }
+
+  @Override
+  public RESULT execute() {
+    Map<LinkableEntityKey, Object> cache = new LinkedHashMap<>();
+    Combinations<LinkableEntityKey> combinations = new Combinations<>();
+    SelectCommand<List<LinkableEntityPool>> command =
+        new SelectCommand<>(
+            query,
+            new LinkableEntityPoolIterationHandler(
+                entityType, associationLinkerTypes, query.isResultMappingEnsured(), cache));
+    List<LinkableEntityPool> entityPools = command.execute();
+    for (LinkableEntityPool entityPool : entityPools) {
+      Map<String, LinkableEntity> associationCandidate = new LinkedHashMap<>();
+      for (LinkableEntity entry : entityPool) {
+        associationCandidate.put(entry.key().propertyPath(), entry);
+      }
+      associate(cache, combinations, associationCandidate);
+    }
+    @SuppressWarnings("unchecked")
+    Stream<ENTITY> stream =
+        (Stream<ENTITY>)
+            cache.entrySet().stream()
+                .filter(e -> e.getKey().belongsToRootEntity())
+                .map(Map.Entry::getValue);
+    return streamReducer.reduce(stream);
+  }
+
+  private void associate(
+      Map<LinkableEntityKey, Object> cache,
+      Combinations<LinkableEntityKey> combinations,
+      Map<String, LinkableEntity> associationCandidate) {
+    for (AssociationLinkerType<?, ?> associationLinkerType : associationLinkerTypes) {
+      LinkableEntity source = associationCandidate.get(associationLinkerType.getSourceName());
+      LinkableEntity target = associationCandidate.get(associationLinkerType.getTargetName());
+      if (source == null || target == null) {
+        continue;
+      }
+      Pair<LinkableEntityKey, LinkableEntityKey> keyPair = new Pair<>(source.key(), target.key());
+      if (combinations.contains(keyPair)) {
+        continue;
+      }
+      @SuppressWarnings("unchecked")
+      BiFunction<Object, Object, Object> linker =
+          (BiFunction<Object, Object, Object>) associationLinkerType.getLinker();
+      Object newEntity = linker.apply(source.entity(), target.entity());
+      if (newEntity != null) {
+        cache.replace(source.key(), newEntity);
+        associationCandidate.replace(
+            associationLinkerType.getSourceName(), new LinkableEntity(source.key(), newEntity));
+      }
+      combinations.add(keyPair);
+    }
+  }
+
+  @Override
+  public Query getQuery() {
+    return query;
+  }
+}

doma-core/src/main/java/org/seasar/doma/jdbc/aggregate/AssociationIdentifier.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright Doma Authors
+ *
+ * Licensed 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
+ *
+ *     https://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 org.seasar.doma.jdbc.aggregate;
+
+import java.util.Objects;
+import org.seasar.doma.jdbc.entity.EntityType;
+
+record AssociationIdentifier(String propertyPath, EntityType<?> entityType) {
+  AssociationIdentifier {
+    Objects.requireNonNull(propertyPath);
+    Objects.requireNonNull(entityType);
+  }
+}