Processing of Review comments.

Using isRoot() instead of path == null.
Rename extendBy to append.
Move getRequiredLeafEntity closer to getLeafEntity.
Replace matches with equals.

Author: schauder

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/JdbcAggregateChangeExecutionContext.java

@@ -203,7 +203,7 @@ private DbAction.WithEntity<?> getIdOwningAction(DbAction.WithEntity<?> action,
 			return action;
 		}
 
-		if (idPath.matches(withDependingOn.getPropertyPath())) {
+		if (idPath.equals(context.getAggregatePath(withDependingOn.getPropertyPath()))) {
 			return action;
 		}
 

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/BasicJdbcConverter.java

@@ -396,7 +396,7 @@ private ReadingContext(RelationalPersistentEntity<T> entity, AggregatePath rootP
 		private <S> ReadingContext<S> extendBy(RelationalPersistentProperty property) {
 			return new ReadingContext<>(
 					(RelationalPersistentEntity<S>) getMappingContext().getRequiredPersistentEntity(property.getActualType()),
-					rootPath.extendBy(property), path.extendBy(property), identifier, key,
+					rootPath.append(property), path.append(property), identifier, key,
 					propertyValueProvider.extendBy(property), backReferencePropertyValueProvider.extendBy(property), accessor);
 		}
 
@@ -457,9 +457,9 @@ private Iterable<Object> resolveRelation(@Nullable Object id, RelationalPersiste
 
 			Identifier identifier = id == null //
 					? this.identifier.withPart(rootPath.getQualifierColumn(), key, Object.class) //
-					: Identifier.of(rootPath.extendBy(property).getReverseColumnName(), id, Object.class);
+					: Identifier.of(rootPath.append(property).getReverseColumnName(), id, Object.class);
 
-			PersistentPropertyPath<? extends RelationalPersistentProperty> propertyPath = path.extendBy(property)
+			PersistentPropertyPath<? extends RelationalPersistentProperty> propertyPath = path.append(property)
 					.getRequiredPersistentPropertyPath();
 
 			return relationResolver.findAllByPath(identifier, propertyPath);

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/JdbcBackReferencePropertyValueProvider.java

@@ -17,9 +17,7 @@
 
 import org.springframework.data.mapping.model.PropertyValueProvider;
 import org.springframework.data.relational.core.mapping.AggregatePath;
-import org.springframework.data.relational.core.mapping.PersistentPropertyPathExtension;
 import org.springframework.data.relational.core.mapping.RelationalPersistentProperty;
-import org.springframework.data.relational.core.sql.IdentifierProcessing;
 
 /**
  * {@link PropertyValueProvider} obtaining values from a {@link ResultSetAccessor}. For a given id property it provides
@@ -47,10 +45,10 @@ class JdbcBackReferencePropertyValueProvider implements PropertyValueProvider<Re
 
 	@Override
 	public <T> T getPropertyValue(RelationalPersistentProperty property) {
-		return (T) resultSet.getObject(basePath.extendBy(property).getReverseColumnNameAlias().getReference());
+		return (T) resultSet.getObject(basePath.append(property).getReverseColumnNameAlias().getReference());
 	}
 
 	public JdbcBackReferencePropertyValueProvider extendBy(RelationalPersistentProperty property) {
-		return new JdbcBackReferencePropertyValueProvider(basePath.extendBy(property), resultSet);
+		return new JdbcBackReferencePropertyValueProvider(basePath.append(property), resultSet);
 	}
 }

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/JdbcPropertyValueProvider.java

@@ -57,10 +57,10 @@ public boolean hasProperty(RelationalPersistentProperty property) {
 	}
 
 	private String getColumnName(RelationalPersistentProperty property) {
-		return basePath.extendBy(property).getColumnAlias().getReference();
+		return basePath.append(property).getColumnAlias().getReference();
 	}
 
 	public JdbcPropertyValueProvider extendBy(RelationalPersistentProperty property) {
-		return new JdbcPropertyValueProvider(basePath.extendBy(property), resultSet);
+		return new JdbcPropertyValueProvider(basePath.append(property), resultSet);
 	}
 }

spring-data-relational/src/main/java/org/springframework/data/relational/core/mapping/AggregatePath.java

@@ -23,6 +23,8 @@
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
+import java.util.Objects;
+
 /**
  * Represents a path within an aggregate starting from the aggregate root.
  *
@@ -69,24 +71,14 @@ public boolean isRoot() {
 		return path == null;
 	}
 
-	/**
-	 * Tests if {@code this} and the argument represent the same path.
-	 *
-	 * @param path to which this path gets compared. May be {@literal null}.
-	 * @return Whence the argument matches the path represented by this instance.
-	 */
-	public boolean matches(@Nullable PersistentPropertyPath<RelationalPersistentProperty> path) {
-		return this.path == null ? path == null || path.isEmpty() : this.path.equals(path);
-	}
-
 	/**
 	 * The name of the column used to reference the id in the parent table.
 	 *
 	 * @throws IllegalStateException when called on an empty path.
 	 */
 	public SqlIdentifier getReverseColumnName() {
 
-		Assert.state(path != null, "Empty paths don't have a reverse column name");
+		Assert.state(!isRoot(), "Empty paths don't have a reverse column name");
 
 		return path.getLeafProperty().getReverseColumnName(this);
 	}
@@ -99,7 +91,7 @@ public SqlIdentifier getReverseColumnName() {
 	 */
 	public AggregatePath getParentPath() {
 
-		if (path == null) {
+		if (isRoot()) {
 			throw new IllegalStateException("The parent path of a root path is not defined.");
 		}
 
@@ -117,7 +109,27 @@ public AggregatePath getParentPath() {
 	 */
 	@Nullable
 	public RelationalPersistentEntity<?> getLeafEntity() {
-		return path == null ? rootType : context.getPersistentEntity(path.getLeafProperty().getActualType());
+		return isRoot() ? rootType : context.getPersistentEntity(path.getLeafProperty().getActualType());
+	}
+
+	/**
+	 * The {@link RelationalPersistentEntity} associated with the leaf of this path or throw {@link IllegalStateException}
+	 * if the leaf cannot be resolved.
+	 *
+	 * @return the required {@link RelationalPersistentEntity} associated with the leaf of this path.
+	 * @throws IllegalStateException if the persistent entity cannot be resolved.
+	 */
+	public RelationalPersistentEntity<?> getRequiredLeafEntity() {
+
+		RelationalPersistentEntity<?> entity = getLeafEntity();
+
+		if (entity == null) {
+
+			throw new IllegalStateException(
+					String.format("Couldn't resolve leaf PersistentEntity for type %s", path.getLeafProperty().getActualType()));
+		}
+
+		return entity;
 	}
 
 	/**
@@ -138,7 +150,7 @@ public AggregatePath getIdDefiningParentPath() {
 
 		AggregatePath parent = getParentPath();
 
-		if (parent.path == null) {
+		if (isRoot()) {
 			return parent;
 		}
 
@@ -149,33 +161,13 @@ public AggregatePath getIdDefiningParentPath() {
 		return parent;
 	}
 
-	/**
-	 * The {@link RelationalPersistentEntity} associated with the leaf of this path or throw {@link IllegalStateException}
-	 * if the leaf cannot be resolved.
-	 *
-	 * @return the required {@link RelationalPersistentEntity} associated with the leaf of this path.
-	 * @throws IllegalStateException if the persistent entity cannot be resolved.
-	 */
-	public RelationalPersistentEntity<?> getRequiredLeafEntity() {
-
-		RelationalPersistentEntity<?> entity = getLeafEntity();
-
-		if (entity == null) {
-
-			throw new IllegalStateException(
-					String.format("Couldn't resolve leaf PersistentEntity for type %s", path.getLeafProperty().getActualType()));
-		}
-
-		return entity;
-	}
-
 	public RelationalPersistentProperty getRequiredIdProperty() {
-		return this.path == null ? rootType.getRequiredIdProperty() : getRequiredLeafEntity().getRequiredIdProperty();
+		return isRoot() ? rootType.getRequiredIdProperty() : getRequiredLeafEntity().getRequiredIdProperty();
 
 	}
 
 	public int getLength() {
-		return path == null ? 0 : path.getLength();
+		return isRoot() ? 0 : path.getLength();
 	}
 
 	/**
@@ -185,7 +177,7 @@ public int getLength() {
 	 */
 	@Nullable
 	public SqlIdentifier getQualifierColumn() {
-		return path == null ? null : path.getLeafProperty().getKeyColumn();
+		return isRoot() ? null : path.getLeafProperty().getKeyColumn();
 	}
 
 	/**
@@ -196,7 +188,7 @@ public SqlIdentifier getQualifierColumn() {
 	@Nullable
 	public Class<?> getQualifierColumnType() {
 
-		if (path == null) {
+		if (isRoot()) {
 			return null;
 		}
 		if (!path.getLeafProperty().isQualified()) {
@@ -211,14 +203,14 @@ public Class<?> getQualifierColumnType() {
 	 * @return if the leaf property is embedded.
 	 */
 	public boolean isEmbedded() {
-		return path != null && path.getLeafProperty().isEmbedded();
+		return !isRoot() && path.getLeafProperty().isEmbedded();
 	}
 
 	/**
 	 * @return {@literal true} when this is an empty path or the path references an entity.
 	 */
 	public boolean isEntity() {
-		return path == null || path.getLeafProperty().isEntity();
+		return isRoot() || path.getLeafProperty().isEntity();
 	}
 
 	/**
@@ -235,7 +227,7 @@ private AggregatePath getTableOwningAncestor() {
 	@Nullable
 	private SqlIdentifier assembleTableAlias() {
 
-		Assert.state(path != null, "Path is null");
+		Assert.state(!isRoot(), "Path is null");
 
 		RelationalPersistentProperty leafProperty = path.getLeafProperty();
 		String prefix;
@@ -273,7 +265,7 @@ public SqlIdentifier getTableAlias() {
 
 		AggregatePath tableOwner = getTableOwningAncestor();
 
-		return tableOwner.path == null ? null : tableOwner.assembleTableAlias();
+		return tableOwner.isRoot() ? null : tableOwner.assembleTableAlias();
 
 	}
 
@@ -295,7 +287,7 @@ public SqlIdentifier getQualifiedTableName() {
 	 */
 	public SqlIdentifier getColumnName() {
 
-		Assert.state(path != null, "Path is null");
+		Assert.state(!isRoot(), "Path is null");
 
 		return assembleColumnName(path.getLeafProperty().getColumnName());
 	}
@@ -323,12 +315,12 @@ public SqlIdentifier getReverseColumnNameAlias() {
 	public String toString() {
 		return "AggregatePath["
 				+ (rootType == null ? path.getBaseProperty().getOwner().getType().getName() : rootType.getName()) + "]"
-				+ ((path == null) ? "/" : path.toDotPath());
+				+ ((isRoot()) ? "/" : path.toDotPath());
 	}
 
 	private SqlIdentifier assembleColumnName(SqlIdentifier suffix) {
 
-		Assert.state(path != null, "Path is null");
+		Assert.state(!isRoot(), "Path is null");
 
 		if (path.getLength() <= 1) {
 			return suffix;
@@ -353,7 +345,7 @@ private SqlIdentifier prefixWithTableAlias(SqlIdentifier columnName) {
 	}
 
 	public String toDotPath() {
-		return path == null ? "" : path.toDotPath();
+		return isRoot() ? "" : path.toDotPath();
 	}
 
 	/**
@@ -364,7 +356,7 @@ public String toDotPath() {
 	 */
 	public boolean isMultiValued() {
 
-		return path != null && //
+		return !isRoot() && //
 				(path.getLeafProperty().isCollectionLike() //
 						|| path.getLeafProperty().isQualified() //
 						|| getParentPath().isMultiValued() //
@@ -376,27 +368,27 @@ public boolean isMultiValued() {
 	 * @see RelationalPersistentProperty#isMap()
 	 */
 	public boolean isMap() {
-		return path != null && path.getLeafProperty().isMap();
+		return !isRoot() && path.getLeafProperty().isMap();
 	}
 
 	/**
 	 * @return {@literal true} when this is references a {@link java.util.List} or {@link java.util.Map}.
 	 */
 	public boolean isQualified() {
-		return path != null && path.getLeafProperty().isQualified();
+		return !isRoot() && path.getLeafProperty().isQualified();
 	}
 
 	public RelationalPersistentProperty getRequiredLeafProperty() {
 
-		if (path == null) {
+		if (isRoot()) {
 			throw new IllegalStateException("root path does not have a leaf property");
 		}
 		return path.getLeafProperty();
 	}
 
 	public RelationalPersistentProperty getBaseProperty() {
 
-		if (path == null) {
+		if (isRoot()) {
 			throw new IllegalStateException("root path does not have a base property");
 		}
 		return path.getBaseProperty();
@@ -413,15 +405,15 @@ public SqlIdentifier getIdColumnName() {
 	 * @return {@literal true} when this is references a {@link java.util.Collection} or an array.
 	 */
 	public boolean isCollectionLike() {
-		return path != null && path.getLeafProperty().isCollectionLike();
+		return !isRoot() && path.getLeafProperty().isCollectionLike();
 	}
 
 	/**
 	 * @return whether the leaf end of the path is ordered, i.e. the data to populate must be ordered.
 	 * @see RelationalPersistentProperty#isOrdered()
 	 */
 	public boolean isOrdered() {
-		return path != null && path.getLeafProperty().isOrdered();
+		return !isRoot() && path.getLeafProperty().isOrdered();
 	}
 
 	/**
@@ -430,9 +422,9 @@ public boolean isOrdered() {
 	 * @param property must not be {@literal null}.
 	 * @return Guaranteed to be not {@literal null}.
 	 */
-	public AggregatePath extendBy(RelationalPersistentProperty property) {
+	public AggregatePath append(RelationalPersistentProperty property) {
 
-		PersistentPropertyPath<? extends RelationalPersistentProperty> newPath = path == null //
+		PersistentPropertyPath<? extends RelationalPersistentProperty> newPath = isRoot() //
 				? context.getPersistentPropertyPath(property.getName(), rootType.getType()) //
 				: context.getPersistentPropertyPath(path.toDotPath() + "." + property.getName(),
 						path.getBaseProperty().getOwner().getType());
@@ -442,7 +434,7 @@ public AggregatePath extendBy(RelationalPersistentProperty property) {
 
 	public PersistentPropertyPath<? extends RelationalPersistentProperty> getRequiredPersistentPropertyPath() {
 
-		Assert.state(path != null, "path must not be null");
+		Assert.state(!isRoot(), "path must not be null");
 		return path;
 	}
 
@@ -453,15 +445,30 @@ public PersistentPropertyPath<? extends RelationalPersistentProperty> getRequire
 	public SqlIdentifier getEffectiveIdColumnName() {
 
 		AggregatePath owner = getTableOwningAncestor();
-		return owner.path == null ? owner.getRequiredLeafEntity().getIdColumn() : owner.getReverseColumnName();
+		return owner.isRoot() ? owner.getRequiredLeafEntity().getIdColumn() : owner.getReverseColumnName();
 	}
 
 	@Nullable
 	public PersistentPropertyPathExtension getPathExtension() {
 
-		if (path == null) {
+		if (isRoot()) {
 			return new PersistentPropertyPathExtension(context, rootType);
 		}
 		return new PersistentPropertyPathExtension(context, path);
 	}
+
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+		AggregatePath that = (AggregatePath) o;
+		return Objects.equals(context, that.context) && Objects.equals(rootType, that.rootType) && Objects.equals(path, that.path);
+	}
+
+	@Override
+	public int hashCode() {
+
+		return Objects.hash(context, rootType, path);
+	}
 }