DATAGRAPH-545 - Add SingleLabelTypeRepresentationStrategy

spring-data-neo4j/src/main/java/org/springframework/data/neo4j/support/typerepresentation/SingleLabelBasedNodeTypeRepresentationStrategy.java

@@ -0,0 +1,123 @@
+/**
+ * Copyright 2011 the original author or 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
+ *
+ *      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 org.springframework.data.neo4j.support.typerepresentation;
+
+import org.neo4j.graphdb.DynamicLabel;
+import org.neo4j.graphdb.Label;
+import org.neo4j.graphdb.Node;
+import org.neo4j.helpers.collection.ClosableIterable;
+import org.neo4j.helpers.collection.IteratorUtil;
+import org.springframework.data.neo4j.core.GraphDatabase;
+import org.springframework.data.neo4j.core.NodeTypeRepresentationStrategy;
+import org.springframework.data.neo4j.support.mapping.StoredEntityType;
+import org.springframework.data.neo4j.support.mapping.WrappedIterableClosableIterable;
+import org.springframework.data.neo4j.support.query.CypherQueryEngine;
+
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+/**
+ * Provides a Node Type Representation Strategy which makes use of a single Label per type.
+ */
+public class SingleLabelBasedNodeTypeRepresentationStrategy implements NodeTypeRepresentationStrategy {
+
+    public static final String SDN_LABEL_STRATEGY = "SDN_LABEL_STRATEGY";
+
+    protected GraphDatabase graphDb;
+    protected final Class<Node> clazz;
+    protected final LabelBasedStrategyCypherHelper cypherHelper;
+    protected CypherQueryEngine queryEngine;
+
+    public SingleLabelBasedNodeTypeRepresentationStrategy(GraphDatabase graphDb) {
+        this.graphDb = graphDb;
+        this.clazz = Node.class;
+        this.queryEngine = graphDb.queryEngine();
+        this.cypherHelper = new LabelBasedStrategyCypherHelper(queryEngine);
+        markSDNLabelStrategyInUse();
+    }
+
+    @Override
+    public void writeTypeTo(Node state, StoredEntityType type) {
+        if (type == null || !type.isNodeEntity()) return;
+
+        Label sdnLabel = DynamicLabel.label(type.getAlias().toString());
+        if (state.hasLabel(sdnLabel)) {
+            return; // already there
+        }
+        addLabelsForEntityHierarchy(state, type);
+    }
+
+    /**
+     * For each level in the entity hierarchy, this method will assign a
+     * label (the label name is based on the alias associated with the
+     * entity type at each level). Additionally, a special label is added
+     * as the primary SDN marker Label.
+     */
+    private void addLabelsForEntityHierarchy(Node state, StoredEntityType type) {
+        cypherHelper.setLabelsOnNode(state.getId(), getAllHierarchyLabelsForType(type));
+    }
+
+    private Set<String> getAllHierarchyLabelsForType(StoredEntityType type) {
+        return Collections.singleton(type.getAlias().toString());
+    }
+
+    /**
+     * Ensures that a special label (SDN_LABEL_STRATEGY) exists in the graph,
+     * and if it does not, it is added. This label serves
+     * as an indicator that the Labeling strategy has/is going to be used on this
+     * data set.
+     */
+    private void markSDNLabelStrategyInUse() {
+        cypherHelper.createMarkerLabel(SDN_LABEL_STRATEGY);
+    }
+
+    @Override
+    public <U> ClosableIterable<Node> findAll(StoredEntityType type) {
+        Iterable<Node> rin = cypherHelper.getNodesWithLabel(type.getAlias().toString());
+        return new WrappedIterableClosableIterable(rin);
+    }
+
+    @Override
+    public long count(StoredEntityType type) {
+        return cypherHelper.countNodesWithLabel(type.getAlias().toString());
+    }
+
+    @Override
+    public Object readAliasFrom(Node state) {
+        if (state == null)
+            throw new IllegalArgumentException("Node is null");
+
+        Label label = IteratorUtil.firstOrNull(state.getLabels());
+        String labelName = label != null ? label.name() : null;
+        if (labelName != null) return labelName;
+        throw new IllegalStateException("No primary SDN label exists .. (i.e one starting with " + ") ");
+    }
+
+    @Override
+    public void preEntityRemoval(Node state) {
+    }
+
+    @Override
+    public boolean isLabelBased() {
+        return true;
+    }
+
+    public static boolean isStrategyAlreadyInUse(GraphDatabase graphDatabaseService) {
+        return graphDatabaseService.getAllLabelNames().contains(SDN_LABEL_STRATEGY);
+    }
+}