From 08faa52ef4a0adbf9423cfebe0191a98567c6890 Mon Sep 17 00:00:00 2001
From: Oliver Gierke <ogierke@pivotal.io>
Date: Fri, 28 Nov 2014 16:05:17 +0100
Subject: [PATCH] DATAMONGO-1108 - Performance improvements in
 BasicMongoPersistentEntity.

BasicMongoPersistentEntity.getCollection() now avoids repeated SpEL-parsing and evaluating in case no SpEL expression is used. Parsing is happening at most once now. Evaluation is skipped entirely if the configured collection String is not or does not contain an expression.
---
 .../mapping/BasicMongoPersistentEntity.java   | 52 +++++++++++++++----
 .../BasicMongoPersistentEntityUnitTests.java  |  6 +++
 2 files changed, 47 insertions(+), 11 deletions(-)

diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntity.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntity.java
index 1de1072ab..6d814d871 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntity.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntity.java
@@ -35,6 +35,7 @@ import org.springframework.data.mongodb.MongoCollectionUtils;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.expression.Expression;
 import org.springframework.expression.ParserContext;
+import org.springframework.expression.common.LiteralExpression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.util.Assert;
@@ -54,31 +55,36 @@ public class BasicMongoPersistentEntity<T> extends BasicPersistentEntity<T, Mong
 		MongoPersistentEntity<T>, ApplicationContextAware {
 
 	private static final String AMBIGUOUS_FIELD_MAPPING = "Ambiguous field mapping detected! Both %s and %s map to the same field name %s! Disambiguate using @Field annotation!";
+	private static final SpelExpressionParser PARSER = new SpelExpressionParser();
+
 	private final String collection;
 	private final String language;
-	private final SpelExpressionParser parser;
+
 	private final StandardEvaluationContext context;
+	private final Expression expression;
 
 	/**
 	 * Creates a new {@link BasicMongoPersistentEntity} with the given {@link TypeInformation}. Will default the
 	 * collection name to the entities simple type name.
 	 * 
-	 * @param typeInformation
+	 * @param typeInformation must not be {@literal null}.
 	 */
 	public BasicMongoPersistentEntity(TypeInformation<T> typeInformation) {
 
 		super(typeInformation, MongoPersistentPropertyComparator.INSTANCE);
 
-		this.parser = new SpelExpressionParser();
-		this.context = new StandardEvaluationContext();
-
 		Class<?> rawType = typeInformation.getType();
 		String fallback = MongoCollectionUtils.getPreferredCollectionName(rawType);
 
-		if (rawType.isAnnotationPresent(Document.class)) {
-			Document d = rawType.getAnnotation(Document.class);
-			this.collection = StringUtils.hasText(d.collection()) ? d.collection() : fallback;
-			this.language = StringUtils.hasText(d.language()) ? d.language() : "";
+		Document document = rawType.getAnnotation(Document.class);
+
+		this.expression = detectExpression(document);
+		this.context = new StandardEvaluationContext();
+
+		if (document != null) {
+
+			this.collection = StringUtils.hasText(document.collection()) ? document.collection() : fallback;
+			this.language = StringUtils.hasText(document.language()) ? document.language() : "";
 		} else {
 			this.collection = fallback;
 			this.language = "";
@@ -101,8 +107,7 @@ public class BasicMongoPersistentEntity<T> extends BasicPersistentEntity<T, Mong
 	 * @see org.springframework.data.mongodb.core.mapping.MongoPersistentEntity#getCollection()
 	 */
 	public String getCollection() {
-		Expression expression = parser.parseExpression(collection, ParserContext.TEMPLATE_EXPRESSION);
-		return expression.getValue(context, String.class);
+		return expression == null ? collection : expression.getValue(context, String.class);
 	}
 
 	/*
@@ -236,6 +241,31 @@ public class BasicMongoPersistentEntity<T> extends BasicPersistentEntity<T, Mong
 		return null;
 	}
 
+	/**
+	 * Returns a SpEL {@link Expression} frór the collection String expressed in the given {@link Document} annotation if
+	 * present or {@literal null} otherwise. Will also return {@literal null} it the collection {@link String} evaluates
+	 * to a {@link LiteralExpression} (indicating that no subsequent evaluation is necessary).
+	 * 
+	 * @param document can be {@literal null}
+	 * @return
+	 */
+	private static Expression detectExpression(Document document) {
+
+		if (document == null) {
+			return null;
+		}
+
+		String collection = document.collection();
+
+		if (!StringUtils.hasText(collection)) {
+			return null;
+		}
+
+		Expression expression = PARSER.parseExpression(document.collection(), ParserContext.TEMPLATE_EXPRESSION);
+
+		return expression instanceof LiteralExpression ? null : expression;
+	}
+
 	/**
 	 * Handler to collect {@link MongoPersistentProperty} instances and check that each of them is mapped to a distinct
 	 * field name.
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntityUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntityUnitTests.java
index 4ad9439d5..251692198 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntityUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntityUnitTests.java
@@ -55,6 +55,9 @@ public class BasicMongoPersistentEntityUnitTests {
 		assertThat(entity.getCollection(), is("35"));
 	}
 
+	/**
+	 * @see DATAMONGO-65, DATAMONGO-1108
+	 */
 	@Test
 	public void collectionAllowsReferencingSpringBean() {
 
@@ -69,6 +72,9 @@ public class BasicMongoPersistentEntityUnitTests {
 		entity.setApplicationContext(context);
 
 		assertThat(entity.getCollection(), is("reference"));
+
+		provider.collectionName = "otherReference";
+		assertThat(entity.getCollection(), is("otherReference"));
 	}
 
 	/**