Optimistic Lock implementation based on _etag field (#396)

* Optimistic Lock first implementation

* Ignore warnings on "_etag" field name not matching Java conventions

* Fix JUnit test that was checking on wrong illegal arguments

* Update precondition not met message to match new version

* Precondition is not met to is not met

Author: dsibilio

.codacy.yml

@@ -0,0 +1,3 @@
+exclude_paths:
+  - 'src/test/java/com/microsoft/azure/spring/data/cosmosdb/domain/Person.java'
+  - 'src/test/java/com/microsoft/azure/spring/data/cosmosdb/repository/support/DocumentDbEntityInformationUnitTest.java'

HowToContribute.md

@@ -15,7 +15,7 @@ mvnw clean install
 ```
 
 ## Test
-There're 3 profiles: `dev`, `integration-test-azure` and `integration-test-emulator`. Default profile is `dev`. Profile `integration-test-azure` will trigger integration test execution against Azure Cosmos DB. Profile `integration-test-emulator` will trigger integration test execution against [Azure Cosmos DB Emulator](https://docs.microsoft.com/en-us/azure/cosmos-db/local-emulator), you need to follow the link to setup emualator before test execution.
+There're 3 profiles: `dev`, `integration-test-azure` and `integration-test-emulator`. Default profile is `dev`. Profile `integration-test-azure` will trigger integration test execution against Azure Cosmos DB. Profile `integration-test-emulator` will trigger integration test execution against [Azure Cosmos DB Emulator](https://docs.microsoft.com/en-us/azure/cosmos-db/local-emulator), you need to follow the link to setup emulator before test execution.
 
 - Run unit tests
 ```bash

src/main/java/com/microsoft/azure/spring/data/cosmosdb/common/Memoizer.java

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Microsoft Corporation. All rights reserved.
+ * Licensed under the MIT License. See LICENSE in the project root for
+ * license information.
+ */
+package com.microsoft.azure.spring.data.cosmosdb.common;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Function;
+
+/**
+ * Memoize function computation results
+ * @author Domenico Sibilio
+ *
+ */
+public class Memoizer<I, O> {
+
+    private final Map<I, O> cache = new ConcurrentHashMap<>();
+    
+    private Memoizer() {}
+    
+    public static <I, O> Function<I, O> memoize(Function<I, O> function) {
+        return new Memoizer<I, O>().internalMemoize(function);
+    }
+    
+    private Function<I, O> internalMemoize(Function<I, O> function) {
+        return input -> cache.computeIfAbsent(input, function);
+    }
+    
+}

src/main/java/com/microsoft/azure/spring/data/cosmosdb/core/DocumentDbOperations.java

@@ -11,6 +11,7 @@
 import com.microsoft.azure.spring.data.cosmosdb.core.convert.MappingDocumentDbConverter;
 import com.microsoft.azure.spring.data.cosmosdb.core.query.DocumentQuery;
 import com.microsoft.azure.spring.data.cosmosdb.repository.support.DocumentDbEntityInformation;
+
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 
@@ -20,7 +21,7 @@ public interface DocumentDbOperations {
 
     String getCollectionName(Class<?> entityClass);
 
-    DocumentCollection createCollectionIfNotExists(DocumentDbEntityInformation information);
+    DocumentCollection createCollectionIfNotExists(DocumentDbEntityInformation<?, ?> information);
 
     <T> List<T> findAll(Class<T> entityClass);
 
@@ -38,7 +39,7 @@ public interface DocumentDbOperations {
 
     <T> void upsert(String collectionName, T object, PartitionKey partitionKey);
 
-    <T> void deleteById(String collectionName, Object id, PartitionKey partitionKey);
+    void deleteById(String collectionName, Object id, PartitionKey partitionKey);
 
     void deleteAll(String collectionName, Class<?> domainClass);
 

src/main/java/com/microsoft/azure/spring/data/cosmosdb/core/DocumentDbTemplate.java

@@ -17,6 +17,7 @@
 import org.apache.commons.lang3.reflect.FieldUtils;
 
 import org.springframework.data.annotation.Id;
+import org.springframework.data.annotation.Version;
 import org.springframework.data.repository.core.support.AbstractEntityInformation;
 import org.springframework.lang.NonNull;
 import org.springframework.util.ReflectionUtils;
@@ -31,12 +32,14 @@
 
 public class DocumentDbEntityInformation<T, ID> extends AbstractEntityInformation<T, ID> {
 
+    private static final String ETAG = "_etag";
     private Field id;
     private Field partitionKeyField;
     private String collectionName;
     private Integer requestUnit;
     private Integer timeToLive;
     private IndexingPolicy indexingPolicy;
+    private boolean isVersioned;
 
     public DocumentDbEntityInformation(Class<T> domainClass) {
         super(domainClass);
@@ -53,6 +56,7 @@ public DocumentDbEntityInformation(Class<T> domainClass) {
         this.requestUnit = getRequestUnit(domainClass);
         this.timeToLive = getTimeToLive(domainClass);
         this.indexingPolicy = getIndexingPolicy(domainClass);
+        this.isVersioned = getIsVersioned(domainClass);
     }
 
     @SuppressWarnings("unchecked")
@@ -86,6 +90,10 @@ public IndexingPolicy getIndexingPolicy() {
         return this.indexingPolicy;
     }
 
+    public boolean isVersioned() {
+        return isVersioned;
+    }
+
     public String getPartitionKeyFieldName() {
         if (partitionKeyField == null) {
             return null;
@@ -239,5 +247,13 @@ private Collection<ExcludedPath> getIndexingPolicyExcludePaths(Class<?> domainCl
 
         return pathsCollection;
     }
+
+    private boolean getIsVersioned(Class<T> domainClass) {
+        final Field findField = ReflectionUtils.findField(domainClass, ETAG);
+        return findField != null 
+                && findField.getType() == String.class
+                && findField.isAnnotationPresent(Version.class);
+    }
+
 }
 

src/main/java/com/microsoft/azure/spring/data/cosmosdb/repository/support/DocumentDbEntityInformation.java

@@ -0,0 +1,57 @@
+/**
+ * Copyright (c) Microsoft Corporation. All rights reserved.
+ * Licensed under the MIT License. See LICENSE in the project root for
+ * license information.
+ */
+package com.microsoft.azure.spring.data.cosmosdb.common;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
+import java.util.stream.IntStream;
+
+/**
+ * 
+ * @author Domenico Sibilio
+ *
+ */
+public class MemoizerUnitTest {
+    private static final String KEY = "key_1";
+    private static final Map<String, AtomicInteger> countMap = new HashMap<>();
+    private static final Function<String, Integer> memoizedFunction =
+            Memoizer.memoize(MemoizerUnitTest::incrCount);
+
+    @Before
+    public void setUp() {
+        countMap.put(KEY, new AtomicInteger(0));
+    }
+    
+    @Test
+    public void testMemoizedFunctionShouldBeCalledOnlyOnce() {
+        IntStream
+        .range(0, 10)
+        .forEach(number -> memoizedFunction.apply(KEY));
+        
+        assertEquals(1, countMap.get(KEY).get());
+    }
+    
+    @Test
+    public void testDifferentMemoizersShouldNotShareTheSameCache() {
+        IntStream
+        .range(0, 10)
+        .forEach(number -> Memoizer.memoize(MemoizerUnitTest::incrCount).apply(KEY));
+        
+        assertEquals(10, countMap.get(KEY).get());
+    }
+
+    private static int incrCount(String key) {
+        return countMap.get(key).incrementAndGet();
+    }
+
+}