DATACMNS-135 - Added basic infrastructure to support historiography of data.

Added interfaces for common abstractions needed to implement historiography. A Revision is an entity associated with some RevisionMetadata. That in turn consists of a revision number and date at least and is backed by a implementation specific delegate. The Revisions wrapper class allows accessing the latest revision from a list of Revision instances no matter what order they are in. A RevisionRepository allows access the revision an entity was changed in the last time, access all Revisions of an entity as well as paged access to it.

spring-data-commons-core/src/test/java/org/springframework/data/history/RevisionUnitTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012 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.history;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+
+/**
+ * Unit tests for {@link RevisionMetadata}.
+ * 
+ * @author Oliver Gierke
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class RevisionUnitTests {
+
+	@Mock
+	RevisionMetadata<Integer> firstMetadata, secondMetadata;
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void comparesCorrectly() {
+
+		when(firstMetadata.getRevisionNumber()).thenReturn(1);
+		when(secondMetadata.getRevisionNumber()).thenReturn(2);
+
+		Revision<Integer, Object> first = new Revision<Integer, Object>(firstMetadata, new Object());
+		Revision<Integer, Object> second = new Revision<Integer, Object>(secondMetadata, new Object());
+
+		List<Revision<Integer, Object>> revisions = Arrays.asList(second, first);
+		Collections.sort(revisions);
+
+		assertThat(revisions.get(0), is(first));
+		assertThat(revisions.get(1), is(second));
+	}
+}

spring-data-commons-core/src/test/java/org/springframework/data/history/RevisionsUnitTest.java

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+/*
+ * Copyright 2012 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.history;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import java.util.Arrays;
+import java.util.Iterator;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+
+/**
+ * Unit tests for {@link Revisions}.
+ * 
+ * @author Oliver Gierke
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class RevisionsUnitTest {
+
+	@Mock
+	RevisionMetadata<Integer> first, second;
+	Revision<Integer, Object> firstRevision, secondRevision;
+
+	@Before
+	public void setUp() {
+
+		when(first.getRevisionNumber()).thenReturn(0);
+		when(second.getRevisionNumber()).thenReturn(10);
+
+		firstRevision = new Revision<Integer, Object>(first, new Object());
+		secondRevision = new Revision<Integer, Object>(second, new Object());
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void returnsCorrectLatestRevision() {
+
+		Revisions<Integer, Object> revisions = new Revisions<Integer, Object>(Arrays.asList(firstRevision, secondRevision));
+		assertThat(revisions.getLatestRevision(), is(secondRevision));
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void iteratesInCorrectOrder() {
+
+		Revisions<Integer, Object> revisions = new Revisions<Integer, Object>(Arrays.asList(firstRevision, secondRevision));
+		Iterator<Revision<Integer, Object>> iterator = revisions.iterator();
+
+		assertThat(iterator.hasNext(), is(true));
+		assertThat(iterator.next(), is(firstRevision));
+		assertThat(iterator.hasNext(), is(true));
+		assertThat(iterator.next(), is(secondRevision));
+		assertThat(iterator.hasNext(), is(false));
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void reversedRevisionsStillReturnsCorrectLatestRevision() {
+
+		Revisions<Integer, Object> revisions = new Revisions<Integer, Object>(Arrays.asList(firstRevision, secondRevision));
+		assertThat(revisions.reverse().getLatestRevision(), is(secondRevision));
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void iteratesReversedRevisionsInCorrectOrder() {
+
+		Revisions<Integer, Object> revisions = new Revisions<Integer, Object>(Arrays.asList(firstRevision, secondRevision));
+		Iterator<Revision<Integer, Object>> iterator = revisions.reverse().iterator();
+
+		assertThat(iterator.hasNext(), is(true));
+		assertThat(iterator.next(), is(secondRevision));
+		assertThat(iterator.hasNext(), is(true));
+		assertThat(iterator.next(), is(firstRevision));
+		assertThat(iterator.hasNext(), is(false));
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void forcesInvalidlyOrderedRevisionsToBeOrdered() {
+
+		Revisions<Integer, Object> revisions = new Revisions<Integer, Object>(Arrays.asList(secondRevision, firstRevision));
+		Iterator<Revision<Integer, Object>> iterator = revisions.iterator();
+
+		assertThat(iterator.hasNext(), is(true));
+		assertThat(iterator.next(), is(firstRevision));
+		assertThat(iterator.hasNext(), is(true));
+		assertThat(iterator.next(), is(secondRevision));
+		assertThat(iterator.hasNext(), is(false));
+	}
+}