DATACMNS-616 - Fixed field value lookup for private fields in AnnotationDetectionFieldCallback.

We now make the field detected by the callback accessible so that the value lookup doesn't fail for private fields. Added a few more unit tests to verify behavior.

src/test/java/org/springframework/data/util/AnnotationDetectionFieldCallbackUnitTests.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2014 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.util;
+
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * Unit tests for {@link AnnotationDetectionFieldCallback}.
+ * 
+ * @author Oliver Gierke
+ */
+public class AnnotationDetectionFieldCallbackUnitTests {
+
+	/**
+	 * @see DATACMNS-616
+	 */
+	@Test(expected = IllegalArgumentException.class)
+	public void rejectsNullAnnotationType() {
+		new AnnotationDetectionFieldCallback(null);
+	}
+
+	/**
+	 * @see DATACMNS-616
+	 */
+	@Test
+	@SuppressWarnings("rawtypes")
+	public void looksUpValueFromPrivateField() {
+
+		AnnotationDetectionFieldCallback callback = new AnnotationDetectionFieldCallback(Autowired.class);
+		ReflectionUtils.doWithFields(Sample.class, callback);
+
+		assertThat(callback.getType(), is(equalTo((Class) String.class)));
+		assertThat(callback.getValue(new Sample("foo")), is((Object) "foo"));
+	}
+
+	/**
+	 * @see DATACMNS-616
+	 */
+	@Test
+	public void returnsNullForObjectNotContainingAFieldWithTheConfiguredAnnotation() {
+
+		AnnotationDetectionFieldCallback callback = new AnnotationDetectionFieldCallback(Autowired.class);
+		ReflectionUtils.doWithFields(Empty.class, callback);
+
+		assertThat(callback.getType(), is(nullValue()));
+		assertThat(callback.getValue(new Empty()), is(nullValue()));
+	}
+
+	static class Sample {
+
+		@Autowired private final String value;
+
+		public Sample(String value) {
+			this.value = value;
+		}
+	}
+
+	static class Empty {}
+}