DATAKV-99 - Add KeyValueIterator.

We now offer the possibility to iterate through available key/value pairs via a KeyValueIterator. The default implementation for java.util.Map based Adapters is a ForwardingKeyValueIterator delegating to the underlying entrySet iterator.

Original pull request: #7.

src/main/java/org/springframework/data/keyvalue/core/Entry.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2015 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.keyvalue.core;
+
+import java.util.Map;
+
+/**
+ * @author Christoph Strobl
+ * @param <K>
+ * @param <V>
+ */
+public interface Entry<K, V> extends Map.Entry<K, V> {
+
+}

src/main/java/org/springframework/data/keyvalue/core/ForwardingKeyValueIterator.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2015 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.keyvalue.core;
+
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.Map;
+
+/**
+ * @author Christoph Strobl
+ * @param <K>
+ * @param <V>
+ */
+public class ForwardingKeyValueIterator<K, V> implements KeyValueIterator<K, V> {
+
+	private final Iterator<? extends Map.Entry<K, V>> delegate;
+
+	public ForwardingKeyValueIterator(Iterator<? extends java.util.Map.Entry<K, V>> delegate) {
+		this.delegate = delegate;
+	}
+
+	@Override
+	public boolean hasNext() {
+		return delegate.hasNext();
+	}
+
+	@Override
+	public Entry<K, V> next() {
+		return new ForwardingEntry(delegate.next());
+	}
+
+	@Override
+	public void close() throws IOException {
+
+	}
+
+	class ForwardingEntry implements Entry<K, V> {
+
+		private final Map.Entry<K, V> entry;
+
+		public ForwardingEntry(Map.Entry<K, V> entry) {
+			this.entry = entry;
+		}
+
+		@Override
+		public K getKey() {
+			return entry.getKey();
+		}
+
+		@Override
+		public V getValue() {
+			return entry.getValue();
+		}
+
+		@Override
+		public V setValue(V value) {
+			return entry.setValue(value);
+		}
+
+		@Override
+		public String toString() {
+			return entry != null ? entry.toString() : "null";
+		}
+
+	}
+}

src/main/java/org/springframework/data/keyvalue/core/KeyValueAdapter.java

@@ -25,6 +25,7 @@ import org.springframework.data.keyvalue.core.query.KeyValueQuery;
  * {@link KeyValueAdapter} unifies access and shields the underlying key/value specific implementation.
  * 
  * @author Christoph Strobl
+ * @author Thomas Darimont
  */
 public interface KeyValueAdapter extends DisposableBean {
 
@@ -72,6 +73,14 @@ public interface KeyValueAdapter extends DisposableBean {
 	 */
 	Collection<?> getAllOf(Serializable keyspace);
 
+	/**
+	 * Returns a {@link KeyValueIterator} that iterates over all entries. 
+	 * 
+	 * @param keyspace
+	 * @return
+	 */
+	KeyValueIterator<? extends Serializable, ?> entries(Serializable keyspace);
+
 	/**
 	 * Remove all objects of given type.
 	 * 

src/main/java/org/springframework/data/keyvalue/core/KeyValueIterator.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2015 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.keyvalue.core;
+
+import java.io.Closeable;
+import java.util.Iterator;
+
+/**
+ * @author Christoph Strobl
+ * @param <K>
+ * @param <V>
+ */
+public interface KeyValueIterator<K, V> extends Iterator<Entry<K, V>>, Closeable {
+
+}