Add item reader for Redis

Resolves #4446

Author: fmbenhassine

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/redis/RedisItemReader.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2023 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
+ *
+ *          https://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.batch.item.redis;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamException;
+import org.springframework.batch.item.ItemStreamReader;
+import org.springframework.data.redis.core.Cursor;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.core.ScanOptions;
+import org.springframework.util.Assert;
+
+/**
+ * Item reader for Redis based on Spring Data Redis. Uses a {@link RedisTemplate} to query
+ * data. The user should provide a {@link ScanOptions} to specify the set of keys to
+ * query.
+ *
+ * <p>
+ * The implementation is not thread-safe and not restartable.
+ * </p>
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 5.1
+ * @param <K> type of keys
+ * @param <V> type of values
+ */
+public class RedisItemReader<K, V> implements ItemStreamReader<V> {
+
+	private final RedisTemplate<K, V> redisTemplate;
+
+	private final ScanOptions scanOptions;
+
+	private Cursor<K> cursor;
+
+	public RedisItemReader(RedisTemplate<K, V> redisTemplate, ScanOptions scanOptions) {
+		Assert.notNull(redisTemplate, "redisTemplate must not be null");
+		Assert.notNull(scanOptions, "scanOptions must no be null");
+		this.redisTemplate = redisTemplate;
+		this.scanOptions = scanOptions;
+	}
+
+	@Override
+	public void open(ExecutionContext executionContext) throws ItemStreamException {
+		this.cursor = this.redisTemplate.scan(this.scanOptions);
+	}
+
+	@Override
+	public V read() throws Exception {
+		if (this.cursor.hasNext()) {
+			K nextKey = this.cursor.next();
+			return this.redisTemplate.opsForValue().get(nextKey);
+		}
+		else {
+			return null;
+		}
+	}
+
+	@Override
+	public void close() throws ItemStreamException {
+		this.cursor.close();
+	}
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/redis/builder/RedisItemReaderBuilder.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2023 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
+ *
+ *          https://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.batch.item.redis.builder;
+
+import org.springframework.batch.item.redis.RedisItemReader;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.core.ScanOptions;
+
+/**
+ * Builder for {@link RedisItemReader}.
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 5.1
+ * @param <K> type of keys
+ * @param <V> type of values
+ */
+public class RedisItemReaderBuilder<K, V> {
+
+	private RedisTemplate<K, V> redisTemplate;
+
+	private ScanOptions scanOptions;
+
+	/**
+	 * Set the {@link RedisTemplate} to use in the reader.
+	 * @param redisTemplate the template to use
+	 * @return the current builder instance for fluent chaining
+	 */
+	public RedisItemReaderBuilder<K, V> redisTemplate(RedisTemplate<K, V> redisTemplate) {
+		this.redisTemplate = redisTemplate;
+		return this;
+	}
+
+	/**
+	 * Set the {@link ScanOptions} to select the key set.
+	 * @param scanOptions the scan option to use
+	 * @return the current builder instance for fluent chaining
+	 */
+	public RedisItemReaderBuilder<K, V> scanOptions(ScanOptions scanOptions) {
+		this.scanOptions = scanOptions;
+		return this;
+	}
+
+	/**
+	 * Build a new {@link RedisItemReader}.
+	 * @return a new item reader
+	 */
+	public RedisItemReader<K, V> build() {
+		return new RedisItemReader<>(this.redisTemplate, this.scanOptions);
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/redis/RedisItemReaderTests.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2023 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
+ *
+ *          https://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.batch.item.redis;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Answers;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.data.redis.core.Cursor;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.core.ScanOptions;
+
+@ExtendWith(MockitoExtension.class)
+public class RedisItemReaderTests {
+
+	@Mock(answer = Answers.RETURNS_DEEP_STUBS)
+	private RedisTemplate<String, String> redisTemplate;
+
+	@Mock
+	private ScanOptions scanOptions;
+
+	@Mock
+	private Cursor<String> cursor;
+
+	@Test
+	void testRead() throws Exception {
+		// given
+		Mockito.when(this.redisTemplate.scan(this.scanOptions)).thenReturn(this.cursor);
+		Mockito.when(this.cursor.hasNext()).thenReturn(true, true, false);
+		Mockito.when(this.cursor.next()).thenReturn("person:1", "person:2");
+		Mockito.when(this.redisTemplate.opsForValue().get("person:1")).thenReturn("foo");
+		Mockito.when(this.redisTemplate.opsForValue().get("person:2")).thenReturn("bar");
+		RedisItemReader<String, String> redisItemReader = new RedisItemReader<>(this.redisTemplate, this.scanOptions);
+		redisItemReader.open(new ExecutionContext());
+
+		// when
+		String item1 = redisItemReader.read();
+		String item2 = redisItemReader.read();
+		String item3 = redisItemReader.read();
+
+		// then
+		Assertions.assertEquals("foo", item1);
+		Assertions.assertEquals("bar", item2);
+		Assertions.assertNull(item3);
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/redis/builder/RedisItemReaderBuilderTests.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2023 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
+ *
+ *          https://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.batch.item.redis.builder;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.batch.item.redis.RedisItemReader;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.core.ScanOptions;
+import org.springframework.test.util.ReflectionTestUtils;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Test class for {@link RedisItemReaderBuilder}.
+ *
+ * @author Mahmoud Ben Hassine
+ */
+public class RedisItemReaderBuilderTests {
+
+	@Test
+	void testRedisItemReaderCreation() {
+		// given
+		RedisTemplate<String, String> redisTemplate = mock();
+		ScanOptions scanOptions = mock();
+
+		// when
+		RedisItemReader<String, String> reader = new RedisItemReaderBuilder<String, String>()
+			.redisTemplate(redisTemplate)
+			.scanOptions(scanOptions)
+			.build();
+
+		// then
+		assertNotNull(reader);
+		assertEquals(redisTemplate, ReflectionTestUtils.getField(reader, "redisTemplate"));
+		assertEquals(scanOptions, ReflectionTestUtils.getField(reader, "scanOptions"));
+	}
+
+}