Adds an example how to use caching.

Original pull request #630

jdbc/howto/caching/README.adoc

@@ -0,0 +1,6 @@
+== Spring Data JDBC How To cache.
+
+Spring Data JDBC doesn't include any caching for entities.
+But it is trivially combined with Springs Cache abstraction.
+
+This project demonstrates this.

jdbc/howto/caching/pom.xml

@@ -0,0 +1,21 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>spring-data-jdbc-how-to-caching</artifactId>
+
+	<parent>
+		<groupId>org.springframework.data.examples</groupId>
+		<artifactId>spring-data-jdbc-how-to</artifactId>
+		<version>2.0.0.BUILD-SNAPSHOT</version>
+		<relativePath>../pom.xml</relativePath>
+	</parent>
+
+	<name>Spring Data JDBC - How to do caching</name>
+	<description>Sample project for Spring Data JDBC demonstrating how it can be used with Springs caching
+		abstraction.
+	</description>
+	<url>https://projects.spring.io/spring-data-jdbc</url>
+	<inceptionYear>2021</inceptionYear>
+
+</project>

jdbc/howto/caching/src/main/java/example.springdata/jdbc/howto/caching/CachingApplication.java

@@ -0,0 +1,15 @@
+package example.springdata.jdbc.howto.caching;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cache.annotation.EnableCaching;
+
+@EnableCaching
+@SpringBootApplication
+class CachingApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(CachingApplication.class, args);
+	}
+
+}

jdbc/howto/caching/src/main/java/example.springdata/jdbc/howto/caching/Minion.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2021 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 example.springdata.jdbc.howto.caching;
+
+import org.springframework.data.annotation.Id;
+
+public class Minion {
+	@Id
+	Long id;
+	String name;
+
+	Minion(String name) {
+		this.name = name;
+	}
+
+	public Long getId(){
+		return id;
+	}
+}

jdbc/howto/caching/src/main/java/example.springdata/jdbc/howto/caching/MinionRepository.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2021 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 example.springdata.jdbc.howto.caching;
+
+import java.util.Optional;
+
+import org.springframework.cache.annotation.CacheEvict;
+import org.springframework.cache.annotation.Cacheable;
+import org.springframework.data.repository.CrudRepository;
+
+interface MinionRepository extends CrudRepository<Minion, Long> {
+
+	@Override
+	@CacheEvict(value="minions",beforeInvocation = false,key = "#result.id")
+	<S extends Minion> S save(S s);
+
+	@Override
+	@Cacheable("minions")
+	Optional<Minion> findById(Long aLong);
+}

jdbc/howto/caching/src/main/resources/application.properties

@@ -0,0 +1 @@
+logging.level.org.springframework.jdbc.core.JdbcTemplate=DEBUG

jdbc/howto/caching/src/main/resources/schema.sql

@@ -0,0 +1,5 @@
+CREATE TABLE MINION
+(
+    ID              IDENTITY PRIMARY KEY,
+    NAME           VARCHAR(255),
+);

jdbc/howto/caching/src/test/java/example/springdata/jdbc/howto/caching/CachingApplicationTests.java

@@ -0,0 +1,39 @@
+package example.springdata.jdbc.howto.caching;
+
+import java.util.Optional;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class CachingApplicationTests {
+
+	private Long bobsId;
+	@Autowired MinionRepository minions;
+
+	@BeforeEach
+	void setup() {
+
+		Minion bob = minions.save(new Minion("Bob"));
+		bobsId = bob.id;
+	}
+
+	@Test
+	void saveloadMultipleTimes() {
+
+		Optional<Minion> bob = null;
+		for (int i = 0; i < 10; i++) {
+			bob = minions.findById(bobsId);
+		}
+
+		minions.save(bob.get());
+
+		for (int i = 0; i < 10; i++) {
+			bob = minions.findById(bobsId);
+		}
+
+	}
+
+}

jdbc/howto/pom.xml

@@ -21,6 +21,7 @@
 	<modules>
 		<module>bidirectionalexternal</module>
 		<module>bidirectionalinternal</module>
+		<module>caching</module>
 		<module>idgeneration</module>
 	</modules>