#313 - Added examples showing basic usage of Spring Data JDBC.

Original pull request: #324.

jdbc/basics/src/main/java/example/springdata/jdbc/basics/Output.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import lombok.experimental.UtilityClass;
+
+/**
+ * Trivial class to print domain objects to the console in a somewhat readable format.
+ *
+ * @author Jens Schauder
+ */
+@UtilityClass
+public class Output {
+
+	private final Logger LOG = LoggerFactory.getLogger(Output.class);
+
+	public static void list(Iterable<?> categories, String title) {
+
+		StringBuilder message = new StringBuilder(String.format("==== %s ====\n", title));
+
+		categories.forEach(category -> {
+			message.append(category.toString().replace(", ", ",\n\t"));
+		});
+
+		LOG.info(message.toString());
+	}
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/aggregate/AgeGroup.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.aggregate;
+
+/**
+ * Age group for which a {@link LegoSet} is intended.
+ *
+ * @author Jens Schauder
+ */
+public enum AgeGroup {
+
+ 	_0to3,
+ 	_3to8,
+ 	_8to12,
+	_12andOlder
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/aggregate/AggregateConfiguration.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.aggregate;
+
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.jdbc.core.DataAccessStrategy;
+import org.springframework.data.jdbc.core.DefaultDataAccessStrategy;
+import org.springframework.data.jdbc.core.DelegatingDataAccessStrategy;
+import org.springframework.data.jdbc.core.SqlGeneratorSource;
+import org.springframework.data.jdbc.mapping.event.BeforeSave;
+import org.springframework.data.jdbc.mapping.model.*;
+import org.springframework.data.jdbc.repository.config.EnableJdbcRepositories;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
+import org.springframework.lang.Nullable;
+
+import javax.sql.DataSource;
+import java.sql.Clob;
+import java.sql.SQLException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * @author Jens Schauder
+ */
+@Configuration
+@EnableJdbcRepositories
+public class AggregateConfiguration {
+
+	@Bean
+	public ApplicationListener<?> idSetting() {
+
+		final AtomicInteger id = new AtomicInteger(0);
+
+		return (ApplicationListener<BeforeSave>) event -> {
+
+			Object entity = event.getEntity();
+			if (entity instanceof LegoSet) {
+
+				LegoSet legoSet = (LegoSet) entity;
+				if (legoSet.getId() == 0) {
+					legoSet.setId(id.incrementAndGet());
+				}
+
+				Manual manual = legoSet.getManual();
+				if (manual != null) {
+					manual.setId((long) legoSet.getId());
+				}
+			}
+		};
+	}
+
+	@Bean
+	public NamingStrategy namingStrategy() {
+
+		Map<String, String> tableAliases = new HashMap<String, String>();
+		tableAliases.put("Manual", "Handbuch");
+
+		Map<String, String> columnAliases = new HashMap<String, String>();
+		columnAliases.put("LegoSet.intMaximumAge", "maxAge");
+		columnAliases.put("LegoSet.intMinimumAge", "minAge");
+		columnAliases.put("Handbuch.id", "Handbuch_id");
+
+		Map<String, String> reverseColumnAliases = new HashMap<String, String>();
+		reverseColumnAliases.put("manual", "Handbuch_id");
+
+		Map<String, String> keyColumnAliases = new HashMap<String, String>();
+		keyColumnAliases.put("models", "name");
+
+		return new DefaultNamingStrategy() {
+
+			@Override
+			public String getColumnName(JdbcPersistentProperty property) {
+
+				String defaultName = super.getColumnName(property);
+				String key = getTableName(property.getOwner().getType()) + "." + defaultName;
+				return columnAliases.computeIfAbsent(key, __ -> defaultName);
+			}
+
+			@Override
+			public String getTableName(Class<?> type) {
+
+				return tableAliases.computeIfAbsent(super.getTableName(type),key -> key);
+			}
+
+			@Override
+			public String getReverseColumnName(JdbcPersistentProperty property) {
+				return reverseColumnAliases.computeIfAbsent(property.getName(), __ -> super.getReverseColumnName(property));
+			}
+
+			@Override
+			public String getKeyColumn(JdbcPersistentProperty property) {
+				return keyColumnAliases.computeIfAbsent(property.getName(), __ -> super.getKeyColumn(property));
+			}
+		};
+	}
+
+	@Bean
+	public ConversionCustomizer conversionCustomizer() {
+
+		return conversions -> conversions.addConverter(new Converter<Clob, String>() {
+
+			@Nullable
+			@Override
+			public String convert(Clob clob) {
+
+				try {
+
+					return Math.toIntExact(clob.length()) == 0 //
+							? "" //
+							: clob.getSubString(1, Math.toIntExact(clob.length()));
+				} catch (SQLException e) {
+					throw new IllegalStateException("Failed to convert CLOB to String.", e);
+				}
+			}
+		});
+	}
+
+	// temporary workaround for https://jira.spring.io/browse/DATAJDBC-155
+	@Bean
+	DataAccessStrategy defaultDataAccessStrategy(JdbcMappingContext context, DataSource dataSource) {
+
+		NamedParameterJdbcOperations operations = new NamedParameterJdbcTemplate(dataSource);
+
+		DelegatingDataAccessStrategy accessStrategy = new DelegatingDataAccessStrategy();
+
+		accessStrategy.setDelegate(new DefaultDataAccessStrategy( //
+				new SqlGeneratorSource(context), //
+				operations, //
+				context, //
+				accessStrategy) //
+		);
+
+		return accessStrategy;
+	}
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/aggregate/LegoSet.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.aggregate;
+
+import lombok.Data;
+import org.springframework.data.annotation.AccessType;
+import org.springframework.data.annotation.AccessType.Type;
+import org.springframework.data.annotation.Id;
+import org.springframework.data.annotation.Transient;
+
+import java.time.Period;
+import java.time.temporal.ChronoUnit;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A Lego Set consisting of multiple Blocks and a manual
+ *
+ * @author Jens Schauder
+ */
+@Data
+@AccessType(Type.PROPERTY)
+public class LegoSet {
+
+	@Id
+	private int id;
+
+	private String name;
+
+	@Transient
+	private Period minimumAge;
+	@Transient
+	private Period maximumAge;
+
+	/**
+	 * Since Manuals are part of a {@link LegoSet} and only make sense inside a {@link LegoSet} it is considered part of the Aggregate.
+	 */
+	private Manual manual;
+
+	// You can build multiple models from one LegoSet
+	private final Map<String, Model> models = new HashMap<>();
+
+	// conversion for custom types currently has to be done through getters/setter + marking the underlying property with @Transient.
+	public int getIntMinimumAge() {
+		return toInt(this.minimumAge);
+	}
+
+	public void setIntMinimumAge(int years) {
+		minimumAge = toPeriod(years);
+	}
+
+	public int getIntMaximumAge() {
+		return toInt(this.maximumAge);
+	}
+
+	public void setIntMaximumAge(int years) {
+		maximumAge = toPeriod(years);
+	}
+
+
+	private static int toInt(Period period) {
+		return (int) (period == null ? 0 : period.get(ChronoUnit.YEARS));
+	}
+
+	private static Period toPeriod(int years) {
+		return Period.ofYears(years);
+	}
+
+	public void addModel(String name, String description) {
+
+		Model model = new Model();
+		model.name = name;
+		model.description = description;
+		models.put(name, model);
+	}
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/aggregate/LegoSetRepository.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.aggregate;
+
+import org.springframework.data.repository.CrudRepository;
+
+/**
+ * A repository for {@link LegoSet}.
+ * @author Jens Schauder
+ */
+public interface LegoSetRepository extends CrudRepository<LegoSet, Integer> {
+
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/aggregate/Manual.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.aggregate;
+
+import org.springframework.data.annotation.Id;
+
+import lombok.Data;
+
+/**
+ * A manual instructing how to assemble a {@link LegoSet}.
+ *
+ * @author Jens Schauder
+ */
+@Data
+public class Manual {
+
+
+	Manual(String text, String author) {
+
+		this.id = null;
+		this.author = author;
+		this.text = text;
+	}
+
+	@Id
+	private Long id;
+
+	private String author;
+	private String text;
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/aggregate/Model.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.aggregate;
+
+import lombok.ToString;
+import org.springframework.data.annotation.Id;
+
+/**
+ * One of potentially multiple models that can be build from a single {@link LegoSet}.
+ *
+ * No getters or setters needed.
+ *
+ * @author Jens Schauder
+ */
+@ToString
+public class Model {
+
+	@Id
+	String name;
+
+	String description;
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/simpleentity/Category.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.simpleentity;
+
+import java.time.LocalDateTime;
+
+import example.springdata.jdbc.basics.aggregate.AgeGroup;
+import example.springdata.jdbc.basics.aggregate.LegoSet;
+import org.springframework.data.annotation.Id;
+
+import lombok.Data;
+import lombok.Setter;
+
+/**
+ * Coarse classification for {@link LegoSet}s, like "Car", "Plane", "Building" and so on.
+ *
+ * @author Jens Schauder
+ */
+@Data
+public class Category {
+
+	public Category(String name, String description, AgeGroup ageGroup) {
+
+		this.id = null;
+		this.name = name;
+		this.description = description;
+		this.ageGroup = ageGroup;
+	}
+
+	@Id
+	private final Long id;
+
+	private String name;
+	private String description;
+
+	private LocalDateTime created = LocalDateTime.now();
+
+	@Setter
+	private long inserted;
+
+	public void timeStamp() {
+
+		if (inserted == 0) {
+			inserted = System.currentTimeMillis();
+		}
+	}
+
+	private AgeGroup ageGroup;
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/simpleentity/CategoryConfiguration.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.simpleentity;
+
+import org.springframework.context.ApplicationEvent;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.jdbc.core.DataAccessStrategy;
+import org.springframework.data.jdbc.core.DefaultDataAccessStrategy;
+import org.springframework.data.jdbc.core.DelegatingDataAccessStrategy;
+import org.springframework.data.jdbc.core.SqlGeneratorSource;
+import org.springframework.data.jdbc.mapping.event.BeforeSave;
+import org.springframework.data.jdbc.mapping.event.JdbcEvent;
+import org.springframework.data.jdbc.mapping.model.JdbcMappingContext;
+import org.springframework.data.jdbc.repository.config.EnableJdbcRepositories;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
+import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
+
+import javax.sql.DataSource;
+
+/**
+ * Contains infrastructure necessary for creating repositories and two listeners.
+ * <p>
+ * Not that a listener may change an entity without any problem.
+ *
+ * @author Jens Schauder
+ */
+@Configuration
+@EnableJdbcRepositories
+public class CategoryConfiguration {
+
+
+	@Bean
+	public ApplicationListener<?> loggingListener() {
+
+		return (ApplicationListener<ApplicationEvent>) event -> {
+			if (event instanceof JdbcEvent) {
+				System.out.println("received an event: " + event);
+			}
+		};
+	}
+
+
+	@Bean
+	public ApplicationListener<BeforeSave> timeStampingSaveTime() {
+
+		return event -> {
+
+			Object entity = event.getEntity();
+			if (entity instanceof Category) {
+				Category category = (Category) entity;
+				category.timeStamp();
+			}
+		};
+	}
+
+	// temporary workaround for https://jira.spring.io/browse/DATAJDBC-155
+	@Bean
+	DataAccessStrategy defaultDataAccessStrategy(JdbcMappingContext context, DataSource dataSource) {
+
+		NamedParameterJdbcOperations operations = new NamedParameterJdbcTemplate(dataSource);
+
+		DelegatingDataAccessStrategy accessStrategy = new DelegatingDataAccessStrategy();
+
+		accessStrategy.setDelegate(new DefaultDataAccessStrategy( //
+				new SqlGeneratorSource(context), //
+				operations, //
+				context, //
+				accessStrategy) //
+		);
+
+		return accessStrategy;
+	}
+}

jdbc/basics/src/main/java/example/springdata/jdbc/basics/simpleentity/CategoryRepository.java

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+/*
+ * Copyright 2017 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 example.springdata.jdbc.basics.simpleentity;
+
+import org.springframework.data.repository.CrudRepository;
+
+/**
+ * Repository for Categories.
+ *
+ * @author Jens Schauder
+ */
+public interface CategoryRepository extends CrudRepository<Category, Long> {
+
+}

jdbc/basics/src/main/resources/application.properties

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+logging.level.org.springframework.data=INFO
+logging.level.org.springframework.jdbc.core.JdbcTemplate=DEBUG

jdbc/basics/src/main/resources/schema.sql

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+CREATE TABLE IF NOT EXISTS category (id INTEGER IDENTITY PRIMARY KEY, name VARCHAR(100), description VARCHAR(2000), agegroup VARCHAR(20), created DATETIME, inserted BIGINT);
+
+CREATE TABLE IF NOT EXISTS LegoSet (id INTEGER, name VARCHAR(100), minAge INTEGER, maxAge INTEGER);
+CREATE TABLE IF NOT EXISTS Handbuch (handbuch_id INTEGER, author CHAR(100), text CLOB);
+CREATE TABLE IF NOT EXISTS Model (name VARCHAR(100), description CLOB, legoset INTEGER);

jdbc/basics/src/test/java/example/springdata/jdbc/basics/aggregate/AggregateTests.java

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+package example.springdata.jdbc.basics.aggregate;/*
+ * Copyright 2017 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.
+ */
+
+import example.springdata.jdbc.basics.Output;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureJdbc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import java.time.Period;
+
+/**
+ * Demonstrates various possibilities to customize the behavior of a repository.
+ *
+ * @author Jens Schauder
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = AggregateConfiguration.class)
+@AutoConfigureJdbc
+public class AggregateTests {
+
+	@Autowired
+	private LegoSetRepository repository;
+
+	@Test
+	public void exerciseSomewhatComplexEntity() {
+
+		LegoSet smallCar = createLegoSet();
+		smallCar.setManual(new Manual("Just put all the pieces together in the right order", "Jens Schauder"));
+		smallCar.addModel("suv", "SUV with sliding doors.");
+		smallCar.addModel("roadster", "Slick red roadster.");
+
+		repository.save(smallCar);
+		Output.list(repository.findAll(), "Original LegoSet");
+
+		smallCar.getManual().setText("Just make it so it looks like a car.");
+		smallCar.addModel("pickup", "A pickup truck with some tools in the back.");
+
+		repository.save(smallCar);
+		Output.list(repository.findAll(), "Updated");
+
+		smallCar.setManual(new Manual("One last attempt: Just build a car! Ok?", "Jens Schauder"));
+
+		repository.save(smallCar);
+		Output.list(repository.findAll(), "Manual replaced");
+	}
+
+	private LegoSet createLegoSet() {
+
+		LegoSet smallCar = new LegoSet();
+		smallCar.setName("Small Car 01");
+		smallCar.setMinimumAge(Period.ofYears(5));
+		smallCar.setMaximumAge(Period.ofYears(12));
+		return smallCar;
+	}
+}

jdbc/basics/src/test/java/example/springdata/jdbc/basics/simpleentity/SimpleEntityTests.java

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+package example.springdata.jdbc.basics.simpleentity;/*
+ * Copyright 2017 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.
+ */
+
+import example.springdata.jdbc.basics.Output;
+import example.springdata.jdbc.basics.aggregate.AgeGroup;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureJdbc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static java.util.Arrays.asList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Demonstrates simple CRUD operations with a simple entity without any references.
+ *
+ * @author Jens Schauder
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = CategoryConfiguration.class)
+@AutoConfigureJdbc
+public class SimpleEntityTests {
+
+	@Autowired
+	private CategoryRepository repository;
+
+	@Test
+	public void exerciseRepositoryForSimpleEntity() {
+
+		// create some categories
+		Category cars = new Category("Cars", "Anything that has approximately 4 wheels", AgeGroup._3to8);
+
+		Category buildings = new Category("Buildings", null, AgeGroup._12andOlder);
+
+		// save categories
+		repository.saveAll(asList(cars, buildings));
+		Output.list(repository.findAll(), "`Cars` and `Buildings` got saved");
+
+		assertThat(cars.getId()).isNotNull();
+		assertThat(buildings.getId()).isNotNull();
+
+		// update one
+		buildings.setDescription("Famous and impressive buildings incl. the 'bike shed'.");
+		repository.save(buildings);
+		Output.list(repository.findAll(), "`Buildings` has a description");
+
+		// delete stuff again
+		repository.delete(cars);
+		Output.list(repository.findAll(), "`Cars` is gone.");
+
+	}
+}