DATAJDBC-95 - Saving and loading a trivial entity.

Creation of the necessary sql statements is now dynamic and driven in a
trivial way by the entity.

Known issues with the solution that need to get fixed later:

Sql generating code is in the repository and should go somewhere else.

Mapping logic is very trivial and should go in a separate place.

Author: schauder

src/main/java/org/springframework/data/jdbc/repository/EntityRowMapper.java

@@ -0,0 +1,65 @@
+/*
+ * 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 org.springframework.data.jdbc.repository;
+
+import java.lang.reflect.InvocationTargetException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import org.springframework.data.mapping.PersistentEntity;
+import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.data.mapping.PropertyHandler;
+
+/**
+ * @author Jens Schauder
+ */
+class EntityRowMapper<T> implements org.springframework.jdbc.core.RowMapper<T> {
+
+	private final PersistentEntity<T, ?> entity;
+
+	EntityRowMapper(PersistentEntity<T, ?> entity) {
+		this.entity = entity;
+	}
+
+	@Override
+	public T mapRow(ResultSet rs, int rowNum) throws SQLException {
+
+		try {
+
+			T t = createInstance();
+
+			entity.doWithProperties((PropertyHandler) property -> {
+				setProperty(rs, t, property);
+			});
+
+			return t;
+		} catch (Exception e) {
+			throw new RuntimeException(String.format("Could not instantiate %s", entity.getType()));
+		}
+	}
+
+	private T createInstance() throws InstantiationException, IllegalAccessException, InvocationTargetException {
+		return (T) entity.getPersistenceConstructor().getConstructor().newInstance();
+	}
+
+	private void setProperty(ResultSet rs, T t, PersistentProperty property) {
+
+		try {
+			property.getSetter().invoke(t, rs.getObject(property.getName()));
+		} catch (Exception e) {
+			throw new RuntimeException(String.format("Couldn't set property %s.", property.getName()), e);
+		}
+	}
+}

src/main/java/org/springframework/data/jdbc/repository/SimpleJdbcRepository.java

@@ -16,11 +16,17 @@
 package org.springframework.data.jdbc.repository;
 
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
 import javax.sql.DataSource;
+import org.springframework.data.jdbc.mapping.model.JdbcPersistentEntity;
+import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.data.mapping.PropertyHandler;
 import org.springframework.data.repository.CrudRepository;
-import org.springframework.data.repository.core.EntityInformation;
+import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
 
@@ -29,23 +35,25 @@
  */
 public class SimpleJdbcRepository<T, ID extends Serializable> implements CrudRepository<T, ID> {
 
-	private final EntityInformation entityInformation;
+	private final JdbcPersistentEntity<T> entity;
 	private final NamedParameterJdbcOperations template;
 
-	public SimpleJdbcRepository(EntityInformation entityInformation, DataSource dataSource) {
-		this.entityInformation = entityInformation;
+	private final String findOneSql;
+	private final String insertSql;
+
+	public SimpleJdbcRepository(JdbcPersistentEntity<T> entity, DataSource dataSource) {
+
+		this.entity = entity;
 		this.template = new NamedParameterJdbcTemplate(dataSource);
+
+		findOneSql = createFindOneSelectSql();
+		insertSql = createInsertSql();
 	}
 
 	@Override
 	public <S extends T> S save(S entity) {
-		Map<String, Object> parameters = new HashMap<>();
-		parameters.put("id", entityInformation.getId(entity));
-		parameters.put("name", "blah blah");
 
-		template.update(
-				"insert into dummyentity (id, name) values (:id, :name)",
-				parameters);
+		template.update(insertSql, getPropertyMap(entity));
 
 		return entity;
 	}
@@ -57,7 +65,12 @@ public <S extends T> Iterable<S> save(Iterable<S> entities) {
 
 	@Override
 	public T findOne(ID id) {
-		return null;
+
+		return template.queryForObject(
+				findOneSql,
+				new MapSqlParameterSource("id", id),
+				new EntityRowMapper<T>(entity)
+		);
 	}
 
 	@Override
@@ -99,4 +112,45 @@ public void delete(Iterable<? extends T> entities) {
 	public void deleteAll() {
 
 	}
+
+	private String createFindOneSelectSql() {
+
+		String tableName = entity.getType().getSimpleName();
+		String idColumn = entity.getIdProperty().getName();
+
+		return String.format("select * from %s where %s = :id", tableName, idColumn);
+	}
+
+	private String createInsertSql() {
+
+		List<String> propertyNames = new ArrayList<>();
+		entity.doWithProperties((PropertyHandler) persistentProperty -> propertyNames.add(persistentProperty.getName()));
+
+		String insertTemplate = "insert into %s (%s) values (%s)";
+
+		String tableName = entity.getType().getSimpleName();
+
+		String tableColumns = propertyNames.stream().collect(Collectors.joining(", "));
+		String parameterNames = propertyNames.stream().collect(Collectors.joining(", :", ":", ""));
+
+		return String.format(insertTemplate, tableName, tableColumns, parameterNames);
+	}
+
+	private <S extends T> Map<String, Object> getPropertyMap(final S entity) {
+
+		Map<String, Object> parameters = new HashMap<>();
+
+		this.entity.doWithProperties(new PropertyHandler() {
+			@Override
+			public void doWithPersistentProperty(PersistentProperty persistentProperty) {
+				try {
+					parameters.put(persistentProperty.getName(), persistentProperty.getGetter().invoke(entity));
+				} catch (Exception e) {
+					throw new RuntimeException(String.format("Couldn't get value of property %s", persistentProperty.getName()));
+				}
+			}
+		});
+
+		return parameters;
+	}
 }

src/main/java/org/springframework/data/jdbc/repository/support/JdbcRepositoryFactory.java

@@ -39,13 +39,12 @@ public JdbcRepositoryFactory(DataSource dataSource) {
 
 	@Override
 	public <T, ID extends Serializable> EntityInformation<T, ID> getEntityInformation(Class<T> aClass) {
-		JdbcPersistentEntity<T> persistentEntity = (JdbcPersistentEntity<T>) context.getPersistentEntity(aClass);
-		return new JdbcPersistentEntityInformation<T, ID>(persistentEntity);
+		return new JdbcPersistentEntityInformation<T, ID>((JdbcPersistentEntity<T>) context.getPersistentEntity(aClass));
 	}
 
 	@Override
 	protected Object getTargetRepository(RepositoryInformation repositoryInformation) {
-		return new SimpleJdbcRepository(getEntityInformation(repositoryInformation.getDomainType()), dataSource);
+		return new SimpleJdbcRepository(context.getPersistentEntity(repositoryInformation.getDomainType()), dataSource);
 	}
 
 	@Override

src/test/java/org/springframework/data/jdbc/repository/JdbcRepositoryIntegrationTests.java

@@ -48,19 +48,18 @@ public class JdbcRepositoryIntegrationTests {
 
 	private final NamedParameterJdbcTemplate template = new NamedParameterJdbcTemplate(db);
 
+	private final DummyEntityRepository repository = createRepository(db);
+
+	private DummyEntity entity = createDummyEntity();
+
 	@After
-	public void afeter() {
+	public void after() {
 		db.shutdown();
 	}
 
 
 	@Test
 	public void canSaveAnEntity() throws SQLException {
-		DummyEntityRepository repository = createRepository();
-
-		DummyEntity entity = new DummyEntity();
-		entity.setId(23L);
-		entity.setName("Entity Name");
 
 		entity = repository.save(entity);
 
@@ -74,9 +73,31 @@ public void canSaveAnEntity() throws SQLException {
 				count);
 	}
 
-	private DummyEntityRepository createRepository() throws SQLException {
-		JdbcRepositoryFactory jdbcRepositoryFactory = new JdbcRepositoryFactory(db);
-		return jdbcRepositoryFactory.getRepository(DummyEntityRepository.class);
+	@Test
+	public void canSaveAndLoadAnEntity() throws SQLException {
+
+		entity = repository.save(entity);
+
+		DummyEntity reloadedEntity = repository.findOne(entity.getId());
+
+		assertEquals(
+				entity.getId(),
+				reloadedEntity.getId());
+		assertEquals(
+				entity.getName(),
+				reloadedEntity.getName());
+	}
+
+	private static DummyEntityRepository createRepository(EmbeddedDatabase db) {
+		return new JdbcRepositoryFactory(db).getRepository(DummyEntityRepository.class);
+	}
+
+
+	private static DummyEntity createDummyEntity() {
+		DummyEntity entity = new DummyEntity();
+		entity.setId(23L);
+		entity.setName("Entity Name");
+		return entity;
 	}
 
 	private interface DummyEntityRepository extends CrudRepository<DummyEntity, Long> {