DATAJDBC-98 - Update implemented.

New instances get saved with an insert statement. Existing instances get updated. Also added some test to find certain corner cases that I feared may cause problems:

- ID properties being not editable (no setter and final).
- ID properties being primitive.
- ID properties not being named "id"

and fixed the issues resulting from those.

Original pull request: #5.

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

@@ -23,6 +23,7 @@ import java.util.stream.StreamSupport;
 import javax.sql.DataSource;
 import org.springframework.data.jdbc.mapping.model.JdbcPersistentEntity;
 import org.springframework.data.jdbc.mapping.model.JdbcPersistentProperty;
+import org.springframework.data.jdbc.repository.support.JdbcPersistentEntityInformation;
 import org.springframework.data.mapping.PropertyHandler;
 import org.springframework.data.repository.CrudRepository;
 import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
@@ -37,6 +38,7 @@ import org.springframework.jdbc.support.KeyHolder;
 public class SimpleJdbcRepository<T, ID extends Serializable> implements CrudRepository<T, ID> {
 
 	private final JdbcPersistentEntity<T> entity;
+	private final JdbcPersistentEntityInformation<T,ID> entityInformation;
 	private final NamedParameterJdbcOperations template;
 	private final SqlGenerator sql;
 
@@ -45,6 +47,7 @@ public class SimpleJdbcRepository<T, ID extends Serializable> implements CrudRep
 	public SimpleJdbcRepository(JdbcPersistentEntity<T> entity, DataSource dataSource) {
 
 		this.entity = entity;
+		this.entityInformation = new JdbcPersistentEntityInformation<T, ID>(entity);
 		this.template = new NamedParameterJdbcTemplate(dataSource);
 
 		entityRowMapper = new EntityRowMapper<T>(entity);
@@ -54,14 +57,19 @@ public class SimpleJdbcRepository<T, ID extends Serializable> implements CrudRep
 	@Override
 	public <S extends T> S save(S instance) {
 
-		KeyHolder holder = new GeneratedKeyHolder();
+		if (entityInformation.isNew(instance)) {
 
-		template.update(
-				sql.getInsert(),
-				new MapSqlParameterSource(getPropertyMap(instance)),
-				holder);
+			KeyHolder holder = new GeneratedKeyHolder();
 
-		entity.setId(instance, holder.getKey());
+			template.update(
+					sql.getInsert(),
+					new MapSqlParameterSource(getPropertyMap(instance)),
+					holder);
+
+			entity.setId(instance, holder.getKey());
+		} else {
+			template.update(sql.getUpdate(), getPropertyMap(instance));
+		}
 
 		return instance;
 	}

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

@@ -17,6 +17,7 @@ package org.springframework.data.jdbc.repository;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Collector;
 import java.util.stream.Collectors;
 import org.springframework.data.jdbc.mapping.model.JdbcPersistentEntity;
 import org.springframework.data.mapping.PropertyHandler;
@@ -37,9 +38,13 @@ class SqlGenerator {
 	private final String deleteByIdSql;
 	private final String deleteAllSql;
 	private final String deleteByListSql;
+	private final String updateSql;
+	private final List<String> propertyNames = new ArrayList<>();
 
 	<T> SqlGenerator(JdbcPersistentEntity<T> entity) {
 
+		entity.doWithProperties((PropertyHandler) persistentProperty -> propertyNames.add(persistentProperty.getName()));
+
 		findOneSql = createFindOneSelectSql(entity);
 		findAllSql = createFindAllSql(entity);
 		findAllInListSql = createFindAllInListSql(entity);
@@ -48,6 +53,7 @@ class SqlGenerator {
 		countSql = createCountSql(entity);
 
 		insertSql = createInsertSql(entity);
+		updateSql = createUpdateSql(entity);
 
 		deleteByIdSql = createDeleteSql(entity);
 		deleteAllSql = createDeleteAllSql(entity);
@@ -74,6 +80,10 @@ class SqlGenerator {
 		return insertSql;
 	}
 
+	String getUpdate() {
+		return updateSql;
+	}
+
 	String getCount() {
 		return countSql;
 	}
@@ -106,22 +116,26 @@ class SqlGenerator {
 	}
 
 	private <T> String createCountSql(JdbcPersistentEntity<T> entity) {
-		return String.format("select count(*) from %s", entity.getTableName(), entity.getIdColumn());
+		return String.format("select count(*) from %s", entity.getTableName());
 	}
 
 	private String createInsertSql(JdbcPersistentEntity<?> entity) {
 
-		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);
+		return String.format(insertTemplate, entity.getTableName(), tableColumns, parameterNames);
+	}
+
+	private <T> String createUpdateSql(JdbcPersistentEntity<T> entity) {
+
+		String updateTemplate = "update %s set %s where %s = :%s";
+
+		String setClause = propertyNames.stream().map(n -> String.format("%s = :%s", n, n)).collect(Collectors.joining(", "));
+
+		return String.format(updateTemplate, entity.getTableName(), setClause, entity.getIdColumn(), entity.getIdColumn());
 	}
 
 	private String createDeleteSql(JdbcPersistentEntity entity) {
@@ -133,6 +147,7 @@ class SqlGenerator {
 	}
 
 	private String createDeleteByListSql(JdbcPersistentEntity entity) {
-		return String.format("delete from %s where id in (:ids)", entity.getTableName());
+		return String.format("delete from %s where %s in (:ids)", entity.getTableName(), entity.getIdColumn());
 	}
+
 }