DATAJDBC-538 - Fixes lock acquisition for DB2.

The DB2 driver requires one to access the `ResultSet` resulting from a SELECT FOR UPDATE.

See also:
* https://github.com/schauder/db2-locks
* https://stackoverflow.com/questions/61681095/how-to-obtain-a-lock-in-db2-with-select-for-update-without-transferring-data

Original pull request: #216.

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/DefaultDataAccessStrategy.java

@@ -18,9 +18,7 @@ package org.springframework.data.jdbc.core.convert;
 import static org.springframework.data.jdbc.core.convert.SqlGenerator.*;
 
 import java.sql.JDBCType;
-import java.sql.PreparedStatement;
 import java.sql.ResultSet;
-import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -28,7 +26,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Predicate;
 
-import org.springframework.dao.DataAccessException;
 import org.springframework.dao.DataRetrievalFailureException;
 import org.springframework.dao.EmptyResultDataAccessException;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
@@ -40,6 +37,7 @@ import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
 import org.springframework.data.mapping.PersistentPropertyPath;
 import org.springframework.data.mapping.PropertyHandler;
+import org.springframework.data.relational.core.dialect.LockClause;
 import org.springframework.data.relational.core.mapping.PersistentPropertyPathExtension;
 import org.springframework.data.relational.core.mapping.RelationalMappingContext;
 import org.springframework.data.relational.core.mapping.RelationalPersistentEntity;
@@ -47,8 +45,6 @@ import org.springframework.data.relational.core.mapping.RelationalPersistentProp
 import org.springframework.data.relational.core.sql.IdentifierProcessing;
 import org.springframework.data.relational.core.sql.LockMode;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
-import org.springframework.jdbc.core.PreparedStatementCallback;
-import org.springframework.jdbc.core.ResultSetExtractor;
 import org.springframework.jdbc.core.RowMapper;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcOperations;
 import org.springframework.jdbc.core.namedparam.SqlParameterSource;
@@ -254,7 +250,8 @@ public class DefaultDataAccessStrategy implements DataAccessStrategy {
 
 		String acquireLockByIdSql = sql(domainType).getAcquireLockById(lockMode);
 		SqlIdentifierParameterSource parameter = createIdParameterSource(id, domainType);
-		operations.execute(acquireLockByIdSql, parameter, ps -> {ps.execute(); return null;});
+
+		operations.query(acquireLockByIdSql, parameter, ResultSet::next);
 	}
 
 	/*
@@ -265,7 +262,7 @@ public class DefaultDataAccessStrategy implements DataAccessStrategy {
 	public <T> void acquireLockAll(LockMode lockMode, Class<T> domainType) {
 
 		String acquireLockAllSql = sql(domainType).getAcquireLockAll(lockMode);
-		operations.getJdbcOperations().execute(acquireLockAllSql);
+		operations.getJdbcOperations().query(acquireLockAllSql, ResultSet::next);
 	}
 
 	/*

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/repository/JdbcRepositoryConcurrencyIntegrationTests.java

@@ -25,14 +25,18 @@ import lombok.With;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.StringJoiner;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.function.UnaryOperator;
 
+import org.assertj.core.api.Assertions;
 import org.junit.Before;
+import org.junit.BeforeClass;
 import org.junit.ClassRule;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.platform.commons.util.ExceptionUtils;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -86,6 +90,35 @@ public class JdbcRepositoryConcurrencyIntegrationTests {
 	TransactionTemplate transactionTemplate;
 	List<Exception> exceptions;
 
+	@BeforeClass
+	public static void beforeClass() {
+
+		Assertions.registerFormatterForType(CopyOnWriteArrayList.class, l -> {
+
+			StringJoiner joiner = new StringJoiner(", ", "List(", ")");
+			l.forEach(e -> {
+
+				if (e instanceof Throwable) {
+					printThrowable(joiner,(Throwable) e);
+				} else {
+					joiner.add(e.toString());
+				}
+			});
+
+			return joiner.toString();
+		});
+	}
+
+	private static void printThrowable(StringJoiner joiner, Throwable t) {
+
+		joiner.add(t.toString() + ExceptionUtils.readStackTrace(t));
+		if (t.getCause() != null) {
+
+			joiner.add("\ncaused by:\n");
+			printThrowable(joiner, t.getCause());
+		}
+	}
+
 	@Before
 	public void before() {
 

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/testing/Db2DataSourceConfiguration.java

@@ -55,7 +55,7 @@ class Db2DataSourceConfiguration extends DataSourceConfiguration {
 		if (DB_2_CONTAINER == null) {
 
 			LOG.info("DB2 starting...");
-			Db2Container container = new Db2Container();
+			Db2Container container = new Db2Container().withReuse(true);
 			container.start();
 			LOG.info("DB2 started");
 

spring-data-jdbc/src/test/resources/org.springframework.data.jdbc.core/JdbcAggregateTemplateIntegrationTests-db2.sql

@@ -1,3 +1,41 @@
+DROP TABLE MANUAL;
+DROP TABLE LEGO_SET;
+
+DROP TABLE Child_No_Id;
+DROP TABLE ONE_TO_ONE_PARENT;
+
+DROP TABLE ELEMENT_NO_ID;
+DROP TABLE LIST_PARENT;
+
+DROP TABLE BYTE_ARRAY_OWNER;
+
+DROP TABLE CHAIN0;
+DROP TABLE CHAIN1;
+DROP TABLE CHAIN2;
+DROP TABLE CHAIN3;
+DROP TABLE CHAIN4;
+
+DROP TABLE NO_ID_CHAIN0;
+DROP TABLE NO_ID_CHAIN1;
+DROP TABLE NO_ID_CHAIN2;
+DROP TABLE NO_ID_CHAIN3;
+DROP TABLE NO_ID_CHAIN4;
+
+DROP TABLE NO_ID_MAP_CHAIN0;
+DROP TABLE NO_ID_MAP_CHAIN1;
+DROP TABLE NO_ID_MAP_CHAIN2;
+DROP TABLE NO_ID_MAP_CHAIN3;
+DROP TABLE NO_ID_MAP_CHAIN4;
+
+DROP TABLE NO_ID_LIST_CHAIN0;
+DROP TABLE NO_ID_LIST_CHAIN1;
+DROP TABLE NO_ID_LIST_CHAIN2;
+DROP TABLE NO_ID_LIST_CHAIN3;
+DROP TABLE NO_ID_LIST_CHAIN4;
+
+DROP TABLE WITH_READ_ONLY;
+DROP TABLE VERSIONED_AGGREGATE;
+
 CREATE TABLE LEGO_SET
 (
   "id1"  BIGINT GENERATED BY DEFAULT AS IDENTITY (START WITH 1) PRIMARY KEY,

spring-data-jdbc/src/test/resources/org.springframework.data.jdbc.repository/JdbcRepositoryConcurrencyIntegrationTests-db2.sql

@@ -0,0 +1,5 @@
+DROP TABLE element;
+DROP TABLE dummy_entity;
+
+CREATE TABLE dummy_entity ( id BIGINT GENERATED BY DEFAULT AS IDENTITY ( START WITH 1 ) NOT NULL PRIMARY KEY, NAME VARCHAR(100));
+CREATE TABLE element (id BIGINT GENERATED BY DEFAULT AS IDENTITY ( START WITH 1 ) NOT NULL PRIMARY KEY, content BIGINT, Dummy_Entity_key BIGINT,dummy_entity BIGINT);

spring-data-relational/src/main/java/org/springframework/data/relational/core/dialect/Db2Dialect.java

@@ -41,7 +41,7 @@ public class Db2Dialect extends AbstractDialect {
 		 */
 		@Override
 		public String getLimit(long limit) {
-			return "FIRST " + limit + " ROWS ONLY";
+			return "FETCH FIRST " + limit + " ROWS ONLY";
 		}
 
 		/*
@@ -83,7 +83,18 @@ public class Db2Dialect extends AbstractDialect {
 
 	@Override
 	public LockClause lock() {
-		return AnsiDialect.LOCK_CLAUSE;
+
+		return new LockClause() {
+			@Override
+			public String getLock(LockOptions lockOptions) {
+				return "FOR UPDATE WITH RS USE AND KEEP EXCLUSIVE LOCKS";
+			}
+
+			@Override
+			public Position getClausePosition() {
+				return Position.AFTER_ORDER_BY;
+			}
+		};
 	}
 
 	/*