spring - Mixing JdbcTemplate and raw JDBC -

i experiencing strange behaviour can't explain. following code runs fine:

    try (connection connection = datasource.getconnection();          statement statement = connection.createstatement()) {         statement.executeupdate("delete product");      } catch (exception ex) {         throw new runtimeexception(ex);     }      try (connection connection = datasource.getconnection();          statement statement = connection.createstatement()) {          statement.executeupdate("insert product ...");      } catch (sqlexception ex) {         throw new runtimeexception(ex);     } 

however code causes deadlock:

    jdbctemplate.update("delete product");      try (connection connection = datasource.getconnection();          statement statement = connection.createstatement()) {          statement.executeupdate("insert product ...");      } catch (sqlexception ex) {         throw new runtimeexception(ex);     } 

the exception is

java.sql.sqlexception: lock wait timeout exceeded; try restarting transaction

both jdbctemplate , datasource created spring boot , autowired

@autowired private datasource datasource;  @autowired private jdbctemplate jdbctemplate; 

the statements form part of method in service (with @transactional annotation)

can explain why happens?

if want use own jdbc code plays nice connections managed spring's transaction management should use datasourceutils obtain connection -- see http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/jdbc/datasource/datasourceutils.html#getconnection-javax.sql.datasource-

in example, depending on transaction configuration, first statement using jdbctemplate might not committed yet, block next jdbc statement different connection. using datasourceutils, both statements using same connection.