java – jdbc的registerOutParameter中sqlType的含义是什么？

我正在使用jdbc CallableStatement来执行MySQL数据库中的过程.在编写单元测试时,我遇到了关于registerOutParameter方法的奇怪行为.使用过的SQL程序PROCEDURE TEST_DOUBLE( OUT val DOUBLE ) BEGIN SET val = 2.5; E...

我正在使用jdbc CallableStatement来执行MySQL数据库中的过程.在编写单元测试时,我遇到了关于registerOutParameter方法的奇怪行为.

使用过的SQL程序

PROCEDURE TEST_DOUBLE( OUT val DOUBLE ) BEGIN SET val = 2.5; END
PROCEDURE TEST_TEXT( OUT val TEXT ) BEGIN SET val = 'test'; END

测试

statement = connection.prepareCall( "CALL TEST_DOUBLE(?)" );
statement.registerOutParameter( "val" , java.sql.Types.INTEGER );
statement.execute();
statement.getInt( "val" ); //Integer 2
statement.getDouble( "val" ); //Double 2.5
statement.getString( "val" ); //String "2.5"

statement = connection.prepareCall( "CALL TEST_TEXT(?)" );
statement.registerOutParameter( "val" , java.sql.Types.INTEGER );
statement.execute();
statement.getInt( "val" ); //Invalid value for getInt
statement.getDouble( "val" ); //Invalid value for getDouble
statement.getString( "val" ); //String "test"

statement = connection.prepareCall( "CALL TEST_TEXT(?)" );
statement.registerOutParameter( "val" , 0 );
statement.execute();
statement.getInt( "val" ); //Invalid value for getInt
statement.getDouble( "val" ); //Invalid value for getDouble
statement.getString( "val" ); //String "test"

等等…

我的观点是 – 传递给registerOutParameter的值java.sql.Types.*似乎什么都不做……无论我传递的sql类型是什么,一切都取决于调用正确的getter方法和数据库返回的实际值.

我可以在任何地方传递0并且它仍能正常工作吗？
为什么这个参数传递了？
或许这个数据库是相关的,对于其他数据库,它是有意义的吗？

解决方法:

我猜这个参数与数据库有关.甲骨文肯定会关注它：

statement = connection.prepareCall("CALL_TEST_NUMBER(?)");
statement.registerOutParameter("val", java.sql.Types.INTEGER);
statement.execute();
statement.getInt("val");       // 2
statement.getDouble("val");    // 2.5
statement.getString("val");    // "2.5"

statement = connection.prepareCall("CALL TEST_TEXT(?)");
statement.registerOutParameter("val", java.sql.Types.INTEGER);
statement.execute();   //  java.sql.SQLSyntaxErrorException: ORA-01722: invalid number