It can be any expression allowed in DB2 as long as it does not modify any data in SQL or perform any action outside the scope of the DB2 engine.
只要不修改SQL中的数据或不会在DB2引擎以外执行任何操作，则可以使用DB 2允许的任何表达式。
2
If you declare your properties private and attempt to access them from outside the class 'scope (as shown in Listing 7), the PHP engine will throw a fatal error.
如果将属性声明为private并试图从类范围外部访问它(如清单7所示)，PHP引擎将抛出致命错误。
3
Although it's beyond the scope of this article to explain in detail how the jpa2web generator works, here is a summary of the main ideas and method behind the generator engine.