JPA-是否有方法/方法来检索持久性单元信息 [英] JPA - Is there a way/method to retrieve Persistence Unit information

问题描述

我想在代码中找出我的数据源名称.有办法吗? 我正在使用eclipselink.

I'd like to find out my data source name in the code. Is there a way of doing that? I am using eclipselink.

谢谢 更具体地说，我的目标是获得一个jdbc连接对象. 我知道我可以通过以下方式做到这一点:

thanks To be more specific, my aim is to get an jdbc connection object. I know i can do that thru:

datasource = (DataSource) (new InitialContext()).lookup("my_data_source_name")
connection = dataSource.getConnection();

但是我不想在代码中对数据源名称进行硬编码.

But I don't want to hard code the data source name in my code.

我也尝试过

java.sql.Connection connection = em.unwrap(java.sql.Connection.class);

，它总是返回null.

and it always return null.

推荐答案

.unwrap()应该是方法，如在调用em.unwrap(java.sql.Connection.class);时，我还经常得到null，因为它不在交易之内.当这样调用时:

I also used to get null when calling em.unwrap(java.sql.Connection.class); because it was not inside a transaction. When called like this:

em.getTransaction().begin();
java.sql.Connection conn = em.unwrap(java.sql.Connection.class);
// ...
em.getTransaction().commit();

一切正常！

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