从persistence.xml创建实体管理器工厂后如何修改属性 [英] how to modify properties after create entity manager factory from persistence.xml

问题描述

我在META-INF/文件夹中有一个persistence.xml:

i have a persistence.xml in META-INF/ folder:

<persistence-unit name="dev" transaction-type="RESOURCE_LOCAL">
<properties>
  <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost:5432/events" />
  <property name="javax.persistence.jdbc.user" value="postgres" />
  <property name="javax.persistence.jdbc.password" value="" />
  <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver" />
  <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
  <property name="hibernate.connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider" />
  <property name="hibernate.show_sql" value="false" />
</properties>
</persistence-unit>

在Java代码中，我从该persistence.xml创建实体管理器文件

in java code i create entity manager facotry from that persistence.xml

_emf = Persistence.createEntityManagerFactory("dev");
_em = _emf.createEntityManager();

但是我只想动态更改jdbc url/user/password以进行测试，我的计划是将这些参数保存在配置文件中并根据需要读取它们，因此在创建entitymanagerfactory后有没有办法更新它们从persistence.xml?所以它是这样的:

however i want do change only the jdbc url/user/password dynamically for test, my plan is to save those parameters in a config file and read them as needed, so is there a way i can update them after i create entitymanagerfactory from persistence.xml? so it would like this:

_emf = Persistence.createEntityManagerFactory("dev");
_emf.setProperties("url", "test_url");
    ... other setts here ...
_em = _emf.createEntityManager();

谢谢

推荐答案

创建EntityManagerFactory时，可以传递一组属性，这些属性将覆盖persistence.xml中定义的属性，例如:

When you create the EntityManagerFactory, you can pass a set of properties that will override what is defined in persistence.xml, e.g.:

Properties props = new Properties();
props.setProperty("javax.persistence.jdbc.url", "test_url");
_emf = Persistence.createEntityManagerFactory("dev", props);

如果要在创建EntityManagerFactory之后修改连接属性，则必须通过再次调用createEntityManagerFactory()重新创建它.

If you want to modify the connection properties after the EntityManagerFactory was created, you must recreate it by calling createEntityManagerFactory() again.

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