在JPA中获取数据库架构名称(来自EntityManager/EntityManagerFactory)

问题描述

在JPA(EclipseLink 2.4)中，我需要在NativeQuery中指定架构名称:

In JPA (EclipseLink 2.4) I need to specify schema name in NativeQuery:

EntityManager em = emf.createEntityManager();
Query query = em.createNativeQuery("select foo from bar.table");

上面的方法可以工作，但是显然我不喜欢对模式名称进行硬编码，特别是考虑到我已经在orm.xml中指定了它的事实:

Above works but obviously I don't like hardcoding schema name, especially given the fact that I'm already specifying it in orm.xml:

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_2_0.xsd"
    version="2.0">
    <persistence-unit-metadata>
        <persistence-unit-defaults>
            <schema>bar</schema>
        </persistence-unit-defaults>
    </persistence-unit-metadata>
</entity-mappings>

肯定有一种方法可以在运行时从某个地方获取模式名称吗?

Surely there must be a way to get schema name on runtime from somewhere?

推荐答案

如果使用这样的持久性单元:

If using a persistence unit like this:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="">
<persistence-unit name="MY_PU" transaction-type="RESOURCE_LOCAL">
  ...................................
<properties>
  <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://something:5432/MY_DB_NAME"/>
  <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
  <property name="javax.persistence.jdbc.user" value="user"/>
  <property name="javax.persistence.jdbc.password" value="pass"/>
  <property name="eclipselink.logging.level" value="WARNING"/>
</properties>

然后您可以使用EntityManagerFactory提取属性:

You can then use the EntityManagerFactory to extract the properties:

public String getDatabaseName() {
    String dbName = null;
    Map<String, Object> map = emf.getProperties();
    String url = (String) map.get("javax.persistence.jdbc.url");
    if(url != null) {
        dbName = url.substring(url.lastIndexOf("/") + 1);
    }
    return dbName;
}

其中 emf 是已创建的EntityManagerFactory.

where emf is the already created EntityManagerFactory.

emf = Persistence.createEntityManagerFactory("MY_PU");

这篇关于在JPA中获取数据库架构名称(来自EntityManager/EntityManagerFactory)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！