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Change database schema at runtime [message #664304]

Fri, 08 April 2011 10:28

Pavel Zelenka

Messages: 61
Registered: July 2009

Member

Hi,

in my application which uses EclipseLink 1.1.1 I'd like to change database at runtime.
The reason is this: on MySQL server there are several databases with identical structure. Decission which database use is made in application at runtime and it may change during the application lifecycle.
Is the only solution to have one persistent unit for each database?

Thanks for help.

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Re: Change database schema at runtime [message #664690 is a reply to message #664304]

Mon, 11 April 2011 15:37

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

You could either have a different persistence unit for each database.

Or you could have a single persistence unit, but create a different EntityManagerFactory for each database. You would pass a properties into the createEntityManagerFactory, and give the new url for the database.

James : Wiki : Book : Blog : Twitter

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Re: Change database schema at runtime [message #664876 is a reply to message #664690]

Tue, 12 April 2011 11:17

Pavel Zelenka

Messages: 61
Registered: July 2009

Member

Thanks, this is a good idea.

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Re: Change database schema at runtime [message #665064 is a reply to message #664876]

Wed, 13 April 2011 07:35

Pavel Zelenka

Messages: 61
Registered: July 2009

Member

I have one more question. When I try to create EntityManager with properties Map Eclipselink creates it, but it is the same as the first one. It seems like there is some cache. Maybe there is some property that needs to be set. Any help appreciated.

[Updated on: Wed, 13 April 2011 07:36]

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Re: Change database schema at runtime [message #665415 is a reply to message #665064]

Thu, 14 April 2011 14:54

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

If you give it a different URL or DataSource it should create a new one.

What properties are you setting?

James : Wiki : Book : Blog : Twitter

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Re: Change database schema at runtime [message #665456 is a reply to message #665415]

Thu, 14 April 2011 16:39

Pavel Zelenka

Messages: 61
Registered: July 2009

Member

My persistence.xml is:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="myPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider >
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<property name="eclipselink.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="eclipselink.jdbc.user" value="..."/>
<property name="eclipselink.jdbc.password" value="..."/>
<property name="eclipselink.logging.level" value="INFO"/>
</properties>
<class>...</class>
</persistence-unit>
</persistence>

My code is:

private Map<Distributor, EntityManagerFactory> mapPU = new HashMap<Distributor, EntityManagerFactory>();
....
protected void createEntityManagerFactory(Distributor distributor) {
Map properties = new HashMap();
properties.put(PersistenceUnitProperties.JDBC_URL, "jdbc:mysql://192.168.1.14:3306/" + distributor.getDatabase() + "?zeroDateTimeBehavior=convertToNull");
EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPU", properties);
mapPU.put(distributor, emf);
}

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