persistence.xml to import database parameters values from .properties file

Question

Edit: not duplicate but almost

I would like to have my app persistence.xml to be something like

<?xml version="1.0" encoding="UTF-8"?>
<persistence 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"
                version="1.0">
   <persistence-unit name="appName" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <properties>
            <property name="hibernate.dialect" value="${db.dialect'}"/>
            <property name="javax.persistence.jdbc.driver" value="${db.driver}"/>
            <property name="javax.persistence.jdbc.user" value="${db.user}"/>
            <property name="javax.persistence.jdbc.password" value="${db.password}"/>
            <property name="javax.persistence.jdbc.url" value="${db.url}"/>
        </properties>
    </persistence-unit>
</persistence>

getting these placeholder values from a simple text file somewhere in my source folders.

I read about that it's possible when using Spring doing like

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <value>classpath:com/foo/jdbc.properties</value>
    </property>
</bean>

but here we are not using Spring, just Hibernate and some Primefaces.

Is it possible?

Thanks!

Edit: I didn't mention some things, but for reference, I'm also using Shiro Security and Ant to do some stuff. I'll post the solution as an answer. This makes my project have 3 different files with database parameters:

• persistence.xml (Hibernate)
• context.xml (Shiro)
• database.properties (for Flyway tasks in Ant)

Answer 1

I edited to mention I'm using Shiro Security, that also needs some database parameters. I made it need just 1 database parameters location doing these stay in context.xml and referencing it in the others.

1) Ant read context.xml

Context.xml having

<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <!-- Other stuff... -->

    <!-- Shiro's -->
    <Resource name="jdbc/postgres" auth="Container"
        type="javax.sql.DataSource" driverClassName="org.postgresql.Driver"
        url="jdbc:postgresql://url-to-db/database"
        username="user" password="pass" />
</Context>

did using in Ant build.xml

<xmlproperty file="/path/to/context.xml" keepRoot="false" semanticAttributes="true" includeSemanticAttribute="true" />

and then accessing it using

<target name="init-flyway">
    <property name="flyway.url" value="${Resource.url}" />
    <property name="flyway.user" value="${Resource.username}" />
    <property name="flyway.password" value="${Resource.password}" />
    <!-- stuff stuff stuff -->
</target>

2) persistence.xml read context.xml

It is possible to use context's datastore using this

<non-jta-data-source>java:/comp/env/jdbc/postgres</non-jta-data-source>

So, I killed 3 database parameters to just 1.

Thanks for the help!

Answer 2

Instead of defining the properties inside persistence.xml you can define them in a standard properties file (key=value) and pass a Properties object to the createEntityManagerFactory() method, e.g.:

Properties props = new Properties();
props.load(new FileInputStream("/some/path/persistence.properties"));
EntityManagerFactory factory = Persistence.createEntityManagerFactory("appName", props);

Answer 3

If you are using Maven as the build system, you can use Maven filters to replace the values during build time.

Or you can write a simple property placeholder replacement (which is internally used by spring itself)

Reference: https://stackoverflow.com/a/14724719/477435