问题

I would like to use EclipseLink as my JPA engine. We are using a subclass of java.sql.Connection and I would like to know if I can force EclipseLink to use my connection. I would like to set the connection object programmatically.

Something like

MyConnection conn = new MyConnection(JDBC_URL, USR, PWD);
EntityManagerFactory factory = Persistence.createEntityManagerFactory(conn);

回答1:

You can set a custom connection programatically using the following code:

Map properties = new HashMap();

// Configure the internal EclipseLink connection pool
properties.put(JDBC_DRIVER, "oracle.jdbc.OracleDriver");
properties.put(JDBC_URL, "jdbc:oracle:thin:@localhost:1521:ORCL");
properties.put(JDBC_USER, "user-name");
properties.put(JDBC_PASSWORD, "password");
Persistence.createEntityManagerFactory("unit-name", properties);

I found this answer here after a quick google search:

http://eclipse.1072660.n5.nabble.com/Defining-persistence-xml-programatically-td2536.html

I dont believe that there is a way to force Eclipselink to connect using only that java.sql.Connection; not out of the box at least. You could make a simple utility method to pass in said connection and build a properties map as I described above.

public Map convertConnectionToProperties(Connection conn) {
    // Do the mapping

    return theMap;
}

If you take a look at this link you will see that

Persistence.java

createEntityManagerFactory(String persistenceUnitName) 
createEntityManagerFactory(String persistenceUnitName, Map properties)

That is all it can take as parameters. Simply put; what you are asking for simply isn't possible without taking your connection object and adjust it to return something that complies with what createEntityManagerFactory can take in.

class MyConnection {
     // Your code here

    public Map convertToMap() {
        // Do the mapping

        return theMap;
    }

    public String getPersistenceUnitName() {
        return "Some-Name";
    }
}

And then utilize it like this:

MyConnection conn = new MyConnection(JDBC_URL, USR, PWD);
EntityManagerFactory factory = Persistence.createEntityManagerFactory(conn.getPersistenceUnitName(), conn.convertToMap());

回答2:

^{* This solution use Spring Framework.}

javax.sql.DataSource

First you need to wrap your connection in a javax.sql.DataSource, e.g.:

import java.sql.Connection;
import java.sql.SQLException;

import org.springframework.jdbc.datasource.AbstractDataSource;

public class MyDataSource extends AbstractDataSource {

    private static final String JDBC_URL = "jdbc:mysql://localhost/test";
    private static final String USR = "root";
    private static final String PWD = "";

    public Connection getConnection() throws SQLException {
        return new MyConnection(JDBC_URL, USR, PWD);
    }

    public Connection getConnection(String username, String password)
            throws SQLException {
        return new MyConnection(JDBC_URL, USR, PWD);
    }
}

To avoid overwriting all methods, you can extend an existing class in Spring.

javax.persistence.EntityManagerFactory

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;

import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter;

public class Main {

    public static void main(String[] args) {
        LocalContainerEntityManagerFactoryBean bean =
                new LocalContainerEntityManagerFactoryBean();
        bean.setDataSource(new MyDataSource());
        bean.setPersistenceUnitName("TestPU");
        bean.setJpaVendorAdapter(new EclipseLinkJpaVendorAdapter());
        bean.afterPropertiesSet();

        EntityManagerFactory factory = bean.getNativeEntityManagerFactory();
        EntityManager em = factory.createEntityManager();
        em.getTransaction().begin();
        User user = new User();
        user.setFullname("Mister");
        em.persist(user);
        em.getTransaction().commit();
        em.close();
    }

}

NOTES

You may want to need add the next property in your persistence.xml:
```
<property name="eclipselink.weaving" value="false"/>
```

I used a Standalone Maven Project for test the code and the dependencies in the pom.xml looks like this:

<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.31</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.0.5.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-orm</artifactId>
        <version>4.0.5.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>eclipselink</artifactId>
        <version>2.5.1</version>
    </dependency>
</dependencies>

Or if you prefer, the required jars:

mysql-connector-java-5.1.31.jar
spring-context-4.0.5.RELEASE.jar
spring-aop-4.0.5.RELEASE.jar
aopalliance-1.0.jar
spring-beans-4.0.5.RELEASE.jar
spring-core-4.0.5.RELEASE.jar
commons-logging-1.1.3.jar
spring-expression-4.0.5.RELEASE.jar
spring-orm-4.0.5.RELEASE.jar
spring-jdbc-4.0.5.RELEASE.jar
spring-tx-4.0.5.RELEASE.jar
eclipselink-2.5.1.jar
javax.persistence-2.1.0.jar
commonj.sdo-2.1.1.jar

来源：https://stackoverflow.com/questions/24452376/eclipselink-jpa-2-1-user-supplied-connection

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