Changing datasource connection url runtime

Question

I am working on a project which uses spring + hibernate + mysql and c3p0 for connection pooling.

Currently the properties for the connection pool are loaded via prop

Answer 1

<beans:bean id="dataSource"
    class="org.springframework.aop.framework.ProxyFactoryBean">
    <beans:property name="targetSource" ref="swappableDataSource" />
</beans:bean>

<beans:bean id="dummyDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
    destroy-method="close" />

<beans:bean name="swappableDataSource"
    class="org.springframework.aop.target.HotSwappableTargetSource">
    <beans:constructor-arg ref="dummyDataSource" />
</beans:bean>

and some where in your code you can do this.

@Autowired
HotSwappableTargetSource swapable;

public void changeDatasource() throws Exception
{
            swapable.swap(createNewSource();

}


ComboPooledDataSource createNewSource() throws Exception {
    ComboPooledDataSource ds2 = new ComboPooledDataSource();
    ds2.setJdbcUrl(url);
    ds2.setDriverClass(driver);
    ds2.setUser(username);
    ds2.setPassword(password);


    return ds2;
}

Answer 2

AbstractRoutingDataSource is a good choice.

Xml or annotation used like this:

<bean id="ds1" class="..c3p0.DataSource">
    ...
</bean>

<bean id="ds2" class="..c3p0.DataSource">
    ...
</bean>

<bean id="dataSource" class="..xxx.RoutingDataSource">
   <property name="targetDataSources">
      <map key-type="java.lang.String">
         <entry key="ds1" value-ref="ds1"/>
         <entry key="ds2" value-ref="ds2"/>             
      </map>
   </property>
   <property name="defaultTargetDataSource" ref="ds1"/>
</bean>



<bean id="sessionFactory"
    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
    <property name="dataSource" ref="dataSource" /> 
...
</bean>

Then build a class to determine current datasoruce.

public class RoutingDataSource extends AbstractRoutingDataSource {
    private static final ThreadLocal<String> holder = new ThreadLocal<String>();

    protected Object determineCurrentLookupKey()
    {
        return holder.get();
    }

    public static void clear(){
        holder.remove();
    }

    public static void setDataSourceKey(String key){
        holder.set(key);
    }

}

By the way, the 'try-finally' statement is boring!

try{
    RoutingDataSource.setDataSourceKey("ds1");
    myDao.doXXX();
}finally{
    RoutingDataSource.clear();
}

Answer 3

If you are asking for multiple databases connections ..it is possible with hibernate by creating multiple hibernate.cfg.file 's which is some what inappropriate

By following line you can acheive that .

SessionFactory sf = new Configuration().configure("somename.cfg.xml").buildSessionFactory();

When your primary connection not established you have load another hibernate configuration ...otherwise is wont possible .