Override @Autowired property annotation with XML configuration

Question

I've a class EntityLoader that's used to fetch some data from a MySQL database using Hibernate. But now the need is to fetch data from two different databases (MySQL and Oracle in this case). So I want to have two beans of EntityLoader but injecting a different SessionFactory in each one.

EntityLoader is defined as follows:

package com.demo

@Component
public class EntityLoader {

    @Autowired
    private SessionFactory sessionFactory;

    /* Code ... */

    public SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }   
}

And the context configuration is:

<context:component-scan base-package="com.demo" />
<bean id="mysqlSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">

So far it works fine. Over this I have done the following changes:

Exclude EntityLoader from component-scan in order to avoid the auto creation of a EntityLoader
Add mysqlSessionFactory and oracleSessionFactory bean definitions
Add mysqlEntityRepoLoader and oracleEntityRepoLoader bean definitions

Note that in mysqlEntityRepoLoader and oracleEntityRepoLoader I've added the attribute autowired="no" hoping that this would tell Spring to not autowire the SessionFactory and use the defined ref instead.

The resulting configuration is:

<context:component-scan base-package="com.demo">
    <context:exclude-filter type="regex" expression="com.demo.EntityLoader"/>
</context:component-scan>

<bean id="mysqlSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <!-- ... config ... -->
</bean>
<bean id="oracleSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <!-- ... config ... -->
</bean>

<bean id="mysqlEntityRepoLoader" class="com.dome.imserso.api.core.data.EntityRepoLoader" autowire="no">
    <property name="sessionFactory" ref="mysqlSessionFactory"/>
</bean> 
<bean id="oracleEntityRepoLoader" class="com.dome.imserso.api.core.data.EntityRepoLoader" autowire="no">
    <property name="sessionFactory" ref="oracleSessionFactory"/>
</bean>

But it seems that Spring is trying first to autowire the SessionFactory in any case. I get the following error:

No qualifying bean of type [org.hibernate.SessionFactory] is defined: expected single matching bean but found 2: mysqlSessionFactory,oracleSessionFactory

If I remove the @Autowired all works fine. But I would like to maintain it, as this code is part of a generic lib used for other apps where the usual case is to load only from one database.

Is there any way to accomplish it without removing the annotation?

Just remove the `@Component` annotation from your `EntityLoader`? You are manually creating the instances in XML (so no `@Component` necessary), and you are manually wiring in the session factory by calling the `setSessionFactory` method (so no `@Autowired` necessary). — David Lavender, Jun 22 '15 at 12:40
If I remove the annotations then I'll need to configure this bean in XML in all the other apps that uses it. My intention is precisely to avoid that. — Tobías, Jun 22 '15 at 12:51

Qianlong · Accepted Answer · 2015-06-22T13:23:53.417

If you are able to modify your lib which contains EntityLoader, following these 2 step will do the trip :

In EntityLoader make your @Autowired optional:

@Autowired(required=false)
In XML configuration, exclude mysqlSessionFactory and oracleSessionFactory beans from autowire candidates, add autowire-candidate="false" to each sessionFactory:

<bean id="mysqlSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean" autowire-candidate="false">
    <!-- ... config ... -->
</bean>
<bean id="oracleSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean" autowire-candidate="false">
    <!-- ... config ... -->
</bean>

Voilà!

Thanks! You are right! The key is `autowire-candidate = "false"` — Tobías, Jun 22 '15 at 13:23

score 0 · Answer 2 · answered Jun 22 '15 at 12:58

0

It's the component-scan that's causing problems. Your beans are already manually created, but Spring is trying to create another EntityLoader because the component scan is picking up your @Component annotation.

You can tell the component scan (for just your app) to ignore that class:

<context:component-scan ...>
    <context:exclude-filter expression="com\.demo\.EntityLoader" type="regex" />
</context:component-scan>

answered Jun 22 '15 at 12:58

David Lavender

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I'm already using the `exclude-filter` in `component-scan`. In any case, if I remove `@Component` but keep `@Autowired`, the problem persists. – Tobías Jun 22 '15 at 13:08
I think the problem is that spring autowires the property ignoring my xml configuration. As if the annotation has precedence over the xml. – Tobías Jun 22 '15 at 13:11

Override @Autowired property annotation with XML configuration

2 Answers2