CODEWITHSUNDEEP
javaspringdependency-injectionjava-6java-5
Sean Adkinson
Sean Adkinson

Reputation: 8605

Can I ignore BeanCreationException and inject null instead?

We have a situation where our Spring wires up some beans that include ActiveMQ classes built with Java 6. Our application runs on customer's servers, so we can't guarantee that they have Java 6 or later installed. If they happen to have Java 5, the application can't start because of BeanCreationExceptions with the classes that depend on ActiveMQ (root cause being a UnsupportedClassVersionError).

So my question is, is there any way to ignore a BeanCreationException and still start the application? I want to be able to display an error message saying that they need to install Java 6 or later, but since the application can't even start, I never have a chance to do this.

My hunch is that there is no way to do this, because Spring needs to be able to guarantee that my application is built properly after initialization, but I thought I would ask anyway. Any other suggestions for how to accomplish my end goal would also be helpful and appreciated.

We are using Spring 3.0.6

Thanks!

Upvotes: 9

Views: 5042

Answers (3)

skaffman
skaffman

Reputation: 403441

First off, any throwables that are a subclass of java.lang.Error are generally considered to be non-recoverable. So while it's possible to catch them, it's strongly discouraged:

An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. Most such errors are abnormal conditions.

However, if all you're going to do is display an error message, then you should be able to get away with it.

SO to get back to your question, I suggest creating an implementation of Spring's FactoryBean interface, which would try to load the ActiveMQ classes. If it works, then it can return the appropriate object from FactoryBean.getObject. If it fails (via a caught UnsupportedClassVersionError), then it can return either a null, or some other object representing that condition.

Upvotes: 0

Tomasz Nurkiewicz
Tomasz Nurkiewicz

Reputation: 340693

If you can upgrade to Spring 3.1 (stable), take advantage of Java configuration:

@Bean
public SomeBean public someBean() {
    if(isEverythingOkWithJavaVersion()) {
        return new CorrectBean();
    } else {
        return null;
    }
}

or:

@Bean
public SomeBean public someBean() {
    try {
        return new CorrectBean();
    } catch(UnsupportedClassVersionError e) {
        log.warn("", e);
        return null;
    }
}

In older versions of Spring FactoryBean might be used to implement the same logic. Instead of returning null you might also return some fake implementation that you can discover later and warn the user when the application tries to use it.

Upvotes: 4

Markus Kramer
Markus Kramer

Reputation: 411

You could create a factory bean and let it create the actual ActiveMQ bean. If it can't be initialized the factory could return a dummy/mock implementation so things don't break. Later you could ask the factory if everything went alright.

http://static.springsource.org/spring/docs/2.5.x/reference/beans.html#beans-factory-extension-factorybean

Upvotes: 0

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