Spring Hibernate: reload entity mappings

Question

on a web application we use Spring 3.2 and Hibernate 4.1.1 and implement a plugin-like architecture. Plugins can be added and removed on runtime. For each module we defined a separate class loader and create separate child application context on spring. Complete configuration is done using annotations, no XML config for the beans anymore.

Spring Hibernate configuration class

@Configuration
@EnableTransactionManagement
public class HibernateConfigurationFactory {

@Bean
public JndiObjectFactoryBean dataSource() {
    JndiObjectFactoryBean ds = new JndiObjectFactoryBean();
    ds.setJndiName("java:jboss/datasources/OurOwnDS");
    ds.setResourceRef(true);
    return ds;
}

@Bean
public LocalSessionFactoryBean sessionFactory() {
    LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
    sessionFactory.setPackagesToScan("com.foo.bar");
    sessionFactory.setDataSource((DataSource) dataSource().getObject());

    Properties hibernateProperties = new Properties();
    hibernateProperties.put("hibernate.hbm2ddl.auto", "update");

    sessionFactory.setHibernateProperties(hibernateProperties);

    return sessionFactory;
}

@Bean
public HibernateTransactionManager transactionManager() {
    HibernateTransactionManager transactionManager = new HibernateTransactionManager();
    transactionManager.setSessionFactory(sessionFactory().getObject());
    return transactionManager;
}

}

Now the problem: Some plugins contain their own entity (+DAO) classes which are added with the module during runtime.

Is it possible to create some kind of separate context on hibernate (as we do it on spring) or even add/reload the additional entity classes?

Will reloading the EntityManager fit my needs? But what will happen to already loaded entities in the context?

Thanks for any help and comment in advance.

Update: Actually i did the following and solved the issue (but ran into an other issue.. later on).

I create a new DataSource + SessionFactory + TransactionManager for each module/context and insert them to the new child ApplicationContext. Now i use the class loader to scann for all annotated classes and register them manually on the application context and the session factory by using

LocalSessionFactorybean#setAnnotatedClasses(...)

This works quite well... but...

Next Problem: I get a ClassNotFoundException which seems to be a class loader issue. Hibernate uses the system class loader instead of my own pluginClassloader.

Does someone know how to inject own class loader to Hibernate?

Ori Dar · Accepted Answer · 2014-03-11 16:51:28Z

2

Is it feasible to inject Environment and use it as an extra source for Hibernate resources?

@Configuration
@EnableTransactionManagement
public class HibernateConfigurationFactory {

    @Autowired
    Environment env;

    @Bean 
    public LocalSessionFactoryBean sessionFactory() {
        LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
        sessionFactory.setPackagesToScan("com.foo.bar");
        if (env.containsProperty("some.extra.classes.property") {
            sessionFactory.setAnnotatedClasses(some extrapolation here);
            // Or similarly add extra packages for scanning
            ...
        }
    }
}

As for the extra DAO beans, you can use @Profile for that, or - if using Spring 4 - use @Conditional.

EDIT

The Environment is not something you create, it's "there for you" . It's basically a container for Property Source and Profile sets.

A Good reference point is Spring reference documentation, the IoC container chapter. Also you can look at the SpringSource blog. There are few good article by Chris Beams, related to Spring 3.1, but most of the stuff is there.

As an example, you can use something as bellow to bootstrap a child application context:

AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
ConfigurableEnvironment environment = context.getEnvironment();

// this is how you set different properties per a sub context. 
Map subContextMap = new HashMap();
subContextMap.put("some.extra.classes.property", [unique value here]);
environment.getPropertySources().addFirst(new MapPropertySource("SUB_CTX_MAP", subContextMap);

// this is the generic configuration class(es).
context.register(HibernateConfigurationFactory.class);

context.refresh();

edited Mar 11, 2014 at 16:51

answered Mar 11, 2014 at 11:01

Ori Dar

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5 Comments

NeoP5 Over a year ago

Thanks for the reply, it seems that this code posted above is used during application startup (where i don't know the classes yet). I need something that i can fire / add packages manually when the application is already up. But i will check on how to include this.

NeoP5 Over a year ago

Would it be possible to create a new / reload environment?

Ori Dar Over a year ago

If you use separate Contexts (one per module), then each context has it's own Environment object, with different PropertySource attached to it where you can set a different value to the same property if desired.

NeoP5 Over a year ago

Ah nice :) This is a good hint. Currently the context i create for each module are child contexts of the parent global application context. I will try to define a new Environment object for this when creating the context. Do you have some example code on how to archive this?

Ori Dar Over a year ago

@NeoP5, will edit my response to answer your question

Paul · Accepted Answer · 2016-04-22 08:25:07Z

just an update if someone needs to have a similar solution.

I fixed this situation by doing the following:

creation of a new ApplicationContext with the current root context as parent
introducing new class loader to the context and an own Resource-Loader

programmatically i create a new session-factory and transaction-manager to the new context

    // create the datasource bean
    BeanDefinitionBuilder dataSourceBeanBuilder = BeanDefinitionBuilder.rootBeanDefinition(DataSourceConfiguration.class, "createDataSource");
    dataSourceBeanBuilder.addConstructorArgValue(descriptor.getDataSourceDescriptor().getJNDILookupName());
    dataSourceBeanBuilder.addConstructorArgValue(descriptor.getDataSourceDescriptor().isResourceRef());
    moduleContext.registerBeanDefinition("dataSource", dataSourceBeanBuilder.getBeanDefinition());

    // now build the sessionFactor
    BeanDefinitionBuilder sessionFactoryBeanBuilder = BeanDefinitionBuilder.rootBeanDefinition(SessionFactoryFactory.class, "createSessionFactory");
    sessionFactoryBeanBuilder.addConstructorArgReference("dataSource");
    sessionFactoryBeanBuilder.addConstructorArgValue(module.getKey());
    sessionFactoryBeanBuilder.addConstructorArgValue(moduleContext.getModuleResourceLoader());
    sessionFactoryBeanBuilder.addConstructorArgValue(annotatedClasses);
    moduleContext.registerBeanDefinition("sessionFactory", sessionFactoryBeanBuilder.getBeanDefinition());

    // now build the transactionManager
    BeanDefinitionBuilder transactionManagerBeanBuilder = BeanDefinitionBuilder.rootBeanDefinition(HibernateConfigurationFactory.class, "createTransactionManager");
    transactionManagerBeanBuilder.addConstructorArgReference("sessionFactory");
    moduleContext.registerBeanDefinition("transactionManager", transactionManagerBeanBuilder.getBeanDefinition());

call context.refresh() to load and init all entities
call context.start() to start the new context

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