DDevelopment & Design

Using GORM standalone

Few days ago we decided to get rid of Apache iBatis in one of our projects. We couldn’t longer maintain large XML mapping and query descriptors with mix of Java, SQL and XML itself. But we also wanted to avoid switching to another ORM framework with lot of features and DAO layer requirement. We tried to implement some simple Spring JdbcTemplate-based ORM in Groovy, but it (strangely) started to look just like Hibernate… All that aliases in generated SQL’s, need to use javax.presistence annotations etc. The only simple existing solutions were Groovy’s DataSet (which is not working outside Groovy script) and GORM. Googling ‘GORM standalone’ show just few useful, but rather outdated, results. So I was forced to spend couple of hours to write desired 6 lines of code:

ExpandoMetaClass.enableGlobally()
        SessionFactory sessionFactory = ctx.getBean("sessionFactory")
        def grailsApp = new DefaultGrailsApplication([Customer.class] as Class[], null)
        grailsApp.initialise()
        GrailsHibernateUtil.configureHibernateDomainClasses(sessionFactory, grailsApp)
        HibernatePluginSupport.enhanceSessionFactory(sessionFactory, grailsApp, ctx)

And after annotating Customer class:

@Entity
@Table(name = "CUSTOMERS")
class Customer {
    String firstName
    String lastName
}

Now we are able to enjoy DAO-less code in pure Groovy:

Customer.findAll().each{ println it.firstName }         
        Customer.withCriteria { eq('lastName', 'Smith') }.each { Customer c -> println c.firstName }
        Customer.findByFirstNameAndLastName('John', 'Smith')

PS. For unknown reasons, these 6 lines work only with Grails 1.1.x

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Grails render as JSON catch

One of a reasons your controller doesn't render a proper response in JSON format might be wrong package name that you use. It is easy to overlook. Import are on top of a file, you look at your code and everything seems to be fine. Except response is still not in JSON format.

Consider this simple controller:

class RestJsonCatchController {
def grailsJson() {
render([first: 'foo', second: 5] as grails.converters.JSON)
    }

def netSfJson() {
render([first: 'foo', second: 5] as net.sf.json.JSON)
    }
}

And now, with finger crossed... We have a winner!

$ curl localhost:8080/example/restJsonCatch/grailsJson
{"first":"foo","second":5}
$ curl localhost:8080/example/restJsonCatch/netSfJson
{first=foo, second=5}

As you can see only grails.converters.JSON converts your response to JSON format. There is no such converter for net.sf.json.JSON, so Grails has no converter to apply and it renders Map normally.

Conclusion: always carefully look at your imports if you're working with JSON in Grails!

Edit: Burt suggested that this is a bug. I've submitted JIRA issue here: GRAILS-9622 render as class that is not a codec should throw exception