DDevelopment & Design

Unable to instantiate default tuplizer

I wrote few hbm mappings for domain classes in my recent project, and I got exception like that:org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]Of course my first thought was googl…

I wrote few hbm mappings for domain classes in my recent project, and I got exception like that:

org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]

Of course my first thought was googling for it and I found interesting answers. Most commons causes of this exception are:

  • missing getters or setters, what’s more, even a typo or wrong letter case (like getParentproject instead of getParentProject when field in class and mapping file is defined as parentProject)
  • missing default constructor
  • missing dependency for javassist library
My files seemed to be correctly defined, so it had to be missing dependency.

To fix it I’ve added these lines to my pom.xml:

<dependency>
    <groupId>org.javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.18.0-GA</version>
</dependency>

Well, it shouldn’t be a surprise because in full stacktrafe from this error there is an entry:

java.lang.ClassNotFoundException: javassist.util.proxy.MethodFilter

What explicitly indicates where is the root of this problem ;)

(And BTW: in my recent project I’m stuck with quite old version of Hibernate – 3.6.3)

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DDevelopment & Design

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