Hibernate utility for "Grails + Hibernate" application

This is a simple Grails plugin to provide some common utility classes & methods which is used in almost all applications.

Support Grails

Only Grails 4+ applications are supported.

Installation

Add the following to build.gradle file of your Grails 3 application

Under repositories section

maven { url 'https://jitpack.io' }

Under dependencies section

compile "com.wizpanda:kernel-hibernate:0.0.1"       // Use whatever is the latest version

API Uses

Provide a 24 character unique id using CustomIdDomain

By default, Grails domain uses the auto-increment Long id in every domain classes. This id is not secure for many scenarios as it is guessable. An alternative to this approach is to use Hibernate's UUID generator-

static mapping = {
    id generator: "uuid", length: 32
}

The problem here is that the length of the id is quite long i.e. 32 characters. So you can use CustomIdDomain here. To use this, just extend this class to your domain class and remove any String id property & it's mapping (if added)-

package com.wizpanda.user

import com.wizpanda.kernel.hibernate.id.CustomIdDomain

class User extends CustomIdDomain {

    // Note- If there is no mapping defined, make sure to add an empty mapping block as defined below
    static mapping = {
    }

    String email
    String firstName
}

HibernateSessionUtils

This is a utility class to provide some methods. For example, you can use HibernateSessionUtils.flushAndClear() when bulk importing some Grails domain records to prevent the servers from getting out of memory. For example, the below code creates 1 Million domain records in bulk. After a certain number of records, your server will end-up with no memory left because Grails caches those records until the session is flushed.

To prevent that, we added a check which will flush & clear the Hibernate's current session-

(1..1000000).eachWithIndex { int number, int index ->
    
    User user = new User(name: "John Doe", email: "john${number}@example.com")
    user.save()

    if (index % 1000 == 0) {
        HibernateSessionUtils.instance.flushAndClear()
    }
}