DDevelopment & Design

Hibernate Envers with Grails 2.1.0

Our client requires that every entity in his Grails application has to be audited with detailed information: who and when did exactly what? It is a perfect opportunity to use Hibernate Envers! It turned out not as straightforward as I thought, so I wa…

Our client requires that every entity in his Grails application has to be audited with detailed information: who and when did exactly what? It is a perfect opportunity to use Hibernate Envers! It turned out not as straightforward as I thought, so I want to share my experience with you.

Introduction

I use latest release of Grails with version 2.1.0. I’ve created a sample application on github for you as an example – SpOOnman/enversdemo. All files and techniques mentioned here can be found inside it. If you have other experiences with Grails and Envers working together, please share in comments.

Grails Envers plugin

First I’ve searched for a Grails plugin. I’ve found one outdated on google code and a (more modern) on github. This plugin is created by Lucas Ward and it has great introductionary blog post by author. This is a great place to start.

Unfortunately Lucas Ward’s plugin supports Grails up 1.3.7 and it comes with outdated Envers version. I’ve searched through forks and I’ve found most up-to-date fork by Matija Folnovic: https://github.com/mfolnovic/grails-envers-plugin. It supports Grails 2.1 out of the box. Edit: Matija pointed out that credit should go to Jay Hogan and Damir Murat for their work on upgrading Envers plugin to Grails 2.

Matija’s plugin is not packaged nor published so you have to package it by yourself:

Copy grails-envers-0.3-SNAPSHOT.zip (and rename to envers-0.3-SNAPSHOT.zip) to your application’s lib diretory or publish to your company maven repository if you have one. Last step is to include a plugin in your BuildConfig.groovy:

Audit with Envers!

It’s really easy to audit all entities with Envers. All you have to do is to use @Audit annotation on entities. SpOOnman/enversdemo audits Hotels and Bookings:

Envers plugin comes with some handy methods. For example Hotel.findAllRevisions() returns list of previous revisions. Once again I recommend a great blog post by Lucas Ward with many examples.

Grails and transactions

Grails has some glitches working with Envers. Envers is closely tied to database transactions. This means that it runs its listeners at the transaction end, when session is flushed. This is not always the case in Grails and it’s the cause of some problems. You need to make some small modifications to your application to be sure that Envers works fine.

  • controllers – you need to annotate your controllers (or separate controller methods) with @Transactional and for every save you need to flush a session manually, e.g. save(flush: true). Otherwise Envers may not be notified.
  • services in Grails are transactional by default. However you mey explicitily set them with static transactional = true to be sure that this is not altered. I recommend to use session flushing on every save as well.
  • BootStrap.groovy script is not transactional. If you want Envers to audit your changes in this script you need to wrap your inserts with transactions. You can achieve it by using withTransaction closure. You need session flushing too. Take a look at SpOOnman/enversdemo BootStrap.groovy for an example.
  • integration tests wrap every test in a separate transaction that is rolled back at the end of a test, hence Envers won’t work here. You need to disable wrapped transactions with static transactional = false. Remember that your changes are commited to database. To fulfill a contract of an empty database for every test you need to take care of cleaning up a database manually. Here is my sample integration test.

Add User to revision entities

By default Envers comes with a DefaultRevisionEntity class and creates its instance for every change on audited instance. It keeps information about entity revision, date and modification type. It lacks information about a user that made a change. I want to extend it.

There is already a code inside a plugin (here and here) but it’s not packaged with a plugin itself. I guess it’s because it adds dependency to Spring Security. This not a problem for me since I already use Spring Security plugin already in my application. I decided to add missing classes inside my application.

First I need a domain class – UserRevisionEntity. New instance of this class is created for every revision saved by Envers. It is a simple domain class with some extra annotations:

Notice that I’ve made currentUser field nullable. There may be some actions that doesn’t require user to be logged in. Also, there is no user while executing BootStrap.groovy script.

Annotations @RevisionNumber and @RevisionTimestamp are required by Envers as described in documentation. @RevisionEntity annotation configures Envers to use non-default listener – SpringSecurityRevisionListener. It looks simple:

SpringSecurityRevisionListener’s newRevision method fills each UserRevisionEntity instances with currently logged User.

Configuration

Envers offers some configuration options listed on documentation page. Options can be set in persistence.xml. However in Grails there is no persistence.xml. You can add it (and Grails supports it), but I’ve found other way to configure properties. I use System.setProperties to configure Envers and I place it in grails-app/conf/spring/resources.groovy. This is an example to change Envers tables’ prefix and suffix:

Testing

Testing Envers makes sense only with Grails integration tests. As I’ve mentioned earlier you must disable transactions that wrap your tests in order for Envers listeners to work. Also make sure you use withTransaction, session flushing and you’ve marked your controllers as @Transactional. There rules all stand in integration tests too. Example integration test can look like this:

Summary

Hibernate Envers does a great job auditing my application. It is easy to use, despite all the small glitches I’ve mentioned here. Special thanks to plugin authors that package Envers library in a plugin that can be used out of the box. I really recommend it! It would be great to hear all your thoughts on Envers and Grails working together so I can improve this post for others too.

Update 12.04.2013

Lucas Ward has posted updaate entry on Grails Hibernate Envers plugin here: http://www.lucasward.net/2013/04/grails-envers-plugin-update.html. Thanks!

— Previous article

Numery masowo przenoszone do Play

Next article —

Indeksy na kolumnach z wartościami nullowymi cz. 1

You May Also Like
DDevelopment & Design

Spock basics

Spock (homepage) is like its authors say 'testing and specification framework'. Spock combines very elegant and natural syntax with the powerful capabilities. And what is most important it is easy to use.

One note at the very beginning: I assume that you are already familiar with principles of Test Driven Development and you know how to use testing framework like for example JUnit.

So how can I start?


Writing spock specifications is very easy. We need basic configuration of Spock and Groovy dependencies (if you are using mavenized project with Eclipse look to my previous post: Spock, Java and Maven). Once we have everything set up and running smooth we can write our first specs (spec or specification is equivalent for test class in other frameworks like JUnit of TestNG).

What is great with Spock is fact that we can use it to test both Groovy projects and pure Java projects or even mixed projects.


Let's go!


Every spec class must inherit from spock.lang.Specification class. Only then test runner will recognize it as test class and start tests. We will write few specs for this simple class: User class and few tests not connected with this particular class.

We start with defining our class:
import spock.lang.*

class UserSpec extends Specification {

}
Now we can proceed to defining test fixtures and test methods.

All activites we want to perform before each test method, are to be put in def setup() {...} method and everything we want to be run after each test should be put in def cleanup() {...} method (they are equivalents for JUnit methods with @Before and @After annotations).

It can look like this:
class UserSpec extends Specification {
    User user
    Document document

    def setup() {
        user = new User()
        document = DocumentTestFactory.createDocumentWithTitle("doc1")
    }

    def cleanup() {

    }
}
Of course we can use field initialization for instantiating test objects:
class UserSpec extends Specification {
    User user = new User()
    Document document = DocumentTestFactory.createDocumentWithTitle("doc1")

    def setup() {

    }

    def cleanup() {

    }
}

What is more readable or preferred? It is just a matter of taste because according to Spock docs behaviour is the same in these two cases.

It is worth mentioning that JUnit @BeforeClass/@AfterClass are also present in Spock as def setupSpec() {...} and def cleanupSpec() {...}. They will be runned before first test and after last test method.


First tests


In Spock every method in specification class, expect setup/cleanup, is treated by runner as a test method (unless you annotate it with @Ignore).

Very interesting feature of Spock and Groovy is ability to name methods with full sentences just like regular strings:
class UserSpec extends Specification {
    // ...

    def "should assign coment to user"() {
        // ...
    }
}
With such naming convention we can write real specification and include details about specified behaviour in method name, what is very convenient when reading test reports and analyzing errors.

Test method (also called feature method) is logically divided into few blocks, each with its own purpose. Blocks are defined like labels in Java (but they are transformed with Groovy AST transform features) and some of them must be put in code in specific order.

Most basic and common schema for Spock test is:
class UserSpec extends Specification {
    // ...

    def "should assign coment to user"() {
        given:
            // do initialization of test objects
        when:
            // perform actions to be tested
        then:
            // collect and analyze results
    }
}

But there are more blocks like:
  • setup
  • expect
  • where
  • cleanup
In next section I am going to describe each block shortly with little examples.

given block

This block is used to setup test objects and their state. It has to be first block in test and cannot be repeated. Below is little example how can it be used:
class UserSpec extends Specification {
    // ...

    def "should add project to user and mark user as project's owner"() {
        given:
            User user = new User()
            Project project = ProjectTestFactory.createProjectWithName("simple project")
        // ...
    }
}

In this code given block contains initialization of test objects and nothing more. We create simple user without any specified attributes and project with given name. In case when some of these objects could be reused in more feature methods, it could be worth putting initialization in setup method.

when and then blocks

When block contains action we want to test (Spock documentation calls it 'stimulus'). This block always occurs in pair with then block, where we are verifying response for satisfying certain conditions. Assume we have this simple test case:
class UserSpec extends Specification {
    // ...

    def "should assign user to comment when adding comment to user"() {
        given:
            User user = new User()
            Comment comment = new Comment()
        when:
            user.addComment(comment)
        then:
            comment.getUserWhoCreatedComment().equals(user)
    }

    // ...
}

In when block there is a call of tested method and nothing more. After we are sure our action was performed, we can check for desired conditions in then block.

Then block is very well structured and its every line is treated by Spock as boolean statement. That means, Spock expects that we write instructions containing comparisons and expressions returning true or false, so we can create then block with such statements:
user.getName() == "John"
user.getAge() == 40
!user.isEnabled()
Each of lines will be treated as single assertion and will be evaluated by Spock.

Sometimes we expect that our method throws an exception under given circumstances. We can write test for it with use of thrown method:
class CommentSpec extends Specification {
    def "should throw exception when adding null document to comment"() {
        given:
            Comment comment = new Comment()
        when:
            comment.setCommentedDocument(null)
        then:
            thrown(RuntimeException)
    }
}

In this test we want to make sure that passing incorrect parameters is correctly handled by tested method and that method throws an exception in response. In case you want to be certain that method does not throw particular exception, simply use notThrown method.


expect block

Expect block is primarily used when we do not want to separate when and then blocks because it is unnatural. It is especially useful for simple test (and according to TDD rules all test should be simple and short) with only one condition to check, like in this example (it is simple but should show the idea):
def "should create user with given name"() {
    given:
        User user = UserTestFactory.createUser("john doe")
    expect:
        user.getName() == "john doe"
}



More blocks!


That were very simple tests with standard Spock test layout and canonical divide into given/when/then parts. But Spock offers more possibilities in writing tests and provides more blocks.


setup/cleanup blocks

These two blocks have the very same functionality as the def setup and def cleanup methods in specification. They allow to perform some actions before test and after test. But unlike these methods (which are shared between all tests) blocks work only in methods they are defined in. 


where - easy way to create readable parameterized tests

Very often when we create unit tests there is a need to "feed" them with sample data to test various cases and border values. With Spock this task is very easy and straighforward. To provide test data to feature method, we need to use where block. Let's take a look at little the piece of code:

def "should successfully validate emails with valid syntax"() {
    expect:
        emailValidator.validate(email) == true
    where:
        email }

In this example, Spock creates variable called email which is used when calling method being tested. Internally feature method is called once, but framework iterates over given values and calls expect/when block as many times as there are values (however, if we use @Unroll annotation Spock can create separate run for each of given values, more about it in one of next examples).

Now, lets assume that we want our feature method to test both successful and failure validations. To achieve that goal we can create few parameterized variables for both input parameter and expected result. Here is a little example:

def "should perform validation of email addresses"() {
    expect:
        emailValidator.validate(email) == result
    where:
        email         result }
Well, it looks nice, but Spock can do much better. It offers tabular format of defining parameters for test what is much more readable and natural. Lets take a look:
def "should perform validation of email addresses"() {
    expect:
        emailValidator.validate(email) == result
    where:
        email           | result
        "WTF"           | false
        "@domain"       | false
        "foo@bar.com"   | true
        "a@test"        | false
}
In this code, each column of our "table" is treated as a separate variable and rows are values for subsequent test iterations.

Another useful feature of Spock during parameterizing test is its ability to "unroll" each parameterized test. Feature method from previous example could be defined as (the body stays the same, so I do not repeat it):
@Unroll("should validate email #email")
def "should perform validation of email addresses"() {
    // ...
}
With that annotation, Spock generate few methods each with its own name and run them separately. We can use symbols from where blocks in @Unroll argument by preceding it with '#' sign what is a signal to Spock to use it in generated method name.


What next?


Well, that was just quick and short journey  through Spock and its capabilities. However, with that basic tutorial you are ready to write many unit tests. In one of my future posts I am going to describe more features of Spock focusing especially on its mocking abilities.