DDevelopment & Design

Beautiful Failures at 33rd Degree

33rd in Kraków, is rolling baby.Tomorrow, together with Maciek Próchniak, we are giving a talk about failures. There is a problem with failures withing our culture, and by our, I mean central and eastern Europe. In San Fransisco, there are regular meetings, called Mobile Monday, where speakers start by saying how many start ups they have failed, and it’s been seen as a their reference to wisdom. At the very end, they’ve learned a lot from all this failures. And it’s not limited only to San Francisco or Mobile Monday. It’s their culture, every failure gets you smarter. In US it’s OK to fail. Have you heard a story about a Japanese train controller that committed suicide, when two trains in a row have been late because of his mistakes? The Europe may not be that extreme, but it’s still at least inappropriate to admit, that you ever made a mistake. If we never admit, if we never reflect, we never learn. So we are changing the rules for an hour. There is nothing good or bad without a context, and we would like to share the circumstances under which things don’t work. Things like:

  • shared responsibility
  • self organized teams
  • gamification
  • open source
  • metaprogramming
  • ‘enterprise’ technologies

See yoy there.

Solution Architect @ TouK

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DDevelopment & Design

Me on Hadoop on Parleys

Finally I've managed to import my WarJUG presentation to parleys.com. See for yourself :) If you've got problems with opening the parleys' version try the ones uploaded to youtube. Here is part 1: And here is part 2: Finally I've managed to import my WarJUG presentation to parleys.com. See for yourself :) If you've got problems with opening the parleys' version try the ones uploaded to youtube. Here is part 1: And here is part 2:
DDevelopment & Design

Atom Feeds with Spring MVC

How to add feeds (Atom) to your web application with just two classes?
How about Spring MVC?

Here are my assumptions:
  • you are using Spring framework
  • you have some entity, say “News”, that you want to publish in your feeds
  • your "News" entity has creationDate, title, and shortDescription
  • you have some repository/dao, say "NewsRepository", that will return the news from your database
  • you want to write as little as possible
  • you don't want to format Atom (xml) by hand
You actually do NOT need to use Spring MVC in your application already. If you do, skip to step 3.


Step 1: add Spring MVC dependency to your application
With maven that will be: 
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>3.1.0.RELEASE</version>
</dependency>

Step 2: add Spring MVC DispatcherServlet
With web.xml that would be: 
<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-mvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/feed</url-pattern>
</servlet-mapping>
Notice, I set the url-pattern to “/feed” which means I don't want Spring MVC to handle any other urls in my app (I'm using a different web framework for the rest of the app). I also give it a brand new contextConfigLocation, where only the mvc configuration is kept.

Remember that, when you add a DispatcherServlet to an app that already has Spring (from ContextLoaderListener for example), your context is inherited from the global one, so you should not create beans that exist there again, or include xml that defines them. Watch out for Spring context getting up twice, and refer to spring or servlet documentation to understand what's happaning.

Step 3. add ROME – a library to handle Atom format
With maven that is: 
<dependency>
    <groupId>net.java.dev.rome</groupId>
    <artifactId>rome</artifactId>
    <version>1.0.0</version>
</dependency>

Step 4. write your very simple controller 
@Controller
public class FeedController {
    static final String LAST_UPDATE_VIEW_KEY = "lastUpdate";
    static final String NEWS_VIEW_KEY = "news";
    private NewsRepository newsRepository;
    private String viewName;

    protected FeedController() {} //required by cglib

    public FeedController(NewsRepository newsRepository, String viewName) {
        notNull(newsRepository); hasText(viewName);
        this.newsRepository = newsRepository;
        this.viewName = viewName;
    }

    @RequestMapping(value = "/feed", method = RequestMethod.GET)        
    @Transactional
    public ModelAndView feed() {
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName(viewName);
        List<News> news = newsRepository.fetchPublished();
        modelAndView.addObject(NEWS_VIEW_KEY, news);
        modelAndView.addObject(LAST_UPDATE_VIEW_KEY, getCreationDateOfTheLast(news));
        return modelAndView;
    }

    private Date getCreationDateOfTheLast(List<News> news) {
        if(news.size() > 0) {
            return news.get(0).getCreationDate();
        }
        return new Date(0);
    }
}
And here's a test for it, in case you want to copy&paste (who doesn't?):
@RunWith(MockitoJUnitRunner.class)
public class FeedControllerShould {
    @Mock private NewsRepository newsRepository;
    private Date FORMER_ENTRY_CREATION_DATE = new Date(1);
    private Date LATTER_ENTRY_CREATION_DATE = new Date(2);
    private ArrayList<News> newsList;
    private FeedController feedController;

    @Before
    public void prepareNewsList() {
        News news1 = new News().title("title1").creationDate(FORMER_ENTRY_CREATION_DATE);
        News news2 = new News().title("title2").creationDate(LATTER_ENTRY_CREATION_DATE);
        newsList = newArrayList(news2, news1);
    }

    @Before
    public void prepareFeedController() {
        feedController = new FeedController(newsRepository, "viewName");
    }

    @Test
    public void returnViewWithNews() {
        //given
        given(newsRepository.fetchPublished()).willReturn(newsList);
        
        //when
        ModelAndView modelAndView = feedController.feed();
        
        //then
        assertThat(modelAndView.getModel())
                .includes(entry(FeedController.NEWS_VIEW_KEY, newsList));
    }

    @Test
    public void returnViewWithLastUpdateTime() {
        //given
        given(newsRepository.fetchPublished()).willReturn(newsList);

        //when
        ModelAndView modelAndView = feedController.feed();

        //then
        assertThat(modelAndView.getModel())
                .includes(entry(FeedController.LAST_UPDATE_VIEW_KEY, LATTER_ENTRY_CREATION_DATE));
    }

    @Test
    public void returnTheBeginningOfTimeAsLastUpdateInViewWhenListIsEmpty() {
        //given
        given(newsRepository.fetchPublished()).willReturn(new ArrayList<News>());

        //when
        ModelAndView modelAndView = feedController.feed();

        //then
        assertThat(modelAndView.getModel())
                .includes(entry(FeedController.LAST_UPDATE_VIEW_KEY, new Date(0)));
    }
}
Notice: here, I'm using fest-assert and mockito. The dependencies are: 
<dependency>
 <groupId>org.easytesting</groupId>
 <artifactId>fest-assert</artifactId>
 <version>1.4</version>
 <scope>test</scope>
</dependency>
<dependency>
 <groupId>org.mockito</groupId>
 <artifactId>mockito-all</artifactId>
 <version>1.8.5</version>
 <scope>test</scope>
</dependency>

Step 5. write your very simple view
Here's where all the magic formatting happens. Be sure to take a look at all the methods of Entry class, as there is quite a lot you may want to use/fill.
import org.springframework.web.servlet.view.feed.AbstractAtomFeedView;
[...]

public class AtomFeedView extends AbstractAtomFeedView {
    private String feedId = "tag:yourFantastiSiteName";
    private String title = "yourFantastiSiteName: news";
    private String newsAbsoluteUrl = "http://yourfanstasticsiteUrl.com/news/"; 

    @Override
    protected void buildFeedMetadata(Map<String, Object> model, Feed feed, HttpServletRequest request) {
        feed.setId(feedId);
        feed.setTitle(title);
        setUpdatedIfNeeded(model, feed);
    }

    private void setUpdatedIfNeeded(Map<String, Object> model, Feed feed) {
        @SuppressWarnings("unchecked")
        Date lastUpdate = (Date)model.get(FeedController.LAST_UPDATE_VIEW_KEY);
        if (feed.getUpdated() == null || lastUpdate != null || lastUpdate.compareTo(feed.getUpdated()) > 0) {
            feed.setUpdated(lastUpdate);
        }
    }

    @Override
    protected List<Entry> buildFeedEntries(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
        @SuppressWarnings("unchecked")
        List<News> newsList = (List<News>)model.get(FeedController.NEWS_VIEW_KEY);
        List<Entry> entries = new ArrayList<Entry>();
        for (News news : newsList) {
            addEntry(entries, news);
        }
        return entries;
    }

    private void addEntry(List<Entry> entries, News news) {
        Entry entry = new Entry();
        entry.setId(feedId + ", " + news.getId());
        entry.setTitle(news.getTitle());
        entry.setUpdated(news.getCreationDate());
        entry = setSummary(news, entry);
        entry = setLink(news, entry);
        entries.add(entry);
    }

    private Entry setSummary(News news, Entry entry) {
        Content summary = new Content();
        summary.setValue(news.getShortDescription());
        entry.setSummary(summary);
        return entry;
    }

    private Entry setLink(News news, Entry entry) {
        Link link = new Link();
        link.setType("text/html");
        link.setHref(newsAbsoluteUrl + news.getId()); //because I have a different controller to show news at http://yourfanstasticsiteUrl.com/news/ID
        entry.setAlternateLinks(newArrayList(link));
        return entry;
    }

}

Step 6. add your classes to your Spring context
I'm using xml approach. because I'm old and I love xml. No, seriously, I use xml because I may want to declare FeedController a few times with different views (RSS 1.0, RSS 2.0, etc.).

So this is the forementioned spring-mvc.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
        <property name="mediaTypes">
            <map>
                <entry key="atom" value="application/atom+xml"/>
                <entry key="html" value="text/html"/>
            </map>
        </property>
        <property name="viewResolvers">
            <list>
                <bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/>
            </list>
        </property>
    </bean>

    <bean class="eu.margiel.pages.confitura.feed.FeedController">
        <constructor-arg index="0" ref="newsRepository"/>
        <constructor-arg index="1" value="atomFeedView"/>
    </bean>

    <bean id="atomFeedView" class="eu.margiel.pages.confitura.feed.AtomFeedView"/>
</beans>

And you are done.

I've been asked a few times before to put all the working code in some public repo, so this time it's the other way around. I've describe things that I had already published, and you can grab the commit from the bitbucket.

Hope that helps.
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.