DDevelopment & Design

Writing JAXB in Groovy

Suppose you want write a jaxb class in groovy. Why? Because you do not have to write these all getters, setters and other methods. You only have to write your fields down.@XmlRootElement@HashCodeAndEquals@ToStringclass Person { String firstName String …

Suppose you want write a jaxb class in groovy. Why? Because you do not have to write these all getters, setters and other methods. You only have to write your fields down.

@XmlRootElement 
@HashCodeAndEquals 
@ToString 
class Person {
    String firstName String lastName Integer age
}

 

Lets check if we could unmarshal xml to Person class:

def 'should unmarshall person xml to object'(){
    given:
        JAXBContext jc = JAXBContext.newInstance(Person)
        String xml = 'JohnSmith20' 
    expect:
        jc.createUnmarshaller().unmarshal(new StringReader(xml)) == new Person(firstName: 'John', lastName: 'Smith', age: 20)
}

 

When we try this, then we obtain an eception:

com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
groovy.lang.MetaClass is an interface, and JAXB can't handle interfaces.
 this problem is related to the following location:
  at groovy.lang.MetaClass
  at public groovy.lang.MetaClass com.blogspot.przybyszd.jaxbingroovy.Person.getMetaClass()
  at com.blogspot.przybyszd.jaxbingroovy.Person

 at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:445)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.(JAXBContextImpl.java:277)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.(JAXBContextImpl.java:124)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
 at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
 at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
 at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
 at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
 at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
 at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
 at com.blogspot.przybyszd.jaxbingroovy.PersonJaxbTest.should unmarshall person xml to object(PersonJaxbTest.groovy:10)

It is because groovy defines getMetaClass method for us. Marshaller and Unmarshaller use by default

XmlAccessType.PUBLIC_MEMBER what means that public getters and setters should be used during marshalling/unmarshalling. To solve this just add XmlAccessorType annotatnio with XmlAccessType.FIELD on jaxb class:

@XmlRootElement @EqualsAndHashCode @XmlAccessorType(XmlAccessType.FIELD) class Person {
    String firstName String lastName Integer age
}

 

Of course if you want to apply this rule for each jaxb class in package, then you could put XmlAccessorType in pacakge-info.java file.

@XmlAccessorType(XmlAccessType.FIELD) package com.blogspot.przybyszd.jaxbingroovy;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;

 

Great, it works. Now let’s check out marshaller:

def 'should marshall person'() {
    given:
        JAXBContext jc = JAXBContext.newInstance(Person)
        Person p = new Person(firstName: 'John', lastName: 'Smith', age: 20)
        StringWriter sw = new StringWriter()
    when:
        jc.createMarshaller().marshal(p, sw)
    then:
        String xml = sw.toString()
        GPathResult gPathResult = new XmlSlurper().parseText(xml)
        gPathResult.name() == 'person'
        gPathResult.firstName == 'John'
        gPathResult.lastName == 'Smith'
        gPathResult.age == '20'
}

 

And it also works. Source is available here.

— Previous article

Restart or power off Rasperry PI with REST call

Next article —

Groovy, Callable and ExecutorService

You May Also Like
DDevelopment & Design

Spock, Java and Maven

Few months ago I've came across Groovy - powerful language for JVM platform which combines the power of Java with abilities typical for scripting languages (dynamic typing, metaprogramming).

Together with Groovy I've discovered spock framework (https://code.google.com/p/spock/) - specification framework for Groovy (of course you can test Java classes too!). But spock is not only test/specification framework - it also contains powerful mocking tools.

Even though spock is dedicated for Groovy there is no problem with using it for Java classes tests. In this post I'm going to describe how to configure Maven project to build and run spock specifications together with traditional JUnit tests.


Firstly, we need to prepare pom.xml and add necessary dependencies and plugins.

Two obligatory libraries are:
<dependency>
    <groupid>org.spockframework</groupId>
    <artifactid>spock-core</artifactId>
    <version>0.7-groovy-2.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupid>org.codehaus.groovy</groupId>
    <artifactid>groovy-all</artifactId>
    <version>${groovy.version}</version>
    <scope>test</scope>
</dependency>
Where groovy.version is property defined in pom.xml for more convenient use and easy version change, just like this: 
<properties>
    <gmaven-plugin.version>1.4</gmaven-plugin.version>
    <groovy.version>2.1.5</groovy.version>
</properties>

I've added property for gmaven-plugin version for the same reason ;)

Besides these two dependencies, we can use few additional ones providing extra functionality:
  • cglib - for class mocking
  • objenesis - enables mocking classes without default constructor
To add them to the project put these lines in <dependencies> section of pom.xml:
<dependency>
    <groupid>cglib</groupId>
    <artifactid>cglib-nodep</artifactId>
    <version>3.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupid>org.objenesis</groupId>
    <artifactid>objenesis</artifactId>
    <version>1.3</version>
    <scope>test</scope>
</dependency>

And that's all for dependencies section. Now we will focus on plugins necessary to compile Groovy classes. We need to add gmaven-plugin with gmaven-runtime-2.0 dependency in plugins section:
<plugin>
    <groupid>org.codehaus.gmaven</groupId>
    <artifactid>gmaven-plugin</artifactId>
    <version>${gmaven-plugin.version}</version>
    <configuration>
        <providerselection>2.0</providerSelection>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>compile</goal>
                <goal>testCompile</goal>
            </goals>
        </execution>
    </executions>
    <dependencies>
        <dependency>
            <groupid>org.codehaus.gmaven.runtime</groupId>
            <artifactid>gmaven-runtime-2.0</artifactId>
            <version>${gmaven-plugin.version}</version>
            <exclusions>
                <exclusion>
                    <groupid>org.codehaus.groovy</groupId>
                    <artifactid>groovy-all</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupid>org.codehaus.groovy</groupId>
            <artifactid>groovy-all</artifactId>
            <version>${groovy.version}</version>
        </dependency>
    </dependencies>
</plugin>

With these configuration we can use spock and write our first specifications. But there is one issue: default settings for maven-surefire plugin demand that test classes must end with "..Test" postfix, which is ok when we want to use such naming scheme for our spock tests. But if we want to name them like CommentSpec.groovy or whatever with "..Spec" ending (what in my opinion is much more readable) we need to make little change in surefire plugin configuration:
<plugin>
    <groupid>org.apache.maven.plugins</groupId>
    <artifactid>maven-surefire-plugin</artifactId>
    <version>2.15</version>
    <configuration>
        <includes>
            <include>**/*Test.java</include>
            <include>**/*Spec.java</include>
        </includes>
    </configuration>
</plugin>

As you can see there is a little trick ;) We add include directive for standard Java JUnit test ending with "..Test" postfix, but there is also an entry for spock test ending with "..Spec". And there is a trick: we must write "**/*Spec.java", not "**/*Spec.groovy", otherwise Maven will not run spock tests (which is strange and I've spent some time to figure out why Maven can't run my specs).

Little update: instead of "*.java" postfix for both types of tests we can write "*.class" what is in my opinion more readable and clean:
<include>**/*Test.class</include>
<include>**/*Spec.class</include>
(thanks to Tomek Pęksa for pointing this out!)

With such configuration, we can write either traditional JUnit test and put them in src/test/java directory or groovy spock specifications and place them in src/test/groovy. And both will work together just fine :) In one of my next posts I'll write something about using spock and its mocking abilities in practice, so stay in tune.

DDevelopment & Design

Drawing arrows in JavaFX

Some time in the past, I was wondering what's the easiest solution for drawing arrowconnections between shapes. The problem boils down to computing boundary point for given shape, which intersects with connecting line. The solution is not so difficult ...Some time in the past, I was wondering what's the easiest solution for drawing arrowconnections between shapes. The problem boils down to computing boundary point for given shape, which intersects with connecting line. The solution is not so difficult ...
DDevelopment & Design

TouK na targach pracyTouK at the job fair

Zapraszamy na XI Targi Pracy i Praktyk dla Elektroników i Informatyków. Odwiedź nasze stoisko w dniach 4-5 marca w godz. 9:30-15:30. Politechnika Warszawska Pierwsze piętro budynku Wydziału Elektroniki i Techniki Informacyjnych Nowowiejska 15/19We invite you to 11th Job and Internship Fair for Electronic Engineers and IT Specialists. Come and visit our stand between 4-5 March 9:30 am and 15 :30 pm Warsaw University of Technology the first floor of the Electronics faculty building Nowowiejska 15/19