For my Java application I am trying to use ScalaCheck to write some property-based unit tests. For that purpose I need generators, but all the tutorials I can find use a constructor with parameters to generate objects.
The object I need to generate does not have constructor parameters, and I cannot add such a constructor since it is from an external library.
I now have the following (JwtClaims is from the package org.jose4j.jwt):
def genClaims: Gen[JwtClaims] = {
val url = arbString
val username = arbString
val claims = new JwtClaims()
claims.setNotBeforeMinutesInThePast(0)
claims.setExpirationTimeMinutesInTheFuture(60)
claims.setSubject(username) // error about Gen[String] not matching type String
claims
}
Any suggestions on how to write my generator? I have zero knowledge of Scala, so please be patient if I've made an 'obvious' mistake :) My expertise is in Java, and testing using ScalaCheck is my first venture into Scala.
You need to be returning a generator of a claims object, not a claims object. The generator is effectively a function that can return a claims object. The normal way I go about this is with a for comprehension (other people prefer flatMap, but I think this reads more clearly).
def genClaims: Gen[JwtClaims] = {
for {
url <- arbitrary[String]
username <- arbitrary[String]
} yield {
val claims = new JwtClaims()
claims.setNotBeforeMinutesInThePast(0)
claims.setExpirationTimeMinutesInTheFuture(60)
claims.setSubject(username)
claims
}
}
Related
I am new to OWL 2, and I want to parse a ".ttl" file with OWL API, but I found that OWL API is not same as the API I used before. It seems that I should write a "visitor" if I want to get the content within a OWLAxiom or OWLEntity, and so on. I have read some tutorials, but I didn't get the proper way to do it. Also, I found the tutorials searched were use older version of owl api. So I want a detailed example to parse a instance, and store the content to a Java class.
I have made some attempts, my codes are as follows, but I don't know to go on.
OWLOntologyManager manager = OWLManager.createOWLOntologyManager();
File file = new File("./source.ttl");
OWLOntology localAcademic = manager.loadOntologyFromOntologyDocument(file);
Stream<OWLNamedIndividual> namedIndividualStream = localAcademic.individualsInSignature();
Iterator<OWLNamedIndividual> iterator = namedIndividualStream.iterator();
while (iterator.hasNext()) {
OWLNamedIndividual namedIndividual = iterator.next();
}
Instance for example are as follows. Specially, I want store the "#en" in the object of "ecrm:P3_has_note".
<http://data.doremus.org/performance/4db95574-8497-3f30-ad1e-f6f65ed6c896>
a mus:M42_Performed_Expression_Creation ;
ecrm:P3_has_note "Créée par Teodoro Anzellotti, son commanditaire, en novembre 1995 à Rotterdam"#en ;
ecrm:P4_has_time-span <http://data.doremus.org/performance/4db95574-8497-3f30-ad1e-f6f65ed6c896/time> ;
ecrm:P9_consists_of [ a mus:M28_Individual_Performance ;
ecrm:P14_carried_out_by "Teodoro Anzellotti"
] ;
ecrm:P9_consists_of [ a mus:M28_Individual_Performance ;
ecrm:P14_carried_out_by "à Rotterdam"
] ;
efrbroo:R17_created <http://data.doremus.org/expression/2fdd40f3-f67c-30a0-bb03-f27e69b9f07f> ;
efrbroo:R19_created_a_realisation_of
<http://data.doremus.org/work/907de583-5247-346a-9c19-e184823c9fd6> ;
efrbroo:R25_performed <http://data.doremus.org/expression/b4bb1588-dd83-3915-ab55-b8b70b0131b5> .
The contents I want are as follows:
class Instance{
String subject;
Map<String, Set<Object>> predicateToObject = new HashMap<String,Set<Object>>();
}
class Object{
String value;
String type;
String language = null;
}
The version of owlapi I am using is 5.1.0. I download the jar and the doc from there. I just want to know how to get the content I need in the java class.
If there are some tutorials that describe the way to do it, please tell me.
Thanks a lot.
Update: I have known how to do it, when I finish it, I will write an answer, I hope it can help latecomers of OWLAPI.
Thanks again.
What you need, once you have the individual, is to retrieve the data property assertion axioms and collect the literals asserted for each property.
So, in the for loop in your code:
// Let's rename your Object class to Literal so we don't get confused with java.lang.Object
Instance instance = new Instance();
localAcademic.dataPropertyAssertionAxioms()
.forEach(ax -> instance.predicateToObject.put(
ax.getProperty().getIRI().toString(),
Collections.singleton(new Literal(ax.getObject))));
This code assumes properties only appear once - if your properties appear multiple times, you'll have to check whether a set already exists for the property and just add to it instead of replacing the value in the map. I left that out to simplify the example.
A visitor is not necessary for this scenario, because you already know what axiom type you're interested in and what methods to call on it. It could have been written as an OWLAxiomVisitor implementing only visit(OWLDataPropertyAssertionAxiom) but in this case there would be little advantage in doing so.
I'm currently working on an application built in Scala with Spray routing.
So for dealing with a JSON document sent over POST, it's pretty easy to access the variables within the body, as follows;
respondWithMediaType(`application/json`) {
entity(as[String]) { body =>
val msg = (parse(body) \ "msg").extract[String]
val url = (parse(body) \ "url").extractOpt[String]
However, I'm now trying to write an additional query with GET, and am having some issues accessing the parameters sent through with the query.
So, I'm opening with;
get {
respondWithMediaType(`application/json`) {
parameterSeq { params =>
var paramsList = params.toList
So, this works well enough in that I can access the GET params in a sequential order (just by accessing the index) - the problem is, unfortunately I don't think we can expect GET params to always be sent in the correct order.
The list itself prints out in the following format;
List((msg,this is a link to google), (url,http://google.com), (userid,13))
Is there any simple way to access these params? For example, something along the lines of;
var message = paramsList['msg']
println(message) //returns "this is a link to google"
Or am I going about this completely wrong?
Apologies if this is a stupid question - I've only switched over to Scala very recently, and am still getting both acquainted with that, and re-acquainted with Java.
What I usually do is use the parameters directive to parse the data out to a case class which contains all the relevant data:
case class MyParams(msg: String, url: String, userId: Int)
parameters(
"msg".as[String],
"url".as[String],
"userId".as[Int]
).as[MyParams] {
myParams =>
// Here you have the case class containing all the data, already parsed.
}
To build your routes you could use the parameters directives. I'm not sure if this is what you're looking for, anyway you could use them as:
get {
parameters('msg) { (msg) =>
complete(s"The message is '$msg'")
}
}
Spray directives can be easily composed so you can use combine them in any way you want.
I hope that helps you.
I have a Java class "Listings". I use this in my Java MapReduce job as below:
public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
Listings le = new Listings(value.toString());
...
}
I want to run the same job on Spark. So, I am writing this in Scala now. I imported the Java class:
import src.main.java.lists.Listings
I want to create a Listings object in Scala. I am doing this:
val file_le = sc.textFile("file// Path to file")
Listings lists = new Listings(file_le)
I get an error:
value lists is not a member of object src.main.java.lists.Listings
What is the right way to do this?
Based on what you've said, I think you may be forgetting the differences between Scala syntax and Java syntax.
Try this:
val lists: Listings = new Listings(SomeString)
Please note that specifying the type in Scala is completely optional. Also, use a var if you're going to be changing the value of lists.
The way you have it, Scala is trying to interpret it by its ability to call methods/access values of an object without the '.', so you're actually telling Scala this:
Listings.lists = new Listings(SomeString)
I'm relying on an old Java API that kinda sucks and loves to throw null pointer exceptions when data is missing. I want to create a subclass that has option type accessors but preserves the old accessors until I decide I need to create safe accessors for them. Is there a good way to create a subclass from a copy of the original object? I'd like to achieve something like the following:
SafeIssue extends Issue {
def safeMethod: Option[Value] = { //... }
}
val issue = oldapi.getIssue()
val safeIssue = SafeIssue(issue)
//Preserves issue's methods and data if I need them
val unsafeVal = safeIssue.unsafeMethod
val maybeVal = safeIssue.safeMethod
Why not try an implicit conversion instead? This works better with Java APIs that like to create their own objects. So you would
class SafeIssue(issue: Issue) {
def original = issue
def safeFoo = Option(issue.foo)
// ... You must write any of these you need
}
implicit def make_issues_safe(issue: Issue) = new SafeIssue(issue)
Then you can--as long as you've supplied the method--write things like
val yay = Issue.myStaticFactoryMethodThing.safeFoo.map(x => pleaseNoNull(x))
(You can then decide whether you want to carry SafeIssue or Issue around in your code, and you can always get back the Issue from SafeIssue with the exposed original method (or you could make the issue parameter a val.)
Is there a way to create ruby value objects or hashes from java objects in jruby application ? Thank you.
I am not sure whether this is what you are trying to achieve, but to convert a Java object into a ruby hash, you could do something like this:
require 'java'
java_import 'YourJavaClass'
a = YourJavaClass.new
hash = {}
a.java_class.fields.each{ |var| hash[var.name] = var.value(a) }
p hash
This assumes that the instance variables are accessible (public). If they are not, you may need to make them accessible with something like:
a.java_class.declared_fields.each{ |var| var.accessible = true; hash[var.name] = var.value(a) }
(Note that this time it uses declared_fields)
Names and Beans Convention gives us next opportunity for properties with accessors
def java_to_hash(java_obj)
hash = {}
java_obj.methods.grep(/get_/).each do |accessor|
if accessor.eql? "get_class" then
next
end
#get_user_name => user_name
method_name = accessor[4..-1]
if java_obj.respond_to?(method_name)
hash[method_name.to_sym] = java_obj.send(accessor.to_sym)
end
end
hash
end