I am working on a web service using spring-mvc and Jaxb2Marshaller.
I have two classes, both annotated with the same #XmlRootElement name
#XmlRootElement(name="request")
class Foo extends AstractRequest {
}
#XmlRootElement(name="request")
class Bar extends AbstractRequest {
}
All three classes (AbstractRequest, Foo, Bar) are included in the classesToBeBound list in the same order
Now the request that uses Bar works fine. But the one that uses Foo throws a ClassCastException exception during unmarshalling with message Bar cannot be cast to Foo
The controller code is this,
Source source = new StreamSource(new StringReader(body));
Foo request = (Foo) this.jaxb2Marshaller.unmarshal(source);
I guess this is happening because Bar is kind of overriding Foo since it's written after Foo in the list of classes to be bound in the spring-servlet.xml file
However I am also having multiple classes annotated with #XmlRootElement(name="response") and marshalling the response doesn't give any problem.
Is there a way to specify the class to be used by the jaxb2Marshaller for unmarshalling ?
You can pass the class to Jaxb2Marshaller before unmarshal:
Source source = new StreamSource(new StringReader(body));
jaxb2Marshaller.setMappedClass(Foo.class);
Foo request = (Foo) jaxb2Marshaller.unmarshal(source);
You can create an Unmarshaller from the Jaxb2Marshaller, then you can pass the class you want to unmarshal as a parameter to the unmarshal method that takes a Source:
Source source = new StreamSource(new StringReader(body));
Unmarshaller unmarshaller = jaxb2Marshaller.createUnmarshaller();
Foo request = (Foo) unmarshaller.unmarshal(source, Foo.class).getValue();
For more information see:
http://bdoughan.blogspot.com/2011/03/handling-duplicate-xmlrootelement.html
Related
I have a function that runs some code if the object has a certain attribute, and in rare cases if if the object does not have the attribute, it runs different code. It is hard for me to create the object without the attribute for testing. I tried del instance.attribute but got an error. The attribute is actually a #property under the hood.
I have an object instance that has foo attribute. How does one mock it so that when one tries to access instance.foo it raises an AttributeError as usual if there is no attribute?
I tried mock.Mock(side_effect=AttributeError('Boom!')) but it only works with methods.
You could try to use a PropertyMock for the property, and generally you shall be able to set the respective side effect. Here is a simple working example:
from unittest import mock
import pytest
class Foo:
#property
def bar(self):
return "bar"
def test_no_foo():
bar_mock = mock.PropertyMock()
with mock.patch(f"{__name__}.Foo.bar", bar_mock):
bar_mock.side_effect = AttributeError('Boom!')
foo = Foo()
with pytest.raises(AttributeError):
foo.bar
As you patch the property in the class, not in the object, you can can also do this using patch.object if you have access to the object by accessing the class of the object:
def test_no_foo():
bar_mock = mock.PropertyMock()
foo = Foo()
with mock.patch.object(foo.__class__, "bar", bar_mock):
bar_mock.side_effect = AttributeError('Boom!')
with pytest.raises(AttributeError):
foo.bar
I have the following scenario (https://run.dlang.io/is/19OOW9):
import std.stdio;
void main(string[] args)
{
inter1 c1 = new foo();
foo c2 = new foo();
writeln("Origin=interface: ", typeof(c1).stringof);
writeln("Origin=class: ", typeof(c2).stringof);
}
interface inter1 {
}
class foo : inter1 {
}
I work with interfaces and have different implementations for them. Now I need to know which concrete implementation is currently being used. So in the example above, I would like to know from c1 that it is an instance of the class foo.
Is this possible in the language D?
I have already tried the possibilities of object (e.g. TypeInfo_Class) and std.traits. Unfortunately without success.
A workaround is, of course, to provide the interface with a suitable meta method (https://run.dlang.io/is/Xnt0TO):
import std.stdio;
void main(string[] args)
{
inter1 c1 = new foo();
foo c2 = new foo();
writeln("Origin=interface: ", c1.strategyName);
writeln("Origin=class: ", c2.strategyName);
}
interface inter1 {
#property string strategyName() const;
}
class foo : inter1 {
#property string strategyName() const {
return "foo";
}
}
However, this is cumbersome and unusual for D. I can well imagine that there is a better implementation of this.
Best regards
Thorsten
It is quite simple actually: first cast to Object, then fetch the typeid, after a null check:
Object o = cast(Object) your_object;
if(o is null) { /* i don't think this ever happens but you should check anyway */ }
writeln(typeid(o)); // will tell the class name
If you want to call a method on a specific class, you can just cast directly to your class, and again, null check it.
The intermediate cast to Object allows the typeid (aka classinfo) to succeed, whereas calling it directly on an interface always returns the typeid of the interface itself. This is because a D interface is defined to be very thin for maximum compatibility with other languages and doesn't automatically assume run time type information is actually present through it. But the cast to Object tells it you are assuming the RTTI is present, and then typeid will pull it.
Note that the typeid data doesn't provide a whole lot of information... it is mostly just what's needed for dynamic cast, comparison, and other features of the language runtime. But one convenience method it has is a class name and toString methods, which is why the writeln succeeds. But if you're looking for more detailed runtime reflection, you'll have to do it with a CT bridge function, or probably better yet, just write your own methods in the interface.
But if all you need is the class name, use that toString. It gives the fully-qualified name, including module name, so instead of foo, you will get like yourmodule.foo. You can just cut that off if you like by slicing at the dot.
I'm trying to use macro annotations in scala, where my macro annotation would take an argument of another type. It would then use scala reflection to look at the passed in type, and add some methods as appropriate.Eg.
trait MyTrait {
def x: Int
def y: Float
}
#MyAnnotation class MyClass //<-- somehow, this annotation should reference MyTrait
class MyAnnotation(val target: Any) extends StaticAnnotation {
def macroTransform(annottees: Any*) = macro MyAnnotationImpl.impl
}
object MyAnnotationImpl {
def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
// if I can get a handle on the type MyTrait in here
// then I can call .members on it, etc.
...
}
}
Basically, the same thing as Using Scala reflection in Scala macros, except using macro annotations. However, when I try to template my macro annotation with a TypeTag
class MyAnnotation[T](val target: Any) extends StaticAnnotation {
def macroTransform[T](annottees: Any*) = macro MyAnnotationImpl.impl[T]
}
object MyAnnotationImpl {
def impl[T: c.WeakTypeTag](c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
...
}
}
I get
[error] /Users/imran/other_projs/learn_macros/macros/src/main/scala/com/imranrashid/oleander/macros/MacrosWithReflection.scala:7: macro annotation has wrong shape:
[error] required: def macroTransform(annottees: Any*) = macro ...
[error] found : def macroTransform[T](annottees: Any*) = macro ...
[error] class MyAnnotation[T](val target: Any) extends StaticAnnotation {
[error] ^
I've also tried to make the type an argument to my annotation, so I would use it like #MyAnnotation(MyTrait) class Foo .... I can extract the name as a String with something like
val targetTrait = c.prefix.tree match {
case Apply(Select(New(Ident(_)), nme.CONSTRUCTOR), List(Ident(termName))) => termName
}
but, I'm not sure what I can do w/ that String to get back the full type. I've also tried variants like #MyAnnotation(typeOf[MyTrait]) class Foo ..., and then use c.eval on the typeOf inside my macro, but that doesn't compile either.
In macro paradise 2.0.0-SNAPSHOT we have quite a tricky way of accessing type parameters for macro annotations (the situation will improve later on when we have dedicated APIs for that, but right now it's very difficult to introduce new functionality to scala-reflect.jar in macro paradise, so the current API is a bit rough).
For now it's necessary to specify the type parameter on the annotation class and not to declare any type parameters on the macroTransform method. Then, in macro expansion, access c.macroApplication and extract the untyped tree corresponding to the passed type parameter. Afterwards, do c.typeCheck as described in Can't access Parent's Members while dealing with Macro Annotations.
As Eugene points out in his answer it is possible to match on the tree of the whole macro application. Like every Scala method, annotation macro applications can take multiple type argument lists as well as multiple value argument lists.
Consider the macro application of an annotation macro called test:
#test[A, B][C, D](a, b)(c, d) trait Foo
In the implementation of test we can inspect the macro application by
println(show(c.macroApplication))
which will result in:
new test[A, B][C, D](a, b)(c, d).macroTransform(abstract trait Foo extends scala.AnyRef)
To extract the (type/value) parameters from the tree you have to pattern match on the tree. A parser for an arbitrary amount of parameter lists can be found in this project
Using this parser retrieving the first value argument of the macro application is as easy as
val List(List(arg)) = MacroApp(c.macroApplication).termArgs
I'm trying to use DataBindingUtils.bindObjectToInstance(object, source) to copy properties from one object to another using this code (which can be run in the Grails console):
import org.codehaus.groovy.grails.web.binding.DataBindingUtils
class Source {
String foo = 'foo'
String bar = 'bar'
}
class Target {
String foo
String bar
}
def s = new Source()
def t = new Target()
def result = DataBindingUtils.bindObjectToInstance(t, s)
assert t.foo == 'foo'
assert t.bar == 'bar'
But the assertions are failing because the properties of t are null, why?
The data binder (below) in Grails has only implemented binding for a select subset of object types, namely Maps and Web Requests. So binding two arbitrary objects isn't implemented.
https://github.com/grails/grails-core/blob/master/grails-web/src/main/groovy/org/codehaus/groovy/grails/web/binding/DataBindingUtils.java
Consider the following code:
class Foo(var name: String = "bar")
Now i try to get the value and the correct type of it via reflection:
val foo = new Foo
val field = foo.getClass.getDeclaredField("name")
field.setAccessible(true)
//This is where it doesn't work
val value = field.get(????)
I tried things like field.get(foo), but that just returns an java.lang.Object but no String. Basically I need the correct type, because I want to invoke a method on it (e. g. toCharArray).
What is the suggested way to do that?
As others have mentioned, the reflection methods return Object so you have to cast. You may be better using the method that the Scala compiler creates for field access rather than having to change the visibility of the private field. (I'm not even sure if the name private field is guaranteed to be the same as that of the accessor methods.)
val foo = new Foo
val method = foo.getClass.getDeclaredMethod("name")
val value = method.get(foo).asInstanceOf[String]
getDeclaredField is a method of java.lang.Class.
You have to change foo.getDeclaredField("name") to foo.getClass.getDeclaredField("name") (or classOf[Foo].getDeclaredField("name")) to get the field.
You can get the type with getType method in class Field but it won't help you because it returns Class[_]. Given than you know that the type is a String you can always cast the value returned using field.get(foo).asInstanceOf[String]
AFAIK, reflection always work with Object, and you have to cast the results yourself.
This is how one can get list of fieldnames and its value of a case class:
First, using reflection, get fields info as follows -
val TUPLE2_OF_FIELDNAME_TO_GETTERS = typeOf[<CLASS>].members
.filter(!_.isMethod)
.map(x => (x.name.toString, classOf[<CLASS>].getDeclaredMethod(x.name.toString.trim)))
How to use it?
getFieldNameAndValue(obj: <CLASS>): Seq[(String, String)] {
var output = Seq[(String, String)]()
for(fieldToGetter <- TUPLE2_OF_FIELDNAME_TO_GETTERS) {
val fieldNameAsString = fieldToGetter._1
val getter = fieldToGetter._2
val fieldValue = getter.invoke(obj).toString
output += (fieldName, fieldValue)
}
}
foo.getClass.getDeclaredField("name").getString(foo)
should work if you want to avoid asInstanceOf. get* is available for various types