Getting the collection name java reflection

#GETTING THE COLLECTION NAME JAVA REFLECTION HOW TO#
#GETTING THE COLLECTION NAME JAVA REFLECTION CODE#
#GETTING THE COLLECTION NAME JAVA REFLECTION WINDOWS#

Static, strong, safe, nominative, manifestД¬LU, Simula67, Lisp, Smalltalk, Ada 83, C++, C#, Eiffel, Mesa, Modula-3, Oberon, Objective-C, UCSD Pascal, Object Pascal ДЄda 2005, BeanShell, C#, Chapel, Clojure, ECMAScript, Fantom, Gambas, Groovy, Hack, Haxe, J#, Kotlin, PHP, Python, Scala, Seed7, Vala, JavaScript, JS++ First, we try the generic way to determine an element type, and if we're unsuccessful, we head to the non-generic testing portion where we look first for the this indexer property and then if that fails, the Add() method./ 22 March 2022 4 months ago ( 22 March 2022) Now, in GetCollectionElementType(), we're going through the steps I outlined in the concepts portion of the article. All it does is determine if the passed in type is a list. It's a utility method I find myself needing quite a bit when I'm reflecting on collections, so I've provided it here. If ( typeof().IsAssignableFrom(type))ДЇirst, we have an IsList() method which I didn't cover above. If ( 1 = pa.Length & typeof( object) != pa.ParameterType) if it's a collection, we look for an Add() method whose parameter is // anything but object if( typeof().IsAssignableFrom(type)) If ( 1 = ipa.Length & typeof( int) = ipa.ParameterType) If ( ' Item' = prop.Name & typeof( object)!=prop.PropertyType) if it's a list we look for an Item property with an int index parameter // where the property type is anything but object if ( typeof().IsAssignableFrom(type))ДЇoreach ( var prop in type.GetProperties()) now try the non-generic way // if it's a dictionary we always return DictionaryEntry if ( typeof().IsAssignableFrom(type)) If (bt.IsGenericType & bt.GetGenericTypeDefinition() = etype) first try the generic way // this is easy, just query the IEnumerable interface for its generic parameter var etype = typeof(IEnumerable) ДЇoreach ( var bt in type.GetInterfaces()) / public static Type GetCollectionElementType(Type type) / /// The type to query /// The element type of the collection or null if the type was not a collection / /// Retrieves the collection element type from this type If (it.IsGenericType & typeof(IList) = it.GetGenericTypeDefinition()) If ( typeof().IsAssignableFrom(type))ДЇoreach ( var it in type.GetInterfaces()) Throw new ArgumentNullException( ' type') / /// The type to query /// True if the type is a list, otherwise false public static bool IsList(Type type) / /// Indicates whether or not the specified type is a list.

#GETTING THE COLLECTION NAME JAVA REFLECTION CODE#

Like I usually do, I'll post the code nearly in its entirety and then we'll address it top to bottom:Д¬opy Code static partial class ReflectionUtility In practice, I don't think I've seen too many typed enumerator implementations anyway that aren't generic. We could query the Current property on the enumerator's IEnumerator interface but there's no reliable way to get the type of the enumerator without calling GetEnumerator() on an instance. Otherwise, we return null indicating that it's not a collection type. I've found this to be the most reliable way to determine the element type of a collection.ДЇinally if that doesn't work, we look for IEnumerable and if we find it, we return the object type. If that doesn't bear fruit, next we query for IList and if we find it, we look for a public indexer property that takes a single integer parameter, and returns some type other than object.ДЇinally, if we can't find that, we look for ICollection, and look for an Add() method with a single parameter that is not of type object. If we find it, we return DictionaryEntry. The first thing we do is query for the IDictionary interface. Easy peasy, and it works on dictionaries, too.ДЇor getting a non-generic collection element type, we must use some heuristics, unfortunately. NET post 1.1, but prior to that, there was no standard interface for typed collections, due to the impossibility of creating a generic interface that could handle that.ДЇor getting a generic collection type, all we do is query for the IEnumerable interface and then return whatever T is, in this case. I typically run into this while writing code generators. We may sometimes need to get the element type of a collection through reflection. Getting the element type is far more involved for these collections.

#GETTING THE COLLECTION NAME JAVA REFLECTION WINDOWS#

For example, much of Windows Forms as well as the CodeDOM have typed collections like this. These collections are surprisingly common. This will be the case with typed collections that were created before.

What may seem relatively easy at first quickly becomes complicated where typed collections are involved that do not implement IEnumerable.

#GETTING THE COLLECTION NAME JAVA REFLECTION HOW TO#

With this tip, I will endeavor to show you, gentle reader, how to use reflection to query a collection class for its element type.

Getting the collection name java reflection