java reflection instantiate class by name

JAVA REFLECTION INSTANTIATE CLASS BY NAME CODE

The package contains all the required classes like Method and Parameter to work with parameter reflection. Java provides a new feature in which you can get the names of formal parameters of any method or constructor. The getter and setter values are actual method references, allowing us to work with them exactly the same as any other method reference: val prop = this::mutablePropertyĪssertEquals('World', prop.getter()) 4.Next → ← prev Method Parameter Reflection These are exposed in an easier to use way via the get() and set() methods. the property was declared as var, whereas the getter is always available. The setter is only available if we are working with a KMutableProperty – i.e. We can access the actual Property through Method references that are exposed – the getter and setter methods. For example, the Throwable class has a Property ssage by virtue of the fact that there is a method getMessage() defined in it. This includes classes in the Java standard library. These are identified by fields that follow the JavaBeans conventions regarding getter and setter methods. Note that the concept of Properties also works in any non-Kotlin code. Kotlin Property ReferencesĪssertEquals('mutableProperty', mProperty.name)ĪssertTrue(mProperty is KMutableProperty)

val str = 'Hello'īyteArrayInputStream::class.starProjectedType,ĪssertFalse()ĪssertTrue()ĪssertFalse() This includes details about the return type and the parameters, including Kotlin specific details – such as nullability and optionality. In addition to this, we can get more information about the inputs and outputs of the method through this reference. This includes both standard Java details as well as Kotlin specific details such as if the method is an operator or if it’s inline: val byteInputStream = String::byteInputStreamĪssertEquals('byteInputStream', byteInputStream.name) We can also get more details about the method itself, in the same way, that we can for classes. This is known as being a Callable Reference: val str = 'Hello' Once we have obtained a method reference, we can call it as if was really the method in question. However, in Kotlin this method reference can also be used to get reflection information about the target. This looks exactly the same as in Java 8 to obtain a method reference, and we can use it in exactly the same way. In exactly the same way as with classes, we can obtain a reference to a Method or Property using the :: operator.

JAVA REFLECTION INSTANTIATE CLASS BY NAME CODE

As before, this works equally well on code written in standard Java as it does on code written in Kotlin. This includes class properties – defined with val or var, standard class methods, and top-level functions. In a very similar way, we can get access to all of the methods, properties, extensions, and other members of the class: val bigDecimalClass = BigDecimal::class These are all Method references as discussed in the next section. We can create new instances of a class from a Class Reference as well, in much the same way as in Java: val listClass = ArrayList::classĪlternatively, we can access the constructors and use an explicit one if we need to. Println(TestObject::class.objectInstance) Println(TestWithCompanion::panionObjectInstance)

Kotlin adds to this the ability to obtain the Companion Object for an arbitrary class, and the Object instance for an Object class: println(TestWithCompanion::panionObject) In Java, we can already move from a Class to its superclass, interfaces and the outer class it’s enclosed in – if appropriate. We also have ways to move around the class hierarchy. Some of these are standard Java concepts, and others are Kotlin specific concepts.įor example, we can easily find out if a Class is Abstract or Final, but we can also find out if the Class is a Data Class or a Companion Class: val stringClass = String::classĪssertEquals('kotlin.String', stringClass.qualifiedName) Once we have obtained a KClass object, there are some simple things that it can tell us about the class in question. Val kotlinClass: KClass = someClass.kotlin

Java reflection instantiate class by name