org.osgl.util

Class Generics

java.lang.Object

org.osgl.util.Generics

public class Generics
extends Object

Provides utilities for generic relevant operations

Constructor Summary

Constructors

Constructor and Description
Generics()

Method Summary

Modifier and Type	Method and Description
static Map<String,Class>	buildTypeParamImplLookup(Class theClass) Build class type variable name and type variable implementation lookup
static void	buildTypeParamImplLookup(Class theClass, Map<String,Class> lookup)
static <T> Class<T>	classOf(Type type)
static Class<?>	getReturnType(Method method, Class<?> theClass) Return the real return type of a method.
static void	main(String[] args)
static Map<String,Class>	subLookup(Map<String,Class> lookup, String prefix)
static List<Type>	tryGetTypeParamImplementations(Class theClass, Class rootClass) Same function with typeParamImplementations(Class, Class).
static List<Type>	typeParamImplementations(Class theClass, Class rootClass) Returns implementation of type parameters declared in the root class/interface by the given sub class

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Generics

public Generics()

Method Detail

classOf

public static <T> Class<T> classOf(Type type)

typeParamImplementations

public static List<Type> typeParamImplementations(Class theClass,
                                                  Class rootClass)

Returns implementation of type parameters declared in the root class/interface by the given sub class

For example, suppose a super class has generic type params: MyBase<MODEL, QUERY>, and a sub class is declared as MyModel<MyModel, MyQuery>, then passing MyModel.class to this method shall return a list of {MyModel.class, MyQuery.class}

If the specified class doesn’t have generic type declared then it shall return an empty list

Parameters:

theClass - the end class

rootClass - the root class or interface

Returns:

a list of type variable implementation on root class

tryGetTypeParamImplementations

public static List<Type> tryGetTypeParamImplementations(Class theClass,
                                                        Class rootClass)

Same function with typeParamImplementations(Class, Class).

However this method will return an empty list instead of throwing out exception when type parameter not found.

Parameters:

theClass - the end class

rootClass - the root class or interface

Returns:

a list of type variable implementation on root class

subLookup

public static Map<String,Class> subLookup(Map<String,Class> lookup,
                                          String prefix)

buildTypeParamImplLookup

public static Map<String,Class> buildTypeParamImplLookup(Class theClass)

Build class type variable name and type variable implementation lookup

Parameters:

theClass - the class to build the lookup

Returns:

the lookup

buildTypeParamImplLookup

public static void buildTypeParamImplLookup(Class theClass,
                                            Map<String,Class> lookup)

getReturnType

public static Class<?> getReturnType(Method method,
                                     Class<?> theClass)

Return the real return type of a method.

Normally it returns Method.getReturnType()

In case a method is declared in a super type and the return type is declared as a generic TypeVariable, when a sub class with type variable implementation presented, then it shall return the implementation type. E.g

Super type:

public abstract class Foo<T> {
    T getFoo();
}

Sub type:

public class StringFoo extends Foo<String> {
    String getFoo() {return "foo";}
}

Usage of getReturnType:

Method method = Foo.class.getMethod("getFoo");
Class<?> realReturnType = Generics.getReturnType(method, StringFoo.class); // return String.class

Parameters:

method - the method

theClass - the class on which the method is invoked

Returns:

the return type

main

public static void main(String[] args)