Class ReflectionExamples

java.lang.Object

net.jrodolfo.java_evolution.java01.reflection.ReflectionExamples

public class ReflectionExamples
extends Object

Demonstrates reflection, introduced in Java 1.1.

The example keeps reflection declarations raw because generics were added later, in Java 5.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ReflectionExamples.PluginCommand	Simple target class used by the reflection examples.

Constructor Summary

Constructors

Constructor	Description
ReflectionExamples()

Method Summary

Modifier and Type	Method	Description
Object	createCommandByClassName(String className, String commandName)	Creates an object through a constructor selected at runtime.
String	declaredFieldDescription()	Inspects a declared field without reading or changing its value.
String	invokeMethodByName(Object target, String methodName, String argument)	Invokes a method selected by name at runtime.
String	runtimeTypeName(Object value)	Reads the runtime type from an object reference.

Methods inherited from class Object

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

Constructor Details

ReflectionExamples

public ReflectionExamples()

Method Details

runtimeTypeName

public String runtimeTypeName(Object value)

Reads the runtime type from an object reference.

Parameters:

value - object to inspect

Returns:

runtime class name

declaredFieldDescription

public String declaredFieldDescription()
                                throws NoSuchFieldException

Inspects a declared field without reading or changing its value.

Returns:

field name and type

Throws:

NoSuchFieldException - when the field name is wrong

createCommandByClassName

public Object createCommandByClassName(String className,
 String commandName)
                                throws ClassNotFoundException,
NoSuchMethodException,
InvocationTargetException,
InstantiationException,
IllegalAccessException

Creates an object through a constructor selected at runtime.

Parameters:

className - fully qualified class name to load

commandName - constructor argument

Returns:

object created by reflection

Throws:

ClassNotFoundException - when the class name cannot be loaded

NoSuchMethodException - when the constructor signature is wrong

InvocationTargetException - when the constructor throws an exception

InstantiationException - when the class cannot be instantiated

IllegalAccessException - when access checks reject the call

invokeMethodByName

public String invokeMethodByName(Object target,
 String methodName,
 String argument)
                          throws NoSuchMethodException,
InvocationTargetException,
IllegalAccessException

Invokes a method selected by name at runtime.

Parameters:

target - object receiving the method call

methodName - method to invoke

argument - method argument

Returns:

method result

Throws:

NoSuchMethodException - when the method name or signature is wrong

InvocationTargetException - when the invoked method throws an exception

IllegalAccessException - when access checks reject the call