Java Reflection Method Invoke invokeMethod(Method method, Object target, Object[] args)

Description

Invoke the specified Method against the supplied target object with the supplied arguments.

License

Open Source License

Parameter

Parameter	Description
method	the method to invoke
target	the target object to invoke the method on
args	the invocation arguments (may be <code>null</code>)

Return

the invocation result, if any

Declaration

public static Object invokeMethod(Method method, Object target, Object[] args) 

Method Source Code

//package com.java2s;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Main {
    /**//from   w w w .j av a 2 s. c  om
     * Invoke the specified {@link Method} against the supplied target object
     * with the supplied arguments. The target object can be <code>null</code>
     * when invoking a static {@link Method}.
     * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
     * 
     * @param method the method to invoke
     * @param target the target object to invoke the method on
     * @param args the invocation arguments (may be <code>null</code>)
     * @return the invocation result, if any
     */
    public static Object invokeMethod(Method method, Object target, Object[] args) {
        try {
            return method.invoke(target, args);
        } catch (Exception ex) {
            handleReflectionException(ex);
        }
        throw new IllegalStateException("Should never get here");
    }

    /**
     * Handle the given reflection exception. Should only be called if
     * no checked exception is expected to be thrown by the target method.
     * <p>Throws the underlying RuntimeException or Error in case of an
     * InvocationTargetException with such a root cause. Throws an
     * IllegalStateException with an appropriate message else.
     * 
     * @param ex the reflection exception to handle
     */
    public static void handleReflectionException(Exception ex) {
        if (ex instanceof NoSuchMethodException) {
            throw new IllegalStateException("Method not found: " + ex.getMessage());
        }
        if (ex instanceof IllegalAccessException) {
            throw new IllegalStateException("Could not access method: " + ex.getMessage());
        }
        if (ex instanceof InvocationTargetException) {
            handleInvocationTargetException((InvocationTargetException) ex);
        }
        if (ex instanceof RuntimeException) {
            throw (RuntimeException) ex;
        }
        handleUnexpectedException(ex);
    }

    /**
     * Handle the given invocation target exception. Should only be called if
     * no checked exception is expected to be thrown by the target method.
     * <p>Throws the underlying RuntimeException or Error in case of such
     * a root cause. Throws an IllegalStateException else.
     * @param ex the invocation target exception to handle
     */
    public static void handleInvocationTargetException(InvocationTargetException ex) {
        rethrowRuntimeException(ex.getTargetException());
    }

    /**
     * <p>Throws an IllegalStateException with the given exception as root cause.</p>
     * 
     * @param ex the unexpected exception
     */
    private static void handleUnexpectedException(Throwable ex) {
        // Needs to avoid the chained constructor for JDK 1.4 compatibility.
        IllegalStateException isex = new IllegalStateException("Unexpected exception thrown");
        isex.initCause(ex);
        throw isex;
    }

    /**
     * Rethrow the given {@link Throwable exception}, which is presumably the
     * <em>target exception</em> of an {@link InvocationTargetException}.
     * Should only be called if no checked exception is expected to be thrown by
     * the target method.
     * <p>Rethrows the underlying exception cast to an {@link RuntimeException}
     * or {@link Error} if appropriate; otherwise, throws an
     * {@link IllegalStateException}.
     * 
     * @param ex the exception to rethrow
     * @throws RuntimeException the rethrown exception
     */
    public static void rethrowRuntimeException(Throwable ex) {
        if (ex instanceof RuntimeException) {
            throw (RuntimeException) ex;
        }
        if (ex instanceof Error) {
            throw (Error) ex;
        }
        handleUnexpectedException(ex);
    }
}

Related

1. invokeMethod(Method method, Object target, Object... args)
2. invokeMethod(Method method, Object target, Object... args)
3. invokeMethod(Method method, Object target, Object... arguments)
4. invokeMethod(Method method, Object target, Object... params)
5. invokeMethod(Method method, Object target, Object[] args)
6. invokeMethod(Method method, Object theObject, Object[] args)
7. invokeMethod(Method method, Object... arguments)
8. invokeMethod(Object bean, Method method, Object... param)
9. invokeMethod(Object bean, Method method, Object[] args)