Java Reflection Method Invoke invokeMethod(final Object obj, final String methodName, final boolean throwException)

Description

Invoke the named method in the given object or its superclasses.

License

Open Source License

Parameter

Parameter	Description
obj	The object.
methodName	The method name.
throwException	If true, throw an exception if the field value could not be read.

Exception

Parameter	Description
IllegalArgumentException	If the field value could not be read.

Return

The field value.

Declaration

public static Object invokeMethod(final Object obj, final String methodName, final boolean throwException)
        throws IllegalArgumentException

Method Source Code

//package com.java2s;
/*/*w  ww  .  j  av a2  s .c  o m*/
 * This file is part of ClassGraph.
 *
 * Author: Luke Hutchison
 *
 * Hosted at: https://github.com/lukehutch/fast-classpath-scanner
 *
 * --
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Luke Hutchison
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without
 * limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
 * LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
 * EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
 * OR OTHER DEALINGS IN THE SOFTWARE.
 */

import java.lang.reflect.Method;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

public class Main {
    /**
     * Invoke the named method in the given object or its superclasses. If an exception is thrown while trying to
     * call the method, and throwException is true, then IllegalArgumentException is thrown wrapping the cause,
     * otherwise this will return null. If passed a null object, returns null unless throwException is true, then
     * throws IllegalArgumentException.
     * 
     * @param obj
     *            The object.
     * @param methodName
     *            The method name.
     * @param throwException
     *            If true, throw an exception if the field value could not be read.
     * @return The field value.
     * @throws IllegalArgumentException
     *             If the field value could not be read.
     */
    public static Object invokeMethod(final Object obj, final String methodName, final boolean throwException)
            throws IllegalArgumentException {
        if (obj != null) {
            final Class<? extends Object> cls = obj.getClass();

            // Iterate through implemented interfaces, top-down, then superclass to subclasses, top-down
            // (since higher-up superclasses and superinterfaces have the highest chance of being visible)
            final List<Class<?>> reverseAttemptOrder = getReverseMethodAttemptOrder(cls);
            IllegalAccessException illegalAccessException = null;
            for (int i = reverseAttemptOrder.size() - 1; i >= 0; i--) {
                final Class<?> iface = reverseAttemptOrder.get(i);
                try {
                    // Try calling method on interface
                    final Method method = iface.getDeclaredMethod(methodName);
                    try {
                        method.setAccessible(true);
                    } catch (final Exception e) {
                    }
                    return method.invoke(obj);
                } catch (final NoSuchMethodException e) {
                    // Fall through if method not found, since a superinterface might have the method 
                } catch (final IllegalAccessException e) {
                    illegalAccessException = e;
                } catch (final Throwable e) {
                    if (throwException) {
                        throw new IllegalArgumentException("Exception while invoking method \"" + methodName + "\"",
                                e);
                    }
                }
            }
            if (throwException) {
                if (illegalAccessException != null) {
                    throw new IllegalArgumentException("Method \"" + methodName + "\" is not accessible",
                            illegalAccessException);
                } else {
                    throw new IllegalArgumentException("Method \"" + methodName + "\" doesn't exist");
                }
            }
        } else if (throwException) {
            throw new IllegalArgumentException("Can't invoke method on null object");
        }
        return null;
    }

    /**
     * Invoke the named method in the given object or its superclasses. If an exception is thrown while trying to
     * call the method, and throwException is true, then IllegalArgumentException is thrown wrapping the cause,
     * otherwise this will return null. If passed a null object, returns null unless throwException is true, then
     * throws IllegalArgumentException.
     * 
     * @param obj
     *            The object.
     * @param methodName
     *            The method name.
     * @param argType
     *            The type of the parameter.
     * @param arg
     *            The argument value.
     * @param throwException
     *            Whether to throw an exception on failure.
     * @return The result of the method invocation.
     * @throws IllegalArgumentException
     *             If the method could not be invoked.
     */
    public static Object invokeMethod(final Object obj, final String methodName, final Class<?> argType,
            final Object arg, final boolean throwException) throws IllegalArgumentException {
        if (obj != null) {
            final Class<? extends Object> cls = obj.getClass();

            // Iterate through implemented interfaces, top-down, then superclass to subclasses, top-down
            // (since higher-up superclasses and superinterfaces have the highest chance of being visible)
            final List<Class<?>> reverseAttemptOrder = getReverseMethodAttemptOrder(cls);
            IllegalAccessException illegalAccessException = null;
            for (int i = reverseAttemptOrder.size() - 1; i >= 0; i--) {
                final Class<?> iface = reverseAttemptOrder.get(i);
                try {
                    // Try calling method on interface
                    final Method method = iface.getDeclaredMethod(methodName, argType);
                    try {
                        method.setAccessible(true);
                    } catch (final Exception e) {
                    }
                    return method.invoke(obj, arg);
                } catch (final NoSuchMethodException e) {
                    // Fall through if method not found, since a superinterface might have the method 
                } catch (final IllegalAccessException e) {
                    illegalAccessException = e;
                } catch (final Throwable e) {
                    if (throwException) {
                        throw new IllegalArgumentException("Exception while invoking method \"" + methodName + "\"",
                                e);
                    }
                }
            }
            if (throwException) {
                if (illegalAccessException != null) {
                    throw new IllegalArgumentException("Method \"" + methodName + "\" is not accessible",
                            illegalAccessException);
                } else {
                    throw new IllegalArgumentException("Method \"" + methodName + "\" doesn't exist");
                }
            }
        } else if (throwException) {
            throw new IllegalArgumentException("Can't invoke method on null object");
        }
        return null;
    }

    /**
     * Iterate through implemented interfaces, top-down, then superclass to subclasses, top-down (since higher-up
     * superclasses and superinterfaces have the highest chance of being visible).
     */
    private static List<Class<?>> getReverseMethodAttemptOrder(final Class<?> cls) {
        final List<Class<?>> reverseAttemptOrder = new ArrayList<>();

        // Iterate from class to its superclasses
        for (Class<?> c = cls; c != null && c != Object.class; c = c.getSuperclass()) {
            reverseAttemptOrder.add(c);
        }

        // Find interfaces and superinterfaces implemented by this class or its superclasses
        final Set<Class<?>> addedIfaces = new HashSet<>();
        final LinkedList<Class<?>> ifaceQueue = new LinkedList<>();
        for (Class<?> c = cls; c != null; c = c.getSuperclass()) {
            if (c.isInterface()) {
                if (addedIfaces.add(c)) {
                    ifaceQueue.add(c);
                }
            }
            for (final Class<?> iface : c.getInterfaces()) {
                if (addedIfaces.add(iface)) {
                    ifaceQueue.add(iface);
                }
            }
        }
        while (!ifaceQueue.isEmpty()) {
            final Class<?> iface = ifaceQueue.remove();
            reverseAttemptOrder.add(iface);
            final Class<?>[] superIfaces = iface.getInterfaces();
            if (superIfaces.length > 0) {
                for (final Class<?> superIface : superIfaces) {
                    if (addedIfaces.add(superIface)) {
                        ifaceQueue.add(superIface);
                    }
                }
            }
        }
        return reverseAttemptOrder;
    }
}

Java Reflection Method Invoke invokeMethod(final Object obj, final String methodName, final boolean throwException)

Description

License

Parameter

Exception

Return

Declaration

Method Source Code

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