Java tutorial
/* * Copyright 2016 PantherCode * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.panthercode.arctic.core.reflect; import org.apache.commons.lang3.reflect.MethodUtils; import org.panthercode.arctic.core.arguments.ArgumentUtils; import java.io.IOException; import java.lang.annotation.Annotation; import java.lang.reflect.InvocationTargetException; import java.net.URL; import java.net.URLClassLoader; import java.util.ArrayList; import java.util.Enumeration; import java.util.List; import java.util.jar.JarEntry; import java.util.jar.JarFile; /** * Utility class that contains methods to load classes from jar archives and filter lists. * * @author PantherCode */ public class ReflectionUtils { /** * private Constructor */ private ReflectionUtils() { } /** * Invokes a method to a specific object. The order of arguments must matching the signature of the method. * The first argument is the first parameter of the invoked method and so on. * * @param object object to invoke method * @param functionName method getName to invoke * @param arguments parameters the method will be called with * @throws NoSuchMethodException Is thrown if no matching method is found. * @throws IllegalAccessException Is thrown if invocation is not permitted by security. For example the constructor * you would like to call has not modification <tt>public</tt>. * @throws InvocationTargetException Is thrown if an error occurs on invocation. */ public static void invokeMethod(Object object, String functionName, Object... arguments) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { MethodUtils.invokeMethod(object, functionName, arguments); } /** * Invokes a method to a specific object. The order arguments must matching the signature fo the method. * The first argument is the first parameter of the invoked method and so on. * * @param object object to invoke method * @param functionName method getName to invoke * @param returnType class type of returned object * @param arguments parameters the method will be called with * @param <T> type of returned object * @return Returns the output of the invoked method. * @throws NoSuchMethodException Is thrown if no matching mehtod is found. * @throws IllegalAccessException Is thrown if invovation is not permitted by security. security. For example the constructor * you would like to call has not modification <tt>public</tt>. * @throws InvocationTargetException Is thrown if an error occurs on invocation. */ @SuppressWarnings("unchecked") public static <T> T invokeMethod(Object object, String functionName, Class<T> returnType, Object... arguments) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { return (T) MethodUtils.invokeMethod(object, functionName, arguments); } /** * Reads all names of classes as path from a specific jar file. * * @param path filepath to jar file * @return Returns a list of class paths * @throws IOException Is thrown if an error occurs while reading the .jar file. * @throws IllegalArgumentException Is thrown if path is null. */ public static List<String> extractClassNamesFromJar(String path) throws NullPointerException, IOException { ArgumentUtils.assertNotNull(path, "path"); JarFile jarFile = new JarFile(path); List<String> classNameList = new ArrayList<>(); Enumeration<JarEntry> entries = jarFile.entries(); for (JarEntry currentEntry = entries.nextElement(); entries .hasMoreElements(); currentEntry = entries.nextElement()) { if (currentEntry != null && currentEntry.getName().endsWith(".class")) { classNameList.add(currentEntry.getName().replace("/", ".").split("\\.class", 2)[0]); } } return classNameList; } /** * Creates a list of all classes from a specific jar file. * * @param path filepath to jar file * @return Returns a list with all classes in jar file. If jar file doesn't contain any class, the list will be empty. * @throws IOException Is thrown if an error occurs while reading the .jar file. * @throws ClassNotFoundException Is thrown if the class is not found. * @throws IllegalArgumentException Is thrown if path is null. */ public static List<Class<?>> extractClassesFromJar(String path) throws IOException, ClassNotFoundException, IllegalArgumentException { ArgumentUtils.assertNotNull(path, "path"); List<Class<?>> classList = new ArrayList<>(); URL[] urlArray = { new URL("jar:file:" + path + "!/") }; URLClassLoader classLoader = new URLClassLoader(urlArray); for (String className : ReflectionUtils.extractClassNamesFromJar(path)) { classList.add(classLoader.loadClass(className)); } return classList; } /** * Filters a list of classes with a given pattern. * * @param classList list with classes * @param filter pattern for filtering * @return Returns a filtered list. * @throws NullPointerException Is thrown if one of the parameters is <tt>null</tt>. */ public static List<Class<?>> filterClassList(final List<Class<?>> classList, final Class<?> filter) throws NullPointerException { ArgumentUtils.assertNotNull(classList, "list"); ArgumentUtils.assertNotNull(filter, "filter"); final List<Class<?>> filteredList = new ArrayList<>(); for (Class<?> clazz : classList) { if (filter.equals(clazz)) { filteredList.add(clazz); } } return filteredList; } /** * Filters a list of classes with a given pattern. * * @param classList list with classes * @param filter pattern for filtering * @return Returns a filtered list. * @throws NullPointerException Is thrown if one of the parameters is <tt>null</tt>. */ public static List<Class<?>> filterClassListByAnnotation(final List<Class<?>> classList, final Class<? extends Annotation> filter) throws NullPointerException { ArgumentUtils.assertNotNull(classList, "list"); ArgumentUtils.assertNotNull(filter, "filter"); final List<Class<?>> filteredList = new ArrayList<>(); for (Class<?> clazz : classList) { if (clazz.isAnnotationPresent(filter)) { filteredList.add(clazz); } } return filteredList; } /** * Returns a flag that indicates whether the given class is annotated with a specified annotation or not. * * @param clazz class to check * @param annotation annotation to check * @return Returns <tt>true</tt> if the class is annotated with the given annotation; Otherwise <tt>false</tt>. */ public static boolean isAnnotated(final Class<?> clazz, final Class<? extends Annotation> annotation) { return clazz != null && annotation != null && clazz.getAnnotation(annotation) != null; } }