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Java 通过上下文加载类
通过上下文加载类
实例源码：
源代码：
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/*3
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* Copyright 2011-2013 Amazon Technologies, Inc.5
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*7
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* Licensed under the Apache License, Version 2.0 (the "License");9
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* you may not use this file except in compliance with the License.11
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* You may obtain a copy of the License at:13
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*15
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* http://aws.amazon.com/apache2.017
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*19
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* This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES21
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* OR CONDITIONS OF ANY KIND, either express or implied. See the23
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* License for the specific language governing permissions and25
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* limitations under the License.27
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*/29
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//package com.nowjava;31
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public class Main {/** from 时 代 J a v a 公 众 号**/34
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public static void main(String[] argv) throws Exception {36
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String fqcn = "nowjava.com";38
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System.out.println(loadClassViaContext(fqcn));40
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}42
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private static Class<?> loadClassViaContext(String fqcn) {45
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ClassLoader loader = Thread.currentThread().getContextClassLoader();47
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try {49
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return loader == null ? null : loader.loadClass(fqcn);51
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} catch (ClassNotFoundException e) {53
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}55
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return null;57
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}59
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/**62
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* Loads the class via the optionally specified classes in the order of64
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* their specification, and if not found, via the context class loader of66
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* the current thread, and if not found, from the caller class loader as the68
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* last resort.70
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* 72
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* @param fqcn74
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* fully qualified class name of the target class to be loaded76
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* @param classes78
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* class loader providers80
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* @return the class loaded; never null82
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* 84
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* @throws ClassNotFoundException86
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* if failed to load the class88
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*/90
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public static Class<?> loadClass(String fqcn, Class<?> classes)92
/**93
n o w j a v a . c o m - 时 代 Java 提供 94
**/95
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throws ClassNotFoundException {97
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return loadClass(fqcn, true, classes);99
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}101
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/**104
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* If classesFirst is false, loads the class via the context class106
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* loader of the current thread, and if not found, via the class loaders of108
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* the optionally specified classes in the order of their specification, and110
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* if not found, from the caller class loader as the112
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* last resort.114
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* <p>116
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* If classesFirst is true, loads the class via the optionally118
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* specified classes in the order of their specification, and if not found,120
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* via the context class loader of the current thread, and if not found,122
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* from the caller class loader as the last resort.124
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* 126
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* @param fqcn128
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* fully qualified class name of the target class to be loaded130
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* @param classesFirst132
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* true if the class loaders of the optionally specified classes134
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* take precedence over the context class loader of the current136
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* thread; false if the opposite is true.138
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* @param classes140
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* class loader providers142
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* @return the class loaded; never null144
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* 146
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* @throws ClassNotFoundException if failed to load the class148
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*/150
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public static Class<?> loadClass(String fqcn, boolean classesFirst,152
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Class<?> classes) throws ClassNotFoundException {154
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Class<?> target = null;156
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if (classesFirst) {158
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target = loadClassViaClasses(fqcn, classes);160
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if (target == null) {162
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target = loadClassViaContext(fqcn);164
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}166
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} else {168
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target = loadClassViaContext(fqcn);170
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if (target == null) {172
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target = loadClassViaClasses(fqcn, classes);174
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}176
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}178
/**代码未完, 请加载全部代码(NowJava.com).**/执行结果：
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