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Java 通过上下文加载类

欢马劈雪

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通过上下文加载类

实例源码：

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* 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://aws.amazon.com/apache2.0

* This file 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 com.nowjava;

public class Main {/** from 时 代 J a v a 公 众 号**/

public static void main(String[] argv) throws Exception {

String fqcn = "nowjava.com";

System.out.println(loadClassViaContext(fqcn));

}

private static Class<?> loadClassViaContext(String fqcn) {

ClassLoader loader = Thread.currentThread().getContextClassLoader();

try {

return loader == null ? null : loader.loadClass(fqcn);

} catch (ClassNotFoundException e) {

}

return null;

}

/**

* Loads the class via the optionally specified classes in the order of

* their specification, and if not found, via the context class loader of

* the current thread, and if not found, from the caller class loader as the

* last resort.

* @param fqcn

*            fully qualified class name of the target class to be loaded

* @param classes

*            class loader providers

* @return the class loaded; never null

* @throws ClassNotFoundException

*             if failed to load the class

public static Class<?> loadClass(String fqcn, Class<?>... classes)
    /**
    n o w j a   v  a . c o m - 时  代  Java 提供 
    **/

throws ClassNotFoundException {

return loadClass(fqcn, true, classes);

}

/**

* If classesFirst is false, loads the class via the context class

* loader of the current thread, and if not found, via the class loaders of

* the optionally specified classes in the order of their specification, and

* if not found, from the caller class loader as the

* last resort.

* <p>

* If classesFirst is true, loads the class via the optionally

* specified classes in the order of their specification, and if not found,

* via the context class loader of the current thread, and if not found,

* from the caller class loader as the last resort.

* @param fqcn

*            fully qualified class name of the target class to be loaded

* @param classesFirst

*            true if the class loaders of the optionally specified classes

*            take precedence over the context class loader of the current

*            thread; false if the opposite is true.

* @param classes

*            class loader providers

* @return the class loaded; never null

* @throws ClassNotFoundException if failed to load the class

public static Class<?> loadClass(String fqcn, boolean classesFirst,

Class<?>... classes) throws ClassNotFoundException {

Class<?> target = null;

if (classesFirst) {

target = loadClassViaClasses(fqcn, classes);

if (target == null) {

target = loadClassViaContext(fqcn);

}

} else {

target = loadClassViaContext(fqcn);

if (target == null) {

target = loadClassViaClasses(fqcn, classes);

}

}
/**代码未完, 请加载全部代码(NowJava.com).**/

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本文系作者在时代Java发表，未经许可，不得转载。如有侵权，请联系nowjava@qq.com删除。

编辑于 2020-03-26 09:23:272020-03-26 09:23:27

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