com.jfinal.server.undertow.hotswap.HotSwapClassLoader Maven / Gradle / Ivy
/**
* Copyright (c) 2011-2019, James Zhan 詹波 ([email protected]).
*
* 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 com.jfinal.server.undertow.hotswap;
import java.net.URL;
import java.net.URLClassLoader;
import com.jfinal.server.undertow.UndertowConfig;
/**
* HotSwapClassLoader
*/
public class HotSwapClassLoader extends URLClassLoader {
final ClassLoader parent;
protected HotSwapResolver hotSwapResolver;
static {
registerAsParallelCapable();
}
public HotSwapClassLoader(URL[] urls, ClassLoader parent, HotSwapResolver hotSwapResolver) {
super(urls, parent);
this.parent = parent;
this.hotSwapResolver = hotSwapResolver;
}
/**
* 全程避免使用 super.loadClass(...)，以免被 parent 加载到不该加载的类
*/
protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
/**
* 生产环境所有类文件统一加载方式，不再进行额外判断
* 生产环境避免使用 parent 加载，是为了能从额外添加的
* config 目上录下面加载配置文件
*/
if (! UndertowConfig.isDevMode()) {
/* 下面的代码开启后抛异常：ClassNotFoundException: java.lang.Object
* 原因是系统类文件必须要由 parent 加载
Class c = super.findClass(name);
if (c != null) {
if (resolve) {
resolveClass(c);
}
return c;
} */
/**
* 不能启动 return parent.loadClass(name); 因为 parent 没有添加
* config 到 class path 中去，无法实现外部配置文件的加载
*
* 而 super.loadClass(...) 是 HotSwapClassLoader 自己在
* 使用继承过来的方法在加载，HotSwapClassLader 已添加过 config
* 到 class path
*/
return super.loadClass(name, resolve);
}
// ---------
synchronized (getClassLoadingLock(name)) {
// First, check if the class has already been loaded
Class c = findLoadedClass(name);
if (c != null) {
return c;
}
// ---------
if (hotSwapResolver.isSystemClass(name)) {
return parent.loadClass(name);
}
// ---------
if (hotSwapResolver.isHotSwapClass(name)) {
/**
* 使用 "本 ClassLoader" 加载类文件
* 注意：super.loadClass(...) 会触发 parent 加载，绝对不能使用
*/
c = super.findClass(name);
if (c != null) {
if (resolve) {
resolveClass(c);
}
return c;
}
// throw new ClassNotFoundException(name); // TODO
}
// ---------
return parent.loadClass(name);
}
}
}