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classloader

我们一般在系统路径中配置了 "."(当前目录)的classpath,所以如果你在当前目录命令行中运行java HelloWorld, 运行成功。这个类由system classloader去负责载入。 如果在HelloWorld.class中import另外一个在同目录下jar包中的类,如果不指定-classpath XX.jar的话,运行失败。说明system classloader 不会去查找即使时同目录下的jar包。(function(){var a=document.head||document.getElementsByTagName(...

Add a jar file to Java load path at run time

Sometimes it is necessary to amend the class load path at run time. For example, dynamically adding jar files containing user-configurable JDBC data sources. The way this is done is truly monstrous -- the URL Path format was only revealed when a colleague looked into the Java library sources. 1 2 import java.net.URL; 3 import java.io.IOException; 4 import java.ne...

Understanding Extension Class Loading

Understanding Extension Class Loading The extension framework makes use of the class-loading delegation mechanism. When the runtime environment needs to load a new class for an application, it looks for the class in the following locations, in order: Bootstrap classes: the runtime classes in rt.jar, internationalization classes in i18n.jar, and others. Installed exten...

JAVA类动态载入的实现

1 前言 前段时间因为项目的需要,我搞了一套类似Servlet重新载入的一个框架,实现了类的动态载入过程。本文写了一些我的学习成果以及心得供大家分享一下。 2 类载入的原理 (下面引用网上的一篇文章): 当JVM(Java虚拟机)启动时,会形成由三个类加载器组成的初始类加载器层次结构: bootstrap classloader | extension classloader | ...

Modify Classpath At Runtime

I've seen a lot of forum posts about how to modify the classpath at runtime and a lot of answers saying it can't be done. I needed to add JDBC driver JARs at runtime so I figured out the following method. The system classloader (ClassLoader.getSystemClassLoader()) is a subclass of URLClassLoader. It can therefore be casted into a URLClassLoader and used as one. URLClassLoade...

Get a load of that name! Subtle differences in various ways you can dynamically load a class

What is the difference between Class.forName() and ClassLoader.loadClass()? Both methods try to dynamically locate and load a java.lang.Class object corresponding to a given class name. However, their behavior differs regarding which java.lang.ClassLoader they use for class loading and whether or not the resulting Class object is initialized. The most...

Find a way out of the ClassLoader maze System, current, context? Which ClassLoader should you use?

Find a way out of the ClassLoader maze System, current, context? Which ClassLoader should you use? When should I use Thread.getContextClassLoader()? Although not frequently asked, this question is rather tough to correctly answer. It usually comes up during framework programming, when a good deal of dynamic class and resource loading goes on. In general, when loading a reso...

ClassLoader读取相应资源

java使用相对路径读取xml文件:一、xml文件一般的存放位置有三个:1.放在WEB-INF下;2.xml文件放在/WEB-INF/classes目录下或classpath的jar包中;3.放在与解析它的java类同一个包中,不一定是classpath; 二、相对应的两种使用相对路径的读取方法: 方法一:(未验证)将xml文件放在WEB-INF目录下,然后程序代码:InputStream is=getServletContext().getResourceAsStream( "/WEB-INF/xmlfile.xml" ); 方法...

Plugin和App的统一路径接口

在Eclipse插件(Plugin)开发中,需要写一些Test Case(by JUnit),这些Test Case不是以插件方法运行的,而是一些普通的Application。这时要注意到插件和App获取路径的方式是不同的,这时如果你要测试一些项目中的 一些涉及到读文件的一些类,无疑会导致出错,因为在Plugin中可能由Plugin和APP组成,比如JUnit,这时在不同地方调用读文件会出错。为了让Plugin和App路径获取透明化,不防写一个工具类来提供...
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