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...
ajax html
ajax 时request.open("GET", url, true);request.send(null);request.onreadystatechange = addrOper; //-->这个函数不能有参数，对于有传参数的，可以function(){addroper(id);}来写
js删除节点n.parentNode.removeChild(n)document.getElementById("")返回的不是 集合
js中跳出确定对话框if(confirm("Are you sure to delete this address forever?")){ } }else{ }
childNodes—返回节点到子节点的...
xampp apache tomcat
在使用Apache服务器整合Tomcat和PHP5讲 述了整合jsp和php服务的方法，但是，在应用中发现，php和mysql连接始终服务解决，总是提示：无法载入 mysql 扩展。于是，无奈下希望使用php和mysql整合更方便的apache friend的xampp套件，然后再整合tomcat达到目的。整合过程如下：
1 安装好xampp，测试PHP运行正常，安装tomcat（这里我用6.0）。下载【使用Apache服务器整合Tomcat和PHP5】附件中的apache和tomcat连...
如何选择是使用Exception还是RuntimeException呢？
如何选择是使用Exception还是RuntimeException呢？
Java中的Exception来源于C++但是又于C++不同。C++只有一类Exception基类，但是Java有Exception和RuntimeException，虽然RuntimeException也是直接继承自Exception，两者之间的差异在于，RuntimeException可以不必在方法声明时声明，而由JVM内在的机制处理此类异常，此类异常一般意味着开发人员的编码错误等。
以下三点有助于在使用异常机制时，该如何选择...