java-ContextClassLoader的意义

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Thread的实现化过程：

public Thread() {    init(null, null, "Thread-" + nextThreadNum(), 0);}

private void init(ThreadGroup g, Runnable target, String name,                  long stackSize) {    init(g, target, name, stackSize, null);}

private void init(ThreadGroup g, Runnable target, String name,                  long stackSize, AccessControlContext acc) {   .... if (security == null || isCCLOverridden(parent.getClass()))//下面是关键两行： this.contextClassLoader = parent.getContextClassLoader();    else  this.contextClassLoader = parent.contextClassLoader;   //从上面可以看出，具有父子关系（不是继承关系）的线程的ContextClassLoader都一样，在一般的应用//都是由main线程衍生出许多子线程，所以他们的ContextClassLoader都一样。   this.inheritedAccessControlContext =            acc != null ? acc : AccessController.getContext();    this.target = target;    setPriority(priority);    if (parent.inheritableThreadLocals != null)        this.inheritableThreadLocals =            ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);    /* Stash the specified stack size in case the VM cares */    this.stackSize = stackSize;    /* Set thread ID */    tid = nextThreadID();}

那么ContextClassLoader的意义何在？

父Classloader可以使用当前线程Thread.currentthread().getContextLoader()中指定的classloader中加载的类。颠覆了父ClassLoader不能使用子Classloader或者是其它没有直接父子关系的Classloader中加载的类这种情况。这个就是Context Class Loader的意义

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