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java代码收藏 java代码手册( 二 )

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}
}
TMD讨厌的IOException，关闭个流还抛异常，受不了，让我的代码怪异无比... ....
呵呵，抱怨一下，那这个异常我们应该处理呢 ， 还是把它给ignore呢？
先看下apache的comm类是怎样处理的：
Java代码收藏代码
try {
if (input != null) {
input.close();
}
} catch (IOException ioe) {
// ignore
}
Caused by: java.lang.NoClassDefFoundError: Failed resolution of:Lcom/tencent/ysdk/framework/hotfixNoClassDefFoundError 问题原因1：缺少jar包
首先最常见的原因是classpath的配置问题 。例子程序：
本例子程序尝试创建一个新的CallerClassA实例，然后执行他的一个方法，此方法引用了类ReferencingClassA ， 本例子演示了classpath问题导致的NoClassDefFoundError  ， 本例子还打印了当前的classloader chain的情况，以便进一步的分析 。这个打印信息对你以后分析此类问题也很有帮助的：
程序
Java代码收藏代码
public class NoClassDefFoundErrorSimulator {
public static void main(String[] args) {
System.out
.println("java.lang.NoClassDefFoundError Simulator");
// Print current Classloader context
System.out.println("\nCurrent ClassLoader chain: "
+ ClassloaderUtil.getCurrentClassloaderDetail());
// 1. Create a new instance of CallerClassA
CallerClassA caller = new CallerClassA();
// 2. Execute method of the caller
caller.doSomething();
System.out.println("done!");
}
}
Java代码收藏代码
public class CallerClassA {
private final static String CLAZZ = CallerClassA.class.getName();
static {
System.out.println("Classloading of " + CLAZZ + " in progress..."
+ ClassloaderUtil.getCurrentClassloaderDetail());
}
public CallerClassA() {
System.out.println("Creating a new instance of "
+ CallerClassA.class.getName() + "...");
}
public void doSomething() {
// Create a new instance of ReferencingClassA
ReferencingClassA referencingClass = new ReferencingClassA();
}
}
Java代码收藏代码
public class ReferencingClassA {
private final static String CLAZZ = ReferencingClassA.class.getName();
static {
System.out.println("Classloading of " + CLAZZ + " in progress..."
+ ClassloaderUtil.getCurrentClassloaderDetail());
}
public ReferencingClassA() {
System.out.println("Creating a new instance of "
+ ReferencingClassA.class.getName() + "...");
Maps.newHashMap();
}
public void doSomething() {
// nothing to do...
}
}
打印classloader工具类：
Java代码收藏代码
public class ClassloaderUtil {
public static String getCurrentClassloaderDetail() {
StringBuffer classLoaderDetail = new StringBuffer();
StackClassLoader classLoaderStack = new StackClassLoader();
ClassLoader currentClassLoader = Thread.currentThread()
.getContextClassLoader();
classLoaderDetail
.append("\n-----------------------------------------------------------------\n");
// Build a Stack of the current ClassLoader chain
while (currentClassLoader != null) {
classLoaderStack.push(currentClassLoader);
currentClassLoader = currentClassLoader.getParent();
}
// Print ClassLoader parent chain
while (classLoaderStack.size()0) {
ClassLoader classLoader = classLoaderStack.pop();
// Print current
classLoaderDetail.append(classLoader);
if (classLoaderStack.size()0) {
classLoaderDetail.append("\n--- delegation ---\n");
} else {
classLoaderDetail.append(" **Current ClassLoader**");
}
}
classLoaderDetail
.append("\n-----------------------------------------------------------------\n");
return classLoaderDetail.toString();

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