# 功能

简化的异常处理

# 程序示例

	package com.example.google.guava.demo.clazz;

	import com.example.google.guava.demo.exception.InvalidInputException;
	import com.google.common.base.Throwables;

	import java.io.IOException;
	import java.util.List;
	//import org.eclipse.jdt.core.compiler.InvalidInputException;

	/**
	* <p>
	* <code>ThrowablesTest</code>
	* </p>
	* Description:
	*
	* @author Mcchu
	* @date 2017/10/19 9:57
	*/
	public class ThrowablesTest {

	public static void main(String[] args) {

	System.out.println("================1.InvalidInputException==================");

	try {
	showThrowableSqrt();
	}catch (InvalidInputException e){
	// Guava 的异常链处理方法：获得根异常
	Throwable able = Throwables.getRootCause(e);
	// Guava 的异常链处理方法：获得异常的列表
	List throwableList = Throwables.getCausalChain(e);
	System.out.println( able );
	System.out.println( throwableList );
	}

	System.out.println("================2.ArrayIndexOutOfBoundsException==================");

	try {
	showThrowableArray();
	}catch (Exception e){
	// Guava 的异常链处理方法：获得异常堆栈的字符串
	String stackTrace = Throwables.getStackTraceAsString(e);
	System.out.println( stackTrace );
	}

	System.out.println("================3.IOException==================");

	try {
	showThrowableIO();
	}catch (Exception e){
	// 获取堆栈异常信息
	String stackTrace = Throwables.getStackTraceAsString(e);
	System.out.println( stackTrace );
	}
	}

	/**
	* 测试一
	*/
	private static void showThrowableSqrt() throws InvalidInputException{
	try {
	sqrt(-3.0);
	} catch (Throwable e) {
	// 检测异常类型并抛出：
	/*
	* @deprecated Use {@link #throwIfInstanceOf}, which has the same behavior but rejects {@code
	* null}. This method is scheduled to be removed in July 2018.
	*/
	Throwables.propagateIfInstanceOf(e, InvalidInputException.class); // 此方法将于 2018.7 移除
	//Throwables.throwIfInstanceOf(e, InvalidInputException.class);

	/*
	* @deprecated Use {@code throw e} or {@code throw new RuntimeException(e)} directly, or use a
	* combination of {@link #throwIfUnchecked} and {@code throw new RuntimeException(e)}. For
	* background on the deprecation, read <a href="https://goo.gl/Ivn2kc">Why we deprecated
	* {@code Throwables.propagate}</a>. This method is scheduled to be removed in July 2018.
	*/
	Throwables.propagate(e); // 此方法将于 2018.7 移除
	//Throwables.throwIfUnchecked(e);

	}
	}

	/**
	* 测试二
	*/
	private static void showThrowableArray(){
	try {
	int[] data = {1,2,3};
	getValue(data, 4);
	} catch (Throwable e) {
	Throwables.propagateIfInstanceOf(e, IndexOutOfBoundsException.class);
	Throwables.propagate(e);
	}
	}

	/**
	* 测试三
	*/
	private static void showThrowableIO(){
	try {
	dummyIO();
	} catch (Throwable e) {
	Throwables.propagateIfInstanceOf(e, IndexOutOfBoundsException.class);
	Throwables.propagate(e);
	}
	}

	/**
	* 自定义异常测试：InvalidInputException
	* 注意：此处的 InvalidInputException 不是 org.eclipse.jdt.core.compiler.InvalidInputException
	* @param input 传入参数
	* @return 平方根
	* @throws InvalidInputException 自定义异常
	*/
	private static double sqrt(double input) throws InvalidInputException{
	if(input < 0) throw new InvalidInputException("求平方根出了点问题，你再试试！");
	return Math.sqrt(input);
	}

	/**
	* 数组越界异常测试：IndexOutOfBoundsException
	* @param list 整型数组
	* @param index 数组长度
	* @return 数组指定元素
	* @throws IndexOutOfBoundsException 数组越界
	*/
	private static double getValue(int[] list, int index) throws IndexOutOfBoundsException {
	return list[index];
	}

	/**
	* IO 异常测试：IOException
	* @throws IOException io 异常
	*/
	private static void dummyIO() throws IOException {
	throw new IOException();
	}
	}

# 输出结果

com.example.google.guava.demo.exception.InvalidInputException: 求平方根出了点问题，你再试试！
[com.example.google.guava.demo.exception.InvalidInputException: 求平方根出了点问题，你再试试！]
================2.ArrayIndexOutOfBoundsException==================
java.lang.ArrayIndexOutOfBoundsException: 4
	at com.example.google.guava.demo.clazz.ThrowablesTest.getValue(ThrowablesTest.java:132)
	at com.example.google.guava.demo.clazz.ThrowablesTest.showThrowableArray(ThrowablesTest.java:93)
	at com.example.google.guava.demo.clazz.ThrowablesTest.main(ThrowablesTest.java:42)
 
================3.IOException==================
java.lang.RuntimeException: java.io.IOException
	at com.google.common.base.Throwables.propagate(Throwables.java:241)
	at com.example.google.guava.demo.clazz.ThrowablesTest.showThrowableIO(ThrowablesTest.java:108)
	at com.example.google.guava.demo.clazz.ThrowablesTest.main(ThrowablesTest.java:52)
Caused by: java.io.IOException
	at com.example.google.guava.demo.clazz.ThrowablesTest.dummyIO(ThrowablesTest.java:140)
	at com.example.google.guava.demo.clazz.ThrowablesTest.showThrowableIO(ThrowablesTest.java:105)
	... 1 more

# 方法说明 - 传递异常的常用方法

1.RuntimeException propagate(Throwable)：把throwable包装成RuntimeException，用该方法保证异常传递，抛出一个RuntimeException异常
2.void propagateIfInstanceOf(Throwable, Class<X extends Exception>) throws X：当且仅当它是一个X的实例时，传递throwable
3.void propagateIfPossible(Throwable)：当且仅当它是一个RuntimeException和Error时，传递throwable
4.void propagateIfPossible(Throwable, Class<X extends Throwable>) throws X：当且仅当它是一个RuntimeException和Error时，或者是一个X的实例时，传递throwable。

# 附录 - InvalidInputException.java

	package com.example.google.guava.demo.exception;


	/**
	* <p>
	* <code>InvalidInputException</code>
	* </p>
	* Description:
	*
	* @author Mcchu
	* @date 2017/10/19 10:19
	*/
	public class InvalidInputException extends Exception{

	public InvalidInputException( String message ){
	super( message );
	}
	}

# 参考

http://www.yiibai.com/guava/guava_throwables_class.html

http://www.cnblogs.com/peida/p/Guava_Throwables.html

http://outofmemory.cn/java/guava/base/Throwables