简化异常处理的Throwables类

　有时候, 当我们我们捕获异常, 并且像把这个异常传递到下一个try/catch块中。Guava提供了一个异常处理工具类, 可以简单地捕获和重新抛出多个异常。例如：

import java.io.IOException;
import org.junit.Test;
import com.google.common.base.Throwables;

public class ThrowablesTest {

@Test
public void testThrowables(){
try {
throw new Exception();
} catch (Throwable t) {
String ss = Throwables.getStackTraceAsString(t);
System.out.println("ss:"+ss);
Throwables.propagate(t);
}
}

@Test
public void call() throws IOException {
try {
throw new IOException();
} catch (Throwable t) {
Throwables.propagateIfInstanceOf(t, IOException.class);
throw Throwables.propagate(t);
}
}
}

 　　将检查异常转换成未检查异常,例如：

import java.io.InputStream;
import java.net.URL;
import org.junit.Test;
import com.google.common.base.Throwables;

public class ThrowablesTest {

@Test
public void testCheckException(){
try {
URL url = new URL("http://ociweb.com");
final InputStream in = url.openStream();
// read from the input stream
in.close();
} catch (Throwable t) {
throw Throwables.propagate(t);
}
}
}

 　　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。　　使用实例：

import java.io.IOException;
import org.junit.Test;
import com.google.common.base.Throwables;

public class ThrowablesTest {
@Test
public void testThrowables(){
try {
throw new Exception();
} catch (Throwable t) {
String ss = Throwables.getStackTraceAsString(t);
System.out.println("ss:"+ss);
Throwables.propagate(t);
}
}

@Test
public void call() throws IOException {
try {
throw new IOException();
} catch (Throwable t) {
Throwables.propagateIfInstanceOf(t, IOException.class);
throw Throwables.propagate(t);
}
}

public Void testPropagateIfPossible() throws Exception {
try {
throw new Exception();
} catch (Throwable t) {
Throwables.propagateIfPossible(t, Exception.class);
Throwables.propagate(t);
}

return null;
}
}

　　Guava的异常链处理方法：　　1.Throwable getRootCause(Throwable)
　　2.List<Throwable> getCausalChain(Throwable)
　　3.String getStackTraceAsString(Throwable)