抛出适合抽象的异常
抛出的异常应该与调用者执行的任务有联系。此项介绍异常转换（捕获异常并抛出另一个）和异常链（将异常包装在新的异常中以保留异常的因果链）。
private void serializeBillingDetails(BillingResult billingResult,
BillingDetailsType billingDetails) {
try {
final JAXBContext context = JAXBContext
.newInstance(BillingdataType.class);
final ByteArrayOutputStream out = new ByteArrayOutputStream();
final Marshaller marshaller = context.createMarshaller();
marshaller.setProperty("jaxb.formatted.output", Boolean.FALSE);
final BillingdataType billingdataType = new BillingdataType();
billingdataType.getBillingDetails().add(billingDetails);
marshaller.marshal(factory.createBillingdata(billingdataType), out);
final String xml = new String(out.toByteArray(), "UTF-8");
billingResult.setResultXML(xml.substring(
xml.indexOf("") + 13,
xml.indexOf(" ")).trim());
billingResult.setGrossAmount(billingDetails.getOverallCosts()
.getGrossAmount());
billingResult.setNetAmount(billingDetails.getOverallCosts()
.getNetAmount());
} catch (JAXBException | UnsupportedEncodingException ex) {
throw new BillingRunFailed(ex);
}
}上述方法捕获 JAXBException 和 UnsupportedEncodingException，并重新抛出一个适合方法抽象级别的新异常。新的 BillingRunFailed 异常包装了原始异常。所以这是异常链的一个很好的例子。异常链的好处是保留有助于调试问题的低级异常。
