说明： 一个简单的Dom4j解析xml的源程序，很简单，使用了xpath，看其文档，使用xpath时没这么复杂，但是，实际使用时往往不是这样的。 (Dom4j a simple analysis of the source xml is very simple, use the xpath, watch their documents, when using xpath not so complicated, however, when actual use is often not the case.)
