采用SAX方式解析xml
还是老样子，javabean实体类：

JUnit测试：


代码中注释部分的输出是用来看stack实时size大小，有意思，你看出什么了吗：
startElement:1characters:1startElement:2characters:2startElement:3characters:3endElement:2characters:2startElement:3characters:3endElement:2characters:2endElement:1characters:1startElement:2characters:2startElement:3characters:3endElement:2characters:2startElement:3characters:3endElement:2characters:2endElement:1characters:1endElement:0