例子1：Entity的格式
<root>
<data>
<myEntity>
<myField1>1234</myField1>
<myField2>This is demo</myField2>
</myEntity>
</data>
</root>
例子2：EntityList的格式为
<root>
<data>
<list length=2>
<myEntity name="test1">
<myField1>1234</myField1>
<myField2>This is demo</myField2>
</myEntity>
<myEntity name="test2">
<myField1>2345</myField1>
<myField2>This is demo</myField2>
</myEntity>
<list>
</data>
</root>
通过Xpath来访问数据，比如
/root/data /myEntity将访问到例子1中的<myEntity>实体
/root/data/myEntity/ myField1 将访问到例子1中的myField1，结果为1234
/root/data/list/myEntity[@name="test1"]将访问例子2中的<myEntity name="test1"> 实体
/root/data/list/myEntity[@name="test1"]/myField1将访问例子2中的myField1，值为1234