XML中如何通过属性获得对应节点中的内容

Question

<?xml version="1.0" encoding="UTF-8"?><students> <class id="st58"> <student>Jack1</student> <student>Jack2</student> <student>Jack3</student> <student>Jack4</student> </class> <class id="st59"> <student>Tom1</student> <student>Tom2</student> <student>Tom3</student> <student>Tom4</student> </class> <class id="st60"> <student>Mack1</student> <student>Mack2</student> <student>Mack3</student> <student>Mack4</student> </class></students>如上：用DOM解析XML的时候，怎么用相应的id属性得到对应的student节点