xml中含有命名空间后，用普通的xpath只能筛选到根结点
需要在map里加一个xml的namespace
Map map = new HashMap();
map.put("xmlns","http://docbook.org/ns/docbook");
reader.getDocumentFactory().setXPathNamespaceURIs(map);
FileInputStream fin = new FileInputStream(new File(absolutePath));
InputStreamReader is = new InputStreamReader(fin,"UTF-8");
Document document = reader.read(is);
然后再装载ＸＭＬ文件
编写xpath时要带要上xmlns
原来是这样写：document.selectNodes("/book/formerAidText/title")
加上xmlns后：document.selectNodes("/xmlns:book/xmlns:formerAidText/xmlns:title")
如果闲麻烦，加个正则替换
public static String fixedXpath(String xpath)
{
xpath= xpath.replaceAll("/(\\w)", "/"+"xmlns:$1");//replace start with "/"
xpath= xpath.replaceAll("^(\\w)", "xmlns:$1"); //replace start with word
return xpath;
}
原文：http://www.cnblogs.com/zxcgy/p/6697557.html