JDOM2.0.5版本通过xpath读取xml或读取带有命名空间的xml

org.jdom2.xpath.XPath类居然标注过时，无奈之下只能研究api。

发现Use XPathFactory/XPathExpression/XPathBuilder
instead.

也就是说jdom应该是将xpath类的功能进行了更加详细的分类。

根据经验进行了一些类的测试，最后得出了读取xml的两种方式。

第一种方式，通过XPathFactory类读取xml

xml文件的内容如下

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="test.xsl"?>
<homepages xmlns:xlink="http://www.w3.org/1999/xlink">

<homepage xlink:type="simple"
xlink:href="http://www.w3school.com.cn">Visit W3School</homepage>

<homepage xlink:type="simple"
xlink:href="http://www.w3.org">Visit W3C</homepage>

</homepages>

通过SAXBuilder获取document和root

String path = System.getProperty("user.dir") + "\\src\\com\\xml\\file\\test.xml";

SAXBuilder saxBuilder = new SAXBuilder();

Document document = saxBuilder.build(path);

Element root = document.getRootElement();

建立XPathFactory类的对象，需要引入jaxen的jar包，我们使用JaxenXPathFactory类来生成XPathFactory

XPathFactory factory = JaxenXPathFactory.instance();

生产xpath表达式实例对象，并获取结果集

XPathExpression<Object> objs = factory.compile("//homepages");

List<Object> objList = objs.diagnose(root, false).getResult();

完整代码是

String path = System.getProperty("user.dir") + "\\src\\com\\xml\\file\\test.xml";

SAXBuilder saxBuilder = new SAXBuilder();

Document document = saxBuilder.build(path);

Element root = document.getRootElement();

XPathFactory factory = JaxenXPathFactory.instance();

XPathExpression<Object> objs = factory.compile("//homepages");

List<Object> objList = objs.diagnose(root, false).getResult();

第二种方式，通过XPathBuilder获取xpath表达式的实例对象集合

首先来创建一个filter，org.jdom2.filter.Filters中提供给我们了一些过滤器，我们这里选择元素类型的，Filter接口的全名是org.jdom2.filter.Filter

Filter<Element> filter = Filters.element();

生成XPathBuilder对象

XPathBuilder<Element> builder = new XPathBuilder<Element>("//homepages", filter);

根据它的compileWith(XPathFactory factory)方法来获取到我们需要的xpath表达式的实例对象集合

XPathFactory factory = JaxenXPathFactory.instance();

XPathExpression<Element> objs = builder.compileWith(factory);

之后的方式就和方法1一样了。

完整代码是

String path = System.getProperty("user.dir") + "\\src\\com\\xml\\file\\test.xml";

SAXBuilder saxBuilder = new SAXBuilder();

Document document = saxBuilder.build(path);

Element root = document.getRootElement();

Filter<Element> filter = Filters.element();

XPathBuilder<Element> builder = new XPathBuilder<Element>("//homepages", filter);

XPathFactory factory = JaxenXPathFactory.instance();

XPathExpression<Element> objs = builder.compileWith(factory);

List<Element> objList = objs.diagnose(root, false).getResult();	

获取带有命名空间的xml文件内容

使用XPathBuilder的setNamespace方法声明命名空间，Xpath表达式不需要再写"//"，例如

XPathBuilder<Element> builder = new XPathBuilder<Element>("ci:Teacher", filter);

builder.setNamespace("ci", "http://www.test.cn/tuple");