blocks|key|1089132|text|在这里，可以使用Java+SE完成以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1089133|import+java.io.StringReader;
import+javax.xml.xpath.XPath;
import+javax.xml.xpath.XPathFactory;
import+org.xml.sax.InputSource;

public+class+Demo+{

++++public+static+void+main(String[]+args)+throws+Exception+{
++++++++String+xml+=+"<car><manufacturer>toyota</manufacturer></car>";
++++++++String+xpath+=+"/car/manufacturer";
++++++++XPath+xPath+=+XPathFactory.newInstance().newXPath();
++++++++assertEquals("toyota",xPath.evaluate(xpath,+new+InputSource(new+StringReader(xml))));
++++}

}|code-block|syntax|javascript|1089134|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here you go, the following can be done with Java SE:

<pre><code>import java.io.StringReader;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathFactory;
import org.xml.sax.InputSource;

public class Demo {

 public static void main(String[] args) throws Exception {
 String xml = "&lt;car&gt;&lt;manufacturer&gt;toyota&lt;/manufacturer&gt;&lt;/car&gt;";
 String xpath = "/car/manufacturer";
 XPath xPath = XPathFactory.newInstance().newXPath();
 assertEquals("toyota",xPath.evaluate(xpath, new InputSource(new StringReader(xml))));
 }

}
</code></pre>

blocks|key|1089189|text|对于这个用例，XMLUnit库可能是一个完美的选择：http://xmlunit.sourceforge.net/userguide/html/index.html#Xpath%2520Tests|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1089190|它提供了一些附加的断言方法。|1089191|例如：|1089192|assertXpathEvaluatesTo("toyota",+"/car/manufacturer",
++++"<car><manufacturer>toyota</manufacturer></car>");|code-block|syntax|javascript|1089193|entityMap|0|LINK|mutability|MUTABLE|url|http://xmlunit.sourceforge.net/userguide/html/index.html#Xpath%2520Tests^0|Q|1Y|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|C|$K|L]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

For this use case the XMLUnit library may be a perfect fit: 
<a href="http://xmlunit.sourceforge.net/userguide/html/index.html#Xpath%20Tests" rel="noreferrer">http://xmlunit.sourceforge.net/userguide/html/index.html#Xpath%20Tests</a>

It provides some additional assert methods.

For example:

<pre><code>assertXpathEvaluatesTo("toyota", "/car/manufacturer",
 "&lt;car&gt;&lt;manufacturer&gt;toyota&lt;/manufacturer&gt;&lt;/car&gt;");
</code></pre>

blocks|key|874580|text|使用https://github.com/guppy4j/libraries/tree/master/messaging-impl中的Xml类：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|874581|Xml+xml+=+new+Xml("<car><manufacturer>toyota</manufacturer></car>");
assertEquals("toyota",+xml.get("/car/manufacturer"));|code-block|syntax|javascript|874582|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/guppy4j/libraries/tree/master/messaging-impl^0|2|1R|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Using the Xml class from <a href="https://github.com/guppy4j/libraries/tree/master/messaging-impl" rel="nofollow">https://github.com/guppy4j/libraries/tree/master/messaging-impl</a> :

<pre><code>Xml xml = new Xml("&lt;car&gt;&lt;manufacturer&gt;toyota&lt;/manufacturer&gt;&lt;/car&gt;");
assertEquals("toyota", xml.get("/car/manufacturer"));
</code></pre>

blocks|key|874615|text|到目前为止，我已经用三种语言编写了assertXPath()。Ruby和Python是最好的，因为它们还可以通过libxml2解析带有其特性的超文本标记语言，然后在上面运行XPaths。对于XML，或者对于精心控制的超文本标记语言，没有像JavaScript“小于”那样的<故障，下面是我的断言套件：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|874616|private+static+final+XPathFactory+xpathFactory+=+XPathFactory.newInstance();
private+static+final+XPath+xpath+=+xpathFactory.newXPath();

private+static+@NonNull+Document+assertHtml(@NonNull+String+xml)+{
++++try+{
++++++++try+{
++++++++++++DocumentBuilderFactory+factory+=+DocumentBuilderFactory.newInstance();
++++++++++++factory.setNamespaceAware(false);
++++++++++++DocumentBuilder+builder+=+factory.newDocumentBuilder();
++++++++++++ByteArrayInputStream+stream+=+new+ByteArrayInputStream(xml.replaceAll("i+<+len;",+"i+&lt;+len;").getBytes());++//++Because+JavaScript+ruined+HTML's+ability+to+someday+be+real+XML...
++++++++++++return+builder.parse(stream);
++++++++}+catch+(SAXParseException+e)+{
++++++++++++if+(e.getLocalizedMessage().startsWith("Unexpected+token")+&&+!xml.startsWith("<xml>"))
++++++++++++++++return+assertHtml("<xml>"+%2B+xml+%2B+"</xml>");

++++++++++++throw+e;++//++a+GOTO+to+2+lines+down...
++++++++}
++++}+catch+(Throwable+e)+{
++++++++fail(e.getLocalizedMessage());
++++}
++++return+null;
}

private+static+@NonNull+List<String>+assertXPaths(@NonNull+Node+node,+@NonNull+String+xpathExpression)
{
++++NodeList+nodes+=+evaluateXPath(node,+xpathExpression);
++++List<String>+values+=+new+ArrayList<>();

++++if+(nodes+!=+null)
++++++++for+(int+i+=+0;+i+<+nodes.getLength();+i%2B%2B)+{
++++++++++++Node+item+=+nodes.item(i);
++++++++++++++//++item.getTextContent();
++++++++++++++//++item.getNodeName();
++++++++++++values.add(item.getNodeValue());
++++++++}

++++if+(values.size()+==+0)
++++++++fail("XPath+not+found:+"+%2B+xpathExpression+%2B+"\n\nin:+"+%2B+nodeToString(node)+%2B+"\n");

++++return+values;
}

private+static+@NonNull+Node+assertXPath(@NonNull+Node+node,+@NonNull+String+xpathExpression)
{
++++NodeList+nodes+=+evaluateXPath(node,+xpathExpression);

++++if+(nodes+!=+null+&&+nodes.getLength()+>+0)
++++++++return+nodes.item(0);

++++fail("XPath+not+found:+"+%2B+xpathExpression+%2B+"\n\nin:+"+%2B+nodeToString(node)+%2B+"\n");
++++return+null;++//++this+can't+happen
}

private+static+NodeList+evaluateXPath(@NonNull+Node+node,+@NonNull+String+xpathExpression)+{
++++NodeList+nodes+=+null;

++++try+{
++++++++XPathExpression+expr+=+xpath.compile(xpathExpression);
++++++++nodes+=+(NodeList)+expr.evaluate(node,+XPathConstants.NODESET);
++++}+catch+(XPathExpressionException+e)+{
++++++++fail(e.getLocalizedMessage());
++++}
++++return+nodes;
}

private+static+void+assertXPath(Node+node,+String+xpathExpression,+String+reference)+{
++++List<String>+nodes+=+assertXPaths(node,+xpathExpression);
++++assertEquals(1,+nodes.size());++//+CONSIDER++decorate+these+assertion+diagnostics+with+nodeToString().+And+don't+check+for+one+text()+-+join+them+all+together
++++assertEquals(reference,+nodes.get(0).trim());++//+CONSIDER++same+complaint:++We+need+to+see+the+nodeToString()+here
}

private+static+void+refuteXPath(@NonNull+Node+node,+@NonNull+String+xpathExpression)+{
++++NodeList+nodes+=+evaluateXPath(node,+xpathExpression);

++++if+(nodes.getLength()+!=+0)
++++++++fail("XPath+should+not+be+found:+"+%2B+xpathExpression);++//+CONSIDER++decorate+this+with+the+contents+of+the+node
}

private+static+@NonNull+String+nodeToString(@NonNull+Node+node)+{
++++StringWriter+sw+=+new+StringWriter();
++++Transformer+t+=+null;

++++try+{
++++++++t+=+TransformerFactory.newInstance().newTransformer();
++++}+catch+(TransformerConfigurationException+e)+{
++++++++fail(e.getLocalizedMessage());
++++}

++++t.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION,+"yes");
++++t.setOutputProperty(OutputKeys.INDENT,+"yes");

++++try+{
++++++++t.transform(new+DOMSource(node),+new+StreamResult(sw));
++++}+catch+(TransformerException+e)+{
++++++++fail(e.getLocalizedMessage());
++++}

++++return+sw.toString();
}|code-block|syntax|javascript|874617|像这样递归地使用它们：|874618|++++Document+doc+=+assertHtml(myHtml);
++++Node+blockquote+=+assertXPath(doc,+"//blockquote[+'summary_7'+=+@id+]");

++++assertXPath(blockquote,+".//span[+contains(.,+'Mammal')+and+strong/text()+=+'anteater'+]");|874619|查找一个节点，然后断言与该节点相关的路径(通过.//)的好处是，在失败时，nodeToString()将只报告节点内容，如我的<blockquote>。断言诊断消息不会包含整个文档，因此非常容易阅读。|874620|entityMap^0|H|D|3S|1|0|0|0|0|N|3|11|E|1R|C|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|R|$]]

I have written <code>assertXPath()</code> in three languages so far. Ruby and Python are the best because they can also parse HTML with its idiosyncrasies via libxml2 and then run XPaths on them. For XML, or for carefully controlled HTML that doesn't have glitches like <code>&lt;</code> for a JavaScript "less than", here's my assertion suite:

<pre><code>private static final XPathFactory xpathFactory = XPathFactory.newInstance();
private static final XPath xpath = xpathFactory.newXPath();

private static @NonNull Document assertHtml(@NonNull String xml) {
 try {
 try {
 DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
 factory.setNamespaceAware(false);
 DocumentBuilder builder = factory.newDocumentBuilder();
 ByteArrayInputStream stream = new ByteArrayInputStream(xml.replaceAll("i &lt; len;", "i &amp;lt; len;").getBytes()); // Because JavaScript ruined HTML's ability to someday be real XML...
 return builder.parse(stream);
 } catch (SAXParseException e) {
 if (e.getLocalizedMessage().startsWith("Unexpected token") &amp;&amp; !xml.startsWith("&lt;xml&gt;"))
 return assertHtml("&lt;xml&gt;" + xml + "&lt;/xml&gt;");

 throw e; // a GOTO to 2 lines down...
 }
 } catch (Throwable e) {
 fail(e.getLocalizedMessage());
 }
 return null;
}

private static @NonNull List&lt;String&gt; assertXPaths(@NonNull Node node, @NonNull String xpathExpression)
{
 NodeList nodes = evaluateXPath(node, xpathExpression);
 List&lt;String&gt; values = new ArrayList&lt;&gt;();

 if (nodes != null)
 for (int i = 0; i &lt; nodes.getLength(); i++) {
 Node item = nodes.item(i);
 // item.getTextContent();
 // item.getNodeName();
 values.add(item.getNodeValue());
 }

 if (values.size() == 0)
 fail("XPath not found: " + xpathExpression + "\n\nin: " + nodeToString(node) + "\n");

 return values;
}

private static @NonNull Node assertXPath(@NonNull Node node, @NonNull String xpathExpression)
{
 NodeList nodes = evaluateXPath(node, xpathExpression);

 if (nodes != null &amp;&amp; nodes.getLength() &gt; 0)
 return nodes.item(0);

 fail("XPath not found: " + xpathExpression + "\n\nin: " + nodeToString(node) + "\n");
 return null; // this can't happen
}

private static NodeList evaluateXPath(@NonNull Node node, @NonNull String xpathExpression) {
 NodeList nodes = null;

 try {
 XPathExpression expr = xpath.compile(xpathExpression);
 nodes = (NodeList) expr.evaluate(node, XPathConstants.NODESET);
 } catch (XPathExpressionException e) {
 fail(e.getLocalizedMessage());
 }
 return nodes;
}

private static void assertXPath(Node node, String xpathExpression, String reference) {
 List&lt;String&gt; nodes = assertXPaths(node, xpathExpression);
 assertEquals(1, nodes.size()); // CONSIDER decorate these assertion diagnostics with nodeToString(). And don't check for one text() - join them all together
 assertEquals(reference, nodes.get(0).trim()); // CONSIDER same complaint: We need to see the nodeToString() here
}

private static void refuteXPath(@NonNull Node node, @NonNull String xpathExpression) {
 NodeList nodes = evaluateXPath(node, xpathExpression);

 if (nodes.getLength() != 0)
 fail("XPath should not be found: " + xpathExpression); // CONSIDER decorate this with the contents of the node
}

private static @NonNull String nodeToString(@NonNull Node node) {
 StringWriter sw = new StringWriter();
 Transformer t = null;

 try {
 t = TransformerFactory.newInstance().newTransformer();
 } catch (TransformerConfigurationException e) {
 fail(e.getLocalizedMessage());
 }

 t.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
 t.setOutputProperty(OutputKeys.INDENT, "yes");

 try {
 t.transform(new DOMSource(node), new StreamResult(sw));
 } catch (TransformerException e) {
 fail(e.getLocalizedMessage());
 }

 return sw.toString();
}
</code></pre>

Use those recursively, like this:

<pre><code> Document doc = assertHtml(myHtml);
 Node blockquote = assertXPath(doc, "//blockquote[ 'summary_7' = @id ]");

 assertXPath(blockquote, ".//span[ contains(., 'Mammal') and strong/text() = 'anteater' ]");
</code></pre>

The benefit of finding a node, then asserting a path relative to that node (via <code>.//</code>) is at failure time <code>nodeToString()</code> will only report the node contents, such as my <code>&lt;blockquote&gt;</code>. The assertion diagnostic message won't contain the entire document, making it very easy to read.

A simple answer needed to a simple question.

For example:

<pre><code>String xml = "&lt;car&gt;&lt;manufacturer&gt;toyota&lt;/manufacturer&gt;&lt;/car&gt;";
String xpath = "/car/manufacturer";
assertEquals("toyota",evaluate(xml, xpath));
</code></pre>

How can I write the evaluate method in simple and readable way that will work for any given well-formed xml and xpath.

Obviously there are loads of ways this can be achieved but the majority seem very verbose.

Any simple ways I'm missing/libraries that can achieve this?

For cases where multiple nodes are returned I just want the string representation of this.

What's a simple way in java to evaluate an xpath on a string and return a result string

Python

Java

一个简单问题所需要的简单答案。例如：String xml = "<car><manufacturer>toyota</manufacturer></car>";String xpath = "/car/manufacturer";assertEquals("toyota",evaluate(xml, xpath));如何以简单且可读的方式编写适用于任何给定的格式良好的xml和xpath的evalu

问在java中，计算字符串上的xpath并返回结果字符串的简单方法是什么
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