HTML DOM到字符串 - Transformer NullPointerException [英] HTML DOM Tree to String - Transformer NullPointerException
问题描述
我正在尝试将org.w3c.dom.Document对象的内容转换为字符串。我获取JBrowser组件中显示的当前页面的Document对象。将文档dom树转换为字符串的最常见方法似乎是使用javax.xml.transform.Transformer。所以我实现了这一点：
I'm trying to convert the content of an org.w3c.dom.Document object into a string. I get the Document object of the current page displayed in the JBrowser component. The most common way to convert a document dom tree into a string seems to be using a javax.xml.transform.Transformer. So I implemented this:
ByteArrayOutputStream baos = new ByteArrayOutputStream();
TransformerFactory.newInstance().newTransformer().transform(
new DOMSource(aDocument), new StreamResult(baos));
return baos.toString();
这适用于简单的网站，但是越复杂，我们得到这个异常的可能性越高：
This works for simple websites, but the more complex they get the higher the probability of me getting this exception:
ERROR: ''
05.07.2012 10:17:09 com.de.test.Demonstrator$1 run
FATAL: null
javax.xml.transform.TransformerException: java.lang.NullPointerException
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:717)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:313)
at com.de.test.DocumentUtils.toHTML(DocumentUtils.java:47)
at com.de.test.Demonstrator$1.run(Demonstrator.java:172)
Caused by: java.lang.NullPointerException
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:178)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:132)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:94)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(TransformerImpl.java:662)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:708)
... 3 more
---------
java.lang.NullPointerException
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:178)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:226)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:132)
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:94)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(TransformerImpl.java:662)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:708)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:313)
at com.de.test.DocumentUtils.toHTML(DocumentUtils.java:47)
at com.de.test.Demonstrator$1.run(Demonstrator.java:172)
经过一些研究发现有关提示，某些文本元素可能为null，这会导致Transformer崩溃。所以我只是这样做：
After some research found out about the hint, that some text elements might be null and that this causes the Transformer to crash. So I did just that:
public static final void traverseLevel(TreeWalker walker, Document aDocument, String indent)
{
// describe current node:
Node parent = walker.getCurrentNode();
if (parent != null && parent.getNodeValue() == null)
parent.setNodeValue(" ");
System.out.println(indent + "- <" + ((Element) parent).getTagName() + ">" + parent.getNodeValue());
// traverse children:
for (Node n = walker.firstChild(); n != null; n = walker.nextSibling())
{
if(n != null)
traverseLevel(walker, aDocument, indent + '\t');
}
System.out.println("</"+ ((Element) parent).getTagName() + ">");
// return position to the current (level up):
walker.setCurrentNode(parent);
}
这是我发现parent.getNodeValue（）总是返回的地方空值。有趣的是，问题也发生在简单的网站上，但变压器仍然输出树的值。任何想法我更换空文本节点有什么问题？还有其他潜在的问题可能会导致这个问题吗？
This is where I found out that "parent.getNodeValue()" always returns null. The funny thing is, that the problem also occurs on simple websites, but the transformer still outputs the tree's values. Any idea what's wrong with my replacement of null text nodes? Are there other potential problems that might cause this issue?
谢谢！
推荐答案
好吧，我找到了一个解决方法来解决我的问题。我已将JBrowser更改为具有convertToHtml（）函数的DJ Project浏览器。我无法解决变形金刚问题，这就是为什么我采取了这条路线。
Ok, I found a workaround for my problem. I've changed the JBrowser to the DJ Project browser which has a convertToHtml() function. I could not solve the Transformer problem that's why I've taken this route.
这篇关于HTML DOM到字符串 - Transformer NullPointerException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
