Java XML解析错误:prolog中不允许有内容

My code write a XML file with the LSSerializer class :

我的代码使用LSSerializer类编写一个XML文件:

DOMImplementation impl = doc.getImplementation();
DOMImplementationLS implLS = (DOMImplementationLS) impl.getFeature("LS","3.0");

LSSerializer ser = implLS.createLSSerializer();

String str = ser.writeToString(doc);
System.out.println(str);

String file = racine+"/"+p.getNom()+".xml";
OutputStreamWriter out = new OutputStreamWriter(new FileOutputStream(file),"UTF-8");
out.write(str);
out.close();

The XML is well-formed, but when I parse it, I get an error.

XML格式良好，但是当我解析它时，我就会得到一个错误。

Parse code :

解析代码:

File f = new File(racine+"/"+filename);

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(f);

XPathFactory xpfactory = XPathFactory.newInstance();
XPath xp = xpfactory.newXPath();

String expression;

expression = "root/nom";        
String nom = xp.evaluate(expression, doc);

The error :

错误:

[Fatal Error] Terray.xml:1:40: Content is not allowed in prolog.
9 août 2011 19:42:58 controller.MakaluController activatePatient
GRAVE: null
org.xml.sax.SAXParseException: Content is not allowed in prolog.
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:249)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:284)
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:208)
at model.MakaluModel.setPatientActif(MakaluModel.java:147)
at controller.MakaluController.activatePatient(MakaluController.java:59)
at view.ListePatientsPanel.jButtonOKActionPerformed(ListePatientsPanel.java:92)
...

Now, with some research, I found that this error is dure to a "hidden" character at the very beginning of the XML.

现在，通过一些研究，我发现这个错误不会出现在XML开头的“隐藏”字符上。

In fact, I can fix the bug by creating a XML file manually.

事实上，我可以通过手工创建XML文件来修复这个bug。

But where is the error in the XML writing ? (When I try to println the string, there is no space before ths

但是XML写入的错误在哪里呢?(当我尝试打印字符串时，前面没有空格

Solution : change the serializer

I run the solution of UTF-16 encoding for a while, but it was not very stable. So I found a new solution : change the serializer of the XML document, so that the encoding is coherent between the XML header and the file encoding. :

我对UTF-16编码的解决方案运行了一段时间，但它不是很稳定。因此，我找到了一种新的解决方案:更改XML文档的序列化器，以便XML头和文件编码之间的编码是一致的。:

    DOMSource domSource = new DOMSource(doc);
    TransformerFactory tf = TransformerFactory.newInstance();
    Transformer transformer = tf.newTransformer();

    String file = racine+"/"+p.getNom()+".xml";
    OutputStreamWriter out = new OutputStreamWriter(new FileOutputStream(file),"UTF-8");

    transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
    transformer.setOutputProperty(OutputKeys.INDENT,"yes");
    transformer.transform(domSource, new StreamResult(out));

4 个解决方案

#1

But where is the error in the XML writing ?

但是XML写入的错误在哪里呢?

Looks like the error is not in the writing but the parsing. As you have already discovered there is a blank character at the beginning of the file, which causes the error in the parse call in your stach trace:

看起来错误不在书写中，而是在解析过程中。正如您已经发现在文件的开头有一个空白字符，这将导致stach跟踪中的解析调用错误:

Document doc = builder.parse(f);

The reason you do not see the space when you print it out may be simply the encoding you are using. Try changing this line:

打印时看不到空格的原因可能仅仅是您正在使用的编码。试着改变这条线:

OutputStreamWriter out = new OutputStreamWriter(new FileOutputStream(file),"UTF-8");

to use 'UTF-16' or 'US-ASCII'

使用“UTF-16”或“US-ASCII”

#2

I think that it is probably linked to BOM (Byte Order Mark). See Wikipedia

我认为它可能链接到BOM(字节顺序标记)。看到*

You can verify with Notepad++ by example : Open your file and check the "Encoding" Menu to see if you're in "UTF8 without BOM" or "UTF8 with BOM".

您可以通过示例验证Notepad++:打开文件并检查“编码”菜单，看看您是在“没有BOM的UTF8”还是“带有BOM的UTF8”。

#3

Using UTF-16 is the way to go,

使用UTF-16是一种方法，

 OutputStreamWriter out = new OutputStreamWriter(new FileOutputStream(fileName),"UTF-16");

This can read the file with no issues

这可以在没有问题的情况下读取文件。

#4

Try this code:

试试这段代码:

InputStream is = new FileInputStream(file);
Document doc = builder.parse(is , "UTF-8");

#1