Xml – Programmatically creating an XML Document using an XSD

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I need to create XML documents using built-in java org.w3c.dom or jdom packages conforming to a set of XSD files. The XSD files are similar but not the same. In essence, I need to create the XML file as per the XSD given to me dynamically.

What is the best way to do it. I have checked the Validator package, it does not have any features like look-ahead or iterators for the possible elements at a given context node.

Ideally, I am looking at a SAX kind of architecture where I implement an element when I am asked to provide in a context-free manner. The engine should assemble and give me the dom tree at the end.

Is this wheel already been invented?

Thanks..

Best Solution

org.w3c.dom has no support for XML Schemas. For JDom, you can use schemas to validate a document, but there is no support to build documents.

You have two options:

Use JDom to read the schema, analyze it and produce a document according to this XML document (a schema is always a valid XML document, too).
You can use an XML mapper like Castor. Castor can read a Schema and produce a set of Java classes that allow you to produce documents which match said schema.

The latter approach might not work so well in your case since Castor will generate different Java classes for similar XSD structures unless they are defined in the same document, so you can't easily reuse the common code. The workaround is to let Castor generate the code and then write a script or similar to copy/merge the common parts of the XSDs into the same Java package.

Related Solutions

C# – How to Deserialize XML document

How about you just save the xml to a file, and use xsd to generate C# classes?

Write the file to disk (I named it foo.xml)
Generate the xsd: xsd foo.xml
Generate the C#: xsd foo.xsd /classes

Et voila - and C# code file that should be able to read the data via XmlSerializer:

    XmlSerializer ser = new XmlSerializer(typeof(Cars));
    Cars cars;
    using (XmlReader reader = XmlReader.Create(path))
    {
        cars = (Cars) ser.Deserialize(reader);
    }

(include the generated foo.cs in the project)

Xml – What characters do I need to escape in XML documents

If you use an appropriate class or library, they will do the escaping for you. Many XML issues are caused by string concatenation.

XML escape characters

There are only five:

"   &quot;
'   &apos;
<   &lt;
>   &gt;
&   &amp;

Escaping characters depends on where the special character is used.

The examples can be validated at the W3C Markup Validation Service.

Text

The safe way is to escape all five characters in text. However, the three characters ", ' and > needn't be escaped in text:

<?xml version="1.0"?>
<valid>"'></valid>

Attributes

The safe way is to escape all five characters in attributes. However, the > character needn't be escaped in attributes:

<?xml version="1.0"?>
<valid attribute=">"/>

The ' character needn't be escaped in attributes if the quotes are ":

<?xml version="1.0"?>
<valid attribute="'"/>

Likewise, the " needn't be escaped in attributes if the quotes are ':

<?xml version="1.0"?>
<valid attribute='"'/>

Comments

All five special characters must not be escaped in comments:

<?xml version="1.0"?>
<valid>
<!-- "'<>& -->
</valid>

CDATA

All five special characters must not be escaped in CDATA sections:

<?xml version="1.0"?>
<valid>
<![CDATA["'<>&]]>
</valid>

Processing instructions

All five special characters must not be escaped in XML processing instructions:

<?xml version="1.0"?>
<?process <"'&> ?>
<valid/>

XML vs. HTML

HTML has its own set of escape codes which cover a lot more characters.