Een XSD maken van een XML met Trang • Special Agent Squeaky

Houd er rekening mee dat deze blogpost in februari 2011 is gepubliceerd. Afhankelijk van wanneer u hem leest, kunnen bepaalde delen dus verouderd zijn. Helaas kan ik deze berichten niet altijd volledig up-to-date houden om ervoor te zorgen dat de informatie accuraat blijft.

As a web developer, I sometimes find myself stuck with an XML but having no XML schema, such as an XSD - and having an XML schema is the holy grail when working with web services that changes constantly.

There are plenty of XML to XSD generators out there, but my favorite tool I have discovered is Trang. Trang is a multi-format schema converter which can convert between a number of different schema languages. Not XML, but also RELAX NG and DTD - and the best thing about it is that its free.

Here is a quick guide for generating an XSD from an XML using Trang:

Step 1 - Downloading

Visit the project's download page and download the latest version. At the current time, the file trang-20091111.zip is the latest.

Step 2 - Extracting

Extract the ZIP archive and inside you will find a JAR file called trang.jar.

Step 3 - Moving files

Move or copy trang.jar to where you have your XML file. Here I have copied it to the same folder as my "products.xml" is located:

My "products.xml" is a simple XML schema containing two products:

<?xml version="1.0" encoding="utf-8"?>
<products>
    <product>
        <artnbr>A1</artnbr>
        <description>This is the product description for product A1</description>
        <price>123</price>
    </product>
    <product>
        <artnbr>B2</artnbr>
        <description>This is the product description for product B2</description>
        <price>321</price>
    </product>
</products>

Step 4 - Converting

Open a command line and move yourself to the same folder as trang.jar and your XML file is located.

Then type java -jar trang.jar products.xml products.xsd

This will generate "products.xsd" based on your "products.xml".

Opening the newly created "products.xsd" will reveal:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
  <xs:element name="products">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" ref="product"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="product">
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="artnbr"/>
        <xs:element ref="description"/>
        <xs:element ref="price"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="artnbr" type="xs:NCName"/>
  <xs:element name="description" type="xs:string"/>
  <xs:element name="price" type="xs:integer"/>
</xs:schema>

Additional tips

When looking at the XSD, you will notice that Trang will have created different element types, such as xs:NCName and xs:string. Since Trang merely does high educated guesses on how the XSD should be specified - based on the data in the XML - it might get a few elements types wrong.

Because of that, I usually take a brief look at the XSD and replace any very specific element types (in this case the xs:NCName) to more simpler types, such as xs:string.

Geschreven door Special Agent Squeaky. Eerste publicatie 2011-02-14. Laatste update 2011-02-14.