how to configure java.xml.transform.transformer in spring - spring

Question

How can i configure java.xml.transform.Transformer in spring framework ? I need instance of transformer to transform xml to text via xslt. Hence it is critical that the configured transformer should have knowledge of xslt stylesheet. I am not using this in a web project, rather i am using this in a standalone java program.

Answer 1

Well, the Java to configure a Transformer is like this:
Source stylesheetSource = new StreamSource(new File("/path/to/my/stylesheet.xslt"));
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer(stylesheetSource);
If you really want to do this purely in Spring XML, this is the equivalent:
<bean id="stylesheetSource" class="javax.xml.transform.stream.StreamSource">
<property name="systemId" value="/path/to/my/stylesheet.xslt"/>
</bean>
<bean id="transformerFactory" class="javax.xml.transform.TransformerFactory" factory-method="newInstance"/>
<bean id="transformer" factory-bean="transformerFactory" factory-method="newTransformer">
<constructor-arg ref="stylesheetSource"/>
</bean>

Answer 2

You're going to need to get an instance of a Transformer from an appropriate TransformerFactory. You can use the built-in xerces transformer factory or a 3rd party XSLT processor, like saxonica.
Using Spring's IoC you can configure a Xerces XML transformer like this:
<bean id="transformerFactory" class="org.apache.xerces.jaxp.SAXParserFactoryImpl" />
or a saxon XML transformer like this:
<bean id="transformerFactory" class="net.sf.saxon.TransformerFactoryImpl" />
Once you have a TransformerFactory you can use dependency injection to get a new instance of a transformer either inside your bean or using the IoC. Switching to be inside your class you might have some property, say transFact that you need to set:
<bean id="myBean" class="myClass">
<property name="transFact" ref="transformerFactory" />
</bean>
Then in your class:
public class myClass {
// ...
private javax.xml.transformer.TransformerFactory transFact;
public void myMethod(){
StreamSource transformerStream = new StreamSource(getResourceAsStream(pathToXslt));
javax.xml.transformer.Transformer myTrans = transFact.newTransformer(transformerStream);
// now you've got a myTrans
}
// ...
public setTransFact(javax.xml.transformer.TransformerFactory transFact){
this.transFact = transFact;
}
}
Alternatively you can get a new transformer within IoC using the factory-method with a little more effort.

Answer 3

I found this way to provide xsl file from the classpath:
<bean id="errorLogTransformer" factory-bean="transformerFactory" factory-method="newTransformer" >
<constructor-arg>
<bean class="org.springframework.xml.transform.ResourceSource">
<constructor-arg>
<value>classpath:errorLog.xsl</value>
</constructor-arg>
</bean>
</constructor-arg>
</bean>
Pretty ugly, but it works!