[[mvc-view-xslt]]
= XSLT Views

XSLT is a transformation language for XML and is popular as a view technology within web
applications. XSLT can be a good choice as a view technology if your application
naturally deals with XML or if your model can easily be converted to XML. The following
section shows how to produce an XML document as model data and have it transformed with
XSLT in a Spring Web MVC application.

This example is a trivial Spring application that creates a list of words in the
`Controller` and adds them to the model map. The map is returned, along with the view
name of our XSLT view. See xref:web/webmvc/mvc-controller.adoc[Annotated Controllers] for details of Spring Web MVC's
`Controller` interface. The XSLT controller turns the list of words into a simple XML
document ready for transformation.



[[mvc-view-xslt-beandefs]]
== Beans

Configuration is standard for a simple Spring web application: The MVC configuration
has to define an `XsltViewResolver` bean and regular MVC annotation configuration.
The following example shows how to do so:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes",role="primary"]
----
	@EnableWebMvc
	@ComponentScan
	@Configuration
	public class WebConfig implements WebMvcConfigurer {

		@Bean
		public XsltViewResolver xsltViewResolver() {
			XsltViewResolver viewResolver = new XsltViewResolver();
			viewResolver.setPrefix("/WEB-INF/xsl/");
			viewResolver.setSuffix(".xslt");
			return viewResolver;
		}
	}
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
----
	@EnableWebMvc
	@ComponentScan
	@Configuration
	class WebConfig : WebMvcConfigurer {

		@Bean
		fun xsltViewResolver() = XsltViewResolver().apply {
			setPrefix("/WEB-INF/xsl/")
			setSuffix(".xslt")	
		}
	}
----
======


[[mvc-view-xslt-controllercode]]
== Controller

We also need a Controller that encapsulates our word-generation logic.

The controller logic is encapsulated in a `@Controller` class, with the
handler method being defined as follows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes",role="primary"]
----
	@Controller
	public class XsltController {

		@RequestMapping("/")
		public String home(Model model) throws Exception {
			Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
			Element root = document.createElement("wordList");

			List<String> words = Arrays.asList("Hello", "Spring", "Framework");
			for (String word : words) {
				Element wordNode = document.createElement("word");
				Text textNode = document.createTextNode(word);
				wordNode.appendChild(textNode);
				root.appendChild(wordNode);
			}

			model.addAttribute("wordList", root);
			return "home";
		}
	}
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
----
	import org.springframework.ui.set

	@Controller
	class XsltController {

		@RequestMapping("/")
		fun home(model: Model): String {
			val document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument()
			val root = document.createElement("wordList")

			val words = listOf("Hello", "Spring", "Framework")
			for (word in words) {
				val wordNode = document.createElement("word")
				val textNode = document.createTextNode(word)
				wordNode.appendChild(textNode)
				root.appendChild(wordNode)
			}

			model["wordList"] = root
			return "home"
		}
	}
----
======

So far, we have only created a DOM document and added it to the Model map. Note that you
can also load an XML file as a `Resource` and use it instead of a custom DOM document.

There are software packages available that automatically 'domify'
an object graph, but, within Spring, you have complete flexibility to create the DOM
from your model in any way you choose. This prevents the transformation of XML playing
too great a part in the structure of your model data, which is a danger when using tools
to manage the DOMification process.



[[mvc-view-xslt-transforming]]
== Transformation

Finally, the `XsltViewResolver` resolves the "`home`" XSLT template file and merges the
DOM document into it to generate our view. As shown in the `XsltViewResolver`
configuration, XSLT templates live in the `war` file in the `WEB-INF/xsl` directory
and end with an `xslt` file extension.

The following example shows an XSLT transform:

[source,xml,indent=0,subs="verbatim,quotes"]
----
	<?xml version="1.0" encoding="utf-8"?>
	<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

		<xsl:output method="html" omit-xml-declaration="yes"/>

		<xsl:template match="/">
			<html>
				<head><title>Hello!</title></head>
				<body>
					<h1>My First Words</h1>
					<ul>
						<xsl:apply-templates/>
					</ul>
				</body>
			</html>
		</xsl:template>

		<xsl:template match="word">
			<li><xsl:value-of select="."/></li>
		</xsl:template>

	</xsl:stylesheet>
----

The preceding transform is rendered as the following HTML:

[source,html,indent=0,subs="verbatim,quotes"]
----
<html>
	<head>
		<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
		<title>Hello!</title>
	</head>
	<body>
		<h1>My First Words</h1>
		<ul>
			<li>Hello</li>
			<li>Spring</li>
			<li>Framework</li>
		</ul>
	</body>
</html>
----