Add FreeMarker support

This commit adds auto-configuration and a starter,
spring-boot-starter-freemarker, for using FreeMarker view templates in
a web application.

A new abstraction, TemplateAvailabilityProvider, has been introduced.
This decouples ErrorMvcAutoConfiguration from the various view
technologies that Spring Boot now supports, allowing it to determine
when a custom error template is provided without knowing the details of
each view technology.

Closes #679

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -80,6 +80,22 @@ content into your application; rather pick only the properties that you need.
 	spring.thymeleaf.content-type=text/html # ;charset=<encoding> is added
 	spring.thymeleaf.cache=true # set to false for hot refresh
 
+	# FREEMARKER ({sc-spring-boot-autoconfigure}}/freemarker/FreeMarkerAutoConfiguration.{sc-ext}[FreeMarkerAutoConfiguration])
+	spring.freemarker.allowRequestOverride=false
+	spring.freemarker.allowSessionOverride=false
+	spring.freemarker.cache=true
+	spring.freemarker.checkTemplateLocation=true
+	spring.freemarker.contentType=text/html
+	spring.freemarker.exposeRequestAttributes=false
+	spring.freemarker.exposeSessionAttributes=false
+	spring.freemarker.exposeSpringMacroHelpers=false
+	spring.freemarker.prefix=
+	spring.freemarker.requestContextAttribute=
+	spring.freemarker.suffix=
+	spring.freemarker.templateEncoding=UTF-8
+	spring.freemarker.templateLoaderPath=classpath:/templates/
+	spring.freemarker.viewNames=
+
 	# INTERNATIONALIZATION ({sc-spring-boot-autoconfigure}/MessageSourceAutoConfiguration.{sc-ext}[MessageSourceAutoConfiguration])
 	spring.messages.basename=messages
 	spring.messages.encoding=UTF-8

spring-boot-docs/src/main/asciidoc/appendix-auto-configuration-classes.adoc

@@ -38,6 +38,9 @@ The following auto-configuration classes are from the `spring-boot-autoconfigure
 |{sc-spring-boot-autoconfigure}/web/EmbeddedServletContainerAutoConfiguration.{sc-ext}[EmbeddedServletContainerAutoConfiguration]
 |{dc-spring-boot-autoconfigure}/web/EmbeddedServletContainerAutoConfiguration.{dc-ext}[javadoc]
 
+|{sc-spring-boot-autoconfigure}/freemarker/FreeMarkerAutoConfiguration.{sc-ext}[FreeMarkerAutoConfiguration]
+|{dc-spring-boot-autoconfigure}/freemarker/FreeMarkerAutoConfiguration.{dc-ext}[javadoc]
+
 |{sc-spring-boot-autoconfigure}/orm/jpa/HibernateJpaAutoConfiguration.{sc-ext}[HibernateJpaAutoConfiguration]
 |{dc-spring-boot-autoconfigure}/orm/jpa/HibernateJpaAutoConfiguration.{dc-ext}[javadoc]
 

spring-boot-docs/src/main/asciidoc/howto.adoc

@@ -809,8 +809,16 @@ added.
   `spring.thymeleaf.suffix`, defaults ``classpath:/templates/'' and ``.html''
   respectively). It can be overridden by providing a bean of the same name.
 
-Checkout {sc-spring-boot-autoconfigure}/web/WebMvcAutoConfiguration.{sc-ext}[`WebMvcAutoConfiguration`]
-and {sc-spring-boot-autoconfigure}/thymeleaf/ThymeleafAutoConfiguration.{sc-ext}[`ThymeleafAutoConfiguration`]
+* If you use FreeMarker you will also have a `FreeMarkerViewResolver` with id
+  ``freeMarkerViewResolver''. It looks for resources in a loader path (externalized to
+  `spring.freemarker.templateLoaderPath`, default ``classpath:/templates/'') by
+  surrounding the view name with a prefix and suffix (externalized to `spring.freemarker.prefix`
+  and `spring.freemarker.suffix`, defaults ``'' and ``.ftl'' respectively). It can be overriden
+  by providing a bean of the same name.
+
+Check out {sc-spring-boot-autoconfigure}/web/WebMvcAutoConfiguration.{sc-ext}[`WebMvcAutoConfiguration`],
+{sc-spring-boot-autoconfigure}/thymeleaf/ThymeleafAutoConfiguration.{sc-ext}[`ThymeleafAutoConfiguration`], and
+{sc-spring-boot-autoconfigure}/freemarker/FreeMarkerAutoConfiguration.{sc-ext}['FreeMarkerAutoConfiguration']
 
 
 
@@ -1145,11 +1153,11 @@ you encounter a server error (machine clients consuming JSON and other media typ
 see a sensible response with the right error code). To switch it off you can set
 `error.whitelabel.enabled=false`, but normally in addition or alternatively to that you
 will want to add your own error page replacing the whitelabel one. If you are using
-Thymeleaf you can do this by adding an `error.html` template. In general what you need is
-a `View` that resolves with a name of `error`, and/or a `@Controller` that handles the
-`/error` path. Unless you replaced some of the default configuration you should find a
-`BeanNameViewResolver` in your `ApplicationContext` so a `@Bean` with id `error` would be
-a simple way of doing that.
+Thymeleaf or FreeMarker you can do this by adding an `error.html` or `error.ftl` template
+respectively. In general what you need is a `View` that resolves with a name of `error`,
+and/or a `@Controller` that handles the `/error` path. Unless you replaced some of the
+default configuration you should find a `BeanNameViewResolver` in your `ApplicationContext`
+so a `@Bean` with id `error` would be a simple way of doing that.
 Look at {sc-spring-boot-autoconfigure}/web/ErrorMvcAutoConfiguration.{sc-ext}[`ErrorMvcAutoConfiguration`] for more options.
 
 
@@ -1251,7 +1259,15 @@ tools.
 === Reload Thymeleaf templates without restarting the container
 If you are using Thymeleaf, then set `spring.thymeleaf.cache` to `false`. See
 {sc-spring-boot-autoconfigure}/thymeleaf/ThymeleafAutoConfiguration.{sc-ext}[`ThymeleafAutoConfiguration`]
-for other template customization options.
+for other Thymeleaf customization options.
+
+
+
+[[howto-reload-freemarker-content]]
+=== Reload FreeMarker templates without restarting the container
+If you are using FreeMarker, then set `spring.freemarker.cache` to `false`. See
+{sc-spring-boot-autoconfigure}/freemarker/FreeMarkerAutoConfiguration.{sc-ext}[`FreeMarkerAutoConfiguration`]
+for other FreeMarker customization options.
 
 
 

spring-boot-docs/src/main/asciidoc/index.adoc

@@ -1,5 +1,5 @@
 = Spring Boot Reference Guide
-Phillip Webb; Dave Syer; Josh Long; Stéphane Nicoll; Rob Winch;
+Phillip Webb; Dave Syer; Josh Long; Stéphane Nicoll; Rob Winch; Andy Wilkinson;
 :doctype: book
 :toc:
 :toclevels: 4

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -892,14 +892,16 @@ and it will be silently ignored by most build tools if you generate a jar.
 [[boot-features-spring-mvc-template-engines]]
 ==== Template engines
 As well as REST web services, you can also use Spring MVC to serve dynamic HTML content.
-Spring MVC supports a variety of templating technologies including: velocity, freemarker,
+Spring MVC supports a variety of templating technologies including: Velocity, FreeMarker,
 and JSPs. Many other templating engines also ship their own Spring MVC integrations.
 
-Spring Boot includes auto-configuration support for the Thymeleaf templating engine.
-Thymeleaf is an XML/XHTML/HTML5 template engine that can work both in web and non-web
-environments. It allows you to create natural templates that can be correctly displayed
-by browsers and therefore work also as static prototypes. Thymeleaf templates will be
-picked up automatically from `src/main/resources/templates`.
+Spring Boot includes auto-configuration support for the Thymeleaf and FreeMarker
+templating engines. Thymeleaf is an XML/XHTML/HTML5 template engine that can work both in
+web and non-web environments. If allows you to create natural templates that can be
+correctly displayed by browsers and therefore work also as static prototypes. Both
+FreeMarker and Thymeleaf templates will be picked up automatically from
+`src/main/resources/templates`.
+
 
 TIP: JSPs should be avoided if possible, there are several
 <<boot-features-jsp-limitations, known limitations>> when using them with embedded

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -229,6 +229,9 @@ and Hibernate.
 |`spring-boot-starter-data-rest`
 |Support for exposing Spring Data repositories over REST via `spring-data-rest-webmvc`.
 
+|`spring-boot-starter-freemarker`
+|Support for the FreeMarker templating engine
+
 |`spring-boot-starter-integration`
 |Support for common `spring-integration` modules.