Make MustacheViewResolver extend AbstractTemplateViewResolver

The Mustache support should still be usable outside a web application
because the properties only use web stuff in that context and don't
have any field or method signatures that depend on web.

Fixes gh-5626

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheAutoConfiguration.java

@@ -113,11 +113,7 @@ public class MustacheAutoConfiguration {
 		@ConditionalOnMissingBean(MustacheViewResolver.class)
 		public MustacheViewResolver mustacheViewResolver(Compiler mustacheCompiler) {
 			MustacheViewResolver resolver = new MustacheViewResolver();
-			resolver.setPrefix(this.mustache.getPrefix());
-			resolver.setSuffix(this.mustache.getSuffix());
-			resolver.setCache(this.mustache.isCache());
-			resolver.setViewNames(this.mustache.getViewNames());
-			resolver.setContentType(this.mustache.getContentType().toString());
+			this.mustache.applyToViewResolver(resolver);
 			resolver.setCharset(this.mustache.getCharsetName());
 			resolver.setCompiler(mustacheCompiler);
 			resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10);

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheProperties.java

@@ -16,7 +16,7 @@
 
 package org.springframework.boot.autoconfigure.mustache;
 
-import org.springframework.boot.autoconfigure.template.AbstractViewResolverProperties;
+import org.springframework.boot.autoconfigure.template.AbstractTemplateViewResolverProperties;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 /**
@@ -26,7 +26,7 @@ import org.springframework.boot.context.properties.ConfigurationProperties;
  * @since 1.2.2
  */
 @ConfigurationProperties(prefix = "spring.mustache")
-public class MustacheProperties extends AbstractViewResolverProperties {
+public class MustacheProperties extends AbstractTemplateViewResolverProperties {
 
 	public static final String DEFAULT_PREFIX = "classpath:/templates/";
 
@@ -42,18 +42,26 @@ public class MustacheProperties extends AbstractViewResolverProperties {
 	 */
 	private String suffix = DEFAULT_SUFFIX;
 
+	public MustacheProperties() {
+		super(DEFAULT_PREFIX, DEFAULT_SUFFIX);
+	}
+
+	@Override
 	public String getPrefix() {
 		return this.prefix;
 	}
 
+	@Override
 	public void setPrefix(String prefix) {
 		this.prefix = prefix;
 	}
 
+	@Override
 	public String getSuffix() {
 		return this.suffix;
 	}
 
+	@Override
 	public void setSuffix(String suffix) {
 		this.suffix = suffix;
 	}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/web/MustacheViewResolver.java

@@ -29,7 +29,7 @@ import org.springframework.beans.propertyeditors.LocaleEditor;
 import org.springframework.core.io.Resource;
 import org.springframework.web.servlet.View;
 import org.springframework.web.servlet.ViewResolver;
-import org.springframework.web.servlet.view.UrlBasedViewResolver;
+import org.springframework.web.servlet.view.AbstractTemplateViewResolver;
 
 /**
  * Spring MVC {@link ViewResolver} for Mustache.
@@ -39,7 +39,7 @@ import org.springframework.web.servlet.view.UrlBasedViewResolver;
  * @author Phillip Webb
  * @since 1.2.2
  */
-public class MustacheViewResolver extends UrlBasedViewResolver {
+public class MustacheViewResolver extends AbstractTemplateViewResolver {
 
 	private Compiler compiler = Mustache.compiler();