Expose constants for Spring application JSON property names

Closes gh-12012

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/SpringApplicationJsonEnvironmentPostProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -56,6 +56,16 @@ import org.springframework.web.context.support.StandardServletEnvironment;
 public class SpringApplicationJsonEnvironmentPostProcessor
 		implements EnvironmentPostProcessor, Ordered {
 
+	/**
+	 * Name of the {@code spring.application.json} property.
+	 */
+	public static String SPRING_APPLICATION_JSON_PROPERTY = "spring.application.json";
+
+	/**
+	 * Name of the {@code SPRING_APPLICATION_JSON} environment variable.
+	 */
+	public static String SPRING_APPLICATION_JSON_ENVIRONMENT_VARIABLE = "SPRING_APPLICATION_JSON";
+
 	private static final String SERVLET_ENVIRONMENT_CLASS = "org.springframework.web."
 			+ "context.support.StandardServletEnvironment";
 
@@ -179,8 +189,8 @@ public class SpringApplicationJsonEnvironmentPostProcessor
 
 	private static class JsonPropertyValue {
 
-		private static final String[] CANDIDATES = { "spring.application.json",
-				"SPRING_APPLICATION_JSON" };
+		private static final String[] CANDIDATES = { SPRING_APPLICATION_JSON_PROPERTY,
+				SPRING_APPLICATION_JSON_ENVIRONMENT_VARIABLE };
 
 		private final PropertySource<?> propertySource;