Update pidfile property and add documentation

Change the pidfile property from `spring.application.pidfile` to
`spring.pidfile` (to save confusion with SpringApplication properties).

Also added documentation and meta-data information.

See gh-1579

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/system/ApplicationPidFileWriter.java

@@ -53,7 +53,7 @@ public class ApplicationPidFileWriter implements
 
 	private static final String[] SYSTEM_PROPERTY_VARIABLES = { "PIDFILE", "pidfile" };
 
-	private static final String SPRING_PROPERTY = "spring.application.pidfile";
+	private static final String SPRING_PROPERTY = "spring.pidfile";
 
 	private static final AtomicBoolean created = new AtomicBoolean(false);
 

spring-boot-actuator/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -3,6 +3,12 @@
     "name": "spring.git.properties",
     "dataType": "java.lang.String",
     "description": "Resource reference to a generated git info properties file."
+  }.
+  {
+    "name": "spring.pidfile",
+    "dataType": "java.lang.String",
+    "description": "The location of the PID file to write (if ApplicationPidFileWriter is used).",
+    sourceType: "org.springframework.boot.actuate.system.ApplicationPidFileWriter"
   }
 ]}
 

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/system/ApplicationPidFileWriterTests.java

@@ -87,7 +87,7 @@ public class ApplicationPidFileWriterTests {
 		File file = this.temporaryFolder.newFile();
 		ConfigurableEnvironment environment = new StandardEnvironment();
 		MockPropertySource propertySource = new MockPropertySource();
-		propertySource.setProperty("spring.application.pidfile", file.getAbsolutePath());
+		propertySource.setProperty("spring.pidfile", file.getAbsolutePath());
 		environment.getPropertySources().addLast(propertySource);
 		ConfigurableApplicationContext context = mock(ConfigurableApplicationContext.class);
 		given(context.getEnvironment()).willReturn(environment);
@@ -103,7 +103,7 @@ public class ApplicationPidFileWriterTests {
 		File file = this.temporaryFolder.newFile();
 		ConfigurableEnvironment environment = new StandardEnvironment();
 		MockPropertySource propertySource = new MockPropertySource();
-		propertySource.setProperty("spring.application.pidfile", file.getAbsolutePath());
+		propertySource.setProperty("spring.pidfile", file.getAbsolutePath());
 		environment.getPropertySources().addLast(propertySource);
 		ApplicationEnvironmentPreparedEvent event = new ApplicationEnvironmentPreparedEvent(
 				new SpringApplication(), new String[] {}, environment);

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

@@ -356,6 +356,9 @@ content into your application; rather pick only the properties that you need.
 	management.contextPath= # default to '/'
 	management.add-application-context-header= # default to true
 
+	# PID FILE ({sc-spring-boot-actuator}/system/ApplicationPidFileWriter.{sc-ext}[ApplicationPidFileWriter])
+	spring.pidfile= # Location of the PID file to write
+
 	# ENDPOINTS ({sc-spring-boot-actuator}/endpoint/AbstractEndpoint.{sc-ext}[AbstractEndpoint] subclasses)
 	endpoints.autoconfig.id=autoconfig
 	endpoints.autoconfig.sensitive=true