Set PID system property before *_LOG_PATTERN system properties

Previously, the PID system property was set after the
CONSOLE_LOG_PATTERN and FILE_LOG_PATTERN system properties. This meant
that the values of the pattern system properties could not reference
the PID system property, i.e. ${PID} would not resolve.

This commit sets the PID system property before the *_LOG_PATTERN
system properties, thereby allowing the latter to reference the
former.

Closes gh-10594

Author: wilkinsona

spring-boot/src/main/java/org/springframework/boot/logging/LoggingSystemProperties.java

@@ -53,10 +53,10 @@ public void apply(LogFile logFile) {
 				.ignoringUnresolvableNestedPlaceholders(this.environment, "logging.");
 		setSystemProperty(propertyResolver, EXCEPTION_CONVERSION_WORD,
 				"exception-conversion-word");
+		setSystemProperty(PID_KEY, new ApplicationPid().toString());
 		setSystemProperty(propertyResolver, CONSOLE_LOG_PATTERN, "pattern.console");
 		setSystemProperty(propertyResolver, FILE_LOG_PATTERN, "pattern.file");
 		setSystemProperty(propertyResolver, LOG_LEVEL_PATTERN, "pattern.level");
-		setSystemProperty(PID_KEY, new ApplicationPid().toString());
 		if (logFile != null) {
 			logFile.applyToSystemProperties();
 		}

spring-boot/src/test/java/org/springframework/boot/logging/LoggingSystemPropertiesTests.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.logging;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.core.env.Environment;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.StandardEnvironment;
+import org.springframework.mock.env.MockEnvironment;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link LoggingSystemProperties}.
+ *
+ * @author Andy Wilkinson
+ */
+public class LoggingSystemPropertiesTests {
+
+	private Set<Object> systemPropertyNames;
+
+	@Before
+	public void captureSystemPropertyNames() {
+		this.systemPropertyNames = new HashSet<Object>(System.getProperties().keySet());
+	}
+
+	@After
+	public void restoreSystemProperties() {
+		System.getProperties().keySet().retainAll(this.systemPropertyNames);
+	}
+
+	@Test
+	public void pidIsSet() {
+		new LoggingSystemProperties(new MockEnvironment()).apply(null);
+		assertThat(System.getProperty(LoggingSystemProperties.PID_KEY)).isNotNull();
+	}
+
+	@Test
+	public void consoleLogPatternIsSet() {
+		new LoggingSystemProperties(new MockEnvironment()
+				.withProperty("logging.pattern.console", "console pattern")).apply(null);
+		assertThat(System.getProperty(LoggingSystemProperties.CONSOLE_LOG_PATTERN))
+				.isEqualTo("console pattern");
+	}
+
+	@Test
+	public void fileLogPatternIsSet() {
+		new LoggingSystemProperties(new MockEnvironment()
+				.withProperty("logging.pattern.file", "file pattern")).apply(null);
+		assertThat(System.getProperty(LoggingSystemProperties.FILE_LOG_PATTERN))
+				.isEqualTo("file pattern");
+	}
+
+	@Test
+	public void consoleLogPatternCanReferencePid() {
+		new LoggingSystemProperties(
+				environment("logging.pattern.console", "${PID:unknown}")).apply(null);
+		assertThat(System.getProperty(LoggingSystemProperties.CONSOLE_LOG_PATTERN))
+				.matches("[0-9]+");
+	}
+
+	@Test
+	public void fileLogPatternCanReferencePid() {
+		new LoggingSystemProperties(environment("logging.pattern.file", "${PID:unknown}"))
+				.apply(null);
+		assertThat(System.getProperty(LoggingSystemProperties.FILE_LOG_PATTERN))
+				.matches("[0-9]+");
+	}
+
+	private Environment environment(String key, Object value) {
+		StandardEnvironment environment = new StandardEnvironment();
+		environment.getPropertySources().addLast(
+				new MapPropertySource("test", Collections.singletonMap(key, value)));
+		return environment;
+	}
+
+}