Consume level and dateformat patterns as system props in Log4j config

Previously LOG_LEVEL_PATTERN and LOG_DATEFORMAT_PATTERN were not
consumed as system properties in log4j2.xml and log4j2-file.xml. As a
result, the logging.pattern.level and logging.pattern.dateformat
configuration properties, which are translated into the
LOG_LEVEL_PATTERN and LOG_DATEFORMAT_PATTERN system properties
respectively had no effect.

This commit updates the log4j2.xml and log4j2-file.xml config files to
consume LOG_LEVEL_PATTERN and LOG_DATEFORMAT_PATTERN as system
properties. When the system property is not set, the configuation falls
back to the default values specified in the config files. Tests for
both log4j2.xml and log4j2-file.xml to verify the behaviour have also
bean added.

Fixes gh-22983

spring-boot-project/spring-boot/src/main/resources/org/springframework/boot/logging/log4j2/log4j2-file.xml

@@ -4,8 +4,8 @@
 		<Property name="LOG_EXCEPTION_CONVERSION_WORD">%xwEx</Property>
 		<Property name="LOG_LEVEL_PATTERN">%5p</Property>
 		<Property name="LOG_DATEFORMAT_PATTERN">yyyy-MM-dd HH:mm:ss.SSS</Property>
-		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{%pid}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
-		<Property name="FILE_LOG_PATTERN">%d{${LOG_DATEFORMAT_PATTERN}} ${LOG_LEVEL_PATTERN} %pid --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${sys:LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${sys:LOG_LEVEL_PATTERN}} %clr{%pid}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="FILE_LOG_PATTERN">%d{${sys:LOG_DATEFORMAT_PATTERN}} ${sys:LOG_LEVEL_PATTERN} %pid --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
 
 	</Properties>
 	<Appenders>

spring-boot-project/spring-boot/src/main/resources/org/springframework/boot/logging/log4j2/log4j2.xml

@@ -4,7 +4,7 @@
 		<Property name="LOG_EXCEPTION_CONVERSION_WORD">%xwEx</Property>
 		<Property name="LOG_LEVEL_PATTERN">%5p</Property>
 		<Property name="LOG_DATEFORMAT_PATTERN">yyyy-MM-dd HH:mm:ss.SSS</Property>
-		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{%pid}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${sys:LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${sys:LOG_LEVEL_PATTERN}} %clr{%pid}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
 		<Property name="FILE_LOG_PATTERN">%d{${LOG_DATEFORMAT_PATTERN}} ${LOG_LEVEL_PATTERN} %pid --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
 	</Properties>
 	<Appenders>

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/logging/log4j2/Log4j2FileXmlTests.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2012-2020 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
+ *
+ *      https://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.log4j2;
+
+import java.io.File;
+
+import org.apache.logging.log4j.core.config.Configuration;
+import org.apache.logging.log4j.core.layout.PatternLayout;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import org.springframework.boot.logging.LoggingSystemProperties;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@code log4j2-file.xml}.
+ *
+ * @author Andy Wilkinson
+ */
+class Log4j2FileXmlTests extends Log4j2XmlTests {
+
+	@BeforeEach
+	void configureLogFile(@TempDir File temp) {
+		System.setProperty(LoggingSystemProperties.LOG_FILE, new File(temp, "test.log").getAbsolutePath());
+	}
+
+	@AfterEach
+	void clearLogFile() {
+		System.clearProperty(LoggingSystemProperties.LOG_FILE);
+	}
+
+	@Test
+	void whenLogExceptionConversionWordIsNotConfiguredThenFileAppenderUsesDefault() {
+		assertThat(fileAppenderPattern()).contains("%xwEx");
+	}
+
+	@Test
+	void whenLogExceptionConversionWordIsSetThenFileAppenderUsesIt() {
+		withSystemProperty(LoggingSystemProperties.EXCEPTION_CONVERSION_WORD, "custom",
+				() -> assertThat(fileAppenderPattern()).contains("custom"));
+	}
+
+	@Test
+	void whenLogLevelPatternIsNotConfiguredThenFileAppenderUsesDefault() {
+		assertThat(fileAppenderPattern()).contains("%5p");
+	}
+
+	@Test
+	void whenLogLevelPatternIsSetThenFileAppenderUsesIt() {
+		withSystemProperty(LoggingSystemProperties.LOG_LEVEL_PATTERN, "custom",
+				() -> assertThat(fileAppenderPattern()).contains("custom"));
+	}
+
+	@Test
+	void whenLogLDateformatPatternIsNotConfiguredThenFileAppenderUsesDefault() {
+		assertThat(fileAppenderPattern()).contains("yyyy-MM-dd HH:mm:ss.SSS");
+	}
+
+	@Test
+	void whenLogDateformatPatternIsSetThenFileAppenderUsesIt() {
+		withSystemProperty(LoggingSystemProperties.LOG_DATEFORMAT_PATTERN, "custom",
+				() -> assertThat(fileAppenderPattern()).contains("custom"));
+	}
+
+	@Override
+	protected String getConfigFileName() {
+		return "log4j2-file.xml";
+	}
+
+	private String fileAppenderPattern() {
+		Configuration configuration = initializeConfiguration();
+		return ((PatternLayout) configuration.getAppender("File").getLayout()).getConversionPattern();
+	}
+
+}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/logging/log4j2/Log4j2XmlTests.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2012-2020 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
+ *
+ *      https://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.log4j2;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.apache.logging.log4j.core.LoggerContext;
+import org.apache.logging.log4j.core.config.Configuration;
+import org.apache.logging.log4j.core.config.ConfigurationFactory;
+import org.apache.logging.log4j.core.config.ConfigurationSource;
+import org.apache.logging.log4j.core.layout.PatternLayout;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.logging.LoggingSystemProperties;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@code log4j2.xml}.
+ *
+ * @author Andy Wilkinson
+ */
+class Log4j2XmlTests {
+
+	@Test
+	void whenLogExceptionConversionWordIsNotConfiguredThenConsoleUsesDefault() {
+		assertThat(consolePattern()).contains("%xwEx");
+	}
+
+	@Test
+	void whenLogExceptionConversionWordIsSetThenConsoleUsesIt() {
+		withSystemProperty(LoggingSystemProperties.EXCEPTION_CONVERSION_WORD, "custom",
+				() -> assertThat(consolePattern()).contains("custom"));
+	}
+
+	@Test
+	void whenLogLevelPatternIsNotConfiguredThenConsoleUsesDefault() {
+		assertThat(consolePattern()).contains("%5p");
+	}
+
+	@Test
+	void whenLogLevelPatternIsSetThenConsoleUsesIt() {
+		withSystemProperty(LoggingSystemProperties.LOG_LEVEL_PATTERN, "custom",
+				() -> assertThat(consolePattern()).contains("custom"));
+	}
+
+	@Test
+	void whenLogLDateformatPatternIsNotConfiguredThenConsoleUsesDefault() {
+		assertThat(consolePattern()).contains("yyyy-MM-dd HH:mm:ss.SSS");
+	}
+
+	@Test
+	void whenLogDateformatPatternIsSetThenConsoleUsesIt() {
+		withSystemProperty(LoggingSystemProperties.LOG_DATEFORMAT_PATTERN, "custom",
+				() -> assertThat(consolePattern()).contains("custom"));
+	}
+
+	protected void withSystemProperty(String name, String value, Runnable action) {
+		String previous = System.setProperty(name, value);
+		action.run();
+		if (previous == null) {
+			System.clearProperty(name);
+		}
+		else {
+			System.setProperty(name, previous);
+		}
+	}
+
+	private String consolePattern() {
+		Configuration configuration = initializeConfiguration();
+		return ((PatternLayout) configuration.getAppender("Console").getLayout()).getConversionPattern();
+	}
+
+	protected Configuration initializeConfiguration() {
+		LoggerContext context = new LoggerContext("test");
+		Configuration configuration = ConfigurationFactory.getInstance().getConfiguration(context,
+				configurationSource());
+		configuration.initialize();
+		return configuration;
+	}
+
+	private ConfigurationSource configurationSource() {
+		try (InputStream in = getClass().getResourceAsStream(getConfigFileName())) {
+			return new ConfigurationSource(in);
+		}
+		catch (IOException ex) {
+			throw new RuntimeException(ex);
+		}
+	}
+
+	protected String getConfigFileName() {
+		return "log4j2.xml";
+	}
+
+}