Merge pull request for #32732 from rgoers

Closes gh-32732

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/log4j2/SpringEnvironmentLookup.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2012-2022 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 org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.LoggerContext;
+import org.apache.logging.log4j.core.config.LoggerContextAware;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.lookup.StrLookup;
+
+import org.springframework.core.env.Environment;
+import org.springframework.util.Assert;
+
+/**
+ * Lookup for Spring properties.
+ *
+ * @author Ralph Goers
+ * @author Phillip Webb
+ */
+@Plugin(name = "spring", category = StrLookup.CATEGORY)
+class SpringEnvironmentLookup implements LoggerContextAware, StrLookup {
+
+	private volatile Environment environment;
+
+	@Override
+	public String lookup(LogEvent event, String key) {
+		return lookup(key);
+	}
+
+	@Override
+	public String lookup(String key) {
+		Assert.state(this.environment != null, "Unable to obtain Spring Environment from LoggerContext");
+		return (this.environment != null) ? this.environment.getProperty(key) : null;
+	}
+
+	@Override
+	public void setLoggerContext(LoggerContext loggerContext) {
+		this.environment = Log4J2LoggingSystem.getEnvironment(loggerContext);
+	}
+
+}

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

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2012-2022 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 org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.core.LoggerContext;
+import org.apache.logging.log4j.core.lookup.Interpolator;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.mock.env.MockEnvironment;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link SpringEnvironmentLookup}.
+ *
+ * @author Phillip Webb
+ */
+class SpringEnvironmentLookupTests {
+
+	private MockEnvironment environment;
+
+	private LoggerContext loggerContext;
+
+	@BeforeEach
+	void setup() {
+		this.environment = new MockEnvironment();
+		this.loggerContext = (LoggerContext) LogManager.getContext(false);
+		this.loggerContext.putObject(Log4J2LoggingSystem.ENVIRONMENT_KEY, this.environment);
+	}
+
+	@AfterEach
+	void cleanup() {
+		this.loggerContext.removeObject(Log4J2LoggingSystem.ENVIRONMENT_KEY);
+	}
+
+	@Test
+	void lookupWhenFoundInEnvironmentReturnsValue() {
+		this.environment.setProperty("test", "test");
+		Interpolator lookup = createLookup(this.loggerContext);
+		assertThat(lookup.lookup("spring:test")).isEqualTo("test");
+	}
+
+	@Test
+	void lookupWhenNotFoundInEnvironmentReturnsNull() {
+		Interpolator lookup = createLookup(this.loggerContext);
+		assertThat(lookup.lookup("spring:test")).isNull();
+	}
+
+	@Test
+	void lookupWhenNoSpringEnvironmentThrowsException() {
+		this.loggerContext.removeObject(Log4J2LoggingSystem.ENVIRONMENT_KEY);
+		Interpolator lookup = createLookup(this.loggerContext);
+		assertThatIllegalStateException().isThrownBy(() -> assertThat(lookup.lookup("spring:test")).isEqualTo("test"))
+				.withMessage("Unable to obtain Spring Environment from LoggerContext");
+	}
+
+	private Interpolator createLookup(LoggerContext context) {
+		Interpolator lookup = new Interpolator();
+		lookup.setConfiguration(context.getConfiguration());
+		lookup.setLoggerContext(context);
+		return lookup;
+	}
+
+}