Return log levels in `/loggers` endpoint payload

Update `LoggersEndpoint` to additionally return the log levels actually
supported by the system.

Fixes gh-7396

spring-boot-actuator/pom.xml

@@ -338,6 +338,11 @@
 			<artifactId>hsqldb</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.skyscreamer</groupId>
+			<artifactId>jsonassert</artifactId>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework</groupId>
 			<artifactId>spring-test</artifactId>

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/LoggersEndpoint.java

@@ -20,6 +20,9 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.NavigableSet;
+import java.util.Set;
+import java.util.TreeSet;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.logging.LogLevel;
@@ -35,8 +38,7 @@ import org.springframework.util.Assert;
  * @since 1.5.0
  */
 @ConfigurationProperties(prefix = "endpoints.loggers")
-public class LoggersEndpoint
-		extends AbstractEndpoint<Map<String, LoggersEndpoint.LoggerLevels>> {
+public class LoggersEndpoint extends AbstractEndpoint<Map<String, Object>> {
 
 	private final LoggingSystem loggingSystem;
 
@@ -51,18 +53,31 @@ public class LoggersEndpoint
 	}
 
 	@Override
-	public Map<String, LoggerLevels> invoke() {
+	public Map<String, Object> invoke() {
 		Collection<LoggerConfiguration> configurations = this.loggingSystem
 				.getLoggerConfigurations();
 		if (configurations == null) {
 			return Collections.emptyMap();
 		}
-		Map<String, LoggerLevels> result = new LinkedHashMap<String, LoggerLevels>(
+		Map<String, Object> result = new LinkedHashMap<String, Object>();
+		result.put("levels", getLevels());
+		result.put("loggers", getLoggers(configurations));
+		return result;
+	}
+
+	private NavigableSet<LogLevel> getLevels() {
+		Set<LogLevel> levels = this.loggingSystem.getSupportedLogLevels();
+		return new TreeSet<LogLevel>(levels).descendingSet();
+	}
+
+	private Map<String, LoggerLevels> getLoggers(
+			Collection<LoggerConfiguration> configurations) {
+		Map<String, LoggerLevels> loggers = new LinkedHashMap<String, LoggerLevels>(
 				configurations.size());
 		for (LoggerConfiguration configuration : configurations) {
-			result.put(configuration.getName(), new LoggerLevels(configuration));
+			loggers.put(configuration.getName(), new LoggerLevels(configuration));
 		}
-		return result;
+		return loggers;
 	}
 
 	public LoggerLevels invoke(String name) {

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/autoconfigure/EndpointAutoConfigurationTests.java

@@ -130,7 +130,9 @@ public class EndpointAutoConfigurationTests {
 	public void loggersEndpointHasLoggers() throws Exception {
 		load(CustomLoggingConfig.class, EndpointAutoConfiguration.class);
 		LoggersEndpoint endpoint = this.context.getBean(LoggersEndpoint.class);
-		Map<String, LoggerLevels> loggers = endpoint.invoke();
+		Map<String, Object> result = endpoint.invoke();
+		Map<String, LoggerLevels> loggers = (Map<String, LoggerLevels>) result
+				.get("loggers");
 		assertThat(loggers.size()).isGreaterThan(0);
 	}
 

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/LoggersEndpointTests.java

@@ -17,6 +17,9 @@
 package org.springframework.boot.actuate.endpoint;
 
 import java.util.Collections;
+import java.util.EnumSet;
+import java.util.Map;
+import java.util.Set;
 
 import org.junit.Test;
 
@@ -45,12 +48,21 @@ public class LoggersEndpointTests extends AbstractEndpointTests<LoggersEndpoint>
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
 	public void invokeShouldReturnConfigurations() throws Exception {
 		given(getLoggingSystem().getLoggerConfigurations()).willReturn(Collections
 				.singletonList(new LoggerConfiguration("ROOT", null, LogLevel.DEBUG)));
-		LoggerLevels levels = getEndpointBean().invoke().get("ROOT");
-		assertThat(levels.getConfiguredLevel()).isNull();
-		assertThat(levels.getEffectiveLevel()).isEqualTo("DEBUG");
+		given(getLoggingSystem().getSupportedLogLevels())
+				.willReturn(EnumSet.allOf(LogLevel.class));
+		Map<String, Object> result = getEndpointBean().invoke();
+		Map<String, LoggerLevels> loggers = (Map<String, LoggerLevels>) result
+				.get("loggers");
+		Set<LogLevel> levels = (Set<LogLevel>) result.get("levels");
+		LoggerLevels rootLevels = loggers.get("ROOT");
+		assertThat(rootLevels.getConfiguredLevel()).isNull();
+		assertThat(rootLevels.getEffectiveLevel()).isEqualTo("DEBUG");
+		assertThat(levels).containsExactly(LogLevel.OFF, LogLevel.FATAL, LogLevel.ERROR,
+				LogLevel.WARN, LogLevel.INFO, LogLevel.DEBUG, LogLevel.TRACE);
 	}
 
 	public void invokeWhenNameSpecifiedShouldReturnLevels() throws Exception {

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/mvc/LoggersMvcEndpointTests.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.actuate.endpoint.mvc;
 
 import java.util.Collections;
+import java.util.EnumSet;
 
 import org.junit.After;
 import org.junit.Before;
@@ -80,18 +81,23 @@ public class LoggersMvcEndpointTests {
 				.alwaysDo(MockMvcResultHandlers.print()).build();
 	}
 
+	@Before
 	@After
-	public void reset() {
+	public void resetMocks() {
 		Mockito.reset(this.loggingSystem);
+		given(this.loggingSystem.getSupportedLogLevels())
+				.willReturn(EnumSet.allOf(LogLevel.class));
 	}
 
 	@Test
 	public void getLoggerShouldReturnAllLoggerConfigurations() throws Exception {
 		given(this.loggingSystem.getLoggerConfigurations()).willReturn(Collections
 				.singletonList(new LoggerConfiguration("ROOT", null, LogLevel.DEBUG)));
+		String expected = "{\"levels\":[\"OFF\",\"FATAL\",\"ERROR\",\"WARN\",\"INFO\",\"DEBUG\",\"TRACE\"],"
+				+ "\"loggers\":{\"ROOT\":{\"configuredLevel\":null,\"effectiveLevel\":\"DEBUG\"}}}";
+		System.out.println(expected);
 		this.mvc.perform(get("/loggers")).andExpect(status().isOk())
-				.andExpect(content().string(equalTo("{\"ROOT\":{\"configuredLevel\":"
-						+ "null,\"effectiveLevel\":\"DEBUG\"}}")));
+				.andExpect(content().json(expected));
 	}
 
 	@Test

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

@@ -17,7 +17,9 @@
 package org.springframework.boot.logging;
 
 import java.util.HashMap;
+import java.util.LinkedHashSet;
 import java.util.Map;
+import java.util.Set;
 
 import org.springframework.core.env.Environment;
 import org.springframework.core.io.ClassPathResource;
@@ -193,7 +195,9 @@ public abstract class AbstractLoggingSystem extends LoggingSystem {
 
 		public void map(LogLevel system, T nativeLevel) {
 			this.systemToNative.put(system, nativeLevel);
-			this.nativeToSystem.put(nativeLevel, system);
+			if (!this.nativeToSystem.containsKey(nativeLevel)) {
+				this.nativeToSystem.put(nativeLevel, system);
+			}
 		}
 
 		public LogLevel convertNativeToSystem(T level) {
@@ -204,6 +208,10 @@ public abstract class AbstractLoggingSystem extends LoggingSystem {
 			return this.systemToNative.get(level);
 		}
 
+		public Set<LogLevel> getSupported() {
+			return new LinkedHashSet<LogLevel>(this.nativeToSystem.values());
+		}
+
 	}
 
 }

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

@@ -17,9 +17,11 @@
 package org.springframework.boot.logging;
 
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
@@ -94,6 +96,15 @@ public abstract class LoggingSystem {
 		return null;
 	}
 
+	/**
+	 * Returns a set of the {@link LogLevel LogLevels} that are actually supported by the
+	 * logging system.
+	 * @return the supported levels
+	 */
+	public Set<LogLevel> getSupportedLogLevels() {
+		return EnumSet.allOf(LogLevel.class);
+	}
+
 	/**
 	 * Sets the logging level for a given logger.
 	 * @param loggerName the name of the logger to set

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

@@ -22,6 +22,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.List;
+import java.util.Set;
 import java.util.logging.Level;
 import java.util.logging.LogManager;
 import java.util.logging.Logger;
@@ -113,6 +114,11 @@ public class JavaLoggingSystem extends AbstractLoggingSystem {
 		}
 	}
 
+	@Override
+	public Set<LogLevel> getSupportedLogLevels() {
+		return LEVELS.getSupported();
+	}
+
 	@Override
 	public void setLogLevel(String loggerName, LogLevel level) {
 		Assert.notNull(level, "Level must not be null");

spring-boot/src/main/java/org/springframework/boot/logging/log4j2/Log4J2LoggingSystem.java

@@ -22,6 +22,7 @@ import java.net.URL;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Set;
 
 import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
@@ -197,6 +198,11 @@ public class Log4J2LoggingSystem extends Slf4JLoggingSystem {
 		getLoggerContext().reconfigure();
 	}
 
+	@Override
+	public Set<LogLevel> getSupportedLogLevels() {
+		return LEVELS.getSupported();
+	}
+
 	@Override
 	public void setLogLevel(String loggerName, LogLevel logLevel) {
 		Level level = LEVELS.convertSystemToNative(logLevel);

spring-boot/src/main/java/org/springframework/boot/logging/logback/LogbackLoggingSystem.java

@@ -22,6 +22,7 @@ import java.security.ProtectionDomain;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Set;
 
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.LoggerContext;
@@ -238,6 +239,11 @@ public class LogbackLoggingSystem extends Slf4JLoggingSystem {
 		return new LoggerConfiguration(logger.getName(), level, effectiveLevel);
 	}
 
+	@Override
+	public Set<LogLevel> getSupportedLogLevels() {
+		return LEVELS.getSupported();
+	}
+
 	@Override
 	public void setLogLevel(String loggerName, LogLevel level) {
 		ch.qos.logback.classic.Logger logger = getLogger(loggerName);

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

@@ -19,6 +19,7 @@ package org.springframework.boot.logging.java;
 import java.io.File;
 import java.io.FileFilter;
 import java.io.IOException;
+import java.util.EnumSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.logging.Level;
@@ -148,6 +149,13 @@ public class JavaLoggingSystemTests extends AbstractLoggingSystemTests {
 				null);
 	}
 
+	@Test
+	public void getSupportedLevels() {
+		assertThat(this.loggingSystem.getSupportedLogLevels())
+				.isEqualTo(EnumSet.of(LogLevel.TRACE, LogLevel.DEBUG, LogLevel.INFO,
+						LogLevel.WARN, LogLevel.ERROR, LogLevel.OFF));
+	}
+
 	@Test
 	public void setLevel() throws Exception {
 		this.loggingSystem.beforeInitialize();

spring-boot/src/test/java/org/springframework/boot/logging/log4j2/Log4J2LoggingSystemTests.java

@@ -22,6 +22,7 @@ import java.io.File;
 import java.io.FileReader;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.List;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -122,6 +123,12 @@ public class Log4J2LoggingSystemTests extends AbstractLoggingSystemTests {
 		this.loggingSystem.initialize(null, "classpath:log4j2-nonexistent.xml", null);
 	}
 
+	@Test
+	public void getSupportedLevels() {
+		assertThat(this.loggingSystem.getSupportedLogLevels())
+				.isEqualTo(EnumSet.allOf(LogLevel.class));
+	}
+
 	@Test
 	public void setLevel() throws Exception {
 		this.loggingSystem.beforeInitialize();

spring-boot/src/test/java/org/springframework/boot/logging/logback/LogbackLoggingSystemTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.logging.logback;
 
 import java.io.File;
 import java.io.FileReader;
+import java.util.EnumSet;
 import java.util.List;
 import java.util.logging.Handler;
 import java.util.logging.LogManager;
@@ -162,6 +163,13 @@ public class LogbackLoggingSystemTests extends AbstractLoggingSystemTests {
 				"classpath:logback-nonexistent.xml", null);
 	}
 
+	@Test
+	public void getSupportedLevels() {
+		assertThat(this.loggingSystem.getSupportedLogLevels())
+				.isEqualTo(EnumSet.of(LogLevel.TRACE, LogLevel.DEBUG, LogLevel.INFO,
+						LogLevel.WARN, LogLevel.ERROR, LogLevel.OFF));
+	}
+
 	@Test
 	public void setLevel() throws Exception {
 		this.loggingSystem.beforeInitialize();