@Endpoint(id = "loggers")
public class LoggersEndpoint {
    private final LoggingSystem loggingSystem;
    private final LoggerGroups loggerGroups;
    /**
     * Create a new {@link LoggersEndpoint} instance.
     * @param loggingSystem the logging system to expose
     * @param loggerGroups the logger group to expose
     */
    public LoggersEndpoint(LoggingSystem loggingSystem, LoggerGroups loggerGroups) {
        Assert.notNull(loggingSystem, "LoggingSystem must not be null");
        Assert.notNull(loggerGroups, "LoggerGroups must not be null");
        this.loggingSystem = loggingSystem;
        this.loggerGroups = loggerGroups;
    }
    @ReadOperation
    public Map<String, Object> loggers() {
        Collection<LoggerConfiguration> configurations = this.loggingSystem.getLoggerConfigurations();
        if (configurations == null) {
            return Collections.emptyMap();
        }
        Map<String, Object> result = new LinkedHashMap<>();
        result.put("levels", getLevels());
        result.put("loggers", getLoggers(configurations));
        result.put("groups", getGroups());
        return result;
    }
    private Map<String, LoggerLevels> getGroups() {
        Map<String, LoggerLevels> groups = new LinkedHashMap<>();
        this.loggerGroups.forEach((group) -> groups.put(group.getName(),
                new GroupLoggerLevels(group.getConfiguredLevel(), group.getMembers())));
        return groups;
    }
    @ReadOperation
    public LoggerLevels loggerLevels(@Selector String name) {
        Assert.notNull(name, "Name must not be null");
        LoggerGroup group = this.loggerGroups.get(name);
        if (group != null) {
            return new GroupLoggerLevels(group.getConfiguredLevel(), group.getMembers());
        }
        LoggerConfiguration configuration = this.loggingSystem.getLoggerConfiguration(name);
        return (configuration != null) ? new SingleLoggerLevels(configuration) : null;
    }
    @WriteOperation
    public void configureLogLevel(@Selector String name, @Nullable LogLevel configuredLevel) {
        Assert.notNull(name, "Name must not be empty");
        LoggerGroup group = this.loggerGroups.get(name);
        if (group != null && group.hasMembers()) {
            group.configureLogLevel(configuredLevel, this.loggingSystem::setLogLevel);
            return;
        }
        this.loggingSystem.setLogLevel(name, configuredLevel);
    }
    //......
}

public final class LoggerGroups implements Iterable<LoggerGroup> {
    private final Map<String, LoggerGroup> groups = new ConcurrentHashMap<>();
    public LoggerGroups() {
    }
    public LoggerGroups(Map<String, List<String>> namesAndMembers) {
        putAll(namesAndMembers);
    }
    public void putAll(Map<String, List<String>> namesAndMembers) {
        namesAndMembers.forEach(this::put);
    }
    private void put(String name, List<String> members) {
        put(new LoggerGroup(name, members));
    }
    private void put(LoggerGroup loggerGroup) {
        this.groups.put(loggerGroup.getName(), loggerGroup);
    }
    public LoggerGroup get(String name) {
        return this.groups.get(name);
    }
    @Override
    public Iterator<LoggerGroup> iterator() {
        return this.groups.values().iterator();
    }
}

public final class LoggerGroup {
    private final String name;
    private final List<String> members;
    private LogLevel configuredLevel;
    LoggerGroup(String name, List<String> members) {
        this.name = name;
        this.members = Collections.unmodifiableList(new ArrayList<>(members));
    }
    public String getName() {
        return this.name;
    }
    public List<String> getMembers() {
        return this.members;
    }
    public boolean hasMembers() {
        return !this.members.isEmpty();
    }
    public LogLevel getConfiguredLevel() {
        return this.configuredLevel;
    }
    public void configureLogLevel(LogLevel level, BiConsumer<String, LogLevel> configurer) {
        this.configuredLevel = level;
        this.members.forEach((name) -> configurer.accept(name, level));
    }
}

@Override
    public void setLogLevel(String loggerName, LogLevel level) {
        ch.qos.logback.classic.Logger logger = getLogger(loggerName);
        if (logger != null) {
            logger.setLevel(LEVELS.convertSystemToNative(level));
        }
    }

public synchronized void setLevel(Level newLevel) {
        if (level == newLevel) {
            // nothing to do;
            return;
        }
        if (newLevel == null && isRootLogger()) {
            throw new IllegalArgumentException("The level of the root logger cannot be set to null");
        }

        level = newLevel;
        if (newLevel == null) {
            effectiveLevelInt = parent.effectiveLevelInt;
            newLevel = parent.getEffectiveLevel();
        } else {
            effectiveLevelInt = newLevel.levelInt;
        }

        if (childrenList != null) {
            int len = childrenList.size();
            for (int i = 0; i < len; i++) {
                Logger child = (Logger) childrenList.get(i);
                // tell child to handle parent levelInt change
                child.handleParentLevelChange(effectiveLevelInt);
            }
        }
        // inform listeners
        loggerContext.fireOnLevelChange(this, newLevel);
    }

public class LoggingApplicationListener implements GenericApplicationListener {
    private static final ConfigurationPropertyName LOGGING_LEVEL = ConfigurationPropertyName.of("logging.level");
    private static final ConfigurationPropertyName LOGGING_GROUP = ConfigurationPropertyName.of("logging.group");
    private static final Bindable<Map<String, LogLevel>> STRING_LOGLEVEL_MAP = Bindable.mapOf(String.class,
            LogLevel.class);
    private static final Bindable<Map<String, List<String>>> STRING_STRINGS_MAP = Bindable
            .of(ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, String.class).asMap());
    /**
     * The default order for the LoggingApplicationListener.
     */
    public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 20;
    /**
     * The name of the Spring property that contains a reference to the logging
     * configuration to load.
     */
    public static final String CONFIG_PROPERTY = "logging.config";
    /**
     * The name of the Spring property that controls the registration of a shutdown hook
     * to shut down the logging system when the JVM exits.
     * @see LoggingSystem#getShutdownHandler
     */
    public static final String REGISTER_SHUTDOWN_HOOK_PROPERTY = "logging.register-shutdown-hook";
    /**
     * The name of the {@link LoggingSystem} bean.
     */
    public static final String LOGGING_SYSTEM_BEAN_NAME = "springBootLoggingSystem";
    /**
     * The name of the {@link LogFile} bean.
     * @since 2.2.0
     */
    public static final String LOG_FILE_BEAN_NAME = "springBootLogFile";
    /**
     * The name of the{@link LoggerGroups} bean.
     * @since 2.2.0
     */
    public static final String LOGGER_GROUPS_BEAN_NAME = "springBootLoggerGroups";
    private static final Map<String, List<String>> DEFAULT_GROUP_LOGGERS;
    static {
        MultiValueMap<String, String> loggers = new LinkedMultiValueMap<>();
        loggers.add("web", "org.springframework.core.codec");
        loggers.add("web", "org.springframework.http");
        loggers.add("web", "org.springframework.web");
        loggers.add("web", "org.springframework.boot.actuate.endpoint.web");
        loggers.add("web", "org.springframework.boot.web.servlet.ServletContextInitializerBeans");
        loggers.add("sql", "org.springframework.jdbc.core");
        loggers.add("sql", "org.hibernate.SQL");
        loggers.add("sql", "org.jooq.tools.LoggerListener");
        DEFAULT_GROUP_LOGGERS = Collections.unmodifiableMap(loggers);
    }
    private static final Map<LogLevel, List<String>> SPRING_BOOT_LOGGING_LOGGERS;
    static {
        MultiValueMap<LogLevel, String> loggers = new LinkedMultiValueMap<>();
        loggers.add(LogLevel.DEBUG, "sql");
        loggers.add(LogLevel.DEBUG, "web");
        loggers.add(LogLevel.DEBUG, "org.springframework.boot");
        loggers.add(LogLevel.TRACE, "org.springframework");
        loggers.add(LogLevel.TRACE, "org.apache.tomcat");
        loggers.add(LogLevel.TRACE, "org.apache.catalina");
        loggers.add(LogLevel.TRACE, "org.eclipse.jetty");
        loggers.add(LogLevel.TRACE, "org.hibernate.tool.hbm2ddl");
        SPRING_BOOT_LOGGING_LOGGERS = Collections.unmodifiableMap(loggers);
    }
    //......
}

{
    "levels": [
        "OFF",
        "ERROR",
        "WARN",
        "INFO",
        "DEBUG",
        "TRACE"
    ],
    "loggers": {
        "ROOT": {
            "configuredLevel": "INFO",
            "effectiveLevel": "INFO"
        },
        "Validator": {
            "configuredLevel": null,
            "effectiveLevel": "INFO"
        }
    },
    "groups": {
        "web": {
            "configuredLevel": null,
            "members": [
                "org.springframework.core.codec",
                "org.springframework.http",
                "org.springframework.web",
                "org.springframework.boot.actuate.endpoint.web",
                "org.springframework.boot.web.servlet.ServletContextInitializerBeans"
            ]
        },
        "sql": {
            "configuredLevel": null,
            "members": [
                "org.springframework.jdbc.core",
                "org.hibernate.SQL",
                "org.jooq.tools.LoggerListener"
            ]
        }
    }
}