LoggingApplicationListener
日志组件的处理是LoggingApplicationListener实现的。LoggingApplicationListener#onApplicationEvent，监听事件。如果实现接口GenericApplicationListener，可以允许适配事件类型。
private static final Class<?>[] EVENT_TYPES = { ApplicationStartingEvent.class,
ApplicationEnvironmentPreparedEvent.class, ApplicationPreparedEvent.class, ContextClosedEvent.class,
ApplicationFailedEvent.class };
@Override
public boolean supportsEventType(ResolvableType resolvableType) {
return isAssignableFrom(resolvableType.getRawClass(), EVENT_TYPES);
}
@Override
public boolean supportsSourceType(Class<?> sourceType) {
return isAssignableFrom(sourceType, SOURCE_TYPES);
}
private boolean isAssignableFrom(Class<?> type, Class<?>... supportedTypes) {
if (type != null) {
for (Class<?> supportedType : supportedTypes) {
if (supportedType.isAssignableFrom(type)) {
return true;
}
}
}
return false;
}
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationStartingEvent) {
onApplicationStartingEvent((ApplicationStartingEvent) event);
}
else if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
}
else if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent((ApplicationPreparedEvent) event);
}
else if (event instanceof ContextClosedEvent
&& ((ContextClosedEvent) event).getApplicationContext().getParent() == null) {
onContextClosedEvent();
}
else if (event instanceof ApplicationFailedEvent) {
onApplicationFailedEvent();
}
}
startingEvent
LoggingApplicationListener#onApplicationStartingEvent，启动事件。
private void onApplicationStartingEvent(ApplicationStartingEvent event) {
this.loggingSystem = LoggingSystem.get(event.getSpringApplication().getClassLoader());
this.loggingSystem.beforeInitialize();
}
LoggingSystem#get(java.lang.ClassLoader)，遍历SYSTEMS，判断logback、log4j2和jdk的log的相关类是否存在，产生对应的实例。
private static final Map<String, String> SYSTEMS;
static {
Map<String, String> systems = new LinkedHashMap<>();
systems.put("ch.qos.logback.core.Appender", "org.springframework.boot.logging.logback.LogbackLoggingSystem");
systems.put("org.apache.logging.log4j.core.impl.Log4jContextFactory",
"org.springframework.boot.logging.log4j2.Log4J2LoggingSystem");
systems.put("java.util.logging.LogManager", "org.springframework.boot.logging.java.JavaLoggingSystem");
SYSTEMS = Collections.unmodifiableMap(systems);
}
public static LoggingSystem get(ClassLoader classLoader) {
String loggingSystem = System.getProperty(SYSTEM_PROPERTY);
if (StringUtils.hasLength(loggingSystem)) {
if (NONE.equals(loggingSystem)) {
return new NoOpLoggingSystem();
}
return get(classLoader, loggingSystem);
}
return SYSTEMS.entrySet().stream().filter((entry) -> ClassUtils.isPresent(entry.getKey(), classLoader))
.map((entry) -> get(classLoader, entry.getValue())).findFirst()
.orElseThrow(() -> new IllegalStateException("No suitable logging system located"));
}
Log4J2LoggingSystem#beforeInitialize。
- 如果获取到的类是
Log4J2LoggingSystem，进行初始化。 - 调用父类的
beforeInitialize，配置SLF4JBridgeHandler - 加FILTER，目的是
log4j2没有初始化完毕时是不能使用的，此时所有的处理都是DENY,就不会打印日志了
@Override
public void beforeInitialize() {
LoggerContext loggerContext = getLoggerContext();
if (isAlreadyInitialized(loggerContext)) {
return;
}
super.beforeInitialize();
loggerContext.getConfiguration().addFilter(FILTER);
}
private LoggerContext getLoggerContext() {
return (LoggerContext) LogManager.getContext(false);
}
Slf4JLoggingSystem#beforeInitialize，移除jdk默认的日志输出器，安装适配jdk的日志的slf4j的输出器。
@Override
public void beforeInitialize() {
super.beforeInitialize();
configureJdkLoggingBridgeHandler();
}
private void configureJdkLoggingBridgeHandler() {
try {
if (isBridgeJulIntoSlf4j()) {
removeJdkLoggingBridgeHandler();
SLF4JBridgeHandler.install();
}
}
catch (Throwable ex) {
// Ignore. No java.util.logging bridge is installed.
}
}
Slf4JLoggingSystem#removeJdkLoggingBridgeHandler，移除默认的jdk的日志输出器。
private void removeJdkLoggingBridgeHandler() {
try {
removeDefaultRootHandler();
SLF4JBridgeHandler.uninstall();
}
catch (Throwable ex) {
// Ignore and continue
}
}
private void removeDefaultRootHandler() {
try {
Logger rootLogger = LogManager.getLogManager().getLogger("");
Handler[] handlers = rootLogger.getHandlers();
if (handlers.length == 1 && handlers[0] instanceof ConsoleHandler) {
rootLogger.removeHandler(handlers[0]);
}
}
catch (Throwable ex) {
// Ignore and continue
}
}
SLF4JBridgeHandler#install，安装SLF4JBridgeHandler。
public static void install() {
LogManager.getLogManager().getLogger("").addHandler(new SLF4JBridgeHandler());
}
EnvironmentPreparedEvent
LoggingApplicationListener#onApplicationEnvironmentPreparedEvent
private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
if (this.loggingSystem == null) {
this.loggingSystem = LoggingSystem.get(event.getSpringApplication().getClassLoader());
}
initialize(event.getEnvironment(), event.getSpringApplication().getClassLoader());
}
protected void initialize(ConfigurableEnvironment environment, ClassLoader classLoader) {
new LoggingSystemProperties(environment).apply();
this.logFile = LogFile.get(environment);
if (this.logFile != null) {
this.logFile.applyToSystemProperties();
}
this.loggerGroups = new LoggerGroups(DEFAULT_GROUP_LOGGERS);
initializeEarlyLoggingLevel(environment);
initializeSystem(environment, this.loggingSystem, this.logFile);
initializeFinalLoggingLevels(environment, this.loggingSystem);
registerShutdownHookIfNecessary(environment, this.loggingSystem);
}
LogFile#get，获取logging.file.name和logging.file.path属性，构造LogFile。
public static LogFile get(PropertyResolver propertyResolver) {
String file = propertyResolver.getProperty(FILE_NAME_PROPERTY);
String path = propertyResolver.getProperty(FILE_PATH_PROPERTY);
if (StringUtils.hasLength(file) || StringUtils.hasLength(path)) {
return new LogFile(file, path);
}
return null;
}
LoggingApplicationListener#initializeSystem，初始化Log4J2LoggingSystem。
private void initializeSystem(ConfigurableEnvironment environment, LoggingSystem system, LogFile logFile) {
LoggingInitializationContext initializationContext = new LoggingInitializationContext(environment);
String logConfig = environment.getProperty(CONFIG_PROPERTY);
if (ignoreLogConfig(logConfig)) {
system.initialize(initializationContext, null, logFile);
}
else {
try {
system.initialize(initializationContext, logConfig, logFile);
}
catch (Exception ex) {
Throwable exceptionToReport = ex;
while (exceptionToReport != null && !(exceptionToReport instanceof FileNotFoundException)) {
exceptionToReport = exceptionToReport.getCause();
}
exceptionToReport = (exceptionToReport != null) ? exceptionToReport : ex;
// NOTE: We can't use the logger here to report the problem
System.err.println("Logging system failed to initialize using configuration from '" + logConfig + "'");
exceptionToReport.printStackTrace(System.err);
throw new IllegalStateException(ex);
}
}
}
Log4J2LoggingSystem#initialize，移除过滤器，进行父类初始化。
public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {
LoggerContext loggerContext = getLoggerContext();
if (isAlreadyInitialized(loggerContext)) {
return;
}
loggerContext.getConfiguration().removeFilter(FILTER);
super.initialize(initializationContext, configLocation, logFile);
markAsInitialized(loggerContext);
}
AbstractLoggingSystem#initialize，获取指定路径下的文件配置，进行重新初始化
public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {
if (StringUtils.hasLength(configLocation)) {
initializeWithSpecificConfig(initializationContext, configLocation, logFile);
return;
}
initializeWithConventions(initializationContext, logFile);
}
private void initializeWithConventions(LoggingInitializationContext initializationContext, LogFile logFile) {
String config = getSelfInitializationConfig();
if (config != null && logFile == null) {
// self initialization has occurred, reinitialize in case of property changes
reinitialize(initializationContext);
return;
}
if (config == null) {
config = getSpringInitializationConfig();
}
if (config != null) {
loadConfiguration(initializationContext, config, logFile);
return;
}
loadDefaults(initializationContext, logFile);
}
protected String getSelfInitializationConfig() {
return findConfig(getStandardConfigLocations());
}
@Override
protected void reinitialize(LoggingInitializationContext initializationContext) {
getLoggerContext().reconfigure();
}
Log4J2LoggingSystem#getStandardConfigLocations，根据如下路径加载配置。
@Override
protected String[] getStandardConfigLocations() {
return getCurrentlySupportedConfigLocations();
}
private String[] getCurrentlySupportedConfigLocations() {
List<String> supportedConfigLocations = new ArrayList<>();
addTestFiles(supportedConfigLocations);
supportedConfigLocations.add("log4j2.properties");
if (isClassAvailable("com.fasterxml.jackson.dataformat.yaml.YAMLParser")) {
Collections.addAll(supportedConfigLocations, "log4j2.yaml", "log4j2.yml");
}
if (isClassAvailable("com.fasterxml.jackson.databind.ObjectMapper")) {
Collections.addAll(supportedConfigLocations, "log4j2.json", "log4j2.jsn");
}
supportedConfigLocations.add("log4j2.xml");
return StringUtils.toStringArray(supportedConfigLocations);
}
Slf4j适配
常见的使用方式
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
private Logger logger = LoggerFactory.getLogger(LogTest.class);
LoggerFactory#getLogger()，获取日志工厂，执行初始化。初始化之后执行StaticLoggerBinder.getSingleton().getLoggerFactory();。
public static Logger getLogger(String name) {
ILoggerFactory iLoggerFactory = getILoggerFactory();
return iLoggerFactory.getLogger(name);
}
public static ILoggerFactory getILoggerFactory() {
if (INITIALIZATION_STATE == 0) {
Class var0 = LoggerFactory.class;
synchronized(LoggerFactory.class) {
if (INITIALIZATION_STATE == 0) {
INITIALIZATION_STATE = 1;
performInitialization();
}
}
}
switch(INITIALIZATION_STATE) {
case 1:
return SUBST_FACTORY;
case 2:
throw new IllegalStateException("org.slf4j.LoggerFactory in failed state. Original exception was thrown EARLIER. See also http://www.slf4j.org/codes.html#unsuccessfulInit");
case 3:
return StaticLoggerBinder.getSingleton().getLoggerFactory();
case 4:
return NOP_FALLBACK_FACTORY;
default:
throw new IllegalStateException("Unreachable code");
}
}
private static final void performInitialization() {
bind();
if (INITIALIZATION_STATE == 3) {
versionSanityCheck();
}
}
LoggerFactory#bind，找到合适的StaticLoggerBinder，进行初始化。
private final static void bind() {
try {
Set<URL> staticLoggerBinderPathSet = null;
// skip check under android, see also
// http://jira.qos.ch/browse/SLF4J-328
if (!isAndroid()) {
staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();
reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
}
// the next line does the binding
StaticLoggerBinder.getSingleton();
INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;
reportActualBinding(staticLoggerBinderPathSet);
} catch (NoClassDefFoundError ncde) {
String msg = ncde.getMessage();
if (messageContainsOrgSlf4jImplStaticLoggerBinder(msg)) {
INITIALIZATION_STATE = NOP_FALLBACK_INITIALIZATION;
Util.report("Failed to load class \"org.slf4j.impl.StaticLoggerBinder\".");
Util.report("Defaulting to no-operation (NOP) logger implementation");
Util.report("See " + NO_STATICLOGGERBINDER_URL + " for further details.");
} else {
failedBinding(ncde);
throw ncde;
}
} catch (java.lang.NoSuchMethodError nsme) {
String msg = nsme.getMessage();
if (msg != null && msg.contains("org.slf4j.impl.StaticLoggerBinder.getSingleton()")) {
INITIALIZATION_STATE = FAILED_INITIALIZATION;
Util.report("slf4j-api 1.6.x (or later) is incompatible with this binding.");
Util.report("Your binding is version 1.5.5 or earlier.");
Util.report("Upgrade your binding to version 1.6.x.");
}
throw nsme;
} catch (Exception e) {
failedBinding(e);
throw new IllegalStateException("Unexpected initialization failure", e);
} finally {
postBindCleanUp();
}
}
LoggerFactory#findPossibleStaticLoggerBinderPathSet，寻找当前系统中路径是org/slf4j/impl/StaticLoggerBinder.class的文件。log4j2和logback分别都有对应的适配实现。
static Set<URL> findPossibleStaticLoggerBinderPathSet() {
// use Set instead of list in order to deal with bug #138
// LinkedHashSet appropriate here because it preserves insertion order
// during iteration
Set<URL> staticLoggerBinderPathSet = new LinkedHashSet<URL>();
try {
ClassLoader loggerFactoryClassLoader = LoggerFactory.class.getClassLoader();
Enumeration<URL> paths;
if (loggerFactoryClassLoader == null) {
paths = ClassLoader.getSystemResources(STATIC_LOGGER_BINDER_PATH);
} else {
paths = loggerFactoryClassLoader.getResources(STATIC_LOGGER_BINDER_PATH);
}
while (paths.hasMoreElements()) {
URL path = paths.nextElement();
staticLoggerBinderPathSet.add(path);
}
} catch (IOException ioe) {
Util.report("Error getting resources from path", ioe);
}
return staticLoggerBinderPathSet;
}
log4j2适配slf4j
log4j2的适配，获取日志工厂Log4jLoggerFactory，实现了ILoggerFactory。
public final class StaticLoggerBinder implements LoggerFactoryBinder {
public static String REQUESTED_API_VERSION = "1.6";
private static final String LOGGER_FACTORY_CLASS_STR = Log4jLoggerFactory.class.getName();
private static final StaticLoggerBinder SINGLETON = new StaticLoggerBinder();
private final ILoggerFactory loggerFactory = new Log4jLoggerFactory();
private StaticLoggerBinder() {
}
public static StaticLoggerBinder getSingleton() {
return SINGLETON;
}
public ILoggerFactory getLoggerFactory() {
return this.loggerFactory;
}
}
logback适配slf4j
logback初始化，获取ILoggerFactory，返回的是LoggerContext。LoggerContext实现ILoggerFactory。
public class StaticLoggerBinder implements LoggerFactoryBinder {
/**
* Declare the version of the SLF4J API this implementation is compiled
* against. The value of this field is usually modified with each release.
*/
// to avoid constant folding by the compiler, this field must *not* be final
public static String REQUESTED_API_VERSION = "1.7.16"; // !final
final static String NULL_CS_URL = CoreConstants.CODES_URL + "#null_CS";
/**
* The unique instance of this class.
*/
private static StaticLoggerBinder SINGLETON = new StaticLoggerBinder();
private static Object KEY = new Object();
static {
SINGLETON.init();
}
private boolean initialized = false;
private LoggerContext defaultLoggerContext = new LoggerContext();
private final ContextSelectorStaticBinder contextSelectorBinder = ContextSelectorStaticBinder.getSingleton();
private StaticLoggerBinder() {
defaultLoggerContext.setName(CoreConstants.DEFAULT_CONTEXT_NAME);
}
public static StaticLoggerBinder getSingleton() {
return SINGLETON;
}
/**
* Package access for testing purposes.
*/
void init() {
try {
try {
new ContextInitializer(defaultLoggerContext).autoConfig();
} catch (JoranException je) {
Util.report("Failed to auto configure default logger context", je);
}
// logback-292
if (!StatusUtil.contextHasStatusListener(defaultLoggerContext)) {
StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
}
contextSelectorBinder.init(defaultLoggerContext, KEY);
initialized = true;
} catch (Exception t) { // see LOGBACK-1159
Util.report("Failed to instantiate [" + LoggerContext.class.getName() + "]", t);
}
}
public ILoggerFactory getLoggerFactory() {
if (!initialized) {
return defaultLoggerContext;
}
if (contextSelectorBinder.getContextSelector() == null) {
throw new IllegalStateException("contextSelector cannot be null. See also " + NULL_CS_URL);
}
return contextSelectorBinder.getContextSelector().getLoggerContext();
}
public String getLoggerFactoryClassStr() {
return contextSelectorBinder.getClass().getName();
}
}
