logback源碼分析-1.初始化
源碼基於logback 1.1.7java
首先看個demo：node
根據類名獲取Logger，這裏是用slf4j提供的工廠來獲取logger的：api
private static final Logger logger = LoggerFactory.getLogger("className");
進入getLogger方法：併發
public static Logger getLogger(String name) {
ILoggerFactory iLoggerFactory = getILoggerFactory();
return iLoggerFactory.getLogger(name);
}
首先獲取ILoggerFactory，而後根據name獲取Logger。app
getILoggerFactory方法：ui
public static ILoggerFactory getILoggerFactory() {
if (INITIALIZATION_STATE == UNINITIALIZED) {
INITIALIZATION_STATE = ONGOING_INITIALIZATION;
//執行初始化
performInitialization();
}
switch (INITIALIZATION_STATE) {
//初始化成功則調用logback的StaticLoggerBinder返回LoggerFactory
case SUCCESSFUL_INITIALIZATION:
return StaticLoggerBinder.getSingleton().getLoggerFactory();
//沒有找到StaticLoggerBinder這個類
case NOP_FALLBACK_INITIALIZATION:
return NOP_FALLBACK_FACTORY;
//版本不對，或者StaticLoggerBinder包路徑不對，或者其餘
case FAILED_INITIALIZATION:
throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);
//線程A已經快執行完performInitialization的時候，INITIALIZATION_STATE設置成SUCCESSFUL_INITIALIZATION，
//線程B剛開始調用performInitialization，又將INITIALIZATION_STATE修改爲ONGOING_INITIALIZATION
//線程A執行到switch代碼，就會跳轉到這裏,返回TEMP_FACTORY
//TEMP_FACTORY如其名，調用它的getLogger方法獲取到SubstituteLogger。
//使用SubstituteLogger的info、error等方法打印日誌的時候會判斷它的_delegate屬性是否爲空
//一開始_delegate爲空，返回一個臨時的NOPLogger.NOP_LOGGER實例,該實例什麼也不作
//後期performInitialization方法中會調用fixSubstitutedLoggers方法，從新設置_delegate爲正確的logger。
case ONGOING_INITIALIZATION:
// support re-entrant behavior.
// See also http://bugzilla.slf4j.org/show_bug.cgi?id=106
return TEMP_FACTORY;
}
throw new IllegalStateException("Unreachable code");
}
下面看看執行初始化的方法 performInitialization：this
private final static void performInitialization() {
bind();
if (INITIALIZATION_STATE == SUCCESSFUL_INITIALIZATION) {
//版本檢查
versionSanityCheck();
}
}
private final static void bind() {
try {
//查找org/slf4j/impl/StaticLoggerBinder.class，可能存在多個
Set<URL> staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();
reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
// the next line does the binding
//若是沒有StaticLoggerBinder class這裏調用便會異常
StaticLoggerBinder.getSingleton();
//設置狀態爲成功初始化
INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;
//若是StaticLoggerBinder class個數大於1個，則進行上報實際綁定的類型
reportActualBinding(staticLoggerBinderPathSet);
//修復併發調用getILoggerFactory時出現狀態爲ONGOING_INITIALIZATION且獲取到的logger爲TEMP_FACTORY的問題
//解決方法是設置每一個SubstituteLogger的_delegate爲正確的logger
fixSubstitutedLoggers();
} 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.indexOf("org.slf4j.impl.StaticLoggerBinder.getSingleton()") != -1) {
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);
}
}
執行完performInitialization方法後，狀態被設置成SUCCESSFUL_INITIALIZATION，而後執行StaticLoggerBinder.getSingleton().getLoggerFactory()。url
在這以前先看看StaticLoggerBinder的靜態代碼塊：spa
private static StaticLoggerBinder SINGLETON = new StaticLoggerBinder();
private static Object KEY = new Object();
static {
//StaticLoggerBinder單例調用init方法
SINGLETON.init();
}
private boolean initialized = false;
//生成默認的LoggerContext
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;
}
void init() {
try {
try {
//建立ContextInitializer，調用autoConfig解析配置文件
new ContextInitializer(defaultLoggerContext).autoConfig();
} catch (JoranException je) {
Util.report("Failed to auto configure default logger context", je);
}
// logback-292
//打印logback內部error、warn信息
//若是沒有配置StatusListener,則使用StatusPrinter的stdout方式打印
//配置StatusListener的代碼實如今ContextInitializer#autoConfig()方法第一行
//內部產生的error、warn等日誌在StaticLoggerBinder.defaultLoggerContext.sm中維護的。
//好比以前autoConfig方法中解析xml配置時出現error或者warn日誌會在sm中存儲，而後在此處打印
if (!StatusUtil.contextHasStatusListener(defaultLoggerContext)) {
StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext);
}
contextSelectorBinder.init(defaultLoggerContext, KEY);
//initialized初始爲false，init成功設置成true
initialized = true;
} catch (Throwable t) {
// we should never get here
Util.report("Failed to instantiate [" + LoggerContext.class.getName() + "]", t);
}
}
接下來分析ContextInitializer.autoConfig：線程
public void autoConfig() throws JoranException {
//解析在環境變量中配置的StatusListener實現類，若是配置的話生成相應的實例，
//調用其start方法，上報過去一段時間logback內部日誌
StatusListenerConfigHelper.installIfAsked(loggerContext);
//獲取logback配置文件URL
URL url = findURLOfDefaultConfigurationFile(true);
if (url != null) {
//解析logback配置文件，核心
configureByResource(url);
} else {
Configurator c = EnvUtil.loadFromServiceLoader(Configurator.class);
if (c != null) {
try {
c.setContext(loggerContext);
c.configure(loggerContext);
} catch (Exception e) {
throw new LogbackException(String.format("Failed to initialize Configurator: %s using ServiceLoader", c != null ? c.getClass()
.getCanonicalName() : "null"), e);
}
} else {
//設置默認的config，後期日誌直接輸出到控制檯
BasicConfigurator basicConfigurator = new BasicConfigurator();
basicConfigurator.setContext(loggerContext);
basicConfigurator.configure(loggerContext);
}
}
}
下面分析下ContextInitializer.configureByResource(url)：
public void configureByResource(URL url) throws JoranException {
if (url == null) {
throw new IllegalArgumentException("URL argument cannot be null");
}
final String urlString = url.toString();
//logback配置是groovy文件
if (urlString.endsWith("groovy")) {
if (EnvUtil.isGroovyAvailable()) {
// avoid directly referring to GafferConfigurator so as to avoid
// loading groovy.lang.GroovyObject . See also http://jira.qos.ch/browse/LBCLASSIC-214
GafferUtil.runGafferConfiguratorOn(loggerContext, this, url);
} else {
StatusManager sm = loggerContext.getStatusManager();
sm.add(new ErrorStatus("Groovy classes are not available on the class path. ABORTING INITIALIZATION.", loggerContext));
}
} else if (urlString.endsWith("xml")) {
//logback配置文件是xml。咱們主要分析該狀況下的配置
//首先建立一個配置器，設置好loggerContext後，根據url進行配置解析
JoranConfigurator configurator = new JoranConfigurator();
configurator.setContext(loggerContext);
configurator.doConfigure(url);
} else {
throw new LogbackException("Unexpected filename extension of file [" + url.toString() + "]. Should be either .groovy or .xml");
}
}
JoranConfigurator.doConfigure(url)代碼以下：
public final void doConfigure(URL url) throws JoranException {
InputStream in = null;
try {
//將該url添加到watch list中
informContextOfURLUsedForConfiguration(getContext(), url);
URLConnection urlConnection = url.openConnection();
// per http://jira.qos.ch/browse/LBCORE-105
// per http://jira.qos.ch/browse/LBCORE-127
//若是設置成true的話，當這個配置文件在一個jar中的時候，jar被鎖住。若是應用須要從新加載的話會出現問題。
//因此設置成false。
urlConnection.setUseCaches(false);
in = urlConnection.getInputStream();
//將logback配置轉換成流進行解析
doConfigure(in);
} catch (IOException ioe) {
String errMsg = "Could not open URL [" + url + "].";
addError(errMsg, ioe);
throw new JoranException(errMsg, ioe);
} finally {
if (in != null) {
try {
in.close();
} catch (IOException ioe) {
String errMsg = "Could not close input stream";
addError(errMsg, ioe);
throw new JoranException(errMsg, ioe);
}
}
}
}
//將InputStream轉換成sax的InputSource對象，而後調用doConfigure進行解析
public final void doConfigure(InputStream inputStream) throws JoranException {
doConfigure(new InputSource(inputStream));
}
// this is the most inner form of doConfigure whereto other doConfigure
// methods ultimately delegate
public final void doConfigure(final InputSource inputSource) throws JoranException {
long threshold = System.currentTimeMillis();
// if (!ConfigurationWatchListUtil.wasConfigurationWatchListReset(context)) {
// informContextOfURLUsedForConfiguration(getContext(), null);
// }
SaxEventRecorder recorder = new SaxEventRecorder(context);
//將xml的<tag>bodyStr</tag>解析成StartEvent，BodyEvent，EndEvent,保存到recorder.saxEventList中
//若是解析期間遇到warn、error、fatalError狀況則會生成信息存入StaticLoggerBinder.defaultLoggerContext.sm中
//後期將會將這些日誌輸出
recorder.recordEvents(inputSource);
//根據xml每一個element對應的event來進行解析
doConfigure(recorder.saxEventList);
// no exceptions a this level
StatusUtil statusUtil = new StatusUtil(context);
if (statusUtil.noXMLParsingErrorsOccurred(threshold)) {
addInfo("Registering current configuration as safe fallback point");
registerSafeConfiguration(recorder.saxEventList);
}
}
public void doConfigure(final List<SaxEvent> eventList) throws JoranException {
//將大部分的element path包裝成ElementSelector並映射一個Action,好比xml中configuration/logger element path映射成LoggerAction
//當解析到<configuration><logger>時會觸發LoggerAction的begin方法
//當解析到<configuration><logger>bodyStr 時會觸發LoggerAction的body方法，固然logger element是沒有body的
//當解析到<configuration><logger>bodyStr</logger> 時會觸發LoggerAction的end方法
//action的映射關係存在JoranConfigurator#interpreter中
buildInterpreter();
// disallow simultaneous configurations of the same context
synchronized (context.getConfigurationLock()) {
//解析eventList
interpreter.getEventPlayer().play(eventList);
}
}
以下是一個簡單的logback.xml demo:
<?xml version="1.0" encoding="UTF-8"?>
<configuration xmlns="http://www.padual.com/java/logback.xsd">
<appender name="WARN" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>/Users/apple/Documents/UNKONESERVER/warn.log</file>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- 按天回滾 daily -->
<fileNamePattern>/Users/apple/Documents/UNKONESERVER/warn.%d{yyyy-MM-dd}.log</fileNamePattern>
<!-- 日誌最大的保存天數 -->
<maxHistory>2</maxHistory>
</rollingPolicy>
<encoder>
<pattern>%msg%n</pattern>
</encoder>
</appender>
<logger name="com.logback.test" level="debug"
additivity="false">
<appender-ref ref="WARN" />
</logger>
<root level="debug">
</root>
</configuration>
轉換成SaxEvent list即是這個樣子：
eventList = {ArrayList@982} size = 26
0 = {StartEvent@999} "StartEvent(configuration) [2,63]"
1 = {StartEvent@1000} "StartEvent(appendername="WARN" class="ch.qos.logback.core.rolling.RollingFileAppender") [4,83]"
2 = {StartEvent@1001} "StartEvent(file) [5,15]"
3 = {BodyEvent@1002} "BodyEvent(/Users/apple/Documents/UNKONESERVER/warn.log)5,61"
4 = {EndEvent@1003} " EndEvent(file) [5,66]"
5 = {StartEvent@1004} "StartEvent(rollingPolicyclass="ch.qos.logback.core.rolling.TimeBasedRollingPolicy") [6,83]"
6 = {StartEvent@1005} "StartEvent(fileNamePattern) [8,30]"
7 = {BodyEvent@1006} "BodyEvent(/Users/apple/Documents/UNKONESERVER/warn.%d{yyyy-MM-dd}.log)8,91"
8 = {EndEvent@1007} " EndEvent(fileNamePattern) [8,107]"
9 = {StartEvent@1008} "StartEvent(maxHistory) [10,25]"
10 = {BodyEvent@1009} "BodyEvent(2)10,28"
11 = {EndEvent@1010} " EndEvent(maxHistory) [10,39]"
12 = {EndEvent@1011} " EndEvent(rollingPolicy) [11,25]"
13 = {StartEvent@1012} "StartEvent(encoder) [12,18]"
14 = {StartEvent@1013} "StartEvent(pattern) [13,22]"
15 = {BodyEvent@1014} "BodyEvent(%msg%n)13,30"
16 = {EndEvent@1015} " EndEvent(pattern) [13,38]"
17 = {EndEvent@1016} " EndEvent(encoder) [14,19]"
18 = {EndEvent@1017} " EndEvent(appender) [15,16]"
19 = {StartEvent@1018} "StartEvent(loggername="com.logback.test" level="debug" additivity="false") [18,32]"
20 = {StartEvent@1019} "StartEvent(appender-refref="WARN") [19,36]"
21 = {EndEvent@1020} " EndEvent(appender-ref) [19,36]"
22 = {EndEvent@1021} " EndEvent(logger) [20,14]"
23 = {StartEvent@1022} "StartEvent(rootlevel="debug") [23,25]"
24 = {EndEvent@1023} " EndEvent(root) [25,12]"
25 = {EndEvent@1024} " EndEvent(configuration) [27,17]"
對應26個event。 下面分析EventPlayer中play方法如何對event list進行遍歷處理。 很清晰的看到event分紅三種：StartEvent、BodyEvent、EndEvent。這個三種最終會調用對應action的begin、body、end方法:
public void play(List<SaxEvent> aSaxEventList) {
eventList = aSaxEventList;
SaxEvent se;
for (currentIndex = 0; currentIndex < eventList.size(); currentIndex++) {
se = eventList.get(currentIndex);
if (se instanceof StartEvent) {
interpreter.startElement((StartEvent) se);
// invoke fireInPlay after startElement processing
interpreter.getInterpretationContext().fireInPlay(se);
}
if (se instanceof BodyEvent) {
// invoke fireInPlay before characters processing
interpreter.getInterpretationContext().fireInPlay(se);
interpreter.characters((BodyEvent) se);
}
if (se instanceof EndEvent) {
// invoke fireInPlay before endElement processing
interpreter.getInterpretationContext().fireInPlay(se);
interpreter.endElement((EndEvent) se);
}
}
}
- satrtEvent
public void startElement(StartEvent se) {
//設置event在xml中的locator信息，好比在多少行多少列
setDocumentLocator(se.getLocator());
//處理start event
startElement(se.namespaceURI, se.localName, se.qName, se.attributes);
}
private void startElement(String namespaceURI, String localName, String qName, Attributes atts) {
//首先選擇localName爲tagName，若是localName爲空則選擇qName
String tagName = getTagName(localName, qName);
//將這個startEvent的tagName推入elementPath棧中，後期處理對應的endEvent時，觸發endElement方法彈出該tagName
elementPath.push(tagName);
if (skip != null) {
// every startElement pushes an action list
pushEmptyActionList();
return;
}
//根據elementPath查找相應的action list，
//好比elementPath推入了兩個數據[configuration][appender]，則會找到AppenderAction。
//Interpreter中ruleStore並不維護全部elementPath對應的action，
//好比[configuration][appender][file]，在ruleStore中找不到對應的action。
//logback提供了兩種隱式action：NestedComplexPropertyIA、NestedBasicPropertyIA，
//1.[configuration][appender][file]對應的action是NestedBasicPropertyIA，
//由於它屬於簡單的內嵌式action，file屬於appender的一個屬性，而file element沒有內嵌element，只有一個body。
//2.[configuration][appender][rollingPolicy]對應的action是NestedComplexPropertyIA，
//由於它屬於複雜的內嵌式action，rollingPolicy屬於appender的一個屬性，可是，rollingPolicy element還擁有本身的內嵌element
List<Action> applicableActionList = getApplicableActionList(elementPath, atts);
if (applicableActionList != null) {
//將action list推入actionlistStacl棧中，後續會用到
actionListStack.add(applicableActionList);
//遍歷applicableActionList，觸發每一個action的begin方法，正常applicableActionList中只有一個元素
callBeginAction(applicableActionList, tagName, atts);
} else {
// every startElement pushes an action list
pushEmptyActionList();
String errMsg = "no applicable action for [" + tagName + "], current ElementPath is [" + elementPath + "]";
cai.addError(errMsg);
}
}
void callBeginAction(List<Action> applicableActionList, String tagName, Attributes atts) {
if (applicableActionList == null) {
return;
}
Iterator<Action> i = applicableActionList.iterator();
while (i.hasNext()) {
Action action = (Action) i.next();
// now let us invoke the action. We catch and report any eventual
// exceptions
try {
//真正的處理start event的邏輯，即該element path對應action的begin方法
action.begin(interpretationContext, tagName, atts);
} catch (ActionException e) {
skip = elementPath.duplicate();
cai.addError("ActionException in Action for tag [" + tagName + "]", e);
} catch (RuntimeException e) {
skip = elementPath.duplicate();
cai.addError("RuntimeException in Action for tag [" + tagName + "]", e);
}
}
}
- bodyEvent
public void characters(BodyEvent be) {
setDocumentLocator(be.locator);
//獲取body文本
String body = be.getText();
List<Action> applicableActionList = actionListStack.peek();
if (body != null) {
body = body.trim();
if (body.length() > 0) {
// System.out.println("calling body method with ["+body+ "]");
callBodyAction(applicableActionList, body);
}
}
}
private void callBodyAction(List<Action> applicableActionList, String body) {
if (applicableActionList == null) {
return;
}
Iterator<Action> i = applicableActionList.iterator();
while (i.hasNext()) {
Action action = i.next();
try {
//觸發該element path對應action的body方法
action.body(interpretationContext, body);
} catch (ActionException ae) {
cai.addError("Exception in end() methd for action [" + action + "]", ae);
}
}
}
- endEvent
public void endElement(EndEvent endEvent) {
setDocumentLocator(endEvent.locator);
endElement(endEvent.namespaceURI, endEvent.localName, endEvent.qName);
}
private void endElement(String namespaceURI, String localName, String qName) {
// given that an action list is always pushed for every startElement, we
// need
// to always pop for every endElement
List<Action> applicableActionList = (List<Action>) actionListStack.pop();
if (skip != null) {
if (skip.equals(elementPath)) {
skip = null;
}
} else if (applicableActionList != EMPTY_LIST) {
callEndAction(applicableActionList, getTagName(localName, qName));
}
// given that we always push, we must also pop the pattern
//把在startElement方法中推入的元素彈出來
elementPath.pop();
}
private void callEndAction(List<Action> applicableActionList, String tagName) {
if (applicableActionList == null) {
return;
}
// logger.debug("About to call end actions on node: [" + localName + "]");
Iterator<Action> i = applicableActionList.iterator();
while (i.hasNext()) {
Action action = i.next();
// now let us invoke the end method of the action. We catch and report
// any eventual exceptions
try {
//觸發當前element path對應action的end方法
action.end(interpretationContext, tagName);
} catch (ActionException ae) {
// at this point endAction, there is no point in skipping children as
// they have been already processed
cai.addError("ActionException in Action for tag [" + tagName + "]", ae);
} catch (RuntimeException e) {
// no point in setting skip
cai.addError("RuntimeException in Action for tag [" + tagName + "]", e);
}
}
}
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