Tomcat9如何加載server.xml
小編給大家分享一下Tomcat9如何加載server.xml，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！
1.Tomcat啟動
org.apache.catalina.startup.Bootstrap.main(String args[])
?public?static?void?main(String?args[])?{
????????synchronized?(daemonLock)?{
????????????if?(daemon?==?null)?{
????????????????Bootstrap?bootstrap?=?new?Bootstrap();
????????????????try?{
????????????????????bootstrap.init();?//初始化類加載器
????????????????}?catch?(Throwable?t)?{
????????????????????handleThrowable(t);
????????????????????t.printStackTrace();
????????????????????return;
????????????????}
????????????????daemon?=?bootstrap;
????????????}?else?{
????????????????Thread.currentThread().setContextClassLoader(daemon.catalinaLoader);
????????????}
????????}
????????//根據傳入的不同指令，進行相應處理
????????try?{
????????????String?command?=?"start";
????????????if?(args.length?>?0)?{
????????????????command?=?args[args.length?-?1];
????????????}
????????????if?(command.equals("startd"))?{
????????????????args[args.length?-?1]?=?"start";
????????????????daemon.load(args);
????????????????daemon.start();
????????????}?else?if?(command.equals("stopd"))?{
????????????????args[args.length?-?1]?=?"stop";
????????????????daemon.stop();
????????????}?else?if?(command.equals("start"))?{
????????????????daemon.setAwait(true);
????????????????daemon.load(args);
????????????????daemon.start();
????????????????if?(null?==?daemon.getServer())?{
????????????????????System.exit(1);
????????????????}
????????????}?else?if?(command.equals("stop"))?{
????????????????daemon.stopServer(args);
????????????}?else?if?(command.equals("configtest"))?{
????????????????daemon.load(args);
????????????????if?(null?==?daemon.getServer())?{
????????????????????System.exit(1);
????????????????}
????????????????System.exit(0);
????????????}?else?{
????????????????log.warn("Bootstrap:?command?\""?+?command?+?"\"?does?not?exist.");
????????????}
????????}?catch?(Throwable?t)?{
????????????if?(t?instanceof?InvocationTargetException?&&
????????????????????t.getCause()?!=?null)?{
????????????????t?=?t.getCause();
????????????}
????????????handleThrowable(t);
????????????t.printStackTrace();
????????????System.exit(1);
????????}
????}
在main方法中主要為兩部分邏輯：
調用bootstrap.init()進行初始化
根據傳入不同的指令進行相應的處理，本文主要分析start指定，即服務啟動。啟動服務start主要調用了org.apache.catalina.startup.Catalina.load()和start()方法
org.apache.catalina.startup.Bootstrap.init()
?public?void?init()?throws?Exception?{
????????initClassLoaders();?//初始化類加載
????????Thread.currentThread().setContextClassLoader(catalinaLoader);?//設置當前線程的類加載器為catalinaLoader
????????SecurityClassLoad.securityClassLoad(catalinaLoader);?//啟用java安全管理的處理
????????//通過反射的方式實例化org.apache.catalina.startup.Catalina，并設置父類加載器為sharedLoader
????????if?(log.isDebugEnabled())
????????????log.debug("Loading?startup?class");
????????Class<?>?startupClass?=?catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
????????Object?startupInstance?=?startupClass.getConstructor().newInstance();
????????if?(log.isDebugEnabled())
????????????log.debug("Setting?startup?class?properties");
????????String?methodName?=?"setParentClassLoader";
????????Class<?>?paramTypes[]?=?new?Class[1];
????????paramTypes[0]?=?Class.forName("java.lang.ClassLoader");
????????Object?paramValues[]?=?new?Object[1];
????????paramValues[0]?=?sharedLoader;
????????Method?method?=
????????????startupInstance.getClass().getMethod(methodName,?paramTypes);
????????method.invoke(startupInstance,?paramValues);
????????catalinaDaemon?=?startupInstance;
????}
類加載器的初始化，創建commonLoader、catalinaLoader、sharedLoader，具體可參考上一篇 《Tomcat9源代碼淺析-類加載體系》
啟用java安全管理的處理
通過反射的方式實例化org.apache.catalina.startup.Catalina，并設置父類加載器為sharedLoader
org.apache.catalina.security.SecurityClassLoad
public?final?class?SecurityClassLoad?{
????public?static?void?securityClassLoad(ClassLoader?loader)?throws?Exception?{
????????securityClassLoad(loader,?true);
????}
????static?void?securityClassLoad(ClassLoader?loader,?boolean?requireSecurityManager)?throws?Exception?{
????????if?(requireSecurityManager?&&?System.getSecurityManager()?==?null)?{
????????????return;
????????}
????????loadCorePackage(loader);
????????loadCoyotePackage(loader);
????????loadLoaderPackage(loader);
????????loadRealmPackage(loader);
????????loadServletsPackage(loader);
????????loadSessionPackage(loader);
????????loadUtilPackage(loader);
????????loadJavaxPackage(loader);
????????loadConnectorPackage(loader);
????????loadTomcatPackage(loader);
????}
當時使用Java SecurityManager時，會提前加載一些必要的java類，以避免觸發權限異常AccessControlException
2.server.xml解析框架
2.1 SAX
Tomcat中使用SAX解析server.xml文件。SAX解析方式會逐行的解析XML文檔，當遇到標簽時會觸發解析處理器，采用事件處理的方式解析XML，它的優點是不需要將完整的XML文檔加載進內存，可以在讀取文檔的同時就進行解析，節省內存，適合解析超大XML，主要方法有：
startDocument()：文檔解析開始時調用，該方法只會調用一次
startElement(String uri, String localName, String qName, Attributes attributes):標簽解析開始時調用
endElement(String uri, String localName, String qName)：標簽（節點）解析結束后調用
endDocument()：文檔解析結束后調用，該方法只會調用一次
2.2 規則Rules
Tomcat將server.xml的解析抽象為規則，利用Java的引用傳遞，通過有副作用的void方法，對xml進行解析，規則調用的順序與xml解析的順序是一致的，即start方法是正序，end方法是逆序。
規則中包含以下方法：
begin：Degister.startElement 方法調用
body、end：Degister.endElement方法中調用，先調用body，再調用end
finish：Degister.endDocument方法中調用
Tomcat中常見的規則類型：
ObjectCreateRule 創建對應class的對象實例，并放到Designer的堆棧成員屬性中
SetPropertiesRule 獲取堆棧中棧頂的元素，并將xml元素的屬性賦值給對象實例
SetNextRule 調用父節點的實例對象，將當前對象作為參數，反射調用某個方法
ListenerCreateRule 當Listener標簽有optional屬性為true時，創建實例異常時，強制添加OptionalListener實例
ConnectorCreateRule 創建Connector實例
SetAllPropertiesRule 主體功能與SetPropertiesRule 一致，這個Rule可以排除一些屬性的設置
AddPortOffsetRule Set portOffset on all the connectors based on portOffset in the Server
CertificateCreateRule 實例化SSLHostConfigCertificate
3.server.xml解析源代碼解析
org.apache.catalina.startup.Catalina.load()
public?void?load()?{
????????if?(loaded)?{
????????????return;
????????}
????????loaded?=?true;
????????long?t1?=?System.nanoTime();
????????initDirs();
????????//?Before?digester?-?it?may?be?needed
????????initNaming();
????????//?讀取conf/server.xml
????????ConfigFileLoader.setSource(new?CatalinaBaseConfigurationSource(Bootstrap.getCatalinaBaseFile(),?getConfigFile()));
????????File?file?=?configFile();
????????//?創建xml解析Digester?
????????Digester?digester?=?createStartDigester();
????????try?(ConfigurationSource.Resource?resource?=?ConfigFileLoader.getSource().getServerXml())?{
????????????InputStream?inputStream?=?resource.getInputStream();
????????????InputSource?inputSource?=?new?InputSource(resource.getURI().toURL().toString());
????????????inputSource.setByteStream(inputStream);
????????????digester.push(this);
????????????digester.parse(inputSource);?//解析xml
????????}?catch?(Exception?e)?{
????????????log.warn(sm.getString("catalina.configFail",?file.getAbsolutePath()),?e);
????????????if?(file.exists()?&&?!file.canRead())?{
????????????????log.warn(sm.getString("catalina.incorrectPermissions"));
????????????}
????????????return;
????????}
????????//設置server的屬性
????????getServer().setCatalina(this);
????????getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
????????getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
????????//?Stream?redirection
????????initStreams();
????????//?初始化server
????????try?{
????????????getServer().init();
????????}?catch?(LifecycleException?e)?{
????????????if?(Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE"))?{
????????????????throw?new?java.lang.Error(e);
????????????}?else?{
????????????????log.error(sm.getString("catalina.initError"),?e);
????????????}
????????}
????????long?t2?=?System.nanoTime();
????????if(log.isInfoEnabled())?{
????????????log.info(sm.getString("catalina.init",?Long.valueOf((t2?-?t1)?/?1000000)));
????????}
????}
Bootstrap中start指令邏輯，通過反射調用Catalina.load()
Catalina.load() 讀取conf/server.xml，創建解析xml的Digester
開始初始化server
org.apache.catalina.startup.Catalina.createStartDigester()
?protected?Digester?createStartDigester()?{
????????long?t1=System.currentTimeMillis();
????????//?Initialize?the?digester
????????Digester?digester?=?new?Digester();
????????digester.setValidating(false);
????????digester.setRulesValidation(true);
????????Map<Class<?>,?List<String>>?fakeAttributes?=?new?HashMap<>();
????????//?Ignore?className?on?all?elements
????????List<String>?objectAttrs?=?new?ArrayList<>();
????????objectAttrs.add("className");
????????fakeAttributes.put(Object.class,?objectAttrs);
????????//?Ignore?attribute?added?by?Eclipse?for?its?internal?tracking
????????List<String>?contextAttrs?=?new?ArrayList<>();
????????contextAttrs.add("source");
????????fakeAttributes.put(StandardContext.class,?contextAttrs);
????????//?Ignore?Connector?attribute?used?internally?but?set?on?Server
????????List<String>?connectorAttrs?=?new?ArrayList<>();
????????connectorAttrs.add("portOffset");
????????fakeAttributes.put(Connector.class,?connectorAttrs);
????????digester.setFakeAttributes(fakeAttributes);
????????digester.setUseContextClassLoader(true);
????????//?Configure?the?actions?we?will?be?using
????????digester.addObjectCreate("Server",
?????????????????????????????????"org.apache.catalina.core.StandardServer",
?????????????????????????????????"className");
????????digester.addSetProperties("Server");
????????digester.addSetNext("Server",
????????????????????????????"setServer",
????????????????????????????"org.apache.catalina.Server");
????????digester.addObjectCreate("Server/GlobalNamingResources",
?????????????????????????????????"org.apache.catalina.deploy.NamingResourcesImpl");
????????digester.addSetProperties("Server/GlobalNamingResources");
????????digester.addSetNext("Server/GlobalNamingResources",
????????????????????????????"setGlobalNamingResources",
????????????????????????????"org.apache.catalina.deploy.NamingResourcesImpl");
????????digester.addRule("Server/Listener",
????????????????new?ListenerCreateRule(null,?"className"));
????????digester.addSetProperties("Server/Listener");
????????digester.addSetNext("Server/Listener",
????????????????????????????"addLifecycleListener",
????????????????????????????"org.apache.catalina.LifecycleListener");
????????digester.addObjectCreate("Server/Service",
?????????????????????????????????"org.apache.catalina.core.StandardService",
?????????????????????????????????"className");
????????digester.addSetProperties("Server/Service");
????????digester.addSetNext("Server/Service",
????????????????????????????"addService",
????????????????????????????"org.apache.catalina.Service");
????????digester.addObjectCreate("Server/Service/Listener",
?????????????????????????????????null,?//?MUST?be?specified?in?the?element
?????????????????????????????????"className");
????????digester.addSetProperties("Server/Service/Listener");
????????digester.addSetNext("Server/Service/Listener",
????????????????????????????"addLifecycleListener",
????????????????????????????"org.apache.catalina.LifecycleListener");
????????//Executor
????????digester.addObjectCreate("Server/Service/Executor",
?????????????????????????"org.apache.catalina.core.StandardThreadExecutor",
?????????????????????????"className");
????????digester.addSetProperties("Server/Service/Executor");
????????digester.addSetNext("Server/Service/Executor",
????????????????????????????"addExecutor",
????????????????????????????"org.apache.catalina.Executor");
????????digester.addRule("Server/Service/Connector",
?????????????????????????new?ConnectorCreateRule());
????????digester.addRule("Server/Service/Connector",?new?SetAllPropertiesRule(
????????????????new?String[]{"executor",?"sslImplementationName",?"protocol"}));
????????digester.addSetNext("Server/Service/Connector",
????????????????????????????"addConnector",
????????????????????????????"org.apache.catalina.connector.Connector");
????????digester.addRule("Server/Service/Connector",?new?AddPortOffsetRule());
????????digester.addObjectCreate("Server/Service/Connector/SSLHostConfig",
?????????????????????????????????"org.apache.tomcat.util.net.SSLHostConfig");
????????digester.addSetProperties("Server/Service/Connector/SSLHostConfig");
????????digester.addSetNext("Server/Service/Connector/SSLHostConfig",
????????????????"addSslHostConfig",
????????????????"org.apache.tomcat.util.net.SSLHostConfig");
????????digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
?????????????????????????new?CertificateCreateRule());
????????digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
?????????????????????????new?SetAllPropertiesRule(new?String[]{"type"}));
????????digester.addSetNext("Server/Service/Connector/SSLHostConfig/Certificate",
????????????????????????????"addCertificate",
????????????????????????????"org.apache.tomcat.util.net.SSLHostConfigCertificate");
????????digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
?????????????????????????????????"org.apache.tomcat.util.net.openssl.OpenSSLConf");
????????digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf");
????????digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
????????????????????????????"setOpenSslConf",
????????????????????????????"org.apache.tomcat.util.net.openssl.OpenSSLConf");
????????digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
?????????????????????????????????"org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
????????digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd");
????????digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
????????????????????????????"addCmd",
????????????????????????????"org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
????????digester.addObjectCreate("Server/Service/Connector/Listener",
?????????????????????????????????null,?//?MUST?be?specified?in?the?element
?????????????????????????????????"className");
????????digester.addSetProperties("Server/Service/Connector/Listener");
????????digester.addSetNext("Server/Service/Connector/Listener",
????????????????????????????"addLifecycleListener",
????????????????????????????"org.apache.catalina.LifecycleListener");
????????digester.addObjectCreate("Server/Service/Connector/UpgradeProtocol",
??????????????????????????????????null,?//?MUST?be?specified?in?the?element
??????????????????????????????????"className");
????????digester.addSetProperties("Server/Service/Connector/UpgradeProtocol");
????????digester.addSetNext("Server/Service/Connector/UpgradeProtocol",
????????????????????????????"addUpgradeProtocol",
????????????????????????????"org.apache.coyote.UpgradeProtocol");
????????//?Add?RuleSets?for?nested?elements
????????digester.addRuleSet(new?NamingRuleSet("Server/GlobalNamingResources/"));
????????digester.addRuleSet(new?EngineRuleSet("Server/Service/"));
????????digester.addRuleSet(new?HostRuleSet("Server/Service/Engine/"));
????????digester.addRuleSet(new?ContextRuleSet("Server/Service/Engine/Host/"));
????????addClusterRuleSet(digester,?"Server/Service/Engine/Host/Cluster/");
????????digester.addRuleSet(new?NamingRuleSet("Server/Service/Engine/Host/Context/"));
????????//?When?the?'engine'?is?found,?set?the?parentClassLoader.
????????digester.addRule("Server/Service/Engine",
?????????????????????????new?SetParentClassLoaderRule(parentClassLoader));
????????addClusterRuleSet(digester,?"Server/Service/Engine/Cluster/");
????????long?t2=System.currentTimeMillis();
????????if?(log.isDebugEnabled())?{
????????????log.debug("Digester?for?server.xml?created?"?+?(?t2-t1?));
????????}
????????return?digester;
????}
此方法創建解析server.xml的Digester，根據server.xml的元素標簽，為每個標簽設置相應的規則組，在解析標簽時進行調用。
由此也可以得到結論，server.xml的結構就是Tomcat容器內部的結構，通過對server.xml的解析規則的執行，實例化出Tomcat容器結構。
以下為Tomcat9默認的server.xml
<?xml?version="1.0"?encoding="UTF-8"?> <Server?port="8005"?shutdown="SHUTDOWN"> ??<Listener?className="org.apache.catalina.startup.VersionLoggerListener"?/> ??<Listener?className="org.apache.catalina.core.AprLifecycleListener"?SSLEngine="on"?/> ??<Listener?className="org.apache.catalina.core.JreMemoryLeakPreventionListener"?/> ??<Listener?className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener"?/> ??<Listener?className="org.apache.catalina.core.ThreadLocalLeakPreventionListener"?/> ??<GlobalNamingResources> ????<Resource?name="UserDatabase"?auth="Container" ??????????????type="org.apache.catalina.UserDatabase" ??????????????description="User?database?that?can?be?updated?and?saved" ??????????????factory="org.apache.catalina.users.MemoryUserDatabaseFactory" ??????????????pathname="conf/tomcat-users.xml"?/> ??</GlobalNamingResources> ??<Service?name="Catalina"> ????<Connector?port="8080"?protocol="HTTP/1.1" ???????????????connectionTimeout="20000" ???????????????redirectPort="8443"?/> ????<Connector?port="8009"?protocol="AJP/1.3"?redirectPort="8443"?/> ????<Engine?name="Catalina"?defaultHost="localhost"> ??????<Realm?className="org.apache.catalina.realm.LockOutRealm"> ????????<!--?This?Realm?uses?the?UserDatabase?configured?in?the?global?JNDI ?????????????resources?under?the?key?"UserDatabase".??Any?edits ?????????????that?are?performed?against?this?UserDatabase?are?immediately ?????????????available?for?use?by?the?Realm.??--> ????????<Realm?className="org.apache.catalina.realm.UserDatabaseRealm" ???????????????resourceName="UserDatabase"/> ??????</Realm> ??????<Host?name="localhost"??appBase="webapps" ????????????unpackWARs="true"?autoDeploy="true"> ????????<Valve?className="org.apache.catalina.valves.AccessLogValve"?directory="logs" ???????????????prefix="localhost_access_log"?suffix=".txt" ???????????????pattern="%h?%l?%u?%t?"%r"?%s?%b"?/> ??????</Host> ????</Engine> ??</Service> </Server>
其結構見下圖：
Server代表服務器,一個Tomcat只有一個Server
Service 代表服務: 一個Server可以對外提供多個服務
Connector連接器: service服務的核心組成之一,主要是鏈接客戶端請求
Container容器：service服務的核心組成之一，主要是執行業務邏輯，這里按層級為Engine、Host、Context
Wrapper：對應Servlet的定義
以上是“Tomcat9如何加載server.xml”這篇文章的所有內容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內容對大家有所幫助，如果還想學習更多知識，歡迎關注蝸牛博客行業資訊頻道！
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