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！
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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(jù)傳入的不同指令，進(jìn)行相應(yīng)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(diào)用bootstrap.init()進(jìn)行初始化
根據(jù)傳入不同的指令進(jìn)行相應(yīng)的處理，本文主要分析start指定，即服務(wù)啟動。啟動服務(wù)start主要調(diào)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(shè)置當(dāng)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(shí)例化org.apache.catalina.startup.Catalina，并設(shè)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(chuàng)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(shí)例化org.apache.catalina.startup.Catalina，并設(shè)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(dāng)時使用Java SecurityManager時，會提前加載一些必要的java類，以避免觸發(fā)權(quán)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(dāng)遇到標(biāo)簽時會觸發(fā)解析處理器，采用事件處理的方式解析XML，它的優(yōu)點(diǎn)是不需要將完整的XML文檔加載進(jìn)內(nèi)存，可以在讀取文檔的同時就進(jìn)行解析，節(jié)省內(nèi)存，適合解析超大XML，主要方法有：
startDocument()：文檔解析開始時調(diào)用，該方法只會調(diào)用一次
startElement(String uri, String localName, String qName, Attributes attributes):標(biāo)簽解析開始時調(diào)用
endElement(String uri, String localName, String qName)：標(biāo)簽（節(jié)點(diǎn)）解析結(jié)束后調(diào)用
endDocument()：文檔解析結(jié)束后調(diào)用，該方法只會調(diào)用一次
2.2 規(guī)則Rules
Tomcat將server.xml的解析抽象為規(guī)則，利用Java的引用傳遞，通過有副作用的void方法，對xml進(jìn)行解析，規(guī)則調(diào)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(guī)則中包含以下方法：
begin：Degister.startElement 方法調(diào)用
body、end：Degister.endElement方法中調(diào)用，先調(diào)用body，再調(diào)用end
finish：Degister.endDocument方法中調(diào)用
Tomcat中常見的規(guī)則類型：
ObjectCreateRule 創(chuàng)建對應(yīng)class的對象實(shí)例，并放到Designer的堆棧成員屬性中
SetPropertiesRule 獲取堆棧中棧頂?shù)脑?，并將xml元素的屬性賦值給對象實(shí)例
SetNextRule 調(diào)用父節(jié)點(diǎn)的實(shí)例對象，將當(dāng)前對象作為參數(shù)，反射調(diào)用某個方法
ListenerCreateRule 當(dāng)Listener標(biāo)簽有optional屬性為true時，創(chuàng)建實(shí)例異常時，強(qiáng)制添加OptionalListener實(shí)例
ConnectorCreateRule 創(chuàng)建Connector實(shí)例
SetAllPropertiesRule 主體功能與SetPropertiesRule 一致，這個Rule可以排除一些屬性的設(shè)置
AddPortOffsetRule Set portOffset on all the connectors based on portOffset in the Server
CertificateCreateRule 實(shí)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(chuàng)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(shè)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(diào)用Catalina.load()
Catalina.load() 讀取conf/server.xml，創(chuàng)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(chuàng)建解析server.xml的Digester，根據(jù)server.xml的元素標(biāo)簽，為每個標(biāo)簽設(shè)置相應(yīng)的規(guī)則組，在解析標(biāo)簽時進(jìn)行調(diào)用。
由此也可以得到結(jié)論，server.xml的結(jié)構(gòu)就是Tomcat容器內(nèi)部的結(jié)構(gòu)，通過對server.xml的解析規(guī)則的執(zhí)行，實(shí)例化出Tomcat容器結(jié)構(gòu)。
以下為Tomcat9默認(rèn)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(jié)構(gòu)見下圖：
Server代表服務(wù)器,一個Tomcat只有一個Server
Service 代表服務(wù): 一個Server可以對外提供多個服務(wù)
Connector連接器: service服務(wù)的核心組成之一,主要是鏈接客戶端請求
Container容器：service服務(wù)的核心組成之一，主要是執(zhí)行業(yè)務(wù)邏輯，這里按層級為Engine、Host、Context
Wrapper：對應(yīng)Servlet的定義
以上是“Tomcat9如何加載server.xml”這篇文章的所有內(nèi)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(nèi)容對大家有所幫助，如果還想學(xué)習(xí)更多知識，歡迎關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道！
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