Tomcat 生命周期管理及源码分析

几个问题

Java 编写的 Web Application 为什么能够监听一个port？
Web Application 都没有main函数, 那么该web从哪个入口函数启动的呢？

答案都是依据 tomact 或 Websphere 这些server实现的，以Tomcat为例，最重要的就是Tomcat的生命周期管理特性.

Tomcat 生命周期管理

Tomcat startup 源代码解析

主要顺序: Bootstrap.java#main() —> init() —> load() —> start()

init():
1. initClassLoaders
2.  Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
   Object startupInstance = startupClass.newInstance();
load():
1. Method method = catalinaDaemon.getClass().getMethod("load", paramTypes);
    method.invoke(catalinaDaemon, param);
2. Catalina.load()
    Digester digester = createStartDigester();   //very important
        inputSource.setByteStream("conf/server.xml");        在该位置解析server.xml,根据xml生成Server/Service/Listener/Context/Executor/Connector/Engine等,执行相应配置的class.
        digester.push(this);
        digester.parse(inputSource);
    getServer().init();
StandardContext  will parser web.xml and config context.
start():
1. Method method = catalinaDaemon.getClass().getMethod("start", (Class [] )null);
        method.invoke(catalinaDaemon, (Object [])null);
2.  getServer().start();    ==>  LifecycleBase.start()    or   WebappClassLoaderBase.start()

/**
 * Create and configure the Digester we will be using for startup.
 * @return the main digester to parse server.xml
 */
protected Digester createStartDigester() {            // 解析server.xml并初始化的主要入口函数
    long t1=System.currentTimeMillis();
    // Initialize the digester
    Digester digester = new Digester();
    digester.setValidating(false);
    digester.setRulesValidation(true);
    Map<Class<?>, List<String>> fakeAttributes = new HashMap<>();
    List<String> attrs = new ArrayList<>();
    attrs.add("className");
    fakeAttributes.put(Object.class, attrs);
    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.addObjectCreate("Server/Listener",
                             null, // MUST be specified in the element
                             "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.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/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;
}

2017-07-22