tomcat解析(二)Bootstrap.init

org.apache.catalina.startup.Bootstrap沒有靜態塊,因此將直接運行其main方法的,main方法如下:

/** * Main method, used for testing only. * * @param args Command line arguments to be processed */ public static void main(String args[]) { if (daemon == null) { daemon = new Bootstrap(); try { daemon.init(); } catch (Throwable t) { t.printStackTrace(); return; } } try { String command = "start"; if (args.length > 0) { command = args[args.length - 1]; } if (command.equals("startd")) { args[0] = "start"; daemon.load(args); daemon.start(); } else if (command.equals("stopd")) { args[0] = "stop"; daemon.stop(); } else if (command.equals("start")) { daemon.setAwait(true); daemon.load(args); daemon.start(); } else if (command.equals("stop")) { daemon.stopServer(args); } else { log.warn("Bootstrap: command /"" + command + "/" does not exist."); } } catch (Throwable t) { t.printStackTrace(); } }

有趣的是,其註釋裏寫着used for testing only,但實際上卻的確是從這裏啓動的(起碼我認爲是,有其它高見請盡情留言於我):)

main方法的內容很清晰,實例化了一個Bootstrap對象,並依次調用其init、load及start方法.本文將只講述init()方法:),方法內容如下:

/** * Initialize daemon. */ public void init() throws Exception { // Set Catalina path setCatalinaHome(); setCatalinaBase(); initClassLoaders(); Thread.currentThread().setContextClassLoader(catalinaLoader); SecurityClassLoad.securityClassLoad(catalinaLoader); // Load our startup class and call its process() method if (log.isDebugEnabled()) log.debug("Loading startup class"); Class startupClass = catalinaLoader.loadClass ("org.apache.catalina.startup.Catalina"); Object startupInstance = startupClass.newInstance(); // Set the shared extensions class loader 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; }

該方法調用了幾位方法完全服務器的初步初始化，setCatalinaHome()及setCatalinaBase()方法就不說了,根據名字應該可以看得出來是設置catalina.home及catalina.base兩個變量的,是調用System.setProperty方法設置到系統變量中，init裏其它主要的內容包括以下三個方面

1.initClassLoaders ，初始化類加載器
  該方法用於實例化3個ClassLoader對象commonLoader、catalinaLoader及sharedLoader,實例化時用的是如下代碼:

private void initClassLoaders() { try { commonLoader = createClassLoader("common", null); if( commonLoader == null ) { // no config file, default to this loader - we might be in a 'single' env. commonLoader=this.getClass().getClassLoader(); } catalinaLoader = createClassLoader("server", commonLoader); sharedLoader = createClassLoader("shared", commonLoader); } catch (Throwable t) { log.error("Class loader creation threw exception", t); System.exit(1); } }

createClassLoader如下

private ClassLoader createClassLoader(String name, ClassLoader parent) throws Exception { String value = CatalinaProperties.getProperty(name + ".loader"); if ((value == null) || (value.equals(""))) return parent; ArrayList repositoryLocations = new ArrayList(); ArrayList repositoryTypes = new ArrayList(); int i; StringTokenizer tokenizer = new StringTokenizer(value, ","); while (tokenizer.hasMoreElements()) { String repository = tokenizer.nextToken(); // Local repository boolean replace = false; String before = repository; while ((i=repository.indexOf(CATALINA_HOME_TOKEN))>=0) { replace=true; if (i>0) { repository = repository.substring(0,i) + getCatalinaHome() + repository.substring(i+CATALINA_HOME_TOKEN.length()); } else { repository = getCatalinaHome() + repository.substring(CATALINA_HOME_TOKEN.length()); } } while ((i=repository.indexOf(CATALINA_BASE_TOKEN))>=0) { replace=true; if (i>0) { repository = repository.substring(0,i) + getCatalinaBase() + repository.substring(i+CATALINA_BASE_TOKEN.length()); } else { repository = getCatalinaBase() + repository.substring(CATALINA_BASE_TOKEN.length()); } } if (replace && log.isDebugEnabled()) log.debug("Expanded " + before + " to " + replace); // Check for a JAR URL repository try { URL url=new URL(repository); repositoryLocations.add(repository); repositoryTypes.add(ClassLoaderFactory.IS_URL); continue; } catch (MalformedURLException e) { // Ignore } if (repository.endsWith("*.jar")) { repository = repository.substring (0, repository.length() - "*.jar".length()); repositoryLocations.add(repository); repositoryTypes.add(ClassLoaderFactory.IS_GLOB); } else if (repository.endsWith(".jar")) { repositoryLocations.add(repository); repositoryTypes.add(ClassLoaderFactory.IS_JAR); } else { repositoryLocations.add(repository); repositoryTypes.add(ClassLoaderFactory.IS_DIR); } } String[] locations = (String[]) repositoryLocations.toArray(new String[0]); Integer[] types = (Integer[]) repositoryTypes.toArray(new Integer[0]); ClassLoader classLoader = ClassLoaderFactory.createClassLoader (locations, types, parent); // Retrieving MBean server MBeanServer mBeanServer = null; if (MBeanServerFactory.findMBeanServer(null).size() > 0) { mBeanServer = (MBeanServer) MBeanServerFactory.findMBeanServer(null).get(0); } else { mBeanServer = MBeanServerFactory.createMBeanServer(); } // Register the server classloader ObjectName objectName = new ObjectName("Catalina:type=ServerClassLoader,name=" + name); mBeanServer.registerMBean(classLoader, objectName); return classLoader; }

    String value = CatalinaProperties.getProperty(name + ".loader");
    CatalinaProperties的getProperty是靜態方法,是從CatalinaProperties持有的properties對象中取值,而該類有一個靜態塊,即是用於初始化該properties對象,靜態塊代碼如下:

/** * Load properties. */ private static void loadProperties() { InputStream is = null; Throwable error = null; try { String configUrl = getConfigUrl(); if (configUrl != null) { is = (new URL(configUrl)).openStream(); } } catch (Throwable t) { // Ignore } if (is == null) { try { File home = new File(getCatalinaBase()); File conf = new File(home, "conf"); File properties = new File(conf, "catalina.properties"); is = new FileInputStream(properties); } catch (Throwable t) { // Ignore } } if (is == null) { try { is = CatalinaProperties.class.getResourceAsStream ("/org/apache/catalina/startup/catalina.properties"); } catch (Throwable t) { // Ignore } } if (is != null) { try { properties = new Properties(); properties.load(is); is.close(); } catch (Throwable t) { error = t; } } if ((is == null) || (error != null)) { // Do something log.warn("Failed to load catalina.properties", error); // That's fine - we have reasonable defaults. properties=new Properties(); } // Register the properties as system properties Enumeration enumeration = properties.propertyNames(); while (enumeration.hasMoreElements()) { String name = (String) enumeration.nextElement(); String value = properties.getProperty(name); if (value != null) { System.setProperty(name, value); } } }

其中getConfigUrl()方法如下
    /**
     * Get the value of the configuration URL.
     */
    private static String getConfigUrl() {
        return System.getProperty("catalina.config");
    }
可看出表態塊loadProperties用於依次獲取catalina.config變量所設置的配置文件、catalina.base變量路徑中的catalina.properties及
/org/apache/catalina/startup/catalina.properties來初始化其Properties對象（前者取不到才使用後者），
並且將該對象的每一個屬性也設置到系統屬性中，
catalina.properties中有效的配置如下
package.access=sun.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper.,sun.beans. package.definition=sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper. common.loader=${catalina.home}/lib,${catalina.home}/lib/*.jar server.loader= shared.loader= tomcat.util.buf.StringCache.byte.enabled=true 
在創建commonLoader時所用代碼
String value = CatalinaProperties.getProperty(name + ".loader");
將取到如下字符串
${catalina.home}/lib,${catalina.home}/lib/*.jar,在將{catalina.home}轉化爲真正代表文件路徑的路徑字符串後調用URLClassLoader類的構造方法實例化commonClassLoader，緊接着使用下列語句生成MBeanServer對象mBeanServer,這部分內容是JMX的東東，有興趣的同學可以深入研究，這裏就不多講了mBeanServer = MBeanServerFactory.createMBeanServer();並且將commonClassLoader以Catalina:type=ServerClassLoader,name=common的ObjectName對象註冊到該MBean服務器中，而實例化catalinaLoader及sharedLoader時因server.loader及shared.loader沒有設置屬性值，
且以commonLoader爲父節點，所以最終這兩個變量與commonLoader變量將指向同一個對象,catalinaLoader及sharedLoader則分別以
Catalina:type=ServerClassLoader,name=server及Catalina:type=ServerClassLoader,name=shared進行註冊

2.實例化org.apache.catalina.startup.Catalina對象

可看到這一部分代碼如下: Class startupClass = catalinaLoader.loadClass ("org.apache.catalina.startup.Catalina"); Object startupInstance = startupClass.newInstance(); // Set the shared extensions class loader 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);

實例化org.apache.catalina.startup.Catalina對象，然後調用其setParentClassLoader方法，參數爲sharedLoader,在實例化Catalina對象的時候,會調用其父類Embedded的構造方法,其中的setSecurityProtection方法包含了從catalina.properties讀取package.definition及package.access來設置java包的安全訪問權限

3.讓catalinaDaemon引用startupInstance
  如第2點所言，startupInstance爲org.apache.catalina.startup.Catalina的實例對象

 

至此Bootstrap的init方法執行完成,下一章再講Bootstrap.load及start的內容