tomcat解析(十二)StandardHost

首先看構造方法:
       /** * Create a new StandardHost component with the default basic Valve. */ public StandardHost() { super(); pipeline.setBasic(new StandardHostValve()); }

可看到與StandardEngine如出一轍,具體對象作用我們將等到處理客戶端請求處理說明

在上文看到在StandardEngine的start方法裏又會調用StandardHost的start方法,因此下面這個將主要說明一下該方法的內容
<一>start方法
      /** * Start this host. * * @exception LifecycleException if this component detects a fatal error * that prevents it from being started */ public synchronized void start() throws LifecycleException { if( started ) { return; } if( ! initialized ) init(); // Look for a realm - that may have been configured earlier. // If the realm is added after context - it'll set itself. if( realm == null ) { ObjectName realmName=null; try { realmName=new ObjectName( domain + ":type=Realm,host=" + getName()); if( mserver.isRegistered(realmName ) ) { mserver.invoke(realmName, "init", new Object[] {}, new String[] {} ); } } catch( Throwable t ) { log.debug("No realm for this host " + realmName); } } // Set error report valve if ((errorReportValveClass != null) && (!errorReportValveClass.equals(""))) { try { boolean found = false; if(errorReportValveObjectName != null) { ObjectName[] names = ((StandardPipeline)pipeline).getValveObjectNames(); for (int i=0; !found && i<names.length; i++) if(errorReportValveObjectName.equals(names[i])) found = true ; } if(!found) { Valve valve = (Valve) Class.forName(errorReportValveClass) .newInstance(); addValve(valve); errorReportValveObjectName = ((ValveBase)valve).getObjectName() ; } } catch (Throwable t) { log.error(sm.getString ("standardHost.invalidErrorReportValveClass", errorReportValveClass), t); } } if(log.isDebugEnabled()) { if (xmlValidation) log.debug(sm.getString("standardHost.validationEnabled")); else log.debug(sm.getString("standardHost.validationDisabled")); } super.start(); }
    所調用的init()方法如下:
    public void init() { if( initialized ) return; initialized=true; // already registered. if( getParent() == null ) { try { // Register with the Engine ObjectName serviceName=new ObjectName(domain + ":type=Engine"); HostConfig deployer = new HostConfig(); addLifecycleListener(deployer); if( mserver.isRegistered( serviceName )) { if(log.isDebugEnabled()) log.debug("Registering "+ serviceName +" with the Engine"); mserver.invoke( serviceName, "addChild", new Object[] { this }, new String[] { "org.apache.catalina.Container" } ); } } catch( Exception ex ) { log.error("Host registering failed!",ex); } } if( oname==null ) { // not registered in JMX yet - standalone mode try { StandardEngine engine=(StandardEngine)parent; domain=engine.getName(); if(log.isDebugEnabled()) log.debug( "Register host " + getName() + " with domain "+ domain ); oname=new ObjectName(domain + ":type=Host,host=" + this.getName()); controller = oname; Registry.getRegistry(null, null) .registerComponent(this, oname, null); } catch( Throwable t ) { log.error("Host registering failed!", t ); } } }
    這裏有做判斷是否將該StandardHost實例設置爲上一StandardEngine的child數組內,若沒有則調用該方法進行處理,並同時添加LifecycleListener,類型爲HostConfig,事實上在Catalina解析XML的時候,已經有這兩步的Rule相應的設置了,因此其實這裏只做一下保險處理.另外還是一些註冊對象對象.
    調度完init方法後,依然調用了其父類的start方法,即ContainerBase.start(),這個方法在StandardEngine那篇已看過了,其實內容就是調用StandardHost對象上的Lifecycle監聽者的各個相應方法以及各子對象的start方法,其中也有child對象組的start方法,該子對象是何類呢?這個需要看StandardContext類的實例化的方法調用相關的Rule設置內容便可知曉,其實對於哪個對象將會是哪個對象的父級或子級對象,可直接看server.xml文件即可,因爲這些層級都是依照server.xml裏元素的層級關係而來的,這裏子對象類爲StandardContext類
如StandardEngine一樣,在調用super.start時,會觸發相應的Lifecycle事件,因此會調用其監聽器HostConfig的相應處理方法,方法內容如下:
       /** * Process the START event for an associated Host. * * @param event The lifecycle event that has occurred */ public void lifecycleEvent(LifecycleEvent event) { if (event.getType().equals(Lifecycle.PERIODIC_EVENT)) check(); // Identify the host we are associated with try { host = (Host) event.getLifecycle(); if (host instanceof StandardHost) { setDeployXML(((StandardHost) host).isDeployXML()); setUnpackWARs(((StandardHost) host).isUnpackWARs()); setXmlNamespaceAware(((StandardHost) host).getXmlNamespaceAware()); setXmlValidation(((StandardHost) host).getXmlValidation()); } } catch (ClassCastException e) { log.error(sm.getString("hostConfig.cce", event.getLifecycle()), e); return; } // Process the event that has occurred if (event.getType().equals(Lifecycle.START_EVENT)) start(); else if (event.getType().equals(Lifecycle.STOP_EVENT)) stop(); }
    當事件名爲Lifecycle.PERIODIC_EVENT時,將調用check方法,這個事件是在ContainerBase.start()裏的threadStart()啓動的線程裏觸發的,但其實check裏所做的內容與下邊的Lifecycle.START_EVENT所做的事是相似的,我們可看一下START_EVENT對應的start方法的內容
   /** * Process a "start" event for this Host. */ public void start() { if (log.isDebugEnabled()) log.debug(sm.getString("hostConfig.start")); try { ObjectName hostON = new ObjectName(host.getObjectName()); oname = new ObjectName (hostON.getDomain() + ":type=Deployer,host=" + host.getName()); Registry.getRegistry(null, null).registerComponent (this, oname, this.getClass().getName()); } catch (Exception e) { log.error(sm.getString("hostConfig.jmx.register", oname), e); } if (host.getDeployOnStartup()) deployApps(); }
    如果該設置啓動的時候部署,則會執行deployApps,而默認StandardHost是設置爲true的,再看deployApps如下:
    /** * Deploy applications for any directories or WAR files that are found * in our "application root" directory. */ protected void deployApps() { File appBase = appBase(); File configBase = configBase(); // Deploy XML descriptors from configBase deployDescriptors(configBase, configBase.list()); // Deploy WARs, and loop if additional descriptors are found deployWARs(appBase, appBase.list()); // Deploy expanded folders deployDirectories(appBase, appBase.list()); }
1.deployDescriptors
    部署xml文件對應的context
    這句代碼將得到context配置文件的路徑
    File configBase = configBase(); /** * Return a File object representing the "configuration root" directory * for our associated Host. */ protected File configBase() { if (configBase != null) { return configBase; } File file = new File(System.getProperty("catalina.base"), "conf"); Container parent = host.getParent(); if ((parent != null) && (parent instanceof Engine)) { file = new File(file, parent.getName()); } file = new File(file, host.getName()); try { configBase = file.getCanonicalFile(); } catch (IOException e) { configBase = file; } return (configBase); }
    通過查看server.xml可看到Engine.getName()="Catalina",host.getName="localhost",因此這裏將返回
    ${catalina.base}/conf/Catalina/localhost/目錄
    deployDescriptors(configBase, configBase.list());如下:
   /** * Deploy XML context descriptors. */ protected void deployDescriptors(File configBase, String[] files) { if (files == null) return; for (int i = 0; i < files.length; i++) { if (files[i].equalsIgnoreCase("META-INF")) continue; if (files[i].equalsIgnoreCase("WEB-INF")) continue; File contextXml = new File(configBase, files[i]); if (files[i].toLowerCase().endsWith(".xml")) { // Calculate the context path and make sure it is unique String nameTmp = files[i].substring(0, files[i].length() - 4); String contextPath = "/" + nameTmp.replace('#', '/'); if (nameTmp.equals("ROOT")) { contextPath = ""; } if (isServiced(contextPath)) continue; String file = files[i]; deployDescriptor(contextPath, contextXml, file); } } }
    取得configBase目錄下的xml文件,計算其contextPath(部署後在瀏覽器上打路徑時http://localhost:8080/後面的內容),然後調用deployDescriptor方法,如下:
    /** * @param contextPath * @param contextXml * @param file */ protected void deployDescriptor(String contextPath, File contextXml, String file) { if (deploymentExists(contextPath)) { return; } DeployedApplication deployedApp = new DeployedApplication(contextPath); // Assume this is a configuration descriptor and deploy it if(log.isDebugEnabled()) { log.debug(sm.getString("hostConfig.deployDescriptor", file)); } Context context = null; try { synchronized (digester) { try { context = (Context) digester.parse(contextXml); if (context == null) { log.error(sm.getString("hostConfig.deployDescriptor.error", file)); return; } } finally { digester.reset(); } } if (context instanceof Lifecycle) { Class clazz = Class.forName(host.getConfigClass()); LifecycleListener listener = (LifecycleListener) clazz.newInstance(); ((Lifecycle) context).addLifecycleListener(listener); } context.setConfigFile(contextXml.getAbsolutePath()); context.setPath(contextPath); // Add the associated docBase to the redeployed list if it's a WAR boolean isExternalWar = false; boolean isExternal = false; if (context.getDocBase() != null) { File docBase = new File(context.getDocBase()); if (!docBase.isAbsolute()) { docBase = new File(appBase(), context.getDocBase()); } // If external docBase, register .xml as redeploy first if (!docBase.getCanonicalPath().startsWith( appBase().getAbsolutePath() + File.separator)) { isExternal = true; deployedApp.redeployResources.put (contextXml.getAbsolutePath(), new Long(contextXml.lastModified())); deployedApp.redeployResources.put(docBase.getAbsolutePath(), new Long(docBase.lastModified())); if (docBase.getAbsolutePath().toLowerCase().endsWith(".war")) { isExternalWar = true; } } else { log.warn(sm.getString("hostConfig.deployDescriptor.localDocBaseSpecified", docBase)); // Ignore specified docBase context.setDocBase(null); } } host.addChild(context); // Get paths for WAR and expanded WAR in appBase String name = null; String path = context.getPath(); if (path.equals("")) { name = "ROOT"; } else { if (path.startsWith("/")) { name = path.substring(1); } else { name = path; } } File expandedDocBase = new File(appBase(), name); if (context.getDocBase() != null) { // first assume docBase is absolute expandedDocBase = new File(context.getDocBase()); if (!expandedDocBase.isAbsolute()) { // if docBase specified and relative, it must be relative to appBase expandedDocBase = new File(appBase(), context.getDocBase()); } } // Add the eventual unpacked WAR and all the resources which will be // watched inside it if (isExternalWar && unpackWARs) { deployedApp.redeployResources.put(expandedDocBase.getAbsolutePath(), new Long(expandedDocBase.lastModified())); deployedApp.redeployResources.put (contextXml.getAbsolutePath(), new Long(contextXml.lastModified())); addWatchedResources(deployedApp, expandedDocBase.getAbsolutePath(), context); } else { // Find an existing matching war and expanded folder if (!isExternal) { File warDocBase = new File(expandedDocBase.getAbsolutePath() + ".war"); if (warDocBase.exists()) { deployedApp.redeployResources.put(warDocBase.getAbsolutePath(), new Long(warDocBase.lastModified())); } } if (expandedDocBase.exists()) { deployedApp.redeployResources.put(expandedDocBase.getAbsolutePath(), new Long(expandedDocBase.lastModified())); addWatchedResources(deployedApp, expandedDocBase.getAbsolutePath(), context); } else { addWatchedResources(deployedApp, null, context); } // Add the context XML to the list of files which should trigger a redeployment if (!isExternal) { deployedApp.redeployResources.put (contextXml.getAbsolutePath(), new Long(contextXml.lastModified())); } } } catch (Throwable t) { log.error(sm.getString("hostConfig.deployDescriptor.error", file), t); } if (context != null && host.findChild(context.getName()) != null) { deployed.put(contextPath, deployedApp); } }
    實例化一個代表每一個部署的context的對象
    DeployedApplication deployedApp = new DeployedApplication(contextPath);
    對contextXml進行解析,生成一個context實例,爲其設置LifecycleListener,將其加到Host的children Map裏,這裏調用的是ContainerBase.addChild,可看到在加入該MAP外,會調用child的start方法,這裏先不進行細講,下篇再講StandardContext.start();查看相應context的xml裏的docBase是否存在,存在則判斷是tomcat外部文件系統的還是在${catalina.base}/webapps下的,判斷是war包還是文件夾格式,分別加入deployedApp及deployed,如
    deployedApp.redeployResources.put(warDocBase.getAbsolutePath(),new Long(warDocBase.lastModified()));
    app.reloadResources.put(resource.getAbsolutePath(),new Long(resource.lastModified()));
    deployed.put(contextPath, deployedApp);
2.deployWARs
    部署webapps下war包對應的context,爲何是webapps目錄呢?是在appBase代碼中確定的
    File appBase = appBase();
  deployWARs(appBase, appBase.list());
  appBase方法如下:
  /** * Return a File object representing the "application root" directory * for our associated Host. */ protected File appBase() { if (appBase != null) { return appBase; } File file = new File(host.getAppBase()); if (!file.isAbsolute()) file = new File(System.getProperty("catalina.base"), host.getAppBase()); try { appBase = file.getCanonicalFile(); } catch (IOException e) { appBase = file; } return (appBase); }
    而host.getAppBase()取的是StandardHost的appBase屬性,默認爲空,但在實例化StandardHost的時候便爲其賦了值,具體什麼值是根據server.xml裏的<Host>配置的
3.deployDirectories
    使用類似的過程部署webapps目錄下的工程目錄
<二>check方法
   /** * Check status of all webapps. */ protected void check() { if (host.getAutoDeploy()) { // Check for resources modification to trigger redeployment DeployedApplication[] apps = (DeployedApplication[]) deployed.values().toArray(new DeployedApplication[0]); for (int i = 0; i < apps.length; i++) { if (!isServiced(apps[i].name)) checkResources(apps[i]); } // Hotdeploy applications deployApps(); } } checkResources如下: /** * Check resources for redeployment and reloading. */ protected synchronized void checkResources(DeployedApplication app) { String[] resources = (String[]) app.redeployResources.keySet().toArray(new String[0]); for (int i = 0; i < resources.length; i++) { File resource = new File(resources[i]); if (log.isDebugEnabled()) log.debug("Checking context[" + app.name + "] redeploy resource " + resource); if (resource.exists()) { long lastModified = ((Long) app.redeployResources.get(resources[i])).longValue(); if ((!resource.isDirectory()) && resource.lastModified() > lastModified) { // Undeploy application if (log.isInfoEnabled()) log.info(sm.getString("hostConfig.undeploy", app.name)); ContainerBase context = (ContainerBase) host.findChild(app.name); try { host.removeChild(context); } catch (Throwable t) { log.warn(sm.getString ("hostConfig.context.remove", app.name), t); } try { context.destroy(); } catch (Throwable t) { log.warn(sm.getString ("hostConfig.context.destroy", app.name), t); } // Delete other redeploy resources for (int j = i + 1; j < resources.length; j++) { try { File current = new File(resources[j]); current = current.getCanonicalFile(); if ((current.getAbsolutePath().startsWith(appBase().getAbsolutePath() + File.separator)) || (current.getAbsolutePath().startsWith(configBase().getAbsolutePath()))) { if (log.isDebugEnabled()) log.debug("Delete " + current); ExpandWar.delete(current); } } catch (IOException e) { log.warn(sm.getString ("hostConfig.canonicalizing", app.name), e); } } deployed.remove(app.name); return; } } else { long lastModified = ((Long) app.redeployResources.get(resources[i])).longValue(); if (lastModified == 0L) { continue; } // Undeploy application if (log.isInfoEnabled()) log.info(sm.getString("hostConfig.undeploy", app.name)); ContainerBase context = (ContainerBase) host.findChild(app.name); try { host.removeChild(context); } catch (Throwable t) { log.warn(sm.getString ("hostConfig.context.remove", app.name), t); } try { context.destroy(); } catch (Throwable t) { log.warn(sm.getString ("hostConfig.context.destroy", app.name), t); } // Delete all redeploy resources for (int j = i + 1; j < resources.length; j++) { try { File current = new File(resources[j]); current = current.getCanonicalFile(); if ((current.getAbsolutePath().startsWith(appBase().getAbsolutePath() + File.separator)) || (current.getAbsolutePath().startsWith(configBase().getAbsolutePath()))) { if (log.isDebugEnabled()) log.debug("Delete " + current); ExpandWar.delete(current); } } catch (IOException e) { log.warn(sm.getString ("hostConfig.canonicalizing", app.name), e); } } // Delete reload resources as well (to remove any remaining .xml descriptor) String[] resources2 = (String[]) app.reloadResources.keySet().toArray(new String[0]); for (int j = 0; j < resources2.length; j++) { try { File current = new File(resources2[j]); current = current.getCanonicalFile(); if ((current.getAbsolutePath().startsWith(appBase().getAbsolutePath() + File.separator)) || ((current.getAbsolutePath().startsWith(configBase().getAbsolutePath()) && (current.getAbsolutePath().endsWith(".xml"))))) { if (log.isDebugEnabled()) log.debug("Delete " + current); ExpandWar.delete(current); } } catch (IOException e) { log.warn(sm.getString ("hostConfig.canonicalizing", app.name), e); } } deployed.remove(app.name); return; } } resources = (String[]) app.reloadResources.keySet().toArray(new String[0]); for (int i = 0; i < resources.length; i++) { File resource = new File(resources[i]); if (log.isDebugEnabled()) log.debug("Checking context[" + app.name + "] reload resource " + resource); long lastModified = ((Long) app.reloadResources.get(resources[i])).longValue(); if ((!resource.exists() && lastModified != 0L) || (resource.lastModified() != lastModified)) { // Reload application if(log.isInfoEnabled()) log.info(sm.getString("hostConfig.reload", app.name)); Container context = host.findChild(app.name); try { ((Lifecycle) context).stop(); } catch (Exception e) { log.warn(sm.getString ("hostConfig.context.restart", app.name), e); } // If the context was not started (for example an error // in web.xml) we'll still get to try to start try { ((Lifecycle) context).start(); } catch (Exception e) { log.warn(sm.getString ("hostConfig.context.restart", app.name), e); } // Update times app.reloadResources.put(resources[i], new Long(resource.lastModified())); app.timestamp = System.currentTimeMillis(); return; } } }
    通過比對context的被關注的resources來判斷是否有做過變更,如果是的話即將該context刪除,這裏的被關注的resources我們將在Context一文中進行說明
    最後又調用deployApps對context重新部署