tomcat源码分析 MBeanFactory#createStandardContext过程

zxcvb12

　　这个方法主要是启动一个web项目，
　　可以想象一下，所有跟web项目配置相关的信息，都会在这个方法里间接调用到，listener, servlet, filter等在web.xml配置的信息，还有一些通过注解配置的信息，tomcat都会扫描出来，并做初始化工作。
　　1、生成StandardContext实例，并设置属性。



// Create a new StandardContext instance
StandardContext context = new StandardContext();
path = getPathStr(path);
context.setPath(path);
context.setDocBase(docBase);
context.setXmlValidation(xmlValidation);
context.setXmlNamespaceAware(xmlNamespaceAware);
context.setTldValidation(tldValidation);
context.setTldNamespaceAware(tldNamespaceAware);
　　2、生成ContextConfig实例。ContextConfig实现了LifecycleListener接口，该接口最重要的方法是



public void lifecycleEvent(LifecycleEvent event);
　　在ContextConfig实现这个方法，并注册到StandardContext上，对StandardContext实例触发的一些重要事件做出回应。



ContextConfig contextConfig = new ContextConfig();
context.addLifecycleListener(contextConfig);
　　
　　
　　3、设置StandardContext的config属性，即根据哪个配置文件加载这个项目的。
　　在我这个环境下是：file:/....../conf/Catalina/localhost/ROOT.xml
　　4、以MBean的方式调用HostConfig的manageApp方法，参数即为StandardContext实例。
　　这一步将StandardContext添加到Host上，



host.addChild(context);
　　5、在addChild过程中，将调用StandardContext的startInternal进行初始化工作。
　　



/**
* Start this component and implement the requirements
* of {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
*
* @exception LifecycleException if this component detects a fatal error
*  that prevents this component from being used
*/
@Override
protected synchronized void startInternal() throws LifecycleException {
if(log.isDebugEnabled())
log.debug("Starting " + getBaseName());
// Send j2ee.state.starting notification
if (this.getObjectName() != null) {
Notification notification = new Notification("j2ee.state.starting",
this.getObjectName(), sequenceNumber.getAndIncrement());
broadcaster.sendNotification(notification);
}
setConfigured(false);
boolean ok = true;
// Currently this is effectively a NO-OP but needs to be called to
// ensure the NamingResources follows the correct lifecycle
if (namingResources != null) {
namingResources.start();
}
// Add missing components as necessary
if (webappResources == null) {   // (1) Required by Loader
if (log.isDebugEnabled())
log.debug("Configuring default Resources");
try {
if ((getDocBase() != null) && (getDocBase().endsWith(".war")) &&
(!(new File(getBasePath())).isDirectory()))
setResources(new WARDirContext());
else
setResources(new FileDirContext());
} catch (IllegalArgumentException e) {
log.error("Error initializing resources: " + e.getMessage());
ok = false;
}
}
if (ok) {
if (!resourcesStart()) {
log.error( "Error in resourceStart()");
ok = false;
}
}
if (getLoader() == null) {
WebappLoader webappLoader = new WebappLoader(getParentClassLoader());
webappLoader.setDelegate(getDelegate());
setLoader(webappLoader);
}
// Initialize character set mapper
        getCharsetMapper();
// Post work directory
        postWorkDirectory();
// Validate required extensions
boolean dependencyCheck = true;
try {
dependencyCheck = ExtensionValidator.validateApplication
(getResources(), this);
} catch (IOException ioe) {
log.error("Error in dependencyCheck", ioe);
dependencyCheck = false;
}
if (!dependencyCheck) {
// do not make application available if depency check fails
ok = false;
}
// Reading the "catalina.useNaming" environment variable
String useNamingProperty = System.getProperty("catalina.useNaming");
if ((useNamingProperty != null)
&& (useNamingProperty.equals("false"))) {
useNaming = false;
}
if (ok && isUseNaming()) {
if (getNamingContextListener() == null) {
NamingContextListener ncl = new NamingContextListener();
ncl.setName(getNamingContextName());
ncl.setExceptionOnFailedWrite(getJndiExceptionOnFailedWrite());
addLifecycleListener(ncl);
setNamingContextListener(ncl);
}
}
// Standard container startup
if (log.isDebugEnabled())
log.debug("Processing standard container startup");

// Binding thread
ClassLoader oldCCL = bindThread();
try {
if (ok) {
// Start our subordinate components, if any
if ((loader != null) && (loader instanceof Lifecycle))
((Lifecycle) loader).start();
// since the loader just started, the webapp classloader is now
// created.
// By calling unbindThread and bindThread in a row, we setup the
// current Thread CCL to be the webapp classloader
                unbindThread(oldCCL);
oldCCL = bindThread();
// Initialize logger again. Other components might have used it
// too early, so it should be reset.
logger = null;
getLogger();
if ((cluster != null) && (cluster instanceof Lifecycle))
((Lifecycle) cluster).start();
Realm realm = getRealmInternal();
if ((realm != null) && (realm instanceof Lifecycle))
((Lifecycle) realm).start();
if ((resources != null) && (resources instanceof Lifecycle))
((Lifecycle) resources).start();
// Notify our interested LifecycleListeners
fireLifecycleEvent(Lifecycle.CONFIGURE_START_EVENT, null);
// Start our child containers, if not already started
for (Container child : findChildren()) {
if (!child.getState().isAvailable()) {
child.start();
}
}
// Start the Valves in our pipeline (including the basic),
// if any
if (pipeline instanceof Lifecycle) {
((Lifecycle) pipeline).start();
}
// Acquire clustered manager
Manager contextManager = null;
if (manager == null) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("standardContext.cluster.noManager",
Boolean.valueOf((getCluster() != null)),
Boolean.valueOf(distributable)));
}
if ( (getCluster() != null) && distributable) {
try {
contextManager = getCluster().createManager(getName());
} catch (Exception ex) {
log.error("standardContext.clusterFail", ex);
ok = false;
}
} else {
contextManager = new StandardManager();
}
}
// Configure default manager if none was specified
if (contextManager != null) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("standardContext.manager",
contextManager.getClass().getName()));
}
setManager(contextManager);
}
if (manager!=null && (getCluster() != null) && distributable) {
//let the cluster know that there is a context that is distributable
//and that it has its own manager
                    getCluster().registerManager(manager);
}
}
} finally {
// Unbinding thread
            unbindThread(oldCCL);
}
if (!getConfigured()) {
log.error( "Error getConfigured");
ok = false;
}
// We put the resources into the servlet context
if (ok)
getServletContext().setAttribute
(Globals.RESOURCES_ATTR, getResources());
// Initialize associated mapper
        mapper.setContext(getPath(), welcomeFiles, resources);
// Binding thread
oldCCL = bindThread();
if (ok ) {
if (getInstanceManager() == null) {
javax.naming.Context context = null;
if (isUseNaming() && getNamingContextListener() != null) {
context = getNamingContextListener().getEnvContext();
}
Map injectionMap = buildInjectionMap(
getIgnoreAnnotations() ? new NamingResources(): getNamingResources());
setInstanceManager(new DefaultInstanceManager(context,
injectionMap, this, this.getClass().getClassLoader()));
getServletContext().setAttribute(
InstanceManager.class.getName(), getInstanceManager());
}
}
try {
// Create context attributes that will be required
if (ok) {
getServletContext().setAttribute(
JarScanner.class.getName(), getJarScanner());
}
// Set up the context init params
            mergeParameters();
// Call ServletContainerInitializers
for (Map.Entry