Tomcat源码---请求处理四(2)

对以上的StandardWrapperValve#invoke进行说解

 

1.   if (!unavailable) {  
2.                 //servlet行行在这一步  
3.                 servlet = wrapper.allocate();  
4.             }  

 

 

public Servlet allocate() throws ServletException {

        // If we are currently unloading this servlet, throw an exception
        if (unloading)
            throw new ServletException
              (sm.getString("standardWrapper.unloading", getName()));

        boolean newInstance = false;
        
        // If not SingleThreadedModel, return the same instance every time
        //在我们平时中没有设置,默认是单线程实例,这一步实现每一次都返回相同的实例
        if (!singleThreadModel) {

            // Load and initialize our instance if necessary
            if (instance == null) {
                synchronized (this) {
                    //在实例为空时才创建
                    if (instance == null) {
                        try {
                            if (log.isDebugEnabled())
                                log.debug("Allocating non-STM instance");
                            //创建实例
                            instance = loadServlet();
                            // For non-STM, increment here to prevent a race
                            // condition with unload. Bug 43683, test case #3
                            if (!singleThreadModel) {
                                newInstance = true;
                               //
                                countAllocated.incrementAndGet();
                            }
                        } catch (ServletException e) {
                            throw e;
                        } catch (Throwable e) {
                            throw new ServletException
                                (sm.getString("standardWrapper.allocate"), e);
                        }
                    }
                }
            }

            if (!singleThreadModel) {
                if (log.isTraceEnabled())
                    log.trace("  Returning non-STM instance");
                // For new instances, count will have been incremented at the
                // time of creation
                if (!newInstance) {
                    countAllocated.incrementAndGet();
                }
                return (instance);
            }
        }

        //每一次都返回一个实例存放在instancePool中
        synchronized (instancePool) {

            while (countAllocated.get() >= nInstances) {
                // Allocate a new instance if possible, or else wait
                if (nInstances < maxInstances) {
                    try {
                        instancePool.push(loadServlet());
                        nInstances++;
                    } catch (ServletException e) {
                        throw e;
                    } catch (Throwable e) {
                        throw new ServletException
                            (sm.getString("standardWrapper.allocate"), e);
                    }
                } else {
                    try {
                        instancePool.wait();
                    } catch (InterruptedException e) {
                        ;
                    }
                }
            }
            if (log.isTraceEnabled())
                log.trace("  Returning allocated STM instance");
            countAllocated.incrementAndGet();
            return (Servlet) instancePool.pop();

        }

    }

   以上这一步在我们平时使用时会经常遇到,,servlet的创建是一个多线程单实例的,所以共享全局变量,所以在使用servlet

时应尽量避免定义全局变量

对#loadServlet进行详解

 

 public synchronized Servlet loadServlet() throws ServletException {

        // Nothing to do if we already have an instance or an instance pool
        //如果有实例时直接返回
        if (!singleThreadModel && (instance != null))
            return instance;

        PrintStream out = System.out;
        if (swallowOutput) {
            SystemLogHandler.startCapture();
        }

        Servlet servlet;
        try {
            long t1=System.currentTimeMillis();
            // If this "servlet" is really a JSP file, get the right class.
            // HOLD YOUR NOSE - this is a kludge that avoids having to do special
            // case Catalina-specific code in Jasper - it also requires that the
            // servlet path be replaced by the <jsp-file> element content in
            // order to be completely effective
            //所访问的servlet的类路径名
            String actualClass = servletClass;
            if ((actualClass == null) && (jspFile != null)) {
                Wrapper jspWrapper = (Wrapper)
                    ((Context) getParent()).findChild(Constants.JSP_SERVLET_NAME);
                if (jspWrapper != null) {
                    actualClass = jspWrapper.getServletClass();
                    // Merge init parameters
                    String paramNames[] = jspWrapper.findInitParameters();
                    for (int i = 0; i < paramNames.length; i++) {
                        if (parameters.get(paramNames[i]) == null) {
                            parameters.put
                                (paramNames[i], 
                                 jspWrapper.findInitParameter(paramNames[i]));
                        }
                    }
                }
            }

            // Complain if no servlet class has been specified
            if (actualClass == null) {
                unavailable(null);
                throw new ServletException
                    (sm.getString("standardWrapper.notClass", getName()));
            }

            // Acquire an instance of the class loader to be used
            
            Loader loader = getLoader();
            if (loader == null) {
                unavailable(null);
                throw new ServletException
                    (sm.getString("standardWrapper.missingLoader", getName()));
            }
            //获取werbappclassloader
            ClassLoader classLoader = loader.getClassLoader();

            // Special case class loader for a container provided servlet
            //  
            if (isContainerProvidedServlet(actualClass) && 
                    ! ((Context)getParent()).getPrivileged() ) {
                // If it is a priviledged context - using its own
                // class loader will work, since it's a child of the container
                // loader
                classLoader = this.getClass().getClassLoader();
            }

            // Load the specified servlet class from the appropriate class loader
            Class classClass = null;
            try {
                if (SecurityUtil.isPackageProtectionEnabled()){
                    final ClassLoader fclassLoader = classLoader;
                    final String factualClass = actualClass;
                    try{
                        classClass = (Class)AccessController.doPrivileged(
                                new PrivilegedExceptionAction(){
                                    public Object run() throws Exception{
                                        if (fclassLoader != null) {
                                            //进行类加载
                                            return fclassLoader.loadClass(factualClass);
                                        } else {
                                            return Class.forName(factualClass);
                                        }
                                    }
                        });
                    } catch(PrivilegedActionException pax){
                        Exception ex = pax.getException();
                        if (ex instanceof ClassNotFoundException){
                            throw (ClassNotFoundException)ex;
                        } else {
                            getServletContext().log( "Error loading "
                                + fclassLoader + " " + factualClass, ex );
                        }
                    }
                } else {
                    if (classLoader != null) {
                        classClass = classLoader.loadClass(actualClass);
                    } else {
                        classClass = Class.forName(actualClass);
                    }
                }
            } catch (ClassNotFoundException e) {
                unavailable(null);
                getServletContext().log( "Error loading " + classLoader + " " + actualClass, e );
                throw new ServletException
                    (sm.getString("standardWrapper.missingClass", actualClass),
                     e);
            }

            if (classClass == null) {
                unavailable(null);
                throw new ServletException
                    (sm.getString("standardWrapper.missingClass", actualClass));
            }

            // Instantiate and initialize an instance of the servlet class itself
            try {
                servlet = (Servlet) classClass.newInstance();
                // Annotation processing
                if (!((Context) getParent()).getIgnoreAnnotations()) {
                    if (getParent() instanceof StandardContext) {
                       ((StandardContext)getParent()).getAnnotationProcessor().processAnnotations(servlet);
                       ((StandardContext)getParent()).getAnnotationProcessor().postConstruct(servlet);
                    }
                }
            } catch (ClassCastException e) {
                unavailable(null);
                // Restore the context ClassLoader
                throw new ServletException
                    (sm.getString("standardWrapper.notServlet", actualClass), e);
            } catch (Throwable e) {
                unavailable(null);
              
                // Added extra log statement for Bugzilla 36630:
                // http://issues.apache.org/bugzilla/show_bug.cgi?id=36630
                if(log.isDebugEnabled()) {
                    log.debug(sm.getString("standardWrapper.instantiate", actualClass), e);
                }

                // Restore the context ClassLoader
                throw new ServletException
                    (sm.getString("standardWrapper.instantiate", actualClass), e);
            }

            // Check if loading the servlet in this web application should be
            // allowed
            if (!isServletAllowed(servlet)) {
                throw new SecurityException
                    (sm.getString("standardWrapper.privilegedServlet",
                                  actualClass));
            }

            // Special handling for ContainerServlet instances
            if ((servlet instanceof ContainerServlet) &&
                  (isContainerProvidedServlet(actualClass) ||
                    ((Context)getParent()).getPrivileged() )) {
                ((ContainerServlet) servlet).setWrapper(this);
            }

            classLoadTime=(int) (System.currentTimeMillis() -t1);
            // Call the initialization method of this servlet
           //该Servlet的初始化,只实现一次
            try {
                instanceSupport.fireInstanceEvent(InstanceEvent.BEFORE_INIT_EVENT,
                                                  servlet);

                if( Globals.IS_SECURITY_ENABLED) {

                    Object[] args = new Object[]{((ServletConfig)facade)};
                    SecurityUtil.doAsPrivilege("init",
                                               servlet,
                                               classType,
                                               args);
                    args = null;
                } else {
                    servlet.init(facade);
                }

                // Invoke jspInit on JSP pages
                //jsp转换成servlet的初始化
                if ((loadOnStartup >= 0) && (jspFile != null)) {
                    // Invoking jspInit
                    DummyRequest req = new DummyRequest();
                    req.setServletPath(jspFile);
                    req.setQueryString(Constants.PRECOMPILE + "=true");
                    DummyResponse res = new DummyResponse();

                    if( Globals.IS_SECURITY_ENABLED) {
                        Object[] args = new Object[]{req, res};
                        SecurityUtil.doAsPrivilege("service",
                                                   servlet,
                                                   classTypeUsedInService,
                                                   args);
                        args = null;
                    } else {
                        servlet.service(req, res);
                    }
                }
                instanceSupport.fireInstanceEvent(InstanceEvent.AFTER_INIT_EVENT,
                                                  servlet);
            } catch (UnavailableException f) {
                instanceSupport.fireInstanceEvent(InstanceEvent.AFTER_INIT_EVENT,
                                                  servlet, f);
                unavailable(f);
                throw f;
            } catch (ServletException f) {
                instanceSupport.fireInstanceEvent(InstanceEvent.AFTER_INIT_EVENT,
                                                  servlet, f);
                // If the servlet wanted to be unavailable it would have
                // said so, so do not call unavailable(null).
                throw f;
            } catch (Throwable f) {
                getServletContext().log("StandardWrapper.Throwable", f );
                instanceSupport.fireInstanceEvent(InstanceEvent.AFTER_INIT_EVENT,
                                                  servlet, f);
                // If the servlet wanted to be unavailable it would have
                // said so, so do not call unavailable(null).
                throw new ServletException
                    (sm.getString("standardWrapper.initException", getName()), f);
            }

            // Register our newly initialized instance
            singleThreadModel = servlet instanceof SingleThreadModel;
            if (singleThreadModel) {
                if (instancePool == null)
                    instancePool = new Stack();
            }
            fireContainerEvent("load", this);

            loadTime=System.currentTimeMillis() -t1;
        } finally {
            if (swallowOutput) {
                String log = SystemLogHandler.stopCapture();
                if (log != null && log.length() > 0) {
                    if (getServletContext() != null) {
                        getServletContext().log(log);
                    } else {
                        out.println(log);
                    }
                }
            }
        }
        return servlet;

    }

 从以上步骤可得到该servlet的实例,并用已经初始化过

现在对StandardWrapperValve#invoke

 

1.       //这里面开始对过滤器进行处理  
2.                             filterChain.doFilter(request.getRequest(),   
3.                                     response.getResponse()); 

 

这里面对过滤器进行了执行ApplicationFilterChain#doFilter

 

public void doFilter(ServletRequest request, ServletResponse response)
        throws IOException, ServletException {

        if( Globals.IS_SECURITY_ENABLED ) {
            final ServletRequest req = request;
            final ServletResponse res = response;
            try {
                java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedExceptionAction() {
                        public Object run() 
                            throws ServletException, IOException {
                            internalDoFilter(req,res);
                            return null;
                        }
                    }
                );
            } catch( PrivilegedActionException pe) {
                Exception e = pe.getException();
                if (e instanceof ServletException)
                    throw (ServletException) e;
                else if (e instanceof IOException)
                    throw (IOException) e;
                else if (e instanceof RuntimeException)
                    throw (RuntimeException) e;
                else
                    throw new ServletException(e.getMessage(), e);
            }
        } else {
           //这一步才是真正的执行
            internalDoFilter(request,response);
        }
    }

 #internalDoFilter(rquest,response)

 

 private void internalDoFilter(ServletRequest request, 
                                  ServletResponse response)
        throws IOException, ServletException {

        // Call the next filter if there is one
        if (pos < n) {
            ApplicationFilterConfig filterConfig = filters[pos++];
            Filter filter = null;
            try {
                //获取过滤器
                filter = filterConfig.getFilter();
                support.fireInstanceEvent(InstanceEvent.BEFORE_FILTER_EVENT,
                                          filter, request, response);
                
                if( Globals.IS_SECURITY_ENABLED ) {
                    final ServletRequest req = request;
                    final ServletResponse res = response;
                    Principal principal = 
                        ((HttpServletRequest) req).getUserPrincipal();

                    Object[] args = new Object[]{req, res, this};
                    SecurityUtil.doAsPrivilege
                        ("doFilter", filter, classType, args, principal);
                    
                    args = null;
                } else {  
                    //进行过滤
                    filter.doFilter(request, response, this);
                }

                support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
                                          filter, request, response);
            } catch (IOException e) {
                if (filter != null)
                    support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
                                              filter, request, response, e);
                throw e;
            } catch (ServletException e) {
                if (filter != null)
                    support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
                                              filter, request, response, e);
                throw e;
            } catch (RuntimeException e) {
                if (filter != null)
                    support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
                                              filter, request, response, e);
                throw e;
            } catch (Throwable e) {
                if (filter != null)
                    support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
                                              filter, request, response, e);
                throw new ServletException
                  (sm.getString("filterChain.filter"), e);
            }
            return;
        }

        // We fell off the end of the chain -- call the servlet instance
        try {
            if (Globals.STRICT_SERVLET_COMPLIANCE) {
                lastServicedRequest.set(request);
                lastServicedResponse.set(response);
            }

            support.fireInstanceEvent(InstanceEvent.BEFORE_SERVICE_EVENT,
                                      servlet, request, response);
            if ((request instanceof HttpServletRequest) &&
                (response instanceof HttpServletResponse)) {
                    
                if( Globals.IS_SECURITY_ENABLED ) {
                    final ServletRequest req = request;
                    final ServletResponse res = response;
                    Principal principal = 
                        ((HttpServletRequest) req).getUserPrincipal();
                    Object[] args = new Object[]{req, res};
                    SecurityUtil.doAsPrivilege("service",
                                               servlet,
                                               classTypeUsedInService, 
                                               args,
                                               principal);   
                    args = null;
                } else {  
                    servlet.service((HttpServletRequest) request,
                                    (HttpServletResponse) response);
                }
            } else {
                //有过滤器,先过滤再执行servlet的service的方法
                servlet.service(request, response);
            }
            support.fireInstanceEvent(InstanceEvent.AFTER_SERVICE_EVENT,
                                      servlet, request, response);
        } catch (IOException e) {
            support.fireInstanceEvent(InstanceEvent.AFTER_SERVICE_EVENT,
                                      servlet, request, response, e);
            throw e;
        } catch (ServletException e) {
            support.fireInstanceEvent(InstanceEvent.AFTER_SERVICE_EVENT,
                                      servlet, request, response, e);
            throw e;
        } catch (RuntimeException e) {
            support.fireInstanceEvent(InstanceEvent.AFTER_SERVICE_EVENT,
                                      servlet, request, response, e);
            throw e;
        } catch (Throwable e) {
            support.fireInstanceEvent(InstanceEvent.AFTER_SERVICE_EVENT,
                                      servlet, request, response, e);
            throw new ServletException
              (sm.getString("filterChain.servlet"), e);
        } finally {
            if (Globals.STRICT_SERVLET_COMPLIANCE) {
                lastServicedRequest.set(null);
                lastServicedResponse.set(null);
            }
        }

    }

 

这样的过滤器已经执行,servlet也已经执行....接下来做些释放工程

servlet的创建是一个单线程多实例的

是不是应该是多线程单实例?

呵呵，，，写错了，，，已经更正