Struts2源码阅读(五)_FilterDispatcher核心控制器

Dispatcher已经在之前讲过，这就好办了。FilterDispatcher是Struts2的核心控制器，首先看一下init()方法。

public void init(FilterConfig filterConfig) throws ServletException {     try {     this.filterConfig = filterConfig;     initLogging();     //创建dispatcher,前面都已经讲过啰     dispatcher = createDispatcher(filterConfig);     dispatcher.init();     //注入将FilterDispatcher中的变量通过container注入,如下面的staticResourceLoader     dispatcher.getContainer().inject(this);     //StaticContentLoader在BeanSelectionProvider中已经被注入了依赖关系:DefaultStaticContentLoader     //可以在struts-default.xml中的<bean>可以找到     staticResourceLoader.setHostConfig(new FilterHostConfig(filterConfig));     } finally {     ActionContext.setContext(null);     }
}   //下面来看DefaultStaticContentLoader的setHostConfig     public void setHostConfig(HostConfig filterConfig) {     //读取初始参数pakages，调用parse()，解析成类似/org/apache/struts2/static,/template的数组        String param = filterConfig.getInitParameter("packages");     //"org.apache.struts2.static template org.apache.struts2.interceptor.debugging static"     String packages = getAdditionalPackages();     if (param != null) {     packages = param + " " + packages;     }     this.pathPrefixes = parse(packages);     initLogging(filterConfig);     }

现在回去doFilter的方法,每当有一个Request,都会调用这些Filters的doFilter方法

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {     HttpServletRequest request = (HttpServletRequest) req;     HttpServletResponse response = (HttpServletResponse) res;     ServletContext servletContext = getServletContext();     String timerKey = "FilterDispatcher_doFilter: ";     try {     // FIXME: this should be refactored better to not duplicate work with the action invocation     //先看看ValueStackFactory所注入的实现类OgnlValueStackFactory     //new OgnlValueStack     ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();     ActionContext ctx = new ActionContext(stack.getContext());     ActionContext.setContext(ctx);     UtilTimerStack.push(timerKey);     //如果是multipart/form-data就用MultiPartRequestWrapper进行包装
//MultiPartRequestWrapper是StrutsRequestWrapper的子类，两者都是HttpServletRequest实现
//此时在MultiPartRequestWrapper中就会把Files给解析出来,用于文件上传
//所有request都会StrutsRequestWrapper进行包装,StrutsRequestWrapper是可以访问ValueStack
//下面是参见Dispatcher的wrapRequest     // String content_type = request.getContentType();     //if(content_type!= null&&content_type.indexOf("multipart/form-data")!=-1){     //MultiPartRequest multi =getContainer().getInstance(MultiPartRequest.class);     //request =new MultiPartRequestWrapper(multi,request,getSaveDir(servletContext));     //} else {     //     request = new StrutsRequestWrapper(request);     // }     request = prepareDispatcherAndWrapRequest(request, response);     ActionMapping mapping;     try {     //根据url取得对应的Action的配置信息     //看一下注入的DefaultActionMapper的getMapping()方法.Action的配置信息存储在 ActionMapping对象中     mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());     } catch (Exception ex) {     log.error("error getting ActionMapping", ex);     dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);     return;     }     //如果找不到对应的action配置，则直接返回。比如你输入***.jsp等等                                      //这儿有个例外，就是如果path是以“/struts”开头，则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中，当然.class文件除外。如果再没有则跳转到404       if (mapping == null) {     // there is no action in this request, should we look for a static resource?     String resourcePath = RequestUtils.getServletPath(request);     if ("".equals(resourcePath) && null != request.getPathInfo()) {     resourcePath = request.getPathInfo();     }     if (staticResourceLoader.canHandle(resourcePath)) {     // 在DefaultStaticContentLoader中:return serveStatic && (resourcePath.startsWith("/struts") || resourcePath.startsWith("/static"));     staticResourceLoader.findStaticResource(resourcePath, request, response);     } else {     // this is a normal request, let it pass through     chain.doFilter(request, response);     }     // The framework did its job here     return;     }     //正式开始Action的方法     dispatcher.serviceAction(request, response, servletContext, mapping);     } finally {     try {     ActionContextCleanUp.cleanUp(req);     } finally {     UtilTimerStack.pop(timerKey);     }     }
}

//下面是ActionMapper接口的实现类 DefaultActionMapper的getMapping()方法的源代码:     public ActionMapping getMapping(HttpServletRequest request,     ConfigurationManager configManager) {     ActionMapping mapping = new ActionMapping();     String uri = getUri(request);//得到请求路径的URI，如：testAtcion.action或testAction.do     int indexOfSemicolon = uri.indexOf(";");//修正url的带;jsessionid 时找不到而且的bug     uri = (indexOfSemicolon > -1) ? uri.substring(0, indexOfSemicolon) : uri;     uri = dropExtension(uri, mapping);//删除扩展名，默认扩展名为action     if (uri == null) {     return null;     }     parseNameAndNamespace(uri, mapping, configManager);//匹配Action的name和namespace     handleSpecialParameters(request, mapping);//去掉重复参数     //如果Action的name没有解析出来，直接返回     if (mapping.getName() == null) {     returnnull;     }     //下面处理形如testAction!method格式的请求路径     if (allowDynamicMethodCalls) {     // handle "name!method" convention.     String name = mapping.getName();     int exclamation = name.lastIndexOf("!");//!是Action名称和方法名的分隔符     if (exclamation != -1) {     mapping.setName(name.substring(0, exclamation));//提取左边为name     mapping.setMethod(name.substring(exclamation + 1));//提取右边的method     }     }     return mapping;     }

从代码中看出，getMapping()方法返回ActionMapping类型的对象，该对象包含三个参数：Action的name、namespace和要调用的方法method。
　　如果getMapping()方法返回ActionMapping对象为null，则FilterDispatcher认为用户请求不是Action，自然另当别论，FilterDispatcher会做一件非常有意思的事：如果请求以/struts开头，会自动查找在web.xml文件中配置的 packages初始化参数，就像下面这样:

<filter>    <filter-name>struts2</filter-name>    <filter-class>    org.apache.struts2.dispatcher.FilterDispatcher     </filter-class>    <init-param>    <param-name>packages</param-name>    <param-value>com.lizanhong.action</param-value>    </init-param>    </filter>

FilterDispatcher会将com.lizanhong.action包下的文件当作静态资源处理，即直接在页面上显示文件内容，不过会忽略扩展名为class的文件。比如在com.lizanhong.action包下有一个aaa.txt的文本文件，其内容为“中华人民共和国”，访问 http://localhost:8081/Struts2Demo/struts/aaa.txt 时会输出txt中的内容
FilterDispatcher.findStaticResource()方法

protected void findStaticResource(String name, HttpServletRequest request, HttpServletResponse response) throws IOException {     if (!name.endsWith(".class")) {//忽略class文件     //遍历packages参数     for (String pathPrefix : pathPrefixes) {     InputStream is = findInputStream(name, pathPrefix);//读取请求文件流     if (is != null) {     ...     // set the content-type header     String contentType = getContentType(name);//读取内容类型     if (contentType != null) {     response.setContentType(contentType);//重新设置内容类型     }     ...     try {     //将读取到的文件流以每次复制4096个字节的方式循环输出     copy(is, response.getOutputStream());     } finally {     is.close();     }     return;     }     }     }     }

如果用户请求的资源不是以/struts开头——可能是.jsp文件，也可能是.html文件，则通过过滤器链继续往下传送，直到到达请求的资源为止。
如果getMapping()方法返回有效的ActionMapping对象，则被认为正在请求某个Action，将调用 Dispatcher.serviceAction(request, response, servletContext, mapping)方法，该方法是处理Action的关键所在。
下面就来看serviceAction,这又回到全局变量dispatcher中了

//Load Action class for mapping and invoke the appropriate Action method, or go directly to the Result.
public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,     ActionMapping mapping) throws ServletException {     //createContextMap方法主要把Application、Session、Request的key value值拷贝到Map中     Map<String, Object> extraContext = createContextMap(request, response, mapping, context);     // If there was a previous value stack, then create a new copy and pass it in to be used by the new Action     ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);     boolean nullStack = stack == null;     if (nullStack) {     ActionContext ctx = ActionContext.getContext();     if (ctx != null) {     stack = ctx.getValueStack();     }     }     if (stack != null) {     extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));     }     String timerKey = "Handling request from Dispatcher";     try {     UtilTimerStack.push(timerKey);     String namespace = mapping.getNamespace();     String name = mapping.getName();     String method = mapping.getMethod();     Configuration config = configurationManager.getConfiguration();     //创建一个Action的代理对象，ActionProxyFactory是创建ActionProxy的工厂     //参考实现类:DefaultActionProxy和DefaultActionProxyFactory     ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(     namespace, name, method, extraContext, true, false);     request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());     // if the ActionMapping says to go straight to a result, do it!     //如果是Result,则直接转向,关于Result,ActionProxy,ActionInvocation下一讲中再分析     if (mapping.getResult() != null) {     Result result = mapping.getResult();     result.execute(proxy.getInvocation());     } else {     //执行Action     proxy.execute();     }     // If there was a previous value stack then set it back onto the request     if (!nullStack) {     request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);     }     } catch (ConfigurationException e) {     // WW-2874 Only log error if in devMode     if(devMode) {     LOG.error("Could not find action or result", e);     }     else {     LOG.warn("Could not find action or result", e);     }     sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);     } catch (Exception e) {     sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);     } finally {     UtilTimerStack.pop(timerKey);     }     }

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