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(注意粗斜体部分)：
<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
protectedvoid 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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