Struts1.3.x中ActionServlet源码分析之执行

执行流程：

1、ActionServlet处理.do的请求 不管是get还是post方式都将转到
    protected void process(HttpServletRequest request, HttpServletResponse response) 方法。
   
2、根据请求对象和servletContext对象选择请求所隶属的模块
    ModuleUtils.getInstance().selectModule(request, getServletContext());
   
3、加载模块配置对象 ModuleConfig config = getModuleConfig(request);

4、加载请求处理对象
    RequestProcessor processor = getProcessorForModule(config);
        if (processor == null) {
            processor = getRequestProcessor(config);
        }
       
5、调用请求对象（processor）对象的
    public void process(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException
    方法处理请求。
   
6、对mutipart请求（上传）进行特殊包装 request = processMultipart(request);

    1、首先判断是否为post方式，如果不是post方式，则肯定不是上传请求，则直接返回request对象
        if (!"POST".equalsIgnoreCase(request.getMethod())) {
            return (request);
        }
       
    2、获取request对象的ContentType，如果ContentType为multipart/form-datade 话则 new 一个 MultipartRequestWrapper 对象返回。否则直接返回request。
        String contentType = request.getContentType();
        if ((contentType != null)
            && contentType.startsWith("multipart/form-data")) {
            return (new MultipartRequestWrapper(request));
        } else {
            return (request);
        }
       
        1、MultipartRequestWrapper继承于HttpServletRequestWrapper。下面是包装代码
            public MultipartRequestWrapper(HttpServletRequest request) {
                super(request);
                this.parameters = new HashMap();
            }
           
7、处理请求路径
    String path = processPath(request, response); 返回的是访问的action的名字
   
8、如果返回值是空， 则方法直接return，结束。
    if (path == null) {
        return;
    }
   
9、把请求的方式（post/get）和action名字记入日志
    if (log.isDebugEnabled()) {
        log.debug("Processing a '" + request.getMethod() + "' for path '"
            + path + "'");
    }
   
10、为当前的用户请求选择对应的local（区域和语言），这是根据浏览器的设置的。涉及到国际化问题。
    // Select a Locale for the current user if requested
    processLocale(request, response);

11、为response对象设置ContentType和no-cache的header信息。
    // Set the content type and no-caching headers if requested
    processContent(request, response);
    processNoCache(request, response);

12、留了一个可以预处理请求的扩展接口。
    // General purpose preprocessing hook
    if (!processPreprocess(request, response)) {
        return;
    }      这里processPreprocess方法只有一句话：return（true）；其实是为了可以扩展，如果要对请求预处理，可以继承这个类，然后重写这个
    protected boolean processPreprocess(HttpServletRequest request,HttpServletResponse response) {
        return (true);
    }
方法。

13、处理以前缓存的信息
    this.processCachedMessages(request, response);
    其实就是清空session里如果存在的struts定义的提示信息和错误信息。   

14、根据request，response，和path（action的名字）返回actionMapping对象。
    // Identify the mapping for this request
    ActionMapping mapping = processMapping(request, response, path);
    if (mapping == null) {
        return;
    }
   
    1、首先去配置文件里找相应的配置信息
        // Is there a mapping for this path?
        ActionMapping mapping = (ActionMapping) moduleConfig.findActionConfig(path);
   
    2、如果有配置则把它放入request，并返回他。
        // If a mapping is found, put it in the request and return it
        if (mapping != null) {
            request.setAttribute(Globals.MAPPING_KEY, mapping);
            return (mapping);
        }
       
    3、找到“未知的映射路径（如果有的话）”。同样找到了就放到request里并返回他。
        // Locate the mapping for unknown paths (if any)
        ActionConfig[] configs = moduleConfig.findActionConfigs();

        for (int i = 0; i < configs.length; i++) {
            if (configs[i].getUnknown()) {
                mapping = (ActionMapping) configs[i];
                request.setAttribute(Globals.MAPPING_KEY, mapping);

                return (mapping);
            }
        }
   
    4、如果还是没有找到mapping信息则发送错误消息，并返回null
        // No mapping can be found to process this request
        String msg = getInternal().getMessage("processInvalid");

        log.error(msg + " " + path);
        response.sendError(HttpServletResponse.SC_NOT_FOUND, msg);

        return null;

15、检查执行这个action所要的所有角色（是否有权访问）
    // Check for any role required to perform this action
    if (!processRoles(request, response, mapping)) {
        return;
    }
   
    1、从actionMapping（mapping）对想里取得角色名称的数组。
        // Is this action protected by role requirements?
        String[] roles = mapping.getRoleNames();
       
    2、如果mapping里没有角色信息（没有配置），就不做处理，直接返回true
        if ((roles == null) || (roles.length < 1)) {
            return (true);
        }
       
    3、依次取出配置了的角色 ，如果用户在角色中 （配置了的所有角色中的任意一个） ，则把用户名和角色名记 录到log里。并返回true。
        // Check the current user against the list of required roles
        for (int i = 0; i < roles.length; i++) {
            if (request.isUserInRole(roles[i])) {
                if (log.isDebugEnabled()) {
                    log.debug(" User '" + request.getRemoteUser()
                        + "' has role '" + roles[i] + "', granting access");
                }

                return (true);
            }
        }
       
    4、如果仍没找到用户所对应的角色，则说明这个用户是非法访问的。则把这个用户名记录到log里，发送错误信息，并返回false。
        // The current user is not authorized for this action
        if (log.isDebugEnabled()) {
            log.debug(" User '" + request.getRemoteUser()
                + "' does not have any required role, denying access");
        }

        response.sendError(HttpServletResponse.SC_FORBIDDEN,
            getInternal().getMessage("notAuthorized", mapping.getPath()));

        return (false);

16、处理与这个请求有关的所有actionForm。（调用processActionForm（）方法返回ActionForm对象）
    // Process any ActionForm bean related to this request
    ActionForm form = processActionForm(request, response, mapping);
   
    1、如果有需要就新建一个ActionForm来供使用。
        // Create (if necessary) a form bean to use
        ActionForm instance = RequestUtils.createActionForm(request, mapping, moduleConfig, servlet);
       
        1、查看mapping里是否配置name属性或attribute属性来指定ActionForm，如果都没有则返回null
            // Is there a form bean associated with this mapping?
            String attribute = mapping.getAttribute();

            if (attribute == null) {
                return (null);
            }
       
        2、通过name属性拿到ActionForm的配置信息
            // Look up the form bean configuration information to use
            String name = mapping.getName();
            FormBeanConfig config = moduleConfig.findFormBeanConfig(name);
       
        3、如果没有与name属性相对应的<form-bean>配置，则在log里记录：没有配置与name对应的formBean，并返回null；
            if (config == null) {
                log.warn("No FormBeanConfig found under '" + name + "'");

                return (null);
            }
           
        4、根据拿到的<form-bean>配置，在相应的范围里（request,session）找ActionForm的实例
            ActionForm instance = lookupActionForm(request, attribute, mapping.getScope());
       
        5、如果找到，并被判定为可用，则返回找到的实例。
            // Can we recycle the existing form bean instance (if there is one)?
            if ((instance != null) && config.canReuse(instance)) {
                return (instance);
            }
       
        6、如果没找到，（前面已经确定配置了formBean）。则新建一个ActionForm对象出来并返回他。
            return createActionForm(config, servlet);
           
            1、首先判断传入的config，如果config为null，则直接返回null
                if (config == null) {
                    return (null);
                }
           
            2、创建并返回一个新的ActionForm对象。这里调用了config对象的createActionForm方法。该方法里肯定用到了反射机制。另外把创建的ActionForm或动态ActionForm的信息存到log里。同样，如果过程中出错，错误信息业将被保存到日志里。
                ActionForm instance = null;

                // Create and return a new form bean instance
                try {
                    instance = config.createActionForm(servlet);

                    if (log.isDebugEnabled()) {
                        log.debug(" Creating new "
                            + (config.getDynamic() ? "DynaActionForm" : "ActionForm")
                            + " instance of type '" + config.getType() + "'");
                        log.trace(" --> " + instance);
                    }
                } catch (Throwable t) {
                    log.error(servlet.getInternal().getMessage("formBean",
                            config.getType()), t);
                }

                return (instance);
               
17、为ActionForm填充数据。
    processPopulate(request, response, form, mapping);
   
    1、首先判断form是否为null，如果是则直接return。
        if (form == null) {
            return;
        }
   
    2、往log里写入一句话提示从这里开始填充formBean
        if (log.isDebugEnabled()) {
            log.debug(" Populating bean properties from this request");
        }
   
    3、设置Servlet。
        form.setServlet(this.servlet);
        （不知道具体作用）
       
    4、执行reset方法重置表单。默认reset方法不做任何事情。这个方法是为了方便扩展。可以继承ActionForm类重写reset方法，这个方法可以用来做设置一些默认值等工作。
        form.reset(mapping, request);
       
    5、如果是上传表单，则获取上传类。（不甚了解）
        if (mapping.getMultipartClass() != null) {
            request.setAttribute(Globals.MULTIPART_KEY,
                mapping.getMultipartClass());
        }
   
    6、填充form
        RequestUtils.populate(form, mapping.getPrefix(), mapping.getSuffix(), request);
       
        1、建立一个HashMap 用于存放属性
            // Build a list of relevant request parameters from this request
            HashMap properties = new HashMap();
           
        2、建立一个Enumeration用于存放参数名
            // Iterator of parameter names
            Enumeration names = null;
       
        3、建立一个Map来存放multipart参数
            // Map for multipart parameters
            Map multipartParameters = null;
       
        4、获取请求的ContentType和Method。并设置multipart表示为false。
            String contentType = request.getContentType();
            String method = request.getMethod();
            boolean isMultipart = false;
           
        5、如果是multipart表单则做上传处理（不甚了解）
            if (bean instanceof ActionForm) {
                ((ActionForm) bean).setMultipartRequestHandler(null);
            }

            MultipartRequestHandler multipartHandler = null;
            if ((contentType != null)
                && (contentType.startsWith("multipart/form-data"))
                && (method.equalsIgnoreCase("POST"))) {
                // Get the ActionServletWrapper from the form bean
                ActionServletWrapper servlet;

                if (bean instanceof ActionForm) {
                    servlet = ((ActionForm) bean).getServletWrapper();
                } else {
                    throw new ServletException("bean that's supposed to be "
                        + "populated from a multipart request is not of type "
                        + "\"org.apache.struts.action.ActionForm\", but type "
                        + "\"" + bean.getClass().getName() + "\"");
                }

                // Obtain a MultipartRequestHandler
                multipartHandler = getMultipartHandler(request);

                if (multipartHandler != null) {
                    isMultipart = true;

                    // Set servlet and mapping info
                    servlet.setServletFor(multipartHandler);
                    multipartHandler.setMapping((ActionMapping) request
                        .getAttribute(Globals.MAPPING_KEY));

                    // Initialize multipart request class handler
                    multipartHandler.handleRequest(request);

                    //stop here if the maximum length has been exceeded
                    Boolean maxLengthExceeded =
                        (Boolean) request.getAttribute(MultipartRequestHandler.ATTRIBUTE_MAX_LENGTH_EXCEEDED);

                    if ((maxLengthExceeded != null)
                        && (maxLengthExceeded.booleanValue())) {
                        ((ActionForm) bean).setMultipartRequestHandler(multipartHandler);
                        return;
                    }

                    //retrieve form values and put into properties
                    multipartParameters =
                        getAllParametersForMultipartRequest(request,
                            multipartHandler);
                    names = Collections.enumeration(multipartParameters.keySet());
                }
            }
           
        6、如果不是上传，则把参数名存到names枚举里面。
            if (!isMultipart) {
                names = request.getParameterNames();
            }
       
        7、遍历这个枚举
            while (names.hasMoreElements())
           
            1、把名字拿出来存到name和stripped变量里
                String name = (String) names.nextElement();
                String stripped = name;
               
            2、去掉name的前缀和后缀（如果有的话（配置文件里可以配置））
                if (prefix != null) {
                    if (!stripped.startsWith(prefix)) {
                        continue;
                    }

                    stripped = stripped.substring(prefix.length());
                }

                if (suffix != null) {
                    if (!stripped.endsWith(suffix)) {
                        continue;
                    }

                    stripped =
                        stripped.substring(0, stripped.length() - suffix.length());
                }
               
            3、获取参数值，分上传和非上传两种方式
                Object parameterValue = null;

                if (isMultipart) {
                    parameterValue = multipartParameters.get(name);
                    parameterValue = rationalizeMultipleFileProperty(bean, name, parameterValue);
                } else {
                    parameterValue = request.getParameterValues(name);
                }
               
            4、如果参数名去掉了前后缀后不是一org.Apache.struts开头则把参数存到定义好的HashMap里
                // Populate parameters, except "standard" struts attributes
                // such as 'org.apache.struts.action.CANCEL'
                if (!(stripped.startsWith("org.apache.struts."))) {
                    properties.put(stripped, parameterValue);
                }
               
        8、调用BeanUtils的方法把formBean的属性填充进去（异常处理那块不是很明白）
            // Set the corresponding properties of our bean
            try {
                BeanUtils.populate(bean, properties);
            } catch (Exception e) {
                throw new ServletException("BeanUtils.populate", e);
            } finally {
                if (multipartHandler != null) {
                    // Set the multipart request handler for our ActionForm.
                    // If the bean isn't an ActionForm, an exception would have been
                    // thrown earlier, so it's safe to assume that our bean is
                    // in fact an ActionForm.
                    ((ActionForm) bean).setMultipartRequestHandler(multipartHandler);
                }
            }
           
    7、加入合适的话就把退出属性设置到request里；（还是不了解）
        // Set the cancellation request attribute if appropriate
        if ((request.getParameter(Globals.CANCEL_PROPERTY) != null)
            || (request.getParameter(Globals.CANCEL_PROPERTY_X) != null)) {
            request.setAttribute(Globals.CANCEL_KEY, Boolean.TRUE);
        }
       
18、验证表单输入的合法性。如果有不合法的则return。（一般不用struts的表单级验证）
    // Validate any fields of the ActionForm bean, if applicable
    try {
        if (!processValidate(request, response, form, mapping)) {
            return;
        }
    } catch (InvalidCancelException e) {
        ActionForward forward = processException(request, response, e, form, mapping);
        processForwardConfig(request, response, forward);
        return;
    } catch (IOException e) {
        throw e;
    } catch (ServletException e) {
        throw e;
    }
   
19、处理mapping指定的forward 和 include
    // Process a forward or include specified by this mapping
    if (!processForward(request, response, mapping)) {
        return;
    }
    if (!processInclude(request, response, mapping)) {
        return;
    }
   
20、创建或者获取一个Action的实例来处理请求。
    // Create or acquire the Action instance to process this request
    Action action = processActionCreate(request, response, mapping);
   
    1、从mapping里取出配置的Action类名
        // Acquire the Action instance we will be using (if there is one)
        String className = mapping.getType();
   
    2、把查找Action实例的动作记入到日志里
        if (log.isDebugEnabled()) {
            log.debug(" Looking for Action instance for class " + className);
        }

    3、在拿到Action实例之前先线程同步synchronized (actions) ，保证只有一个Action实例
   
    4、从map里取出Action返回，（如果有的话），并把结果写入日志
        nstance = (Action) actions.get(className);

        if (instance != null) {
            if (log.isTraceEnabled()) {
                log.trace("  Returning existing Action instance");
            }

            return (instance);
        }
   
    5、如果上面的操作没进行，那说明要新建一个Action实例，把新建实例的动作记录到日志里
        if (log.isTraceEnabled()) {
            log.trace("  Creating new Action instance");
        }
       
    6、创建出Action实例，吧实例放到map里并返回实例
        try {
                instance = (Action) RequestUtils.applicationInstance(className);

                // Maybe we should propagate this exception
                // instead of returning null.
            } catch (Exception e) {
                log.error(getInternal().getMessage("actionCreate",
                        mapping.getPath()), e);

                response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                    getInternal().getMessage("actionCreate", mapping.getPath()));

                return (null);
            }

            actions.put(className, instance);

            if (instance.getServlet() == null) {
                instance.setServlet(this.servlet);
            }
        }

        return (instance);
       
21、再次判断Action是否创建成功，如果没有则方法直接return
        if (action == null) {
            return;
        }
       
22、执行Action的excute方法，获得ActionForward
        // Call the Action instance itself
        ActionForward forward = processActionPerform(request, response, action, form, mapping);
        其中processActionPerform方法调用了action的excute方法：
        protected ActionForward processActionPerform(HttpServletRequest request,
            HttpServletResponse response, Action action, ActionForm form,
            ActionMapping mapping)
            throws IOException, ServletException {
            try {
                return (action.execute(mapping, form, request, response));
            } catch (Exception e) {
                return (processException(request, response, e, form, mapping));
            }
        }
    这里也做了一个处理，如果要在执行excute方法之前做一些操作，就可以覆盖processActionPerform方法。
   
23、更具Actionforward进行转发
        // Process the returned ActionForward instance
        processForwardConfig(request, response, forward);
   
        1、如果ActionForward为空，则方法直接返回
            if (forward == null) {
                return;
            }
           
        2、把接下来处理forward的操作记录到日志里
            if (log.isDebugEnabled()) {
                log.debug("processForwardConfig(" + forward + ")");
            }
       
        3、从mapping里获取forward对应的url，默认用forward的方式转发，如果配了redirect，则用redirect重定向
            String forwardPath = forward.getPath();
            String uri;

            // If the forward can be unaliased into an action, then use the path of the action
            String actionIdPath = RequestUtils.actionIdURL(forward, request, servlet);
            if (actionIdPath != null) {
                forwardPath = actionIdPath;
                ForwardConfig actionIdForward = new ForwardConfig(forward);
                actionIdForward.setPath(actionIdPath);
                forward = actionIdForward;
            }

            // paths not starting with / should be passed through without any
            // processing (ie. they're absolute)
            if (forwardPath.startsWith("/")) {
                // get module relative uri
                uri = RequestUtils.forwardURL(request, forward, null);
            } else {
                uri = forwardPath;
            }

            if (forward.getRedirect()) {
                // only prepend context path for relative uri
                if (uri.startsWith("/")) {
                    uri = request.getContextPath() + uri;
                }

                response.sendRedirect(response.encodeRedirectURL(uri));
            } else {
                doForward(uri, request, response);
            }

 

 

评论

1 楼 monica617 2014-02-18  

讲的还可以

字体和格式再设置为易读模式就更好了