Java struts2请求源码分析案例详解

public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response,
            ActionMapping mapping, ServletContext context) {

        // request map wrapping the http request objects
        Map requestMap = new RequestMap(request);

        // parameters map wrapping the http parameters.  ActionMapping parameters are now handled and applied separately
        Map params = new HashMap(request.getParameterMap());

        // session map wrapping the http session
        Map session = new SessionMap(request);

        // application map wrapping the ServletContext
        Map application = new ApplicationMap(context);
        //requestMap、params、session等Map封装成为一个上下文Map
        Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);

        if (mapping != null) {
            extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
        }
        return extraContext;
    }

public HttpServletRequest wrapRequest(HttpServletRequest oldRequest) throws ServletException {
        HttpServletRequest request = oldRequest;
        try {
            // Wrap request first, just in case it is multipart/form-data
            // parameters might not be accessible through before encoding (ww-1278)
            request = dispatcher.wrapRequest(request, servletContext);
        } catch (IOException e) {
            throw new ServletException("Could not wrap servlet request with MultipartRequestWrapper!", e);
        }
        return request;
    }

public HttpServletRequest wrapRequest(HttpServletRequest request, ServletContext servletContext) throws IOException {
        // don't wrap more than once
        if (request instanceof StrutsRequestWrapper) {
            return request;
        }

        String content_type = request.getContentType();
        //如果content_type是multipart/form-data类型，则将request包装成MultiPartRequestWrapper对象，否则包装成StrutsRequestWrapper对象
        if (content_type != null && content_type.contains("multipart/form-data")) {
            MultiPartRequest mpr = getMultiPartRequest();
            LocaleProvider provider = getContainer().getInstance(LocaleProvider.class);
            request = new MultiPartRequestWrapper(mpr, request, getSaveDir(servletContext), provider);
        } else {
            request = new StrutsRequestWrapper(request, disableRequestAttributeValueStackLookup);
        }

        return request;
    }

public ActionMapping findActionMapping(HttpServletRequest request, HttpServletResponse response, boolean forceLookup) {
        //首先从request对象中取mapping对象，看是否存在
        ActionMapping mapping = (ActionMapping) request.getAttribute(STRUTS_ACTION_MAPPING_KEY);
        //不存在就创建一个
        if (mapping == null || forceLookup) {
            try {
                //首先创建ActionMapper对象，通过ActionMapper对象创建mapping对象
                mapping = dispatcher.getContainer().getInstance(ActionMapper.class).getMapping(request, dispatcher.getConfigurationManager());
                if (mapping != null) {
                    request.setAttribute(STRUTS_ACTION_MAPPING_KEY, mapping);
                }
            } catch (Exception ex) {
                dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
            }
        }

        return mapping;
    }

public ActionMapping getMapping(HttpServletRequest request, ConfigurationManager configManager) {
        ActionMapping mapping = new ActionMapping();
        //获得请求的uri，即请求路径URL中工程名以后的部分，如/userAction.action
        String uri = getUri(request);
        //修正url的带;jsessionid 时找不到的bug
        int indexOfSemicolon = uri.indexOf(";");
        uri = (indexOfSemicolon > -1) ? uri.substring(0, indexOfSemicolon) : uri;
        //删除扩展名，如.action或者.do
        uri = dropExtension(uri, mapping);
        if (uri == null) {
            return null;
        }
        //从uri中分离得到请求的action名、命名空间。
        parseNameAndNamespace(uri, mapping, configManager);
        //处理特殊的请求参数
        handleSpecialParameters(request, mapping);
        //如果允许动态方法调用，即形如/userAction!getAll.action的请求，分离action名和方法名
        return parseActionName(mapping);
    }

protected void parseNameAndNamespace(String uri, ActionMapping mapping, ConfigurationManager configManager) {
        String namespace, name;
        int lastSlash = uri.lastIndexOf("/"); //最后的斜杆的位置
        if (lastSlash == -1) {
            namespace = "";
            name = uri;
        } else if (lastSlash == 0) {
            // ww-1046, assume it is the root namespace, it will fallback to
            // default
            // namespace anyway if not found in root namespace.
            namespace = "/";
            name = uri.substring(lastSlash + 1);
        //允许采用完整的命名空间,即设置命名空间是否必须进行精确匹配
        } else if (alwaysSelectFullNamespace) {
            // Simply select the namespace as everything before the last slash
            namespace = uri.substring(0, lastSlash);
            name = uri.substring(lastSlash + 1);
        } else {
            // Try to find the namespace in those defined, defaulting to ""
            Configuration config = configManager.getConfiguration();
            String prefix = uri.substring(0, lastSlash); //临时的命名空间，将会用来进行匹配
            namespace = "";//将命名空间暂时设为""
            boolean rootAvailable = false;//rootAvailable作用是判断配置文件中是否配置了命名空间"/"
            // Find the longest matching namespace, defaulting to the default
            for (Object cfg : config.getPackageConfigs().values()) { //循环遍历配置文件中的package标签
                String ns = ((PackageConfig) cfg).getNamespace();    //获取每个package标签的namespace属性
                //进行匹配
                if (ns != null && prefix.startsWith(ns) && (prefix.length() == ns.length() || prefix.charAt(ns.length()) == '/')) {
                    if (ns.length() > namespace.length()) {
                        namespace = ns;
                    }
                }
                if ("/".equals(ns)) {
                    rootAvailable = true;
                }
            }

            name = uri.substring(namespace.length() + 1);

            // Still none found, use root namespace if found
            if (rootAvailable && "".equals(namespace)) {
                namespace = "/";
            }
        }

        if (!allowSlashesInActionNames) {
            int pos = name.lastIndexOf('/');
            if (pos > -1 && pos < name.length() - 1) {
                name = name.substring(pos + 1);
            }
        }
        //将分离后的acion名和命名空间保存到mapping对象
        mapping.setNamespace(namespace);
        mapping.setName(cleanupActionName(name));
    }

if (ns != null && prefix.startsWith(ns) && (prefix.length() == ns.length() || prefix.charAt(ns.length()) == '/')) {
    if (ns.length() > namespace.length()) {
        namespace = ns;
    }
}

if (!allowSlashesInActionNames) {
    int pos = name.lastIndexOf('/');
    if (pos > -1 && pos < name.length() - 1) {
        name = name.substring(pos + 1);
    }
}

protected ActionMapping parseActionName(ActionMapping mapping) {
        if (mapping.getName() == null) {
            return null;
        }
        //如果允许动态方法调用
        if (allowDynamicMethodCalls) {
            // handle "name!method" convention.
            String name = mapping.getName();
            int exclamation = name.lastIndexOf("!");
            //如果包含"!"就进行分离
            if (exclamation != -1) {
                //分离出action名
                mapping.setName(name.substring(0, exclamation));
                //分离出方法名
                mapping.setMethod(name.substring(exclamation + 1));
            }
        }
        return mapping;
    }

//如果mapping为空，则认为不是调用action,会调用下一个过滤器链，直到获取到mapping才调用action
                if (mapping == null) {
                    boolean handled = execute.executeStaticResourceRequest(request, response);
                    if (!handled) {
                        chain.doFilter(request, response);
                    }
                } else {
                    //执行action
                    execute.executeAction(request, response, mapping);
                }

public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException {
    dispatcher.serviceAction(request, response, servletContext, mapping);
}

public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,
                              ActionMapping mapping) throws ServletException {
        //封转上下文环境，主要将requestMap、params、session等Map封装成为一个上下文Map
        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();//从mapping对象获取命名空间
            String name = mapping.getName();          //获取请求的action名
            String method = mapping.getMethod();      //获取请求方法
            //得到配置对象
            Configuration config = configurationManager.getConfiguration();
            //根据执行上下文参数，命名空间，名称等创建用户自定义Action的代理对象
            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!
            //如果配置文件中执行的这个action配置了result，就直接转到result
            if (mapping.getResult() != null) {
                Result result = mapping.getResult();
                result.execute(proxy.getInvocation());
            } else {
                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) {
                String reqStr = request.getRequestURI();
                if (request.getQueryString() != null) {
                    reqStr = reqStr + "?" + request.getQueryString();
                }
                LOG.error("Could not find action or result\n" + reqStr, e);
            } else {
                if (LOG.isWarnEnabled()) {
                    LOG.warn("Could not find action or result", e);
                }
            }
            sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);
        } catch (Exception e) {
            if (handleException || devMode) {
                sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
            } else {
                throw new ServletException(e);
            }
        } finally {
            UtilTimerStack.pop(timerKey);
        }
    }