Result-type-Dispatcher

1

 配置文件：

<result name="success" type="dispatcher">
  <param name="location">foo.jsp</param>
</result>

 如果没有写type类型，默认的是dispatcher（就在下面这一行设置的），请看struts-default.xml

拦截器：

    <result-type name="dispatcher" class="org.apache.struts2.dispatcher.ServletDispatcherResult" default="true"/>

 ServletDispatcherResult的代码：

public class ServletDispatcherResult extends StrutsResultSupport {

    private static final long serialVersionUID = -1970659272360685627L;

    private static final Logger LOG = LoggerFactory.getLogger(ServletDispatcherResult.class);

    public ServletDispatcherResult() {
        super();
    }

    public ServletDispatcherResult(String location) {
        super(location);
    }

    /**
     * Dispatches to the given location. Does its forward via a RequestDispatcher. If the
     * dispatch fails a 404 error will be sent back in the http response.
     *
     * @param finalLocation the location to dispatch to.
     * @param invocation    the execution state of the action
     * @throws Exception if an error occurs. If the dispatch fails the error will go back via the
     *                   HTTP request.
     */
    public void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Forwarding to location " + finalLocation);
        }

        PageContext pageContext = ServletActionContext.getPageContext();

        if (pageContext != null) {//如果在jsp范围内（pageContext有效）
            pageContext.include(finalLocation);
        } else {
            HttpServletRequest request = ServletActionContext.getRequest();
            HttpServletResponse response = ServletActionContext.getResponse();
            RequestDispatcher dispatcher = request.getRequestDispatcher(finalLocation);

            //add parameters passed on the location to #parameters
            // see WW-2120
            if (invocation != null && finalLocation != null && finalLocation.length() > 0
                    && finalLocation.indexOf("?") > 0) {
                String queryString = finalLocation.substring(finalLocation.indexOf("?") + 1);
                Map parameters = (Map) invocation.getInvocationContext().getContextMap().get("parameters");
                Map queryParams = UrlHelper.parseQueryString(queryString, true);
                if (queryParams != null && !queryParams.isEmpty())
                    parameters.putAll(queryParams);
            }

            // if the view doesn't exist, let's do a 404
            if (dispatcher == null) {//看看错误的提示大家是不是常见啊，这回知道在哪了吧
                response.sendError(404, "result '" + finalLocation + "' not found");

                return;
            }

            //if we are inside an action tag, we always need to do an include
            Boolean insideActionTag = (Boolean) ObjectUtils.defaultIfNull(request.getAttribute(StrutsStatics.STRUTS_ACTION_TAG_INVOCATION), Boolean.FALSE);

            // If we're included, then include the view
            // Otherwise do forward
            // This allow the page to, for example, set content type
            if (!insideActionTag && !response.isCommitted() && (request.getAttribute("javax.servlet.include.servlet_path") == null)) {
                request.setAttribute("struts.view_uri", finalLocation);
                request.setAttribute("struts.request_uri", request.getRequestURI());

                dispatcher.forward(request, response);
            } else {
                dispatcher.include(request, response);
            }
        }
    }
}