事实是最近读《J2EE设计模式》讲述表达层模式的那几章，书中有一个前端控制器 command模式的workflow例子，就琢磨着可以很简单地扩展成一个MVC框架。
2.»¹ÊÇÏÈÀ´¿´ÏÂÁ½¸öÄ£ÐÍ£ºActionForwardºÍActionModel£¬Ã»Ê²Ã´¶«Î÷£¬ÊôÐÔÒÔ¼°ÏàÓ¦µÄgetter,setter·½·¨£º
-
- /**
- * Àà˵Ã÷:תÏòÄ£ÐÍ
- * @author dennis
- *
- * */
- public class ActionForward {
- private String name; //forwardµÄname
- private String viewUrl; //forwardµÄurl
- public static final ActionForward SUCCESS=new ActionForward("success");
- public static final ActionForward FAIL=new ActionForward("fail");
-
- public ActionForward(String name){
- this.name=name;
- }
-
- public ActionForward(String name, String viewUrl) {
- super();
- this.name = name;
- this.viewUrl = viewUrl;
- }
-
- //...nameºÍviewUrlµÄgetterºÍsetter·½·¨
-
- }
ÎÒÃÇ¿´µ½ActionForwardÔ¤ÏÈ·â×°ÁËSUCCESSºÍFAIL¶ÔÏó¡£
-
- public class ActionModel {
- private String path; // actionµÄpath
-
- private String className; // actionµÄclass
-
- private Map<String, ActionForward> forwards; // actionµÄforward
-
- public ActionModel(){}
-
- public ActionModel(String path, String className,
- Map<String, ActionForward> forwards) {
- super();
- this.path = path;
- this.className = className;
- this.forwards = forwards;
- }
-
-
- //...ÏàÓ¦µÄgetterºÍsetter·½·¨
-
- }
3¡£ÖªµÀÁËÁ½¸öÄ£ÐÍÊÇʲôÑù£¬Ò²Ó¦¸Ã¿ÉÒԲµ½ÎÒÃǵÄÅäÖÃÎļþ´ó¸ÅÊÇʲôÑùµÄÁË£¬ÓëstrutsµÄÅäÖÃÎļþ¸ñʽÀàËÆ£º
-
- <?xml version="1.0" encoding="UTF-8"?>
- <actions>
- <action path="/login"
- class="com.strutslet.demo.LoginAction">
- <forward name="success" url="hello.jsp"/>
- <forward name="fail" url="fail.jsp"/>
- </action>
- </actions>
pathÊÇÔÚÓ¦ÓÃÖн«±»µ÷ÓõÄ·¾¶£¬classÖ¸¶¨Á˵÷ÓõÄÄĸöaction£¬forwardÔªËØÖ¸¶¨ÁËתÏò£¬±ÈÈçÎÒÃÇÕâÀïÈç¹ûÊÇsuccess¾ÍתÏòhello.jsp£¬Ê§°ÜµÄ»°×ªÏòfail.jsp£¬ÕâÀïÅäÖÃÁËdemoÓõ½µÄLoginAction¡£
4¡£Dispacher½Ó¿Ú£¬Ö÷ÒªÊÇgetNextPage·½·¨£¬´Ë·½·¨¸ºÔð»ñµÃÏÂÒ»¸öÒ³Ã潫µ¼ÏòÄÄÀÌṩ¸øÇ°¶Ë¿ØÖÆÆ÷ת·¢¡£
-
- public interface Dispatcher {
- public void setServletContext(ServletContext context);
- public String getNextPage(HttpServletRequest request,ServletContext context);
- }
5¡£5¡£ÔÏÈÊéÖÐʵÏÖÁËÒ»¸öWorkFlowµÄDispatcher£¬°´ÕÕ˳Ðòµ÷ÓÃaction£¬ÊµÏÖ¹¤×÷Á÷µ÷Ó᣶øÎÒÃÇËùÐèÒªµÄÊǸù¾ÝÇëÇóµÄpathµ÷ÓÃÏàÓ¦µÄaction£¬Ö´ÐÐactionµÄexecute·½·¨·µ»ØÒ»¸öActionForward£¬È»ºóµÃµ½ActionForwardµÄviewUrl£¬½«´ËviewUrlÌṩ¸øÇ°¶Ë¿ØÖÆÆ÷ת·¢£¬¿´¿´ËüµÄgetNextPage·½·¨£º
-
- public String getNextPage(HttpServletRequest request, ServletContext context) {
- setServletContext(context);
-
- Map<String, ActionModel> actions = (Map<String, ActionModel>) context
- .getAttribute(Constant.ACTIONS_ATTR); //´ÓServletContextµÃµ½ËùÓÐactionÐÅÏ¢
- String reqPath = (String) request.getAttribute(Constant.REQUEST_ATTR);//·¢ÆðÇëÇóµÄpath
- ActionModel actionModel = actions.get(reqPath); //¸ù¾ÝpathµÃµ½ÏàÓ¦µÄaction
- String forward_name = "";
- ActionForward actionForward;
- try {
- Class c = Class.forName(actionModel.getClassName()); //ÿ¸öÇëÇó¶ÔÓ¦Ò»¸öactionʵÀý
-
- Action action = (Action) c.newInstance();
- actionForward = action.execute(request, context); //Ö´ÐÐactionµÄexecute·½·¨
- forward_name = actionForward.getName();
-
- } catch (Exception e) {
- log.error("can not find action "+actionModel.getClassName());
- e.printStackTrace();
- }
-
- actionForward = actionModel.getForwards().get(forward_name);
- if (actionForward == null) {
- log.error("can not find page for forward "+forward_name);
- return null;
- } else
- return actionForward.getViewUrl(); //·µ»ØActionForwardµÄviewUrl
- }
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