iBATIS demo jpetstore 对 struts 的灵活应用 。

demo中为了减少application 对struts的依赖性，主要做了以下三方面：
1.BeanAction类，demo中将业务处理从原先继承Action类的处理类中分离出来，将原先分离的Action和Form整合在一起作为bean。demo的struts-config.xml中所有请求转向BeanAction,BeanAction 根据请求路径或struts-config.xml中action元素中parameter属性指定的方法名，利用java反射调用bean中的业务处理方法，哪么如何找到bean？。


2.bean 继承自 BaseBean ,BaseBean 继承自 struts 中的ValidatorActionForm类，BaseBean 对 ValidatorActionForm 中的 reset()和validate()方法进行的重写，生成无参数的 reset()和validate()方法由子类重载，减少子类对struts的依赖。这里的无参数 reset()以及bean中的业务处理方法如何获得 HttpServletRequest等参数哪？


3.ActionContext类， BeanAction类利用java.lang.ThreadLocal类将参数绑定到请求的线程中.ActionContext对这些操作进行了封装，在bean中可以通过ActionContext的静态方法获取请求参数。

在demo的struts-config.xml文件中

 <action path="/shop/switchSearchListPage" type="org.apache.struts.beanaction.BeanAction"
            name="catalogBean" scope="session" parameter="switchProductListPage"
            validate="false">
      <forward name="success" path="/catalog/SearchProducts.jsp"/>
    </action>

    <action path="/shop/viewCategory" type="org.apache.struts.beanaction.BeanAction"
            name="catalogBean" scope="session"
            validate="false">
      <forward name="success" path="/catalog/Category.jsp"/>
    </action>

BeanAction类

public class BeanAction extends Action {
  private static final String NO_METHOD_CALL = "*";
  private static final String SUCCESS_FORWARD = "success";

  public final ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception {
    String forward = SUCCESS_FORWARD;
    try {
      if (!(form instanceof BaseBean)) {
        if (form != null) {
          throw new BeanActionException("The form for mapping '" + mapping.getPath() + "' named '" + mapping.getName() + "' was not an instance of BaseBean.  BeanAction requires an BaseBean instance.");
        } else {
          throw new BeanActionException("The form for mapping '" + mapping.getPath() + "' named '" + mapping.getName() + "' was null.  BeanAction requires an BaseBean instance.");
        }
      }
      BaseBean bean = (BaseBean) form;
      ActionContext.initCurrentContext(request, response);
      if (bean != null) {
        // Explicit Method Mapping

        Method method = null;
        String methodName = mapping.getParameter();
        if (methodName != null && !NO_METHOD_CALL.equals(methodName)) {
          try {
            method = bean.getClass().getMethod(methodName, null);
            synchronized (bean) {
              forward = bean.getInterceptor().intercept(new ActionInvoker(bean, method));
            }
          } catch (Exception e) {
            throw new BeanActionException("Error dispatching bean action via method parameter ('" + methodName + "').  Cause: " + e, e);
          }
        }



        // Path Based Method Mapping

        if (method == null && !NO_METHOD_CALL.equals(methodName)) {
          methodName = mapping.getPath();
          if (methodName.length() > 1) {
            int slash = methodName.lastIndexOf("/") + 1;
            methodName = methodName.substring(slash);
            if (methodName.length() > 0) {
              try {
                method = bean.getClass().getMethod(methodName, null);
                synchronized (bean) {
                  forward = bean.getInterceptor().intercept(new ActionInvoker(bean, method));
                }
              } catch (Exception e) {
                throw new BeanActionException("Error dispatching bean action via URL pattern ('" + methodName + "').  Cause: " + e, e);
              }
            }
          }
        }
      }
    } catch (Exception e) {
      forward = "error";
      request.setAttribute("BeanActionException", e);
    }
    return mapping.findForward(forward);
  }
}

ActionContext 类

public class ActionContext {
  private static final ThreadLocal localContext = new ThreadLocal();
  private HttpServletRequest request;
  private HttpServletResponse response;
  private Map cookieMap;
  private Map parameterMap;
  private Map requestMap;
  private Map sessionMap;
  private Map applicationMap;

  public ActionContext() {
    cookieMap = new HashMap();
    parameterMap = new HashMap();
    requestMap = new HashMap();
    sessionMap = new HashMap();
    applicationMap = new HashMap();
  }

  static void initCurrentContext(HttpServletRequest request, HttpServletResponse response) {
    ActionContext ctx = getActionContext();
    ctx.request = request;
    ctx.response = response;
    ctx.cookieMap = null;
    ctx.parameterMap = null;
    ctx.requestMap = null;
    ctx.sessionMap = null;
    ctx.applicationMap = null;
  }

  public Map getCookieMap() {
    if (cookieMap == null) {
      cookieMap = new CookieMap(request);
    }
    return cookieMap;
  }

 ·············

  public HttpServletRequest getRequest() {
    return request;
  }

  public HttpServletResponse getResponse() {
    return response;
  }

  public static ActionContext getActionContext() {
    ActionContext ctx = (ActionContext) localContext.get();
    if (ctx == null) {
      ctx = new ActionContext();
      localContext.set(ctx);
    }
    return ctx;
  }
}

BaseBean 类

public final void reset(ActionMapping mapping, ServletRequest request) {
    ActionContext.initCurrentContext((HttpServletRequest) request, null);
    reset();
  }

URL http://ibatis.apache.org/javadownloads.cgi