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();  }

URLhttp://ibatis.apache.org/javadownloads.cgi