spring mvc 简单解析

由于急需这方面的知识，所以暂时先囫囵吞枣，记下来，有时间再来分享自己的感想，这里先转载下：

关于spring mvc 浅解！

       刚接触spring mvc！看了看内部流程。浅浅的记一下。

       当url为“person.do?do=toEditPage”时程序的走向：
       1，程序会根据后面的person.do后面的do转入spring的控制器
              <servlet>
                <servlet-name>   appfuse</servlet-name>
                 <servlet-class>
                        org.springframework.web.servlet.DispatcherServlet
                 </servlet-class>
                 <load-on-startup>1</load-on-startup>
         </servlet>
           <servlet-mapping>
                    <servlet-name> appfuse</servlet-name>
                    <url-pattern>*.do</url-pattern>      //处理以什么方式结尾的动作
          </servlet-mapping>

       2，根据appfuse 找到 appfuse-servlel.xml 。这个是spring mvc非常重要的配置文件。注明了每一次跳转动作进入的控制器，注入相应的dao层，业务层，以及commond层
   程序会根据/person.do 找到相应的控制器：com.nbw.test.web.action.PersonController。
      <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="viewResolver">
   <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>  
   <property name="prefix" value="/WEB-INF/jsp/"/>   //这个是跳转页面的路径
   <property name="suffix" value=".jsp"/>                   //指定跳转路径下以什么结尾的文件
</bean>

<bean class="org.springframework.web.servlet.mvc.multiaction.ParameterMethodNameResolver" id="paramResolver">
   <property name="paramName" value="do"/>   //这个在指定当控制器有多方法的时候，使用什么样的参数名来获得方法 例如：person.do?do=toEditPage
</bean>
  
//下面当url为person.do的时候请求进入PersonController控制器。
<bean class="com.nbw.test.web.action.PersonController" name="/person.do">
   <property name="methodNameResolver">
    <ref bean="paramResolver"/>         //这是当控制器需要实现多个方法的时候，指定使用哪个方法名，引用上面
   </property>
   <property name="sessionForm">    //是否把form放入session，如果选true，会将form存入session，当再次实例form的时候会根据名字从session取,如果选false则会重新新建一个
    <value>false</value>                        
   </property>
   <property name="commandClass">    //使用哪个command存储页面传过来的参数
    <value>com.nbw.test.domain.Person</value>
   </property>
</bean>
   3，进入com.nbw.test.web.action.PersonController控制器。PersonController     extends AbstractMultiActionFormController extends AbstractFormController extends BaseCommandController
这几个类是spring的核心类，他们会根据appfuse-servlel.xml 里面的配置信息，处理相应的参数，验证以及返回到哪个页面！
   程序会进入AbstractFormController类的handleRequestInternal方法。
   /**
* Handles two cases: form submissions and showing a new form.
* Delegates the decision between the two to {@link #isFormSubmission},
* always treating requests without existing form session attribute
* as new form when using session form mode.
* @see #isFormSubmission
* @see #showNewForm
* @see #processFormSubmission
*/
protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
    throws Exception {

   // Form submission or new form to show?
   //这里会判断是不是post请求如果是就进行判断，如果不是就新建一个
   if (isFormSubmission(request)) {
    // Fetch form object from HTTP session, bind, validate, process submission.
    try {
   // 开始绑定参数，程序会根据appfuse-servlel.xml 指定的 sessionform为ture或者false来决定是从session里面去还是新建一个实例，如果为false进入 formBackingObject 方法，然后程序会调用createCommand方法，在createCommand方法spring会使用 BeanUtils.instantiateClass(this.commandClass)来将参数注入form
     Object command = getCommand(request);
     ServletRequestDataBinder binder = bindAndValidate(request, command);
     BindException errors = new BindException(binder.getBindingResult());
//因为spring不支持 属性为日期型的转换 需要改写这个方法
   //this.convertStringToDate(request, command);
   //在这个方法里程序会根据?do=toEditPage的toEditPage，方法使用反射调用这个方法
     return processFormSubmission(request, response, command, errors);
    }
    catch (HttpSessionRequiredException ex) {
     // Cannot submit a session form if no form object is in the session.
     if (logger.isDebugEnabled()) {
      logger.debug("Invalid submit detected: " + ex.getMessage());
     }
     return handleInvalidSubmit(request, response);
    }
   }

   else {
    // New form to show: render form view.
    return showNewForm(request, response);
   }
}

/**
* Return the form object for the given request.
* <p>Calls {@link #formBackingObject} if not in session form mode.
* Else, retrieves the form object from the session. Note that the form object
* gets removed from the session, but it will be re-added when showing the
* form for resubmission.
* @param request current HTTP request
* @return object form to bind onto
* @throws org.springframework.web.HttpSessionRequiredException
* if a session was expected but no active session (or session form object) found
* @throws Exception in case of invalid state or arguments
* @see #formBackingObject
*/
protected final Object getCommand(HttpServletRequest request) throws Exception {
   // If not in session-form mode, create a new form-backing object.
//假如不从session里取
   if (!isSessionForm()) {
    return formBackingObject(request);
   }

   // Session-form mode: retrieve form object from HTTP session attribute.
   HttpSession session = request.getSession(false);
   if (session == null) {
    throw new HttpSessionRequiredException("Must have session when trying to bind (in session-form mode)");
   }
   String formAttrName = getFormSessionAttributeName(request);
   Object sessionFormObject = session.getAttribute(formAttrName);
   if (sessionFormObject == null) {
    throw new HttpSessionRequiredException("Form object not found in session (in session-form mode)");
   }

   // Remove form object from HTTP session: we might finish the form workflow
   // in this request. If it turns out that we need to show the form view again,
   // we'll re-bind the form object to the HTTP session.
   if (logger.isDebugEnabled()) {
    logger.debug("Removing form session attribute [" + formAttrName + "]");
   }
   session.removeAttribute(formAttrName);

   return currentFormObject(request, sessionFormObject);
}

protected final Object createCommand() throws Exception {
if (this.commandClass == null) {
throw new IllegalStateException( "Cannot create command without commandClass being set - " +
"either set commandClass or (in a form controller) override formBackingObject ");
}
if (logger.isDebugEnabled()) {
logger.debug( "Creating new command of class [ " + this.commandClass.getName() + "] ");
}
return BeanUtils.instantiateClass(this.commandClass);//就这里！！！
}


//利用反射机制调用控制器里的方法
protected ModelAndView processFormSubmission(HttpServletRequest request,
                                                 HttpServletResponse response, Object command, BindException errors)
            throws Exception
            {

                if (errors.hasErrors()) {
                    if (logger.isDebugEnabled()) {
                        logger.debug("Data binding errors: " + errors.getErrorCount());
                    }
                    return showForm(request, response, errors);
                } else {
                    String methodName = methodNameResolver.getHandlerMethodName(request);
                    Method method = null;
                    Method[] methods = this.getClass().getMethods();
      for(int i = 0; i <methods.length ; i++){
       if(methods[i].getName().equals(methodName)){
        method = methods[i];
       }
      }
                  //java
      //Class dd= (Class<T>)((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
      //method = getClass().getMethod(methodName,new Class[]{HttpServletRequest.class, HttpServletResponse.class, (Class<T>)((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0], BindException.class});
                  // method = getClass().getMethod(methodName,new Class[]{HttpServletRequest.class, HttpServletResponse.class, getCommandClass(), BindException.class});

      List params = new ArrayList(4);
      params.add(request);
      params.add(response);
      //Java 5.0
      params.add(getCommandClass().cast(command));
      //Java 1.4
      //params.add(command);
      params.add(errors);
      try{
       return (ModelAndView) method.invoke(this, params.toArray(new Object[params.size()]));
      }
      catch (InvocationTargetException e){
            //找到实际的异常，并抛出
            throw (Exception)e.getTargetException();
      }
      catch(Exception e){
       throw e;
      }
                }
            }

//然后调用 PersonController类的toEditPage方法command已经设置好
//new ModelAndView("test/personEdit","person",command);这个会根据在appfuse-servlel.xml 文件里面的
//<property name="prefix" value="/WEB-INF/jsp/"/>获得路径 /web-inf/jsp/text/
//再根据<property name="suffix" value=".jsp"/>得到返回文件后缀名personEdit.jsp
//所以总的路径是/web-inf/jsp/text/personEdit.jsp
//将command放到person里。person是model名字，command是object。实际是map。在页面根据person取。
/**
* 转向编辑页面
*
* @param request
* @param response
* @param command
* @param errors
* @return
*
* @throws ServletException, IOException
*/
public ModelAndView toEditPage(HttpServletRequest request,
    HttpServletResponse response, Person command, BindException errors)
    throws ServletException, IOException {
   String id = request.getParameter("objectId");
   command = this.personmanager.findById(id);
   return new ModelAndView("test/personEdit","person",command);
}