Struts的工作流程.doc

下图是Struts的工作流程，前边我们提到，所有的请求都提交给ActionServlet来处理。ActionServlet是一个FrontController，它是一个标准的Servlet，它将request转发给RequestProcessor来处理， ActionMapping是ActionConfig的子类，实质上是对struts-config.xml的一个映射，从中可以取得所有的配置信息 RequestProcessor根据提交过来的url，如*.do，从ActionMapping 中得到相应的ActionForn和Action。然后将request的参数对应到ActionForm中，进行form验证。如果验证通过则调用Action的execute()方法来执行Action，最终返回ActionFoward。 ActionFoward是对mapping中一个foward的包装，对应于一个url ActionForm使用了ViewHelper模式，是对HTML中form的一个封装。其中包含有validate方法，用于验证form数据的有效性。ActionForm是一个符合JavaBean规范的类，所有的属性都应满足get和set对应。对于一些复杂的系统，还可以采用DynaActionForm来构造动态的Form，即通过预制参数来生成Form。这样可以更灵活的扩展程序。 ActionErrors是对错误信息的包装，一旦在执行action或者form.validate中出现异常，即可产生一个ActionError并最终加入到ActionErrors。在Form验证的过程中，如果有Error发生，则会将页面重新导向至输入页，并提示错误。 Action是用于执行业务逻辑的RequsestHandler。每个Action都只建立一个instance。Action不是线程安全的，所以不应该在Action中访问特定资源。一般来说，应改使用 Business Delegate 模式来对Business tier进行访问以解除耦合。 Struts提供了多种Action供选择使用。普通的Action只能通过调用execute执行一项任务，而DispatchAction可以根据配置参数执行，而不是仅进入execute()函数，这样可以执行多种任务。如insert,update等。LookupDispatchAction可以根据提交表单按钮的名称来执行函数。 我们可以先回到刚才的例子，理解一下Struts的流程。 下面我们看Struts自带的example实例： 说明：实例二是Struts自带的example程序, 实现了登录，注册，修改功能。代码中大量应用了struts taglib，并且采用validator插件进行form的验证。但是代码树立了一个不好的榜样，即把大量的业务逻辑写在了action中。 部分代码如下： 登录：logon.jsp % page contentType=text/html;charset=UTF-8 language=java % / 声明Taglib% taglib uri=/WEB-INF/struts-bean.tld prefix=bean % taglib uri=/WEB-INF/struts-html.tld prefix=html % html:html locale=truehead/ bean是用来从ApplicationResource中读取i18n信息titlebean:message key=logon.title/titlehtml:base/headbody bgcolor=white/ 错误信息部分html:errors/ 登录form,action为logion.dohtml:form action=/logon focus=usernameonsubmit=return validateLogonForm(this);table border=0 width=100%trth align=rightbean:message key=prompt.username/:/thtd align=lefthtml:text property=username size=16 maxlength=18/td/trtrth align=rightbean:message key=prompt.password bundle=alternate/:/thtd align=lefthtml:password property=password size=16 maxlength=18 redisplay=false/td/trtrtd align=righthtml:submit value=Submit/tdtd align=lefthtml:reset/td/tr/table/html:form/ Validator插件,用于form验证html:javascript formName=logonForm dynamicJavascript=true staticJavascript=false/script language=Javascript1.1 src=staticJavascript.jsp/script/body/html:htmlstruts-config.xml配置form-beans!- Logon form bean -form-bean name=logonForm type=org.apache.struts.validator.DynaValidatorFormform-property name=username type=java.lang.String/form-property name=password type=java.lang.String/form-bean!- Subscription form bean -form-bean name=subscriptionFormtype=org.apache.struts.webapp.example.SubscriptionForm/form-beansaction-mappings!- Edit mail subscription -action path=/editSubscriptiontype=org.apache.struts.webapp.example.EditSubscriptionActionattribute=subscriptionFormscope=requestvalidate=falseforward name=failure path=/mainMenu.jsp/forward name=success path=/subscription.jsp/action.subscriptionForm 是一个标准的ActionForm,其中reset方法用于清除form的值,validate方法用于验证 public final class SubscriptionForm extends ActionForm / The maintenance action we are performing (Create or Edit).private String action = Create;/ Should we auto-connect at startup time?private boolean autoConnect = false;/ The host name.private String host = null;private String password = null;private String type = null;private String username = null;public String getAction() return (this.action); public void setAction(String action) this.action = action; public boolean getAutoConnect() return (this.autoConnect); public void setAutoConnect(boolean autoConnect) this.autoConnect = autoConnect; public String getHost() return (this.host); public void setHost(String host) this.host = host; public String getPassword() return (this.password); public void setPassword(String password) this.password = password; public String getType() return (this.type); public void setType(String type) this.type = type; public String getUsername() return (this.username); public void setUsername(String username) this.username = username; /* Reset all properties to their default values.* param mapping The mapping used to select this instance* param request The servlet request we are processing*/public void reset(ActionMapping mapping, HttpServletRequest request) this.action = Create;this.autoConnect = false;this.host = null;this.password = null;this.type = null;this.username = null;/* Validate the properties that have been set from this HTTP request,* and return an codeActionErrors/code object that encapsulates any* validation errors that have been found. If no errors are found, return* codenull/code or an codeActionErrors/code object with no* recorded error messages.* param mapping The mapping used to select this instance* param request The servlet request we are processing*/public ActionErrors validate(ActionMapping mapping,HttpServletRequest request) ActionErrors errors = new ActionErrors();if (host = null) | (host.length() 1)errors.add(host,new ActionError(error.host.required);if (username = null) | (username.length() 1)errors.add(username,new ActionError(error.username.required);if (password = null) | (password.length() 1)errors.add(password,new ActionError(error.password.required);if (type = null) | (type.length() 1)errors.add(type,new ActionError(error.type.required);else if (!imap.equals(type) & !pop3.equals(type)errors.add(type,new ActionError(error.type.invalid, type);return (errors);logonAction public final class LogonAction extends Action /* Process the specified HTTP request, and create the corresponding HTTP* response (or forward to another web component that will create it).* Return an codeActionForward/code instance describing where and how* control should be forwarded, or codenull/code if the response has* already been completed.* param mapping The ActionMapping used to select this instance* param form The optional ActionForm bean for this request (if any)* param request The HTTP request we are processing* param response The HTTP response we are creating* exception Exception if business logic throws an exception*/public ActionForward execute(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response)throws Exception / Extract attributes we will needLocale locale = getLocale(request);MessageResources messages = getResources(request);User user = null;/ Validate the request parameters specified by the userActionErrors errors = new ActionErrors();String username = (String)PropertyUtils.getSimpleProperty(form, username);String password = (String)PropertyUtils.getSimpleProperty(form, password);UserDatabase database = (UserDatabase)servlet.getServletContext().getAttribute(Constants.DATABASE_KEY);if (database = null)errors.add(ActionErrors.GLOBAL_ERROR,new ActionError(error.database.missing);else user = getUser(database, username);if (user != null) & !user.getPassword().equals(password)user = null;if (user = null)errors.add(ActionErrors.GLOBAL_ERROR,new ActionError(error.password.mismatch);/ Report any errors we have discovered back to the original formif (!errors.isEmpty() saveErrors(request, errors);return (mapping.getInputForward();/ Save our logged-in user in the sessionHttpSession session = request.getSession();session.setAttribute(Constants.USER_KEY, user);if (log.isDebugEnabled() log.debug(LogonAction: User + user.getUsername() + logged on in session + session.getId();/ Remove the obsolete form beanif (mapping.getAttribute() != null) if (request.equals(mapping.getScope()request.removeAttribute(mapping.getAttr