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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。
 点击查看大图
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="true"＞
＜head＞
// bean是用来从applicationresource中读取i18n信息
＜title＞＜bean:message key="logon.title"/＞＜/title＞
＜html:base/＞
＜/head＞
＜body bgcolor="white"＞
// 错误信息部分
＜html:errors/＞
// 登录form,action为logion.do
＜html:form action="/logon" focus="username"
onsubmit="return validatelogonform(this);"＞
＜table border="0" width="100%"＞
＜tr＞
＜th align="right"＞
＜bean:message key="prompt.username"/＞:
＜/th＞
＜td align="left"＞
＜html:text property="username" size="16" maxlength="18"/＞
＜/td＞
＜/tr＞
＜tr＞
＜th align="right"＞
＜bean:message key="prompt.password" bundle="alternate"/＞:
＜/th＞
＜td align="left"＞
＜html:password property="password" size="16" maxlength="18" redisplay="false"/＞
＜/td＞
＜/tr＞
＜tr＞
＜td align="right"＞
＜html:submit value="submit"/＞
＜/td＞
＜td align="left"＞
＜html: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:html＞ |
struts-config.xml配置
＜form-beans＞
＜!-- logon form bean --＞
＜form-bean name="logonform" type="org.apache.struts.validator.dynavalidatorform"＞
＜form-property name="username" type="java.lang.string"/＞
＜form-property name="password" type="java.lang.string"/＞
＜/form-bean＞
＜!-- subscription form bean --＞
＜form-bean name="subscriptionform"type="org.apache.struts.webapp.example.subscriptionform"/＞
＜/form-beans＞
＜action-mappings＞
＜!-- edit mail subscription --＞
＜action path="/editsubscription"
type="org.apache.struts.webapp.example.editsubscriptionaction"
attribute="subscriptionform"
scope="request"
validate="false"＞
＜forward 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 ＜code＞actionerrors＜/code＞ object that encapsulates any
* validation errors that have been found. if no errors are found, return
* ＜code＞null＜/code＞ or an ＜code＞actionerrors＜/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);
}
}
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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 ＜code＞actionforward＜/code＞ instance describing where and how
* control should be forwarded, or ＜code＞null＜/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 need
locale locale = getlocale(request);
messageresources messages = getresources(request);
user user = null;
// validate the request parameters specified by the user
actionerrors 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 form
if (!errors.isempty()) {
saveerrors(request, errors);
return (mapping.getinputforward());
}
// save our logged-in user in the session
httpsession 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 bean
if (mapping.getattribute() != null) {
if ("request".equals(mapping.getscope()))
request.removeattribute(mapping.getattribute());
else
session.removeattribute(mapping.getattribute());
}
// forward control to the specified success uri
return (mapping.findforward("success"));
}
/**
* look up the user, throwing an exception to simulate business logic
* rule exceptions.
*
* @param database database in which to look up the user
* @param username username specified on the logon form
*
* @exception moduleexception if a business logic rule is violated
*/
public user getuser(userdatabase database, string username)
throws moduleexception {
// force an arithmeticexception which can be handled explicitly
if ("arithmetic".equals(username)) {
throw new arithmeticexception();
}
// force an application-specific exception which can be handled
if ("expired".equals(username)) {
throw new expiredpasswordexception(username);
}
// look up and return the specified user
return ((user) database.finduser(username));
}
} |
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