使用 ActionForm

ActionForm是表單的物件化表示，它本身設計為JavaBean，您要繼承org.apache.struts.action.ActionForm來設計一個表單物件，並提供標準的getter與setter方法，必要時可以使用繼承下來的reset()、validate()等方法供 Struts 組件呼叫。

當客戶請求交給了 RequestProcessor 後，RequestProcessor會從 ActionMapping 中得知所使用的ActionForm物件，這是在struts-config.xml中設定的，如果所需的ActionForm還不存在就生成一個，之後一直使用它，ActionMapping與ActionForm物件會被當作參數傳遞給 Action。

在Struts 1.1中，ActionForm生成之後，會執行RequestProcessor的processPopulate()方法，首先它會呼叫 ActionForm的reset()方法，您可以在當中作一些重清ActionForm屬性的動作，然後表單的參數值會與ActionForm的 setter進行比對，如果有名稱符合的就將表單的參數值設定給對應的屬性。

透過繼承ActionForm類別來使用它，下面是一個簡單的例子：

UserForm.java

package onlyfun.caterpillar; 



import javax.servlet.http.*; 

import org.apache.struts.action.*; 



public class UserForm extends ActionForm {

private String username; 

private String password;



public void setUsername(String username) { 

this.username = username; 

} 



public void setPassword(String password) { 

this.password = password; 

} 



public String getUsername() { 

return username; 

}



public String getPassword() {

return password;

} 



public void reset(ActionMapping mapping,

HttpServletRequest request) {

username = null;

password = null;

} 

}

必須在struts-config.xml中定義Action物件使用哪一個ActionForm物件：

struts-config.xml

<?xml version="1.0" encoding="ISO-8859-1" ?>



<!DOCTYPE struts-config PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 1.2//EN"

"http://jakarta.apache.org/struts/dtds/struts-config_1_2.dtd">



<struts-config>

    <form-beans> 

        <form-bean 

            name="userForm" 

            type="onlyfun.caterpillar.UserForm"/> 

    </form-beans>



    <action-mappings> 

        <action 

            path="/login" 

            type="onlyfun.caterpillar.LoginAction"

            name="userForm"> 

            <forward

                name="helloUser" 

                path="/WEB-INF/pages/hello.jsp"/>

            <forward

                name="loginFail" 

                path="/WEB-INF/pages/fail.jsp"/>

        </action> 

    </action-mappings> 

</struts-config>

在這個例子中，<form-bean>標籤定義了所使用的ActionForm物件及其名稱userForm，而在< action>標籤的設定中，LoginAction指定了userForm作為其所使用的ActionForm， LoginAction類別如下：

LoginAction.java

package onlyfun.caterpillar;



import javax.servlet.http.*; 

import org.apache.struts.action.*; 



public class LoginAction extends Action {

public ActionForward execute(

ActionMapping mapping,

ActionForm form,

HttpServletRequest request, 

HttpServletResponse response) 

throws Exception { 

String username = ((UserForm) form).getUsername(); 

String password = ((UserForm) form).getPassword(); 



request.setAttribute("username", username);



if(username.equals("caterpillar") && 

password.equals("1234")) {

return mapping.findForward("helloUser"); 

}



return mapping.findForward("loginFail"); 

} 

}

ActionForm被作為參數傳遞至execute()方法，在驗證使用者的名稱與密碼無誤後，查找helloUser的 ActionForward對象並傳回，這會使得RequestProcessor將請求轉發至hello.jsp：

hello.jsp

<html> 

<head> 

<title>Hello, ${username} !</title> 

</head> 

<body>

<H1>Hello, ${username} !</H1>

<H1>This is your secret gift!!</H1>

</body> 

</html>

如果驗證失敗，則查找loginFail的ActionForward對象並傳回，也就是fail.jsp：

fail.jsp

<html> 

<head> 

<title>Sorry!</title> 

</head> 

<body>

<H1>Sorry, ${username} !</H1> 

<H1>You must provide correct login information!!</H1>

<p>

<a href='/strutsapp/html/form.htm'>Login</a>

</body> 

</html>

最後是一個簡單的登入表單，這是個靜態HTML，放在/strutsapp/html下就可以了：

form.htm

<html> 

<head><title>Login</title></head> 

<body> 

   Please login：<p> 

    <form name="userForm" action="/strutsapp/login.do" method="post"> 

   username <input type="text" name="username"/><br> 

   password <input type="password" name="password"/><p> 

        <input type="submit"/> 

    </form>

</body> 

</html>

ActionForm在Struts中是屬於View組件的一部份，它是物件化的表單，表單的參數會自動設定給 ActionForm，無法對應的就加以忽略，在ActionForm中您可以填入表單值，作一些適當的值轉換，進行基本的資料驗證， ActionForm可以作為表單資料發送至應用程式前的緩衝區，在某些程度上，它是應用程式的防火牆，您可以在ActionForm中避免不正確或不安全的資料進入應用程式。

綜合一下，ActionForm擔任以下的幾個職責：

填寫表單欄位至表單物件屬性中
客戶資料的緩衝區
進行資料完整性、格式驗證
進行屬性值的轉換
進行資料安全性驗證，阻止惡意資料進入應用程式

=================================================================================

=>LoginAction<=

package onlyfun.caterpillar;

import java.util.*;
import javax.servlet.http.*;
import org.apache.struts.action.*;
import org.apache.struts.util.MessageResources;
import org.apache.commons.beanutils.PropertyUtils;

public class LoginAction extends Action {
public ActionForward execute(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
   throws Exception {
  String username = (String) PropertyUtils.getSimpleProperty(form,"username");
  String password = (String) PropertyUtils.getSimpleProperty(form,"password");

  request.setAttribute("username", username);
  if (username.equals("caterpillar") && password.equals("1234")) {
   return mapping.findForward("helloUser");
  }

  Map<String, String> msgModel = new HashMap<String, String>();
  MessageResources messageResources = (MessageResources) getResources(request);
  msgModel.put("namePasswordMismatched", messageResources.getMessage("message.namePasswordMismatched"));
  request.setAttribute("messages", msgModel);
  return mapping.findForward("loginFail");
}
}

=>struts-config.xml<=

<struts-config>
<form-beans>
  <form-bean name="userForm" type="onlyfun.caterpillar.UserForm" />
</form-beans>
<action-mappings>
  <action path="/login" type="onlyfun.caterpillar.LoginAction"
   name="userForm" validate="true" input="/WEB-INF/pages/fail.jsp">
   <forward name="helloUser" path="/WEB-INF/pages/hello.jsp" />
   <forward name="loginFail" path="/WEB-INF/pages/fail.jsp" />
  </action>
</action-mappings>
<message-resources parameter="onlyfun.caterpillar.ApplicationResources" />
</struts-config>

=>fail.jsp<=

<html>
<head>
  <title>Sorry!</title>
</head>
<body>
  <H1>
   ${errors["invalidUsername"]}invalidUsername......
   <br>
   ${errors["invalidPassword"]}invalidPassword......
   <br>
   ${messages["namePasswordMismatched"]}namePasswordMismatched.......
  </H1>
  <p><a href='/va/html/form.htm'>Login</a>
</body>
</html>

=>UserForm<=

package onlyfun.caterpillar;
import java.util.*;
import javax.servlet.http.*;
import org.apache.struts.action.*;
import org.apache.struts.Globals;
import org.apache.struts.util.MessageResources;
public class UserForm extends ActionForm {

private static final long serialVersionUID = 1L;

private String username;
private String password;
public void setUsername(String username) {
  this.username = username;
}
public void setPassword(String password) {
  this.password = password;
}
public String getUsername() {
  return username;
}
public String getPassword() {
  return password;
}
public void reset(ActionMapping mapping,HttpServletRequest req) {
  username = null;
  password = null;
  }
public ActionErrors validate(ActionMapping mapping,HttpServletRequest request) {

  Map<String, String> errModel = new HashMap<String, String>();
  MessageResources messageResources=(MessageResources)request.getAttribute(Globals.MESSAGES_KEY);

  if(getUsername() == null || getUsername().length() < 1){
   String msg = messageResources.getMessage("error.invalidUsername");
   errModel.put("invalidUsername", msg);
   }

  if(getPassword() == null ||getPassword().length() < 1){
    String msg = messageResources.getMessage("error.invalidPassword");
    errModel.put("invalidPassword", msg);
   }

  if(errModel.get("invalidUsername") == null && errModel.get("invalidPassword") == null){
   System.out.println("1");
    return null;
    }else {
       /**
        * 必须与显示该信息的名字相同errors，
        * 例如fail.jsp页面的${errors["invalidUsername"]}
        */
       request.setAttribute("errors", errModel);

    ActionErrors errors = new ActionErrors();
    /**
     * 返回ActionMessages.GLOBAL_MESSAGE为键名的ActionErrors对象
     */
    errors.add(ActionMessages.GLOBAL_MESSAGE,new ActionMessage(""));

    return errors;

    }
}
}

=>form.htm<=

<html>
<head>
  <title>Login</title>
</head>
<body>
  Please login：
  <p>
  <form name="userForm" action="/va/login.do" method="post">
   username
   <input type="text" name="username" />
   <br>
   password
   <input type="password" name="password" />
   <p>
    <input type="submit" />
  </form>
</body>
</html>

posted @ 2008-06-05 16:24 宇晨阅读(325) 评论(0) 收藏举报

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