域模型：
以用戶登錄爲例：
定義一個User類對象us，設置其中變量信息，getter和setter。在LoginAction類中申明一個user類對象(不需要new，Struts2會自行new出一個對像)，以及user的getter和setter。
在用戶登錄的jsp頁面中，提交信息爲：us.XXX，XXX爲user類中成員變量的名字：如us.userName.
User類代碼：
package model;
public class User {
private String userName;
private String userPassword;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserPassword() {
return userPassword;
}
public void setUserPassword(String userPassword) {
this.userPassword = userPassword;
}
}LoginAction代碼：
package action;
import com.opensymphony.xwork2.ActionSupport;
import model.User;
public class LoginAction extends ActionSupport{
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public String execute(){
System.out.println(user.getUserName());
System.out.println(user.getUserPassword());
return this.SUCCESS;
}
}Login.jsp代碼：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title><s:text name="userlogin.title" /></title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<center>
<s:form action="login.action" method="post">
<table>
<tr>
<td>
</td>
<td>
<s:textfield name="user.userName" label="用戶名"/>
</td>
</tr>
<tr>
<td>
</td>
<td>
<s:password name="user.userPassword" label="密碼"/>
</td>
</tr>
<tr>
<td colspan="2" align="right">
<s:submit value="%{getText('userlogin.submit')}" />
</td>
</tr>
</table>
</s:form>
</center>
</body>
</html>
DTO：
當jsp傳遞參數數量與user的成員變量數量不一致時，struts2無法給user模型參數注入,會出現如下報錯信息：
ERROR com.opensymphony.xwork2.interceptor.ParametersInterceptor - Developer Notification (set struts.devMode to false to disable this message):
Unexpected Exception caught setting 'loginname' on 'class com.opensymphony.xwork2.ActionSupport: Error setting expression 'loginname' with value ['admin', ]此時需要使用dto
定義一個UserDTO類，其中包含的成員變量與jsp頁面傳遞的參數完全一致。在UserLogin中聲明一個UserDTO，以及其getter和setter。
再new一個User對象，將UserDTO中User對象需要的成員變量傳遞給User類對象。
User類代碼：
package model;
public class User {
private int userId;
private String userName;
private String userPassword;
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserPassword() {
return userPassword;
}
public void setUserPassword(String userPassword) {
this.userPassword = userPassword;
}
}UserDTO類代碼：
package dto;
public class UserDto {
private String userName;
private String userPassword;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserPassword() {
return userPassword;
}
public void setUserPassword(String userPassword) {
this.userPassword = userPassword;
}
}
LoginAction代碼：
package action;
import com.opensymphony.xwork2.ActionSupport;
import dto.UserDto;
import model.User;
public class LoginAction extends ActionSupport{
private User user= new User();
private UserDto udto;
public UserDto getUdto() {
return udto;
}
public void setUdto(UserDto udto) {
this.udto = udto;
}
public String execute(){
user.setUserName(udto.getUserName());
user.setUserPassword(udto.getUserPassword());
System.out.println(user.getUserName());
System.out.println(user.getUserPassword());
return this.SUCCESS;
}
}
Login.jsp代碼：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title><s:text name="userlogin.title" /></title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<center>
<s:form action="login.action" method="post">
<table>
<tr>
<td>
</td>
<td>
<s:textfield name="udto.userName" label="用戶名"/>
</td>
</tr>
<tr>
<td>
</td>
<td>
<s:password name="udto.userPassword" label="密碼"/>
</td>
</tr>
<tr>
<td colspan="2" align="right">
<s:submit value="%{getText('userlogin.submit')}" />
</td>
</tr>
</table>
</s:form>
</center>
</body>
</html>