关于struts2在页面取值的有关问题

<form action="user/update" method="post">    <table border="0" align="center" width="700">        <tr height="30"><td colspan="2"><s:debug/></td></tr>        <tr height="30"><td colspan="2"><s:fielderror/></td></tr>        <tr height="30"><td>姓：</td><td><input type="text" name="firstname" value="${firstname}"></td></tr>        <tr height="30"><td>名：</td><td><input type="text" name="secondname" value="${secondname}"></td></tr>        <tr height="30"><td>年龄</td><td><input type="text" name="age" value="${age}"></td></tr>        <tr height="30"><td colspan="2"><input type="submit" value="submit">&nbsp;&nbsp;<input type="reset" value="reset"></td></tr>    </table></form>

import javax.annotation.Resource;import org.springframework.context.annotation.Scope;import org.springframework.stereotype.Controller;import com.hktk.entity.user.User;import com.hktk.service.user.UserService;import com.opensymphony.xwork2.ActionSupport;import com.opensymphony.xwork2.ModelDriven;@Controller("updateUserAction")@Scope("prototype")public class UpdateUserAction extends ActionSupport implements ModelDriven<User>{    private static final long serialVersionUID = 1L;    private User user = new User();        private UserService userService;    @Resource    public void setUserService(UserService userService) {        this.userService = userService;    }    public User getUser() {        return user;    }    public void setUser(User user) {        this.user = user;    }    public String update() {        user = userService.load(user.getId());        System.out.println(user);        return INPUT;    }        @Override    public User getModel() {        return getUser();    }}

import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name="t_user")public class User {        private Integer id;    private String firstname;    private String secondname;    private int age;        @Id    @GeneratedValue    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getFirstname() {        return firstname;    }    public void setFirstname(String firstname) {        this.firstname = firstname;    }    public String getSecondname() {        return secondname;    }    public void setSecondname(String secondname) {        this.secondname = secondname;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }}

public class UserInfo {        private Integer id;    private String firstname;    private String secondname;    private int age;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getFirstname() {        return firstname;    }    public void setFirstname(String firstname) {        this.firstname = firstname;    }    public String getSecondname() {        return secondname;    }    public void setSecondname(String secondname) {        this.secondname = secondname;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }}