(转载)struts2的驱动模型

模型驱动即ModelDriver，所谓ModelDriven，意思是直接把实体类当成页面数据的收集对象。

比如，有实体类User如下：

public class User {
    private int id;
    private String username;
    private String password;
    private int age;
    private String address;
    public String getUsername() {
       return username;
    }
    public void setUsername(String username) {
       this.username = username;
    }
    public String getPassword() {
       return password;
    }
    public void setPassword(String password) {
       this.password = password;
    }
    public int getAge() {
       return age;
    }
    public void setAge(int age) {
       this.age = age;
    }
    public String getAddress() {
       return address;
    }
    public void setAddress(String address) {
       this.address = address;
    }
    public int getId() {
       return id;
    }
    public void setId(int id) {
       this.id = id;
    }

}

假如要写一个Action，用来添加User。

第一种做法是直接在Action中定义所有需要的属性，然后在JSP中直接用属性名称来提交数据：

UserAction:

public class UserAction {
    private int id;
    private String username;
    private String password;
    private int age;
    private String address;

    public String add(){

       User user = new User();
       user.setId(id);
       user.setUsername(username);
       user.setPassword(password);
       user.setAge(age);
       user.setAddress(address);

       new UserManager().addUser(user);

       return "success";
    }

    public int getId() {
       return id;
    }
    public void setId(int id) {
       this.id = id;
    }
    public String getUsername() {
       return username;
    }
    public void setUsername(String username) {
       this.username = username;
    }
    public String getPassword() {
       return password;
    }
    public void setPassword(String password) {
       this.password = password;
    }
    public int getAge() {
       return age;
    }
    public void setAge(int age) {
       this.age = age;
    }
    public String getAddress() {
       return address;
    }
    public void setAddress(String address) {
       this.address = address;
    }

}

add_input.jsp:

<form action="test/user.action" method="post">
        <input type="hidden" name="method:add">
        username:<input type="text" name="username"> <br/>
        password:<input type="text" name="password"> <br/>
        age:<input type="text" name="age"> <br/>
        address:<input type="text" name="address"> <br/>
        <input type="submit" name="submit" value="添加用户">
     </form> <br/>

上述做法不好之处是：如果实体类的属性非常多，那么Action中也要定义相同的属性。

第二种做法是将User对象定义到UserAction中，然后在JSP中通过user属性来给user赋值：

UserAction:

public class UserAction {

    private User user;

    public String add(){

       new UserManager().addUser(user);

       return "success";
    }

    public User getUser() {
       return user;
    }

    public void setUser(User user) {
       this.user = user;
    }

}

add_input.jsp:

<form action="test/user.action" method="post">
        <input type="hidden" name="method:add">
        username:<input type="text" name="user.username"> <br/>
        password:<input type="text" name="user.password"> <br/>
        age:<input type="text" name="user.age"> <br/>
        address:<input type="text" name="user.address"> <br/>
        <input type="submit" name="submit" value="添加用户">
     </form> <br/>

这种做法不好的地方是：JSP页面上表单域中的命名变得太长

第三种做法是利用ModelDriven机制，让UserAction实现一个ModelDriven接口，同时实现接口中的方法：getModel()。如下所示：

public class UserAction implements ModelDriven{

    private User user;

    @Override
    public Object getModel() {
       if(user == null){
           user = new User();
       }
       return user;
    }

    public String add(){

       new UserManager().addUser(user);

       return "success";
    }

    public User getUser() {
       return user;
    }

    public void setUser(User user) {
       this.user = user;
    }
}

JSP的代码如下：

<form action="test/user.action" method="post">
        <input type="hidden" name="method:add">
        username:<input type="text" name="username"> <br/>
        password:<input type="text" name="password"> <br/>
        age:<input type="text" name="age"> <br/>
        <input type="submit" name="submit" value="添加用户">
     </form> <br/>