modeldriven<>和getModel的作用

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：

package cn.com.leadfar.struts2.actions;   publicclass User {     privateintid;     private String username;     private String password;     privateintage;     private String address;     public String getUsername() {        returnusername;     }     publicvoid setUsername(String username) {        this.username = username;     }     public String getPassword() {        returnpassword;     }     publicvoid setPassword(String password) {        this.password = password;     }     publicint getAge() {        returnage;     }     publicvoid setAge(int age) {        this.age = age;     }     public String getAddress() {        returnaddress;     }     publicvoid setAddress(String address) {        this.address = address;     }     publicint getId() {        returnid;     }     publicvoid 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:

publicclass UserAction {     privateintid;     private String username;     private String password;     privateintage;     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";     }         publicint getId() {        returnid;     }     publicvoid setId(int id) {        this.id = id;     }     public String getUsername() {        returnusername;     }     publicvoid setUsername(String username) {        this.username = username;     }     public String getPassword() {        returnpassword;     }     publicvoid setPassword(String password) {        this.password = password;     }     publicint getAge() {        returnage;     }     publicvoid setAge(int age) {        this.age = age;     }     public String getAddress() {        returnaddress;     }     publicvoid 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:

publicclass UserAction {         private User user;         public String add(){          new UserManager().addUser(user);               return"success";     }       public User getUser() {        returnuser;     }       publicvoid 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：

publicclass UserAction implements ModelDriven{         private User user;         @Override     public Object getModel() {        if(user == null){            user = new User();        }        returnuser;     }       public String add(){          new UserManager().addUser(user);               return"success";     }       public User getUser() {        returnuser;     }       publicvoid 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/>

 

可见，第三种做法是比较好的，Action和JSP写起来都比较简单。