Struts2中的ModelDriven机制及其运用
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 com.carson.demo.model;
import java.io.Serializable;
public class User implements Serializable {
private String username;
private String password;
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;
}
}
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 String username;
private String password;
public String add(){
User user = new User();
user.setUsername(username);
user.setPassword(password);
return "success";
}
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;
}
}
login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录界面</title>
</head>
<body>
<form action="login" method="post">
<table>
<tr>
<td>用户名：</td>
<td><input type="text" name="username" /> </td>
</tr>
<tr>
<td>密码：</td>
<td><input type="text" name="password" /> </td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="登录" />
<input type="reset" value="重置" /></td>
</tr>
</table>
</form>
</body>
</html>
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 User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录界面</title>
</head>
<body>
<form action="login" method="post">
<table>
<tr>
<td>用户名：</td>
<td><input type="text" name="user.username" /> </td>
</tr>
<tr>
<td>密码：</td>
<td><input type="text" name="user.password" /> </td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="登录" />
<input type="reset" value="重置" /></td>
</tr>
</table>
</form>
</body>
</html>
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 User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录界面</title>
</head>
<body>
<form action="login" method="post">
<table>
<tr>
<td>用户名：</td>
<td><input type="text" name="username" /> </td>
</tr>
<tr>
<td>密码：</td>
<td><input type="text" name="password" /> </td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="登录" />
<input type="reset" value="重置" /></td>
</tr>
</table>
</form>
</body>
</html>
可见，第三种做法是比较好的，Action和JSP写起来都比较简单。
博文参考：http://blog.csdn.net/li_tengfei/article/details/6098145