页面表单

<form action="updateInput.action" method="post">

    <input type="text" name="id"/>

    <input type="submit" value="查询">

</form>

struts.xml配置

<action name="updateInput" class="com.test.UserAction" method="updateInput">

    <result name="update_input">user_update.jsp</result>

</action>

com.test.UserAction

public class UserAction implements ModelDriven {

    private User user;

    @Override

    public Object getModel() {

        if (user == null) {

            user = new User();

        }

        return user;

    }

    public String updateInput() {

        //测试ModelDriven陷阱

        // 根据ID，查询数据库，得到User对象

        Object object = ActionContext.getContext().getValueStack().findValue("#root");

        Connection connection = DBConnection.getConnection();

        PreparedStatement preparedStatement = null;

        ResultSet resultSet = null;

        User user1 = null;

        try {

            System.out.println("查询用户信息");

            preparedStatement = connection

                    .prepareStatement("select * from t_user where id = ?");

            preparedStatement.setInt(1, user.getId());

            resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {

                user1 = new User();

                user1.setId(resultSet.getInt("id"));

                user1.setUsername(resultSet.getString("username"));

                user1.setPassword(resultSet.getString("password"));

//              user = user1;//这样写有问题

//值栈中的user并没有引用user1，所以在页面上取值实际上并没有取到user1的值。

//将user1的属性copy到user中之后，就可以在页面上取到值了。

                BeanUtils.copyProperties(user, user1);

            }

        } catch (Exception e) {

            e.printStackTrace();

        }finally{

            DBConnection.close(resultSet, preparedStatement, connection);

        }

        return "update_input";

    }

}

user_update.jsp

<form action="user_update.action" method="post">

        <input type="hidden" name="method:update">

        id:<input type="text" name="id" value="<s:property value="id"/>"> <br/>

        username:<input type="text" name="username" value="<s:property value="username"/>"> <br/>

        password:<input type="text" name="password" value="<s:property value="password"/>"> <br/>

        <input type="submit" name="submit" value="更新用户">

</form>