Map class field name to column name in myBatis for insert - mybatis

Question

I am using myBatis and trying create a db entry for the class User.
How can i map the different field names to the column names?
Do i need to or should myBatis know of them?
My User class looks like this:
public class User {
private String username;
private String email;
...
and the column names are:
user_name
e_mail
The myBatis create method looks like this:
void createUser(User user)
... i've tried like this:
<insert id="createUser" parameterType="...User">
INSERT INTO users (user_name, e_mail) VALUE
(#{username},#{email})
</insert>
and this:
<insert id="createUser" parameterType="...User">
INSERT INTO users (user_name, e_mail) VALUE
(#{user.username},#{user.email})
</insert>
I keep getting:
Parameter 'username' not found. Available parameters are [1, 0, param1, param2]
respectively Parameter 'user'

Answer 1

Found the answer:
The code should look like this:
void createUser(#Param("user")User user)
<insert id="createUser" parameterType="...User">
INSERT INTO users (user_name, e_mail) VALUE
(#{user.username},#{user.email})
</insert>

Answer 2

You shouldn't have to specify the #param annotation if you have getters/setters for those private variables. You don't indicate in your code snippet that you do. MyBatis should be smart enough to call the getter on the variables assuming you have one. If you look at the docs here http://mybatis.github.com/mybatis-3/sqlmap-xml.html#Parameters they have an example just like what you're doing above (note your first insert mapping is the correct one).
<insert id="insertUser" parameterType="User" >
insert into users (id, username, password)
values (#{id}, #{username}, #{password})
</insert>