i am new to MyBatis,i am unable to find tutorials to learn,present i am going to start working on MyBatis with Spring,i had used session.selectOne(String arg0, Object arg1) but i am not able to understand how it works and what it will do with the second parameter that is Object arg1.
can any one help in this. thank you
The second argument to selectOne and selectList is for a parameter. It can be a primitive if you have very simple needs in your query, say a single integer, or for more complicated queries requiring many values to be interpolated, a bean class instance with the values populated as needed (and containing the proper getters and setters).
In your mapper file you then define the type of the parameter via the parameter attribute, and can then interpolate either inline or with escaping (the former for things that should never be escaped, such as variable table or column names, and the latter for things which should always be escaped, such as values in a WHERE clause).
See the MyBatis doc for more detail: http://mybatis.github.io/mybatis-3/java-api.html
Response to comments from OP:
MapBuilder must be custom code related to Map data structures. There's an ImmutableMap.Builder as part of Guava, but that doesn't seem like what this is. I don't think it's related to Mybatis per se.
It looks like that code is just building up a Map object, and then passing it off to the selectOne query for use within the query definition in the mapper (instead of a custom bean class).
What's the definition on LoginMapper.getUserByUsername in your mapper? In that definition, the contents of the map object are likely being interpolated into the query so dynamic values can be included.