The quick fix:
Going through the iBatis docs can sometimes be tedious.  Fortunately, the solution is simple.  If you open your xml file dealing with the object in question, and go to your resultMap element for the class, you’ll typically have a result element for each column you’re dealing with.  Add an attribute called nullValue with a value to give the object in question in case a NULL is present.  It’s that simple. 

Here’s an example…
You have a table called Employee with several columns and create a POJO like below to hold that data:

public class Employee {
    private int id;
    private String login;
    private String password;
    private int authorityType;
    private boolean passwordExpired;
 
    // ... constructors and setter/getter methods here...
}

Let’s say that authorityType and passwordExpired were NULL values in the database.  Adding the nullValue attribute to the xml file like so would solve your issue:

<resultMap id="EmployeeResult" class="Employee">
  <result property="id"              column="id"                               />
  <result property="login"           column="login"                            />
  <result property="password"        column="password"                         />
  <result property="authorityType"   column="authorityType"   nullValue="1"    />
  <result property="passwordExpired" column="passwordExpired" nullValue="false"/>
</resultMap>