MyBatis Course Mapping: Implementing getCourseById with ResultMap

Lily built a MyBatis application and created an entity class 'Course' in the application. The code is as follows:

public class Course {
    private String cid;
    private String cname;
    private Integer credits;
    //getter and setter omitted here
}

In addition, she created a data table named 'course' in the database, which contains three fields: 'courseId', 'courseName', and 'courseCredits'. Now, she has created a 'CourseMapper' interface and added a query operation with code as follows:

public interface CourseMapper {
    Course getCourseById(String id);
}

To implement the query operation, Lily needs to add a 'CourseMapper.xml' file and implement mapping of the 'getCourseById' method. The correct mapping code snippet to realize the functionality described is:

<select id="getCourseById" resultMap="courseMap">
    select * from course where courseId = #{id}
</select>

<resultMap id="courseMap" type="com.model.Course">
    <id property="cid" column="courseId"/>
    <result property="cname" column="courseName"/>
    <result property="credits" column="courseCredits"/>
</resultMap>

Explanation:

• The <select> element specifies the SQL statement to be executed.
• The #{} syntax is used to specify a parameter placeholder. In this case, the parameter is 'id' and it should be of type String.
• The resultMap attribute is used to specify the result mapping for the query.
• The <resultMap> element specifies how the query results should be mapped to the entity properties.
• The 'id' element specifies the primary key property of the entity.
• The 'result' elements specify the other properties of the entity.
• The 'column' attribute is used to specify the column names in the database table.
• The 'property' attribute is used to specify the property names in the entity class.