Mybatis - 分步查询多个参数传递（association与collection)）

• 场景
  在《Mybatis - collection分步查询》与《Mybatis - association分步查询》中，在对子查询进行传参时仅是单个参数传递。在实际开发中，在子查询执行条件里可能存在多参传递，此时将多参封装成Map即可完成多参传递。因为多参是封装成Map的形式进行多参传递，所以参数的取值必须严格遵守Map的形式。

• 实例
  查询班级名称为XX负责人为YY下的所有学和信息

• Code
  Student.java

public class Student {
  
  private String id;
  private String name;
  private int age;
  private String sex;
  private String className;
  private String chargeMan;

  public void setName (String name) {
    this.name = name;
  }

  public String getName () {
    return this.name;
  }
}

StudentMapper.java

public interface StudentMapper {
  Student getStudentInfoByClassNameAndChargeMan (String className, String chargeMan);
}

StudentMapper.xml

<select id="getStudentInfoByClassNameAndChargeMan" type="com.cat.pojo.Student">
  SELECT name, age, sex FROM student WHERE class_name = #{className} AND charge_man = #{chargeMan}
</select>

ClassInfo.java

public class ClassInfo {

  private int classCode;
  private String className;
  private String chargeName;
  private List<Student> students;

  public void setClassCode (int classCode) {
    this.classCode = classCode;
  }

  public String getClassCode ()  {
    return this.classCode;
  }
}

ClassInfoMapper.java

public interface ClassInfoMapper {
  ClassInfo getStudentsByClassCode (String classCode) ;
}

ClassInfoMapper.xml

<select id="getStudentsByClassCode" resultMap="classAndStudentMap">
  SELECT class_code, class_name, charge_man
  FROM class
  WHERE class_code = #{class_code}
</select>

<resultMap id="classAndStudentMap" type="com.cat.pojo.ClassInfo">
  <result column="class_code" property="classCode" />
  <result column="class_name" property="className" />
  <result column="charge_man" property="chargeMan" />

  <collection property="students" select="com.cat.mapper.StudentMapper.getStudentInfoByClassNameAndChargeMan " column="{className : class_name, chargeMan : charge_man}"/>
</resultMap>