MyBatis 注解一对多

悠悠 2022-05-14 06:22 255阅读 0赞

**示例：注解一对多**

**程序清单：com.po.Student.java**

package com.po;
    public class Student {
    	private Integer id;
    	private String name;
    	private String sex;
    	private Integer age;
    	private Clazz clazz;
    	public Integer getId() {
    		return id;
    	}
    	public void setId(Integer id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getSex() {
    		return sex;
    	}
    	public void setSex(String sex) {
    		this.sex = sex;
    	}
    	public Integer getAge() {
    		return age;
    	}
    	public void setAge(Integer age) {
    		this.age = age;
    	}
    	public Clazz getClazz() {
    		return clazz;
    	}
    	public void setClazz(Clazz clazz) {
    		this.clazz = clazz;
    	}
    	@Override
    	public String toString() {
    		return "Student [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age +  "]";
    	}
    }

**程序清单：com.po.Clazz.java**

package com.po;
    import java.util.List;
    public class Clazz {
    	private Integer id;
    	private String code;
    	private String name;
    	private List<Student> students;
    	public Integer getId() {
    		return id;
    	}
    	public void setId(Integer id) {
    		this.id = id;
    	}
    	public String getCode() {
    		return code;
    	}
    	public void setCode(String code) {
    		this.code = code;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public List<Student> getStudents() {
    		return students;
    	}
    	public void setStudents(List<Student> students) {
    		this.students = students;
    	}
    }

**程序清单：com.mapper.StudentMapper.java**

package com.mapper;
    import java.util.List;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import com.po.Student;
    public interface StudentMapper {
    	@Select("select * from t_student where cid=#{cid}")
    	@Results({@Result(id=true,column="id",property="id"),
    		      @Result(column="name",property="name"),
    		      @Result(column="sex",property="sex"),
    		      @Result(column="age",property="age")})
    	List<Student> getStudentById(Integer cid);
    }

**程序清单：com.mapper.ClazzMapper.java**

package com.mapper;
    import org.apache.ibatis.annotations.Many;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    import com.po.Clazz;
    public interface ClazzMapper {
    	@Select("select * from t_clazz where id=#{id}")
    	@Results({@Result(id=true,column="id",property="id"),
    			  @Result(column="code",property="code"),
    			  @Result(column="name",property="name"),
    			  @Result(column="id",property="students",
    			  many=@Many(select="com.mapper.StudentMapper.getStudentById",fetchType=FetchType.LAZY))})
    	Clazz getClazzById(Integer id);
    }

**程序清单：com.dao.TestDao.java**

@Test
    	public void getClazzById() throws IOException {
    		session=getSqlSession();
    		ClazzMapper cm=session.getMapper(ClazzMapper.class);
    		Clazz clazz=cm.getClazzById(1);
    		System.out.println("Clazz [id="+clazz.getId()+", code="+clazz.getCode()+", name="+clazz.getName()+"]");
    		List<Student> students=clazz.getStudents();
    		for (Student student : students) {
    			System.out.println(student);
    		}
    	}

**运行TestDao的getClazzById()方法，控制台显示如下：**

![70][]

[70]: /images/20220514/bf69479af3c34cd5b0d7cedad1cdd993.png