mybatis resultType和resultMap的区别和使用场景
1.resultType
从这条语句中返回的期望类型的类的完全限定名或别名。 注意如果返回的是集合，那应该设置为集合包含的类型，而不是集合本身。可以使用 resultType 或 resultMap，但不能同时使用。
例如:
1.student实体类
package com.generic.feng.modules.student.entity;
import java.util.List;
import org.hibernate.validator.constraints.Length;
import com.generic.feng.common.entity.DataEntity;
import com.generic.feng.modules.sys.entity.Office;
/**
* 学生管理Entity
* @author gsl
* @version 2018-10-09
*/
public class Student extends DataEntity {
private static final long serialVersionUID = 1L;
private String studentName; // 学生姓名
private String studentNo; // 学生编号
private String phoneNumber; // 手机号
private Office office; // 部门id
private String officeId; // 部门id
private List list;
private String roleId;
public String getRoleId() {
return roleId;
}
public void setRoleId(String roleId) {
this.roleId = roleId;
}
public List getList() {
return list;
}
public void setList(List list) {
this.list = list;
}
public String getOfficeId() {
return officeId;
}
public void setOfficeId(String officeId) {
this.officeId = officeId;
}
public Student() {
super();
}
public Student(String id){
super(id);
}
@Length(min=0, max=255, message="学生姓名长度必须介于 0 和 255 之间")
public String getStudentName() {
return studentName;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
@Length(min=0, max=255, message="学生编号长度必须介于 0 和 255 之间")
public String getStudentNo() {
return studentNo;
}
public void setStudentNo(String studentNo) {
this.studentNo = studentNo;
}
@Length(min=0, max=255, message="手机号长度必须介于 0 和 255 之间")
public String getPhoneNumber() {
return phoneNumber;
}
public void setPhoneNumber(String phoneNumber) {
this.phoneNumber = phoneNumber;
}
public Office getOffice() {
return office;
}
public void setOffice(Office office) {
this.office = office;
}
} 2.mapper.xml
a.id AS "id",
a.student_name AS "studentName",
a.student_no AS "studentNo",
a.phone_number AS "phoneNumber",
a.office_id AS "office.id",
a.create_by AS "createBy.id",
a.create_date AS "createDate",
a.update_by AS "updateBy.id",
a.update_date AS "updateDate",
a.remarks AS "remarks",
a.del_flag AS "delFlag",
o5.name AS "office.name"
LEFT JOIN sys_office o5 ON o5.id = a.office_id
如果数据库的字段和POJO里面的属性不匹配，则可以使用别名来进行映射。如果两者一样就不需要设置别名。
2.resultMap
resultMap 元素是 MyBatis 中最重要最强大的元素。它可以让你从 90% 的 JDBC ResultSets 数据提取代码中解放出来，并在一些情形下允许你进行一些 JDBC 不支持的操作。实际上，在为一些比如连接的复杂语句编写映射代码的时候，一份 resultMap 能够代替实现同等功能的长达数千行的代码。ResultMap 的设计思想是，对于简单的语句根本不需要配置显式的结果映射，而对于复杂一点的语句只需要描述它们的关系就行了。
例子
1.teacher实体类
package com.ruoyi.system.domain;
import org.apache.commons.lang3.builder.ToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;
import com.ruoyi.common.core.domain.BaseEntity;
/**
* 老师基础表 sys_teacher
*
* @author ruoyi
* @date 2019-07-02
*/
public class Teacher extends BaseEntity
{
private static final long serialVersionUID = 1L;
/** 老师主键id */
private String teacherId;
/** 老师姓名 */
private String teacherName;
/** 老师年龄 */
private Integer teacherAge;
/** 删除标志（0代表存在 2代表删除） */
private String delFlag;
public void setTeacherId(String teacherId)
{
this.teacherId = teacherId;
}
public String getTeacherId()
{
return teacherId;
}
public void setTeacherName(String teacherName)
{
this.teacherName = teacherName;
}
public String getTeacherName()
{
return teacherName;
}
public void setTeacherAge(Integer teacherAge)
{
this.teacherAge = teacherAge;
}
public Integer getTeacherAge()
{
return teacherAge;
}
public void setDelFlag(String delFlag)
{
this.delFlag = delFlag;
}
public String getDelFlag()
{
return delFlag;
}
public String toString() {
return new ToStringBuilder(this,ToStringStyle.MULTI_LINE_STYLE)
.append("teacherId", getTeacherId())
.append("teacherName", getTeacherName())
.append("teacherAge", getTeacherAge())
.append("delFlag", getDelFlag())
.append("createBy", getCreateBy())
.append("createTime", getCreateTime())
.append("updateBy", getUpdateBy())
.append("updateTime", getUpdateTime())
.append("remark", getRemark())
.toString();
}
}
2.mapper.xml