mybatis对枚举类型的处理

有时候，我们在数据库中会插入一些字段的值时固定的，比如性别字段，它的值固定只有2个，男或者女； 或者季节字段，只有春夏秋冬4种。有时候在Java类中会采用枚举类型来表达相应的数据库字段，比如如下数据表：

create table student(
id int auto_increment comment '学生ID',
name varchar(50),
gender varchar(10),
primary key(id));

枚举类定义如下：

package com.example.demo.dao;

public enum Gender {
    FEMAIL("女"),
    MAIL("男");

    private String sex;
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }

    Gender(String s){
        this.sex=s;
    }
}

实体类定义如下：

package com.example.demo.dao;

public class Student {
    private int id;
    private String name;
    private Gender gender;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public Gender getGender() {
        return gender;
    }

    public void setGender(Gender gender) {
        this.gender = gender;
    }
}

一.存储枚举的名称，Gender在数据库中值为：FEMAIL

此方式是mybatis对枚举类型的默认处理方式，使用的类型处理器是org.apache.ibatis.type.EnumTypeHandler

SQL如下：

<insert id="insertStudent" parameterType="com.example.demo.dao.Student">
      insert into student(name,gender) values(#{name},#{gender})
  </insert>

对应的Mapper为：

package com.example.demo.dao.mapper;

import com.example.demo.dao.Student;
import org.apache.ibatis.annotations.Mapper;


@Mapper
public interface StudentMapper {
    int insertStudent(Student student);
}

对应的Controller为：

package com.example.demo.controller;

import com.example.demo.dao.Gender;
import com.example.demo.dao.Student;
import com.example.demo.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@EnableAutoConfiguration
@RequestMapping("/student")
public class StudentController {
    @Autowired
    StudentService studentService;


    @GetMapping("/insertStudent")
    int insertStudent(){
        Student student=new Student();
       student.setName("张三");
       student.setGender(Gender.FEMAIL);
     return studentService.insertStudent(student);
    }
}

对应的service为：

package com.example.demo.service.impl;

import com.example.demo.dao.Student;
import com.example.demo.dao.mapper.StudentMapper;
import com.example.demo.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;


@Service
public class StudentServiceImpl implements StudentService {
    @Autowired
    StudentMapper studentMapper;

    @Override
    public int insertStudent(Student student) {
        return studentMapper.insertStudent(student);
    }
}

采用postman测试：

二.存储枚举的索引，FEMAIL在数据库中值为：0

此方式使用的类型处理器是org.apache.ibatis.type.EnumOrdinalTypeHandler,使用 typeHandler 设置类型处理为org.apache.ibatis.type.EnumOrdinalTypeHandler

修改sql为：

  <insert id="insertStudent" parameterType="com.example.demo.dao.Student">
      insert into student(name,gender) values(#{name},#{gender,typeHandler=org.apache.ibatis.type.EnumOrdinalTypeHandler})
  </insert>

采用Postman测试：

 三.存储枚举的值，这里存储“女”

前面两种方式使用mybatis提供的类型处理器，如果想存储上面枚举的值，比如：Gender.FEMAIL的值女,就需要创建一个自定义的类型处理器,只需要继承BaseTypeHandler

自定义类型处理器如下：

package com.example.demo.dao;

import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;
import org.apache.ibatis.type.MappedTypes;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/* 数据库中的数据类型 */
@MappedJdbcTypes(JdbcType.VARCHAR)
/* 转化后的数据类型 */
@MappedTypes(value = Gender.class)
public class MyEnumHandler extends BaseTypeHandler<Gender> {
    @Override
    public void setNonNullParameter(PreparedStatement preparedStatement, int i, Gender gender, JdbcType jdbcType) throws SQLException {
        preparedStatement.setString(i,gender.getSex());
    }

    @Override
    public Gender getNullableResult(ResultSet resultSet, String s) throws SQLException {
        String val=resultSet.getString(s);
        return getEnum(val);
    }

    @Override
    public Gender getNullableResult(ResultSet resultSet, int i) throws SQLException {
        return getEnum(resultSet.getString(i));
    }

    @Override
    public Gender getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        return getEnum(callableStatement.getNString(i));
    }

    /**
     * 根据值获得对应的枚举
     * @param val
     * @return
     */
    private Gender getEnum(String val){
        Class<Gender> sexClass = Gender.class;
        Gender[] sexs = sexClass.getEnumConstants();

        for(Gender se:sexs){
            if(se.getSex().equals(val)){
                return se;
            }
        }
        return null;
    }
}

修改sql：

  <insert id="insertStudent" parameterType="com.example.demo.dao.Student">
      insert into student(name,gender) values(#{name},#{gender,typeHandler=com.example.demo.dao.mapper.MyEnumHandler})
  </insert>