一分钟明白：EnumOrdinalTypeHandler和EnumTypeHandler的区别

 

目录

1.声明一个性别枚举

2.创建User试例

3.EnumOrdinalTypeHandler

4.EnumTypeHandler

---

在开发用，如果使用枚举而又没有在配置中指定类型，mybatis默认使用EnumTypeHandler。EnumTypeHandler和EnumOrdinalTypeHandler区别主要在于数据库存取类型不一样。

1.声明一个性别枚举

public enum SexEnum {
	MALE(1, "男"),
	FEMALE(0, "女");

	private int id;
	private String name;
//get，set方法省略...

2.创建User试例

public class User {
	private Long id;
	private String userName;
	private String password;
	private SexEnum sex;
	private String mobile;
	private String tel;
	private String email;
	private String note;

	/** setter and getter **/

3.EnumOrdinalTypeHandler

配置xml文件使用EnumOrdinalHandler测试

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mybatis02.mapper.UserMapper">
    <resultMap id="userMapper" type="user">
        <result property="id" column="id" />
        <result property="userName" column="user_name" />
        <result property="password" column="password" />
        <result property="sex" column="sex"
            typeHandler="org.apache.ibatis.type.EnumOrdinalTypeHandler"/>
        <result property="mobile" column="mobile" />
        <result property="tel" column="tel" />
        <result property="email" column="email" />
        <result property="note" column="note" />
    </resultMap>
    <select id="getUser" resultMap="userMapper" parameterType="long">
      select id, user_name, password, sex, mobile, tel, email, note from t_user
      where id = #{id}
    </select>
</mapper>

建表语句和数据

create table t_user
(
   id                   int(12) not null auto_increment,
   user_name            varchar(60) not null,
   password             varchar(60) not null,
   sex                  varchar(1) not null,
   mobile               varchar(20) not null,
   tel                  varchar(20),
   email                varchar(60),
   note                 varchar(512),
   primary key (id)
);

insert into  t_user(user_name, `password`, sex, mobile, tel, email, note) 
values('user_name_1', 'pwd1', 1, '13888888888', '010-88888888', 'y666@163.com', 'note_1');

测试案列

	private static void testTypeHandler() {
		Logger log = Logger.getLogger(Chapter4Main.class);
		SqlSession sqlSession = null;
		try {
			sqlSession = SqlSessionFactoryUtils.openSqlSession();
			UserMapper userMapper  = sqlSession.getMapper(UserMapper.class);
			User user = userMapper.getUser(1L);
			log.debug("enum"+user.getSex());
		} finally {
			if (sqlSession != null) {
				sqlSession.close();
			}
		}
	}

输出结果

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'sex' from result set.  Cause: java.lang.NumberFormatException: For input string: "MALE"
### The error may exist in mybatis02/mapper/UserMapper.xml
### The error may involve mybatis02.mapper.UserMapper.getUser
### The error occurred while handling results
### SQL: select id, user_name, password, sex, mobile, tel, email, note from t_user       where id = ?
### Cause: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'sex' from result set.  Cause: java.lang.NumberFormatException: For input string: "MALE"

原因：在使用EnumOrdinalTypeHandler时，mybatis会要求数据库返回一个整数，把这个整数作为其下标，在根据下标找到Enum对应的类型

 按照现有配置，如果查询第二条数据，则不会报错，有兴趣的可以自己拿下代码去试试

4.EnumTypeHandler

EnumTypeHandle是根据数据库返回的名称和枚举进行对应，例如MALE，会进行Enum.valueOf（“MALE”）

SexEnum sexEnum=SexEnum.valueOf("MALE");

之后将xml文件中的typeHandler换成EnumTypeHandler

之后测试就没问题了

两者区别：

EnumTypeHandler：要求数据库返回一个String类型的名称，根据名称去匹配枚举

EnumOrdianlTypeHandler：要求数据返回一个整数作为下标，根据下标匹配枚举