https://my.oschina.net/SEyanlei/blog/188919
mybatis提供了EnumTypeHandler和EnumOrdinalTypeHandler完成枚举类型的转换，两者的功能已经基本满足了日常的使用。但是可能有这样的需求：由于某种原因，我们不想使用枚举的name和ordinal作为数据存储字段。mybatis的自定义转换类出现了。
前提知识
1. mybatis废弃了ibatis的TypeHandlerCallback接口，取而代之的接口是TypeHandler，它与原来的接口略有不同，但是方法类似。（见说明 https://code.google.com/p/mybatis/wiki/DocUpgrade3）
2. BaseTypeHandler是mybatis提供的基础转换类，该类实现了TypeHandler接口并提供很多公用方法，建议每个自定义转换类都继承它。
示例
使用一段代码，将枚举类EnumStatus中的code属性存储到数据库对应字段statusCustom。
自定义转换类
package com.sg.util.typehandler;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import com.sg.bean.EnumStatus;
public class EnumStatusHandler extends BaseTypeHandler<EnumStatus> {
private Class<EnumStatus> type;
private final EnumStatus[] enums;
public EnumStatusHandler(Class<EnumStatus> type) {
if (type ==
null)
throw new IllegalArgumentException(
"Type argument cannot be null");
this.type = type;
this.enums = type.getEnumConstants();
if (
this.enums ==
null)
throw new IllegalArgumentException(type.getSimpleName()
+
" does not represent an enum type.");
}
@Override
public EnumStatus getNullableResult(ResultSet rs, String columnName) throws SQLException {
int i = rs.getInt(columnName);
if (rs.wasNull()) {
return null;
}
else {
return locateEnumStatus(i);
}
}
@Override
public EnumStatus getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
int i = rs.getInt(columnIndex);
if (rs.wasNull()) {
return null;
}
else {
return locateEnumStatus(i);
}
}
@Override
public EnumStatus getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
int i = cs.getInt(columnIndex);
if (cs.wasNull()) {
return null;
}
else {
return locateEnumStatus(i);
}
}
@Override
public void setNonNullParameter(PreparedStatement ps, int i, EnumStatus parameter, JdbcType jdbcType)
throws SQLException {
ps.setInt(i, parameter.getCode());
}
private EnumStatus locateEnumStatus(int code) {
for(EnumStatus status : enums) {
if(status.getCode().equals(Integer.valueOf(code))) {
return status;
}
}
throw new IllegalArgumentException(
"未知的枚举类型：" + code +
",请核对" + type.getSimpleName());
}
}
枚举类
package com.sg.bean;
public enum EnumStatus {
NORMAL(
1,
"正常"),
DELETE(
0,
"删除"),
CANCEL(
2,
"注销");
private EnumStatus(
int code, String
description) {
this.code =
new Integer(code);
this.
description =
description;
}
private Integer code;
private String
description;
public Integer getCode() {
return code;
}
public String getDescription() {
return description;
}
}
实体类
package com.sg.bean;
public class User {
private String id;
private String accountID;
private String userName;
private EnumStatus statusDef;
private EnumStatus statusOrdinal;
private EnumStatus statusCustom;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getAccountID() {
return accountID;
}
public void setAccountID(String accountID) {
this.accountID = accountID;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public EnumStatus getStatusDef() {
return statusDef;
}
public void setStatusDef(EnumStatus statusDef) {
this.statusDef = statusDef;
}
public EnumStatus getStatusOrdinal() {
return statusOrdinal;
}
public void setStatusOrdinal(EnumStatus statusOrdinal) {
this.statusOrdinal = statusOrdinal;
}
public EnumStatus getStatusCustom() {
return statusCustom;
}
public void setStatusCustom(EnumStatus statusCustom) {
this.statusCustom = statusCustom;
}
@Override
public String toString() {
StringBuffer str =
new StringBuffer();
str.append(
"id：");
str.append(id);
str.append(
"\n");
str.append(
"userName：");
str.append(userName);
str.append(
"\n");
str.append(
"statusDef：");
str.append(statusDef.name());
str.append(
"\n");
str.append(
"statusOrdinal：");
str.append(statusOrdinal.name());
str.append(
"\n");
str.append(
"statusCustom：");
str.append(statusCustom.name());
str.append(
"\n");
return str.toString();
}
}
mybatis配置文件
<?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="com.sg.bean.User">
<resultMap type="User" id="userMap">
<id column="id" property="id"/>
<result column="accountID" property="accountID"/>
<result column="userName" property="userName"/>
<result column="statusDef" property="statusDef"/>
<result column="statusOrdinal" property="statusOrdinal" typeHandler="org.apache.ibatis.type.EnumOrdinalTypeHandler"/>
<result column="statusCustom" property="statusCustom" typeHandler="com.sg.util.typehandler.EnumStatusHandler"/>
</resultMap>
<select id="selectUser" resultMap="userMap">
select * from t_user where id = #{id}
</select>
<insert id="insertUser" parameterType="User">
insert into t_user(id,accountID,userName,statusDef,statusOrdinal,statusCustom)
values(
#{id}, #{accountID}, #{userName},
#{statusDef},
#{statusOrdinal, typeHandler=org.apache.ibatis.type.EnumOrdinalTypeHandler},
#{statusCustom, typeHandler=com.sg.util.typehandler.EnumStatusHandler}
)
</insert>
</mapper>
数据库脚本
CREATE TABLE `t_user` (
`id` varchar(
45)
NOT NULL,
`accountID` varchar(
45)
DEFAULT NULL,
`userName` varchar(
45)
DEFAULT NULL,
`statusDef` varchar(
45)
DEFAULT NULL,
`statusOrdinal` varchar(
45)
DEFAULT NULL,
`statusCustom` int(
11)
DEFAULT NULL,
PRIMARY
KEY (
`id`)
)
ENGINE=
InnoDB DEFAULT CHARSET=utf8
COMMENT=
'用户表';
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