springboot + mybatis自定义枚举类型转换

本文参考了网上文章，同时结合了自己的使用。

参考的文章： https://blog.csdn.net/u014527058/article/details/62883573

需要枚举类型转换的过程
1. 前台提交的数据(如从form表单提交的数据) -> controller参数（如实体类）
2. 实体类 -> 数据库 （该过程通常发生在Dao层）
3. 数据库 -> 实体类 （该过程通常发生在Dao层）

实体类

package com.entity;
import com.enumeration.Level;
/**
* 用户
*/
public class User {// get、set方法省略
private String id;
private String name; // 名字
private Level level; // 等级
}

枚举

package com.enumeration;
public enum Level implements BaseEnum{
ORDINARY(1, "普通会员"), GOLDEN(2, "黄金会员");

private Integer value; // 值
private String description; // 描述

private Level(int value, String description) {
this.value = value;
this.description = description;
}

@Override
public Integer getValue() {
return value;
}

public String getDescription() {
return description;
}
}

package com.enumeration;

public interface BaseEnum {
Integer getValue();
}

1.前台提交的数据 -> controller参数

package com.converter;

import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
import org.springframework.core.convert.converter.Converter;
import org.springframework.core.convert.converter.ConverterFactory;
import com.enumeration.BaseEnum;

/**
* 枚举类型转换
*/
public class BaseEnumConverterFactory implements ConverterFactory<String, BaseEnum> {

@SuppressWarnings("rawtypes")
private static final Map<Class, Converter> converterMap = new WeakHashMap<>();

@SuppressWarnings({ "rawtypes", "unchecked" })
@Override
public <T extends BaseEnum> Converter<String, T> getConverter(Class<T> targetType) {
Converter result = converterMap.get(targetType);
if(result == null) {
result = new IntegerStrToEnum<T>(targetType);
converterMap.put(targetType, result);
}
return result;
}

class IntegerStrToEnum<T extends BaseEnum> implements Converter<String, T> {
@SuppressWarnings("unused")
private final Class<T> enumType;
private Map<String, T> enumMap = new HashMap<>();

public IntegerStrToEnum(Class<T> enumType) {
this.enumType = enumType;
T[] enums = enumType.getEnumConstants();
for(T e : enums) {
enumMap.put(e.getValue() + "", e);
}
}

@Override
public T convert(String source) {
T result = enumMap.get(source);
if(result == null) {
throw new IllegalArgumentException("No element matches " + source);
}
return result;
}
}
}

注册ConverterFactory

package com.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.format.FormatterRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import com.converter.BaseEnumConverterFactory;

/**
* mvc 配置
*/
@Configuration
public class WebAppConfigurer implements WebMvcConfigurer {

@Override
public void addFormatters(FormatterRegistry registry) {
// 注册ConverterFactory(类型转换器工厂)
registry.addConverterFactory(new BaseEnumConverterFactory());
}
}

前台传递参数

<form method="post" th:action="@{/user}">
<h2>添加用户</h2>
<div>
<label for="name">用户名字</label>
<input type="text" id="name" name="name" placeholder="名字">
</div>
<div>
<label>用户等级</label>
<label><input type="radio" name="level" value="1" checked>普通会员</label>
<label><input type="radio" name="level" value="2">黄金会员</label>
</div>
<div>
<input type="submit" value="添加" />
</div>
</form>

controller接收参数

/**
* 添加用户
*
* @param user
* @return
*/
@RequestMapping(method = RequestMethod.POST)
public String Add(User user) {
// 代码省略
}

2.实体类 -> 数据库
类型转换实现类

package com.typeHandler;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

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

import com.enumeration.BaseEnum;

public class BaseEnumTypeHandler<E extends BaseEnum> extends BaseTypeHandler<E> {
private Class<E> enumType;
private Map<Integer, E> enumMap = new HashMap<>();

public BaseEnumTypeHandler(Class<E> type) {
if (type == null)
throw new IllegalArgumentException("Type argument cannot be null");
this.enumType = type;

E[] enums = enumType.getEnumConstants();
if (enums == null)
throw new IllegalArgumentException(type.getSimpleName() + " does not represent an enum type.");
for (E e : enums) {
enumMap.put(e.getValue(), e);
}
}

@Override
public void setNonNullParameter(PreparedStatement ps, int i, E parameter, JdbcType jdbcType) throws SQLException {
ps.setInt(i, parameter.getValue());
}

@Override
public E getNullableResult(ResultSet rs, String columnName) throws SQLException {
return get(rs.getInt(columnName));
}

@Override
public E getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
return get(rs.getInt(columnIndex));
}

@Override
public E getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
return get(cs.getInt(columnIndex));
}

private E get(Integer v) {
if (v == null) {
return null;
}

return this.enumMap.get(v);
}

}

mapper文件中对应枚举的字段要指定typeHandler，如

<insert id="insert" parameterType="com.entity.User">
<selectKey keyProperty="id" resultType="String" order="BEFORE">
SELECT UUID()
</selectKey>
INSERT INTO user (id, name, level)
VALUES
(#{id,jdbcType=VARCHAR},
#{name,jdbcType=VARCHAR},
#{level,jdbcType=INTEGER,typeHandler=com.typeHandler.BaseEnumTypeHandler}
)
</insert>

3.数据库 -> 实体类
类型转换实现类和2中一致。
mapper文件中，对应枚举的字段要指定javaType和typeHandler，如

<resultMap id="UserResultMap" type="com.entity.User">
<id column="id" jdbcType="VARCHAR" property="id" />
<result column="name" jdbcType="VARCHAR" property="name" />
<result column="level" jdbcType="INTEGER" property="level"
javaType="com.enumeration.Level" typeHandler="com.typeHandler.BaseEnumTypeHandler" />
</resultMap>

<select id="findAll" resultMap="UserResultMap">
SELECT * from USER
</select>

项目下载地址：
https://gitee.com/luckiness/SpringbootMybatisEnumDemo