Mybatis对于类转换器TypeHandler的简单使用

最新推荐文章于 2025-09-19 09:00:16 发布

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文章标签：

#TypeHandler #mybatis

目录

TypeHandler概念

MyBatis 内置的 TypeHandler

如何自定义typehandler

自定义demo(亲测有效)

TypeHandler概念
MyBatis 中的 TypeHandler 类型处理器用于 JavaType 与 JdbcType 之间的转换，用于 PreparedStatement 设置参数值和从 ResultSet 或 CallableStatement 中取出一个值。MyBatis 内置了大部分基本类型的类型处理器，所以对于基本类型可以直接处理，当我们需要处理其他类型的时候就需要自定义类型处理器
MyBatis 内置的 TypeHandler
在 MyBatis 的 TypeHandlerRegistry 类型中，可以看到内置的类型处理器。内置处理器比较多，这里整理常见的一些。

BooleanTypeHandler：用于 java 类型 boolean，jdbc 类型 bit、boolean

ByteTypeHandler：用于 java 类型 byte，jdbc 类型 TINYINT

ShortTypeHandler：用于 java 类型 short，jdbc 类型 SMALLINT

IntegerTypeHandler：用于 INTEGER 类型

LongTypeHandler：用于 long 类型

FloatTypeHandler：用于 FLOAT 类型

DoubleTypeHandler：用于 double 类型

StringTypeHandler：用于 java 类型 string，jdbc 类型 CHAR、VARCHAR

ArrayTypeHandler：用于 jdbc 类型 ARRAY

BigDecimalTypeHandler：用于 java 类型 BigDecimal，jdbc 类型 REAL、DECIMAL、NUMERIC

DateTypeHandler：用于 java 类型 Date，jdbc 类型 TIMESTAMP

DateOnlyTypeHandler：用于 java 类型 Date，jdbc 类型 DATE

TimeOnlyTypeHandler：用于 java 类型 Date，jdbc 类型 TIME

对于常见的 Enum 类型，内置了 EnumTypeHandler 进行 Enum 名称的转换和 EnumOrdinalTypeHandler 进行 Enum 序数的转换。这两个类型处理器没有在 TypeHandlerRegistry 中注册，如果需要使用必须手动配置。
作者：程序之心
链接：https://www.jianshu.com/p/251cb44e2b82
來源：简书
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。
如何自定义typehandler

两种方式

1.1 ：可以实现TypeHandler<T>接口

public class MyTypeHandler2 implements TypeHandler<List<String>> {
    public void setParameter(PreparedStatement preparedStatement, int i, List<String> strings, JdbcType jdbcType) throws SQLException {
        StringBuffer sb = new StringBuffer();
        for(String s : strings){
            sb.append(s).append(",");
        }
        preparedStatement.setString(i,sb.toString().substring(0,sb.toString().length() - 1));
    }
 
    public List<String> getResult(ResultSet resultSet, String s) throws SQLException {
        String[] arr = resultSet.getString(s).split(",");
        return Arrays.asList(arr);
    }
 
    public List<String> getResult(ResultSet resultSet, int i) throws SQLException {
        String[] arr = resultSet.getString(i).split(",");
        return Arrays.asList(arr);
    }
 
    public List<String> getResult(CallableStatement callableStatement, int i) throws SQLException {
        String[] arr = callableStatement.getString(i).split(",");
        return Arrays.asList(arr);
    }
}

1.2：可以继承 BaseTypeHandler<T>

public class MyTypeHandler extends BaseTypeHandler<List<String>> {
    @Override
    public void setNonNullParameter(PreparedStatement preparedStatement, int i, List<String> list, JdbcType jdbcType) throws SQLException {
        StringBuffer sb = new StringBuffer();
        for(String s : list){
            sb.append(s).append(",");
        }
        preparedStatement.setString(i,sb.toString().substring(0,sb.toString().length() - 1));
    }
 
    @Override
    public List<String> getNullableResult(ResultSet resultSet, String s) throws SQLException {
        String[] arr = resultSet.getString(s).split(",");
        return Arrays.asList(arr);
    }
 
    @Override
    public List<String> getNullableResult(ResultSet resultSet, int i) throws SQLException {
        String[] arr = resultSet.getString(i).split(",");
        return Arrays.asList(arr);
    }
 
    @Override
    public List<String> getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        String[] arr = callableStatement.getString(i).split(",");
        return Arrays.asList(arr);
    }
}

自定义demo(亲测有效)
需求：使用mysql5.7新特性，字段属性为json。可存储json格式数据和数组，前端传值使用String，而接收的时候是json或数组，减少对于数据的转换。json----->String[]
数据库

自定义转换类

package com.timothy.mybatis;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;

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

/*
   <columnOverride column="urls" javaType="java.lang.String[]" typeHandler="JsonStringArrayTypeHandler"/>
 */
@MappedJdbcTypes({JdbcType.VARCHAR})
public class JsonStringArrayTypeHandler extends BaseTypeHandler<String[]> {
    private static final ObjectMapper mapper = new ObjectMapper();

    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, String[] parameter, JdbcType jdbcType) throws SQLException {
        ps.setString(i,toJson(parameter));
    }

        @Override
        public String[] getNullableResult(ResultSet rs, String columnName) throws SQLException {
            return this.toObject(rs.getString(columnName));
        }

    @Override
    public String[] getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return this.toObject(rs.getString(columnIndex));
    }

    @Override
    public String[] getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return this.toObject(cs.getString(columnIndex));
    }

    private String toJson(String[] params) {
        try {
            return mapper.writeValueAsString(params);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "[]";
    }

    private String[] toObject(String content) {
        if (content != null && !content.isEmpty()) {
            try {
                return (String[]) mapper.readValue(content, String[].class);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        } else {
            return null;
        }
    }
}

实体类

package com.timothy.generator.pojo;

public class User {
   
    private Integer id;


    private String name;

    private String[] like;

    private String address;

   
    public Integer getId() {
        return id;
    }

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

  
    public String getName() {
        return name;
    }

   
    public void setName(String name) {
        this.name = name == null ? null : name.trim();
    }

  
    public String[] getLike() {
        return like;
    }

   
    public void setLike(String[] like) {
        this.like = like;
    }

   
    public String getAddress() {
        return address;
    }

   
    public void setAddress(String address) {
        this.address = address == null ? null : address.trim();
    }
}

最重要的是mapper.xml

<?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.timothy.generator.mapper.UserMapper" >
  <resultMap id="BaseResultMap" type="com.timothy.generator.pojo.User" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    <id column="id" property="id" jdbcType="INTEGER" />
    <result column="name" property="name" jdbcType="VARCHAR" />
    <result column="like" property="like" jdbcType="CHAR" typeHandler="com.timothy.mybatis.JsonStringArrayTypeHandler" />
    <result column="address" property="address" jdbcType="CHAR" />
  </resultMap>
  <sql id="Base_Column_List" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    id, name, like, address
  </sql>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    select
    <include refid="Base_Column_List" />
    from user
    where id = #{id,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    delete from user
    where id = #{id,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="com.timothy.generator.pojo.User" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    <selectKey resultType="java.lang.Integer" keyProperty="id" order="BEFORE" >
      select uuid_short()
    </selectKey>
    insert into user (id, name, like,
      address)
    values (#{id,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{like,jdbcType=CHAR,typeHandler=com.timothy.mybatis.JsonStringArrayTypeHandler},
      #{address,jdbcType=CHAR})
  </insert>
  <insert id="insertSelective" parameterType="com.timothy.generator.pojo.User" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    <selectKey resultType="java.lang.Integer" keyProperty="id" order="BEFORE" >
      select uuid_short()
    </selectKey>
    insert into user
    <trim prefix="(" suffix=")" suffixOverrides="," >
      id,
      <if test="name != null" >
        name,
      </if>
      <if test="like != null" >
        like,
      </if>
      <if test="address != null" >
        address,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      #{id,jdbcType=INTEGER},
      <if test="name != null" >
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="like != null" >
        #{like,jdbcType=CHAR,typeHandler=com.timothy.mybatis.JsonStringArrayTypeHandler},
      </if>
      <if test="address != null" >
        #{address,jdbcType=CHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.timothy.generator.pojo.User" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    update user
    <set >
      <if test="name != null" >
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="like != null" >
        like = #{like,jdbcType=CHAR,typeHandler=com.timothy.mybatis.JsonStringArrayTypeHandler},
      </if>
      <if test="address != null" >
        address = #{address,jdbcType=CHAR},
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.timothy.generator.pojo.User" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    update user
    set name = #{name,jdbcType=VARCHAR},
      like = #{like,jdbcType=CHAR,typeHandler=com.timothy.mybatis.JsonStringArrayTypeHandler},
      address = #{address,jdbcType=CHAR}
    where id = #{id,jdbcType=INTEGER}
  </update>

  <select id="findById" resultMap="BaseResultMap" parameterType="Integer">
    SELECT * FROM user WHERE  id = 1
  </select>

</mapper>