14、自定义TypeHandler之String转换为list

mybatis为我们实现了那么多TypeHandler, 随便打开一个TypeHandler，看其源码，都可以看到，它继承自一个抽象类：BaseTypeHandler， 那么我们是不是也能通过继承BaseTypeHandler，从而实现自定义的TypeHandler ? 答案是肯定的， 那么现在下面就为大家演示一下自定义TypeHandler:

StringToListTypeHandler

package com.lf.typehandle;

import com.google.common.base.Joiner;
import com.google.common.base.Splitter;
import com.google.common.base.Strings;
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;
import java.util.ArrayList;
import java.util.List;

/**
* Created by LF on 2017/3/9.
*/

@MappedTypes({List.class})
@MappedJdbcTypes({JdbcType.VARCHAR})
public class StringToListTypeHandler extends BaseTypeHandler<List<String>> {

@Override
public void setNonNullParameter(PreparedStatement ps, int i, List<String> parameter, JdbcType jdbcType) throws SQLException {
String str = Joiner.on(",").skipNulls().join(parameter);
ps.setString(i, str);
}

@Override
public List<String> getNullableResult(ResultSet rs, String columnName) throws SQLException {
return this.stringToList(rs.getString(columnName));
}

@Override
public List<String> getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
return this.stringToList(rs.getString(columnIndex));
}

@Override
public List<String> getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
return this.stringToList(cs.getString(columnIndex));
}

private List<String> stringToList(String str) {
return Strings.isNullOrEmpty(str) ? new ArrayList<>() : Splitter.on(",").splitToList(str);
}
}

此处如果不用注解指定jdbcType, 那么，就可以在配置文件中通过”jdbcType”属性指定， 同理， javaType 也可通过 @MappedTypes指定

配置我们的自定义TypeHandler了

<typeHandlers>
<!--当配置package的时候，mybatis会去配置的package扫描TypeHandler-->
<package name="com.lf.typehandle"></package>
</typeHandlers>

对应的实体和mapper

package com.lf.entity;

@Data
@ToString
@NoArgsConstructor
public class Blog {
private String id;

private String title;

private String url;

private List<String> userid;

}

package com.lf.dao;

import com.lf.entity.Blog;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface BlogMapper {

int deleteByPrimaryKey(String id);

int insertSelective(Blog record);

Blog selectByPrimaryKey(String id);

int updateByPrimaryKeySelective(Blog record);

}

<?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.lf.dao.BlogMapper">
<resultMap id="BaseResultMap" type="com.lf.entity.Blog">
<id column="id" jdbcType="VARCHAR" property="id" />
<result column="title" jdbcType="VARCHAR" property="title" />
<result column="url" jdbcType="VARCHAR" property="url" />
<result column="userid" jdbcType="VARCHAR" property="userid" />
</resultMap>
<sql id="Base_Column_List">
id, title, url, userid
</sql>
<select id="selectByPrimaryKey" parameterType="java.lang.String" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from blog
where id = #{id,jdbcType=VARCHAR}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.String">
delete from blog
where id = #{id,jdbcType=VARCHAR}
</delete>

<insert id="insertSelective" parameterType="com.lf.entity.Blog">
insert into blog
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="id != null">
id,
</if>
<if test="title != null">
title,
</if>
<if test="url != null">
url,
</if>
<if test="userid != null">
userid,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides=",">
<if test="id != null">
#{id,jdbcType=VARCHAR},
</if>
<if test="title != null">
#{title,jdbcType=VARCHAR},
</if>
<if test="url != null">
#{url,jdbcType=VARCHAR},
</if>
<if test="userid != null">
#{userid,jdbcType=VARCHAR},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.lf.entity.Blog">
update blog
<set>
<if test="title != null">
title = #{title,jdbcType=VARCHAR},
</if>
<if test="url != null">
url = #{url,jdbcType=VARCHAR},
</if>
<if test="userid != null">
userid = #{userid,jdbcType=VARCHAR},
</if>
</set>
where id = #{id,jdbcType=VARCHAR}
</update>

</mapper>

数据库的数据

1   偶尔记一下   http://blog.csdn.net/isea533    5,3,3
2   测试  http://www.google.com   1

测试方法

package com.lf;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class App {
public static void main(String[] args) throws IOException {
String resouce = "mybatis-config.xml";
InputStream is = Resources.getResourceAsStream(resouce);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
SqlSession sqlSession = sqlSessionFactory.openSession();
Object one = sqlSession.selectOne("com.lf.dao.BlogMapper.selectByPrimaryKey", "1");
System.err.println(one);
sqlSession.commit();
}
}

输出结果

Blog(id=1, title=偶尔记一下, url=http://blog.csdn.net/isea533, userid=[5, 3, 3])