mysql没有数组这种类型,我们可以以数组格式的字符串加入到数据库,返回值是数组

1.Mapper.xml 返回数组

<resultMap type="返回实体类" id="result" >
		<result property="实体类字段名" column="mysql字段名" typeHandler="处理类"/>
</resultMap>

<select id="Mapper.java的方法名" parameterType="传参类型" resultMap="resultMap的id">
    select pricture from xm_picture
</select>

例如: 

<resultMap type="co.yixiang.modules.service.dto.PictureDto" id="PictureResult" >
		<result property="pictureArr" column="picture" typeHandler="co.yixiang.utils.mybatis.JsonStringArrayTypeHandler"/>
</resultMap>

<!-- parameterType 也可以是实体类 -->
<select id="selectPictureById" parameterType="Long" resultMap="PictureResult">
    select pricture from xm_picture where id = #{id}
</select>

2.Mapper.java 返回数组 @Select注解

@Select("<script>" +
" select picture from xm_picture where id = #{id} " +
"</script>")
@Results({@Result(property="实体类字段名",column="数据库字段名",typeHandler= 处理类.class)})
PictureDto selectById(Long id);

例如

@Select("<script>" +
" select picture from xm_picture where id = #{id} " +
"</script>")
@Results({@Result(property="pictureArr",column="picture",typeHandler= JsonStringArrayTypeHandler.class)})
PictureDto selectById(Long id);

处理类代码

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;

@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;
        }
    }
}