字段类型处理器

Json字段

package com.example.demomybatisplus.data.一对多;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler;
import com.example.demomybatisplus.enums.Demo;
import lombok.AllArgsConstructor;
import lombok.Data;

import java.util.List;

@Data
@TableName(autoResultMap = true)
public class Stu {


    @TableId(type = IdType.ASSIGN_ID)
    private String stuId;

    private String stuName;

    private String classId;

    private String age;

    @TableField(typeHandler = JacksonTypeHandler.class)
    private String[] address;

    @TableField(typeHandler = JacksonTypeHandler.class)
    private List<String> province;

    @TableField(typeHandler = JacksonTypeHandler.class)
    private Object value;

    @TableField(typeHandler = JacksonTypeHandler.class)
    private Demo demo;




}

自定义字段处理

package com.example.demomybatisplus.hander;

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.time.Duration;

@MappedJdbcTypes(value = JdbcType.VARCHAR)
@MappedTypes(value = Duration.class)
public class DurationHander  extends BaseTypeHandler<Duration> {

    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, Duration parameter, JdbcType jdbcType) throws SQLException {
        ps.setString(i,parameter.toString());
    }

    @Override
    public Duration getNullableResult(ResultSet rs, String columnName) throws SQLException {



        return Duration.parse(rs.getString(columnName));
    }

    @Override
    public Duration getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return  Duration.parse(rs.getString(columnIndex));
    }

    @Override
    public Duration getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return Duration.parse(cs.getString(columnIndex));
    }
}

使用：

package com.example.demomybatisplus.data;

import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableName;
import com.example.demomybatisplus.hander.DurationHander;
import lombok.Data;
import org.apache.ibatis.type.JdbcType;

import java.time.Duration;
import java.time.LocalDateTime;

@Data
public class UserData {


    // 登陆时长

    @TableField(typeHandler = DurationHander.class)
    private Duration duration = Duration.between(loginTime,createTime);


}

通用枚举

• 使用 @EnumValue  //  注解枚举属性  --> 存什么到数据库
   
      
  使用 @JsonValue	//标记响应json值  --->前端返回值
  

步骤2: 配置扫描通用枚举

• 注意!! 从 3.5.2 开始无需配置
• 注意!! spring mvc 配置参考，安装集成 MybatisSqlSessionFactoryBean 枚举包扫描，spring boot 例子配置如下：