MyBatis写入Json字段以及Json字段转对象示例详解

@Data
@Builder
@ToString
public class ParameterEntity {
    private String device;
    private String recipe;
    private String parameter;
    private String name;
    private String type;
    private String valueType;
    // 这个字段就对应表中的json字段 
    private ParameterLimiting limiting;
}

  datasource:
    pgsql:
      jdbcUrl: jdbc:postgresql://ip:5432/ams?rewriteBatchedStatements=true&stringtype=unspecified
      username: 
      password: 
      driver-class-name: org.postgresql.Driver

// 这里对应表中字段的类型
@MappedJdbcTypes(JdbcType.OTHER)
// 这里对应实体类的类型
@MappedTypes(ParameterLimiting.class)
public class ParameterLimitingToJsonHandler extends BaseTypeHandler<ParameterLimiting> {
    @Override
    public void setNonNullParameter(PreparedStatement preparedStatement, int i, ParameterLimiting parameterLimiting, JdbcType jdbcType) throws SQLException {
    	// 做写入操作时将对象转成json字符串
        preparedStatement.setObject(i, JSON.toJSONString(parameterLimiting));
    }
    @Override
    public ParameterLimiting getNullableResult(ResultSet resultSet, String s) throws SQLException {
        return null;
    }
    @Override
    public ParameterLimiting getNullableResult(ResultSet resultSet, int i) throws SQLException {
        return null;
    }
    @Override
    public ParameterLimiting getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        return null;
    }
}

<insert id="addParameter" parameterType="com.inventec.dm.entity.po.ParameterEntity">
        INSERT INTO dap.parameter
        ("device", "recipe", "parameter", "name", "type", "valueType", "limiting")
        VALUES (#{device}, #{recipe}, #{parameter}, #{name}, #{type}, #{valueType},
        		<!--  这里需要指定 jdbcType 及 typeHandler 属性，这里的 typeHandler 也就是我们刚写的对象转Json的控制类  -->
                #{limiting,jdbcType=OTHER,typeHandler=com.inventec.dm.config.ParameterLimitingToJsonHandler});
</insert>

<select id="getParametersByDeviceId" resultMap="parameterToParameterEntity">
        SELECT *
        FROM dap.parameter
        WHERE device = #{device};
</select>
<resultMap id="parameterToParameterEntity" type="com.inventec.dm.entity.po.ParameterEntity">
        <result property="device" column="device"/>
        <result property="recipe" column="recipe"/>
        <result property="parameter" column="parameter"/>
        <result property="name" column="name"/>
        <result property="type" column="type"/>
        <result property="valueType" column="valueType"/>
        <-- 这里需要指定jdbcType、javaType、typeHandler属性，其中typeHandler还是上边的转换控制类 -->
        <result property="limiting" column="limiting"
                jdbcType="OTHER" javaType="com.inventec.dm.entity.parameter.ParameterLimiting"
                typeHandler="com.inventec.dm.config.ParameterLimitingToJsonHandler"/>
</resultMap>

@Data
@Builder
@ToString
public class ParameterEntity {
    private String device;
    private String recipe;
    private String parameter;
    private String name;
    private String type;
    private String valueType;
    private ParameterLimiting limiting;
    // 这个实体类中不能有无参构造，否则在映射json字段时不执行有参构造
    // 注意这里最后的一个参数是 Object limiting，而不是 ParameterLimiting limiting
    public ParameterEntity(String device, String recipe, String parameter, String name, String type, String valueType, Object limiting) {
        this.device = device;
        this.recipe = recipe;
        this.parameter = parameter;
        this.name = name;
        this.type = type;
        this.valueType = valueType;
        if (limiting != null) {
            this.limiting = JSON.parseObject(limiting.toString(), ParameterLimiting.class);
        }
    }
}