org.springframework.http.converter.HttpMessageConversionException: 
Type definition error: [simple type, class com.ruoyi.digital.domain.BbCoordInfo]; 
nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException:
 No serializer found for class com.ruoyi.digital.domain.BbCoordInfo and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: com.ruoyi.common.core.web.page.TableDataInfo["rows"]->java.util.ArrayList[0])
Caused by:
 com.fasterxml.jackson.databind.exc.InvalidDefinitionException: 
 No serializer found for class com.ruoyi.digital.domain.BbCoordInfo and no properties discovered to create BeanSerializer 
 (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
  (through reference chain: com.ruoyi.common.core.web.page.TableDataInfo["rows"]->java.util.ArrayList[0])

今天新写了一个功能，各种表单的联表查询功能，具体的SQL语句如下：

<select id="selectBbCoordDetailList" parameterType="Long" resultType="com.ruoyi.digital.domain.BbCoordInfo">
        select g.WS_ID as wsId,g.WS_Name as wsName,b.CID as cId,b.CName as cName ,a.Mac_ID as macId,
               c.Mac_Code as macCode,b.coord_x as coordX,b.coord_y as coordY,d.RunStatus as statusCode,
               e.status_text as statusText,f.Mac_ConnectIP as macIP from BU_Machine_Coord a
                   left join BB_Coord  b on a.Mac_CoordID = b.CID
                   left join BU_Machine_BasicInfo c on a.Mac_ID = c.Mac_ID
                   left join BU_Machine_CurrStatus d on a.Mac_ID = d.Mac_ID
                   left join BB_Status_Info e on d.RunStatus = e.status_id
                   left join BU_Machine_IP f on a.Mac_ID = f.Mac_ID
                   left join BB_WorkShop g on b.WS_ID = g.WS_ID
        <where>
            b.IsDel = 0
            <if test="wsId != null  and wsId != ''"> and g.WS_ID = #{wsId}</if>
        </where>
        order by CID asc
    </select>

接口调用地址：

http://192.168.0.192:9203/coord/detail

后台controller代码：

@GetMapping(value = {"/detail","/detail/{wsId}"})
    public TableDataInfo getDetailInfo(@PathVariable(value = "wsId",required = false) Long wsId){
        startPage();
        List<BbCoordInfo> list = bbCoordService.selectBbCoordDetailList(wsId);
        return getDataTable(list);
    }

实体类：

package com.ruoyi.digital.domain;

import com.ruoyi.common.core.annotation.Excel;

import java.math.BigDecimal;

/**
 * @author layman
 * @description: 机位详细信息
 * @date 2021/11/15
 */
public class BbCoordInfo {
    private static final long serialVersionUID = 1L;

    /** 车间ID */
    private Long wsId;

    /** 车间名称 */
    @Excel(name = "车间名称")
    private String wsName;
}

似乎是缺少序列化。

我看了别的实体类的写法：

public class BbCoord extends BaseEntity

它们都有个 extends BaseEntity

public class BaseEntity implements Serializable

应该是这个导致的，我在我的实体类上添加 extends BaseEntity，这个报错得到修复。