Java 对象转Json字符串 子对象没有值

今天在进行对象转json字符串的时候出现了一个问题

里面的子对象为空，没有获得对应的字段值

public class ProjectDTO {
    private Long id;
    private String name;
    private String code;
    private List projectMembers;
}

public class ProjectMemberDTO implements Serializable {

    private static final long serialVersionUID = 1L;

    @ApiModelProperty(value = "项目角色ID")
    @NotNull(message = "项目角色ID不能为空")
    @JSONField(serialize = false)
    private Long roleId;

    @ApiModelProperty(value = "项目角色名称")
    @JSONField(serialize = false)
    private String roleName;

    @ApiModelProperty(value = "用户信息")
    @JSONField(serialize = false)
    List user;
}

public class SimpleInfoDTO implements Serializable {

    private static final long serialVersionUID = 1L;

    @ApiModelProperty(value = "ID")
    private Long id;

    @ApiModelProperty(value = "名称")
    private String name;

    private List simpleInfoList;
    

{
    "code":"lili",
    "id":12,
    "name":"lili",
    "projectMembers":[
        {
            "roleId":1,
            "user":[
                {
                    "id":0001,
                    "name":"张三"
                }
            ]
        },
        {
            "roleId":2,
            "user":[
                {
                    "id":0002,
                    "name":"李四"
                }
            ]
        }
    ]
}

处理代码：

JSON.toJSONString(ProjectDTO)

得到的值

{
    "code":"lili",
    "id":12,
    "name":"lili",
    "projectMembers":[{}]
}

@JSONField(serialize = false)注释后，就能得到我想要的数据了

public class ProjectMemberDTO implements Serializable {

    private static final long serialVersionUID = 1L;

    @ApiModelProperty(value = "项目角色ID")
    @NotNull(message = "项目角色ID不能为空")
   //@JSONField(serialize = false)注释
    private Long roleId;

    @ApiModelProperty(value = "项目角色名称")
    @JSONField(serialize = false)
    private String roleName;

    @ApiModelProperty(value = "用户信息")
   //@JSONField(serialize = false)注释
    List user;

    @ApiModelProperty(value = "项目成员")
    private String projectMember;

}

@JSONField(ordinal = 1)	
//指定json序列化的顺序

@JSONField(serialize = false)	
//json序列化时忽略该字段

@JSONField(deserialize = false)	
//json反序列化时转成对象将忽略该字段

@JSONField(format = "yyyy-MM-dd-HH:mm:ss")	
//json格式转换

@JSONField(name = "gmtTime",format = "yyyy-MM-dd-HH:mm:ss")	
//指定反序列化的字符串名称