ResponseEntity的实体类无gettersetter方法，无法返回值到前端

Question

后台代码:
package com.leyou.item.web;

import com.leyou.common.vo.PageResult;
import com.leyou.item.pojo.Brand;
import com.leyou.item.service.BrandService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("brand")
public class BrandController {

    @Autowired
    private BrandService brandService;

    @GetMapping("page")
    public ResponseEntity<PageResult<Brand>> queryBrandByPage(
            @RequestParam(value = "page", defaultValue = "1") Integer page,
            @RequestParam(value = "rows", defaultValue = "5") Integer rows,
            @RequestParam(value = "sortBy", required = false) String sortBy,
            @RequestParam(value = "desc", defaultValue = "false") Boolean desc,
            @RequestParam(value = "key", required = false) String key) {
        PageResult<Brand> result = this.brandService.queryBrandByPage(page,rows,sortBy,desc, key);
        if (result == null || result.getItems().size() == 0) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }
        return ResponseEntity.ok(result);
    }
}

实体类

Brand：
package com.leyou.item.pojo;

import tk.mybatis.mapper.annotation.KeySql;

import javax.persistence.Id;
import javax.persistence.Table;

@Table(name = "tb_brand")
public class Brand {
    @Id
    @KeySql(useGeneratedKeys = true)
    private Long id;
    private String name;// 品牌名称
    private String image;// 品牌图片
    private Character letter;
}

 PageResult:
package com.leyou.common.vo;

import lombok.Data;

import java.util.List;

@Data
public class PageResult<T> {
    private Long total;     // 总条数
    private Long totalPage; // 总页数
    private List<T> items;  // 当前页数据

    public PageResult() {
    }

    public PageResult(Long total, List<T> items) {
        this.total = total;
        this.items = items;
    }

    public PageResult(Long total, Long totalPage, List<T> items) {
        this.total = total;
        this.totalPage = totalPage;
        this.items = items;
    }


}

https://img-bbs.csdn.net/uplo...

https://img-bbs.csdn.net/uplo...

打断点发现return的位置其实有值，但是前端无法显示。后来经过排查发现是实体类中，没有写getter setter方法。

问题：既然在PageResult<Brand>中有数据，ResponseEntity类内部只是将其赋值给body返回，为什么不写getter setter方法，在返回后就没有值了呢