1.在数据库中建张表（最大值，字符前缀）

2.mapper中的dao层

根据字符前缀查询

3.mapper.xml文件SQL语句

注：红色圈（存在时更新，不存在是添加。具体访问：）：https://www.cnblogs.com/liaojie970/p/6824773.html

根据字符前缀查询的SQL

4.封装方法（参数拼接）

5.封装方法（字符拼接）

@Service
public class SysAssetsCodeService implements ISysAssetsCodeService {
    private Lock lock = new ReentrantLock();
    @Autowired
    private SysAssetsCodeMapper codeMapper;

    @Override
    @Transactional
    public String getCode(String preFixe,int numCode) {
        try {
            lock.lock();
            int result = codeMapper.insertAssetsCode(preFixe);
            SysAssetsCode sysAssetsCode = codeMapper.selectByPrefix(preFixe);
            if(sysAssetsCode != null && result > 0 ){
                return String.format("%s%"+numCode+"d", preFixe,sysAssetsCode.getMaxinx()).replace(" ", "0");
            }else{
                throw new RuntimeException("获取编码失败");
            }
        } finally {
            lock.unlock();
        }

    }
}

6.Controller控制层

 /**
     * 根据资产编号获取详细信息
     */
    @PreAuthorize("@ss.hasPermi('system:assets:query')")
    @GetMapping(value ={"/", "/{id}"})
    public AjaxResult getInfo(@PathVariable(value = "id", required = false) Long id)
    {
        AjaxResult ajax = AjaxResult.success();
        SysAssets assets = null;
        if(StringUtils.isNotNull(id)){
            assets = assetsService.selectAssetsById(id);
        }else{
            assets = new SysAssets();
            assets.setCodeId(codeService.getCode("YFCX",5));
        }
        ajax.put(AjaxResult.DATA_TAG,assets);
        return ajax;
    }