Java常见问题解决方案

数据对比

Mybaits

增删改查

Mybaits-plus

1. 增删改查

1.1 实体类

/**
 * xx实体类
 */
@TableName("demo_table")
public class DemoTableEntity implements Serializable {

    /**
     * ID
     */
    @TableId
    private String demoId;

    /**
     * 名称
     */
    private String demoName;

    public String getDemoId() {
        return demoId;
    }

    public void setDemoId(String demoId) {
        this.demoId= demoId;
    }

    public String getDemoName() {
        return demoName;
    }

    public void setDemoName(String demoName) {
        this.demoName= demoName;
    }
}

1.2 Controller

@RestController
@RequestMapping("/demoTable")
public class DemoTableController extends BaseController {

    @Autowired
    private DemoTableService demoTableService;

    /**
     * 新增
     * @param demoTableEntity
     * @return
     */
    @PostMapping("/save")
    public AjaxResult save(@RequestBody DemoTableEntity demoTableEntity){
        return toAjax(demoTableService.save(demoTableEntity));
    }

    /**
     * 修改
     * @param demoTableEntity
     * @return
     */
    @PostMapping("/update")
    public AjaxResult update(@RequestBody DemoTableEntity demoTableEntity){
        return toAjax(demoTableService.update(demoTableEntity));
    }

    /**
     * 查询列表
     * @param demoTableEntity
     * @return
     */
    @GetMapping("/selectList")
    public TableDataInfo selectList(DemoTableEntity demoTableEntity){
        startPage();
        List<DemoTableEntity> list = demoTableService.selectList(demoTableEntity);
        return getDataTable(list);
    }

    /**
     * 删除
     * @param id
     * @return
     */
    @DeleteMapping("/delete/{id}")
    public AjaxResult deleteById(@PathVariable String id){
        return toAjax(demoTableService.deleteById(id));
    }
}

1.3 Service

public interface DemoTableService {

    /**
     * 新增服务实例
     * @param demoTableEntity
     * @return
     */
    Integer save(DemoTableEntity demoTableEntity);

    /**
     * 修改服务实例
     * @param demoTableEntity
     * @return
     */
    Integer update(DemoTableEntity demoTableEntity);

    /**
     * 查询服务实例列表
     * @param demoTableEntity
     * @return
     */
    List<DemoTableEntity> selectList(DemoTableEntity demoTableEntity);

    /**
     * 根据id删除服务实例
     * @param id
     * @return
     */
    Integer deleteById(String id);
}

1.4 ServiceImpl

@Service
public class DemoTableServiceImpl implements DemoTableService {

    @Autowired
    private DemoTableMapper demoTableMapper;

    /**
     * 新增服务实例
     * @param demoTableEntity
     * @return
     */
    @Override
    public Integer save(DemoTableEntity demoTableEntity){
        return demoTableMapper.insert(demoTableEntity);
    }

    /**
     * 修改
     * @param demoTableEntity
     * @return
     */
    @Override
    public Integer update(DemoTableEntity demoTableEntity){
        UpdateWrapper<DemoTableEntity> wrapper = new UpdateWrapper<>();
        return demoTableMapper.update(demoTableEntity, wrapper);
    }

    /**
     * 查询列表
     * @param demoTableEntity
     * @return
     */
    @Override
    public List<DemoTableEntity> selectList(DemoTableEntity demoTableEntity){
        QueryWrapper queryWrapper = new QueryWrapper();
        return demoTableMapper.selectList(queryWrapper);
    }

    /**
     * 根据id删除
     * @param id
     * @return
     */
    @Override
    public Integer deleteById(String id){
        return demoTableMapper.deleteById(id);
    }

}

1.5 Mapper

public interface DemoTableMapper extends BaseMapper<DemoTableEntity> {

}

注解

1. @MapperScan

bug场景： 访问 Controller 的接口返回404

// 解决方案： 启动类添加 @MapperScan注解
@MapperScan("com.gientech.armp.empower.mapper.*")

@MapperScan 注解指定了 Mapper 接口所在的包路径为 com.gientech.armp.empower.mapper。这样，在应用启动时，Spring Boot 就会自动扫描该包下的所有 Mapper 接口，并将其实例化后交给 Spring 容器管理。