【自定义注解实现字段检验重复值】

• 前言
• 一、业务场景？
• 二、实现步骤
• • 1.引入依赖
  • 2.新增自定义注解(注解嵌套)
  • 3. 自定义注解类处理器
  • 4. 自定义异常类
  • 5. 全局异常捕获类
  • 6. 实体类上的注解
  • 7. Controller层
  • 结果显示
• 三、踩坑日记
• 四、参考博客

对于一些数据库表字段是唯一索引的，需要在数据插入前做数据重复性检验，并友好返回给前端。例如用户名不能重复，工号不能重复等。对于这些重复判断项目中很多地方都需要用到，想法是直接抽离处理，统一管理，减少重复代码。按照以下步骤配置，字段值重复检验一个注解即可实现。以下是实现步骤，如有疑问，欢迎大家提问和指点。

代码如下（示例）：

    org.springframework.boot
    spring-boot-starter-validation
    2.3.11.RELEASE

@FieldRepeatValidators

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = FieldRepeatValidatorHandler.class)
public @interface FieldRepeatValidators {

    
    String tableName();

    
    String idField() default "id";
    
     
    String idProperty() default "id";
    

    FieldRepeatValidator[] fieldRepeatValidators();

    String message() default "";
    
    Class[] groups() default { };
    
    Class[] payload() default { };
}

@FieldRepeatValidator

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.PARAMETER, ElementType.FIELD, ElementType.TYPE})
public @interface FieldRepeatValidator {

    
    String field();

    
    String message() default "字段内容重复！";

    
    String property();

}

public class FieldRepeatValidatorHandler implements ConstraintValidator, ApplicationContextAware {

    private FieldRepeatValidators fieldRepeatValidators;

    static ApplicationContext application;

    @Override
    @SuppressWarnings("all")
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        application = applicationContext;
    }

    @Override
    public void initialize(FieldRepeatValidators fieldRepeatValidators) {
        this.fieldRepeatValidators = fieldRepeatValidators;
    }

    @Override
    public boolean isValid(Object o, ConstraintValidatorContext constraintValidatorContext) {
        return fieldRepeat(o,fieldRepeatValidators);
    }

    public static boolean fieldRepeat(Object object, FieldRepeatValidators fieldRepeatValidators) {
        JSONObject jsonObject = JSONUtil.parseObj(object);
        String table = fieldRepeatValidators.tableName();
        boolean isUpdate;
        String idField = fieldRepeatValidators.idField();
        String idProperty = fieldRepeatValidators.idProperty();
        isUpdate = jsonObject.containsKey(idProperty);
        Object id = jsonObject.get(idProperty);
        HashMap errors = new HashMap<>();
        for(FieldRepeatValidator fieldRepeatValidator : fieldRepeatValidators.fieldRepeatValidators()){
            String field = fieldRepeatValidator.field();
            String property = fieldRepeatValidator.property();
            String message = fieldRepeatValidator.message();
            Object o = jsonObject.get(property);
            if(Objects.isNull(o)){
                continue;
            }
    
            String sql = StrUtil.format("select count(1) from {} where {} = '{}'",table,field,o);
            if(isUpdate){
                sql = StrUtil.format(sql + " and {} = {}",idField,id);
            }
            JdbcTemplate jdbcTemplate = application.getBean("jdbcTemplate", JdbcTemplate.class);
             Map map = jdbcTemplate.queryForMap(sql);
            if(!map.get("count").equals(0L)){
                errors.put(property,message);
            }
        }
        if(errors.size() != 0){
            throw new FieldRepeatException(errors);
        }
        return true;
    }
}

@Data
public class FieldRepeatException extends ConstraintDeclarationException {

    
    private HashMap errors;
    
    public FieldRepeatException(HashMap errors) {
        this.errors = errors;
    }
}

@RestControllerAdvice()
@Slf4j
public class GlobalControllerExceptionHandler {
    
    @ExceptionHandler(FieldRepeatException.class)
    private R fieldRepeatExceptionHandler(FieldRepeatException e) {
        return R.error("40001","数据检验失败").put("error",e.getErrors()));
    }
}

@Data
@EqualsAndHashCode(callSuper = true)
@ApiModel(value = "User对象", description = "用户表")
@TableName("user")
@FieldRepeatValidators(tableName = "user",idField = "id",fieldRepeatValidators = {
        @FieldRepeatValidator(field = "user_name", property = "userName",message = "用户名重复！"),
        @FieldRepeatValidator(field = "mobile", property = "mobile",message = "电话号码重复！")
})
public class User extends Model {
    
    @TableId(value = "id", type = IdType.AUTO)
    private Integer id;
      
    @ApiModelProperty(value = "用户名")
    private String userName;
    
      
    @ApiModelProperty(value = "电话")
    private String mobile;
    
}

@PostMapping("/save")
@ApiOperation(value = "新增", notes = "传入user")
public R save(@RequestBody @Validated User user) {
    // 增加@Validated注解
   return R.data(userService.save(user));
}

{
    "code":40001,
    "message":"数据检验失败",
    "errors":{
        "userName":"用户名重复！",
        "mobile":"电话号码重复！"    
    }
}

问题：
检验完成，抛出自定义异常会出现: unexpected exception during isValid call
原因：
自定义异常由于继承的是RunTimeException，导致在检验处理类执行isValid()方法时没有正常返回值，而抛出了javax.validation.ValidationException。导致自定义异常无法被全局异常处理类捕获。
解决方法：
自定义异常需要继承ConstraintDeclarationException

public class FieldRepeatException extends ConstraintDeclarationException{}

问题：
javax.validation.ConstraintDefinitionException: HV000074:containsbut does not contain a message parameter
原因：
自定义检验字段注解缺少message参数
解决方法：
添加message参数等

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = FieldRepeatValidatorHandler.class)
public @interface FieldRepeatValidators {
    
    String message() default "";
    Class[] groups() default { };
    Class[] payload() default { };

}

问题：
自定义检验字段注解添加在字段上，只能拿到该字段的当前值。这样的话就不能获取到其他字段的值，其中最重要的是id字段的值。id字段值的作用是判断此次请求是新增还是修改，如果是新增，则只需要判断数据库中是否含有该字段值的记录。如果是修改，则需要判断除了自身id记录外是否还含有该字段值的记录。
解决方法：
自定义检验字段注解在类上，则可以获取到全部字段的值。再通过注解逐一对有需要做重复检验的字段进行检验，返回检验结果。

@FieldRepeatValidators(tableName = "user",idField = "id",fieldRepeatValidators = {
        @FieldRepeatValidator(field = "user_name", property = "userName",message = "用户名重复！"),
        @FieldRepeatValidator(field = "mobile", property = "mobile",message = "电话号码重复！")
})
public class User extends Model {
    
}

https://blog.csdn.net/weixin_44912855/article/details/122720171
https://juejin.cn/post/6844903950768930830#heading-14