「时光不负，创作不停，本文正在参加2022年中总结征文大赛」
一、业务场景？
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。
二、实现步骤
1.引入依赖
代码如下（示例）：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
<version>2.3.11.RELEASE</version>
</dependency>
2.新增自定义注解(注解嵌套)
@FieldRepeatValidators
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = FieldRepeatValidatorHandler.class)
public @interface FieldRepeatValidators {
/**
* 数据表名
* @return
*/
String tableName();
/**
* 数据表id字段名
* @return
*/
String idField() default "id";
/**
* id字段的属性名称
* @return
*/
String idProperty() default "id";
FieldRepeatValidator[] fieldRepeatValidators();
String message() default "";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
@FieldRepeatValidator
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.PARAMETER, ElementType.FIELD, ElementType.TYPE})
public @interface FieldRepeatValidator {
/**
* 注解属性 - 对应校验字段,表字段
* @return
*/
String field();
/**
* 默认错误提示信息
* @return
*/
String message() default "字段内容重复！";
/**
*
* @return 实体类属性
*/
String property();
}
3. 自定义注解类处理器
public class FieldRepeatValidatorHandler implements ConstraintValidator<FieldRepeatValidators, Object>, 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<String, Object> 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) 'count' from {} where {} = '{}'",table,field,o);
if(isUpdate){
sql = StrUtil.format(sql + " and {} = {}",idField,id);
}
JdbcTemplate jdbcTemplate = application.getBean("jdbcTemplate", JdbcTemplate.class);
Map<String, Object> map = jdbcTemplate.queryForMap(sql);
if(!map.get("count").equals(0L)){
errors.put(property,message);
}
}
if(errors.size() != 0){
throw new FieldRepeatException(errors);
}
return true;
}
}
4. 自定义异常类
@Data
public class FieldRepeatException extends ConstraintDeclarationException {
/**
*
* @param cause
*/
private HashMap<String,Object> errors;
public FieldRepeatException(HashMap<String,Object> errors) {
this.errors = errors;
}
}
5. 全局异常捕获类
@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()));
}
}
6. 实体类上的注解
@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<User> {
@TableId(value = "id", type = IdType.AUTO)
private Integer id;
/**
* 用户名
*/
@ApiModelProperty(value = "用户名")
private String userName;
/**
* 电话
*/
@ApiModelProperty(value = "电话")
private String mobile;
}
7. Controller层
@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));
}
结果显示
{
"code":40001,
"message":"数据检验失败",
"errors":{
"userName":"用户名重复！",
"mobile":"电话号码重复！"
}
}
三、踩坑日记
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<? extends Payload>[] 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<User> {
}
