接口参数校验(不使用hibernate-validator，规避大量if else)

引言

编写接口时，常用的参数校验使用hibernate-validator注解+@Validated注解进行参数校验。当遇到一些特殊场景或需求，需要自己对参数进行手动校验时，会出现以下问题：

不可避免的需要对接受的参数进行判断，此时便会出现大量if…else…影响代码可读性，且校验不够优雅。

本文给出一个参数校验方案，给大家一个思路。如果只是想使用，基本校验的已足够。

使用举例

具体项目中是如何使用的，可以参考博客中我正在开发的U-Learning后端开发日志，其中有GitHub项目地址

Before1

@PostMapping("/save")
public ResponseEntity<JsonResult> save(TeacherDto teacher) {
    if(StringUtil.isEmpty(teacher.getTeaName())){
        return ...;
    }
    if(StringUtil.isEmpty(teacher.getTeaNumber())){
        return ...;
    }
    if(StringUtil.isEmpty(teacher.getTeaEmail())){
        return ...;
    }

    //接口处理业务代码
    ...
}

After1

@PostMapping("/save")
public ResponseEntity<JsonResult> save(TeacherDto teacher) {
    ValidatorBuilder.build()
        .on(StringUtil.isEmpty(teacher.getTeaName()), SystemErrorCodeEnum.NAME_CANNOT_BE_NULL)
        .on(StringUtil.isEmpty(teacher.getTeaNumber()), SystemErrorCodeEnum.TEA_NUMBER_CANNOT_BE_NULL)
        .on(StringUtil.isEmpty(teacher.getTeaEmail()), SystemErrorCodeEnum.EMAIL_CANNOT_BE_NULL)
        .doValidate().checkResult();

    //接口处理业务代码
    ...
}

Beafore2

当你只有一个需要校验的参数时，可能会觉得这有些啰嗦

@GetMapping("/delete")
public ResponseEntity<JsonResult> delete(Long id) {
    if(StringUtil.isEmpty(id)){
        return ...;
    }
    //接口处理业务代码
    ...
}

After2

@GetMapping("/delete")
public ResponseEntity<JsonResult> delete(Long id) {
    ValidateHandler.checkParameter(StringUtil.isEmpty(id), SystemErrorCodeEnum.ID_CANNOT_BE_NULL);
    //接口处理业务代码
    ...
}

知识点

涉及到的知识点

1. 建造者模式
2. 链式调用
3. 枚举
4. 异常
5. 继承与多态

拓展所需知识点

1. 委托模式

使用前准备

自定义异常

public class BaseException extends RuntimeException {
    private Integer status = HttpStatus.BAD_REQUEST.value();

    public BaseException(Integer status) {
        this.status = status;
    }

    public BaseException(BaseEnum baseEnum) {
        super(baseEnum.getMessage());
        this.status = baseEnum.getCode();
    }

    public BaseException(String message) {
        super(message);
    }

    public BaseException(String message, Throwable cause) {
        super(message, cause);
    }

    public BaseException(Throwable cause) {
        super(cause);
    }

    public BaseException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }

    public Integer getStatus() {
        return status;
    }
}

举个栗子

@Getter
public class BadRequestException extends BaseException {

    public BadRequestException(String msg) {
        super(msg);
    }

    public BadRequestException(BaseEnum baseEnum) {
        super(baseEnum);
    }
}

统一异常管理

@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {

    /**
     * 处理系统自定义异常
     */
    @ExceptionHandler(BaseException.class)
    public ResponseEntity handleBaseException(BaseException e) {
        String message = StringUtil.isContainChinese(e.getMessage()) ? e.getMessage() : null;
        return ResponseEntityUtil.badRequest(JsonResult.buildErrorMsg(e.getStatus(),
                Optional.ofNullable(message).orElse(MicroErrorCodeEnum.OPERATE_ERROR.getMessage())));
    }

    /**
     * Throwable
     * 接收非系统预测内的异常
     */
    @ExceptionHandler(Throwable.class)
    public ResponseEntity handleThrowable(Throwable e) {
        log.error("系统捕捉Throwable异常并处理 ==> " + e.getMessage(), e);
        String message = StringUtil.isContainChinese(e.getMessage()) ? e.getMessage() : null;
        return ResponseEntityUtil.internalServerError(JsonResult.buildErrorMsg(HttpStatus.INTERNAL_SERVER_ERROR.value(),
                Optional.ofNullable(message).orElse(MicroErrorCodeEnum.SYSTEM_ERROR.getMessage())));
    }
}

自定义枚举

基础枚举接口

public interface BaseEnum {

    Integer getCode();

    String getMessage();
}

举个栗子(根据自己需求创建)

public enum SystemErrorCodeEnum implements BaseEnum {

    /**
     * 后台管理系统错误状态码
     */
    PARAMETER_EMPTY(HttpStatus.BAD_REQUEST, "参数不可为空!"),
    TEACHER_NOT_EXISTS(HttpStatus.BAD_REQUEST, "教师不存在!"),
    ID_CANNOT_BE_NULL(HttpStatus.BAD_REQUEST, "ID不可为空!"),
    EMAIL_CANNOT_BE_NULL(HttpStatus.BAD_REQUEST, "邮箱不可为空!"),
    ;

    private Integer code;
    private String message;

    SystemErrorCodeEnum(HttpStatus httpStatus, String message) {
        this.code = httpStatus.value();
        this.message = message;
    }

    @Override
    public Integer getCode() {
        return code;
    }

    @Override
    public String getMessage() {
        return message;
    }
}

Validate核心代码

校验类context

@Data
@AllArgsConstructor
public class ValidatorContext {

    /** 校验结果 */
    private Boolean checkResult;

    /** 错误信息枚举 */
    private BaseEnum baseEnum;

}

校验类上下文

public class ValidatorHolder {

    /** context集合 */
    private List<ValidatorContext> validatorContexts;

    /** 校验结果 */
    private Boolean result;

    /** 若result = true，保存错误信息 */
    private BaseEnum baseEnum;

    /** 初始化 */
    public ValidatorHolder() {
        this.validatorContexts = new ArrayList<>();
        this.result = true;
        this.baseEnum = null;
    }

    /** 校验链 */
    public ValidatorHolder on(Boolean checkResult, BaseEnum baseEnum){
        if(checkResult != null && baseEnum != null){
            addContext(checkResult, baseEnum);
        }
        return this;
    }

    /** 添加待校验属性和错误信息 */
    private void addContext(Boolean checkResult, BaseEnum baseEnum){
        validatorContexts.add(new ValidatorContext(checkResult, baseEnum));
    }

    /** 校验 */
    public ValidatorHolder doValidate(){
        for (ValidatorContext validatorContext : validatorContexts) {
            if(validatorContext.getCheckResult()){
                result = false;
                baseEnum = validatorContext.getBaseEnum();
                break;
            }
        }
        return this;
    }

    public void checkResult(){
        ValidateHandler.checkValidator(this);
    }

    public Boolean getResult() {
        return result;
    }

    public BaseEnum getBaseEnum() {
        return baseEnum;
    }
}

校验builder类

public class ValidatorBuilder {

    public static ValidatorHolder build(){
        return new ValidatorHolder();
    }
}

校验处理器

参考Guava类库中提供的一个作参数检查的工具类--Preconditions类

public class ValidateHandler {

    /**
     * 判断校验是否成功，若存在错误，抛出异常
     * 针对ValidatorHolder
     */
    public static void checkValidator(ValidatorHolder validator){
        if(! validator.getResult()){
            throw new BadRequestException(validator.getBaseEnum());
        }
    }

    /**
     * 针对单参数校验
     *
     * @param checkResult true:参数错误; false:参数正确
     * @param baseEnum 错误码
     */
    public static void checkParameter(Boolean checkResult, BaseEnum baseEnum){
        if(checkResult){
            throw new BadRequestException(baseEnum);
        }
    }
}