// 典型錯(cuò)誤示范（轉(zhuǎn)載自某小廠祖?zhèn)鞔a）
public String register(UserDTO user) {
    if (user.getName() == null) {
        return"名字不能為空";
    }
    if (user.getAge() == null) {
        return"年齡不能為空";
    }
    if (user.getAge() < 18) {
        return"年齡不能小于18歲";
    }
    if (!user.getPhone().matches("^1[3-9]\\d{9}$")) {
        return"手機(jī)號(hào)不合法";
    }
    // ...后續(xù)還有20個(gè)if...
}

public class UserDTO {
    @NotBlank(message = "名稱要填，皮這一下很開心？")
    private String name;

    @NotNull
    @Min(value = 18, message = "未成年禁止入內(nèi)")
    @Max(60)
    private Integer age;

    @Pattern(regexp = "^1[3-9]\\d{9}$", message = "這手機(jī)號(hào)是哪國(guó)來(lái)的？")
    private String phone;
}

// Controller層啟用校驗(yàn)（新手必知第一步）
@PostMapping("/register")
public Result register(@Valid @RequestBody UserDTO user) {
    // 業(yè)務(wù)代碼...
}

@RestControllerAdvice
publicclass GlobalExceptionHandler {
    
    // 專治各種不服校驗(yàn)
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public Result handleValidException(MethodArgumentNotValidException e) {
        BindingResult result = e.getBindingResult();
        return Result.fail(result.getFieldError().getDefaultMessage());
    }
}

// 返回格式規(guī)范（示例）
publicclass Result<T> {
    private Integer code;
    private String msg;
    private T data;
    
    publicstatic <T> Result<T> fail(String message) {
        returnnew Result<>(500, message, null);
    }
}

@Target({FIELD, PARAMETER})
@Retention(RUNTIME)
@Constraint(validatedBy = ContactValidator.class)
public @interface Contact {
    String message() default "聯(lián)系方式格式錯(cuò)誤";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

// 校驗(yàn)邏輯實(shí)現(xiàn)（不要相信前端的下拉框?。?publicclass ContactValidator implements ConstraintValidator<Contact, String> {
    
    privatestaticfinal Pattern PHONE_PATTERN = Pattern.compile("^1[3-9]\\d{9}$");
    privatestaticfinal Pattern EMAIL_PATTERN = Pattern.compile("^\\w+@\\w+\\.\\w+$");

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        return PHONE_PATTERN.matcher(value).matches() 
               || EMAIL_PATTERN.matcher(value).matches();
    }
}

// 定義校驗(yàn)組別（劃分陣營(yíng)）
publicinterface CreateGroup {}
publicinterface UpdateGroup {}

// DTO根據(jù)場(chǎng)景應(yīng)用分組
publicclass ProductDTO {
    @Null(groups = UpdateGroup.class)
    @NotNull(groups = CreateGroup.class)
    private Long id;

    @NotBlank(groups = {CreateGroup.class, UpdateGroup.class})
    private String name;
}

// 控制層按需激活校驗(yàn)組  
@PostMapping("/create")
public Result create(@Validated(CreateGroup.class) @RequestBody ProductDTO dto) {
    // 創(chuàng)建邏輯
}

@Target(TYPE)
@Retention(RUNTIME)
@Constraint(validatedBy = PasswordValidator.class)
public @interface PasswordValid {
    String message() default "兩次密碼不一致";
    // ...
}

publicclass PasswordValidator implements ConstraintValidator<PasswordValid, UserDTO> {
    
    @Override
    public boolean isValid(UserDTO user, ConstraintValidatorContext context) {
        return user.getPassword().equals(user.getConfirmPassword());
    }
}

// 應(yīng)用到類級(jí)別
@PasswordValid
publicclass UserDTO {
    private String password;
    private String confirmPassword;
}

// 天機(jī)規(guī)則文件（credit_rule.drl）
rule "白領(lǐng)貸基礎(chǔ)校驗(yàn)"
    when
        $req : LoanRequest(
            occupation == "白領(lǐng)", 
            salary > 10000, 
            age >= 25 && age <= 45
        )
    then
        $req.setRiskScore(-10); //加分項(xiàng)
end

rule "高危行業(yè)攔截"
    when
        $req : LoanRequest(
            industry in ("賭博業(yè)", "傳銷"), 
            location.contains("緬甸")
        )
    then
        throw new ValidationException("閣下莫非是緬北戰(zhàn)神？"); 
end

@Configuration
publicclass DroolsConfig {
    
    @Bean
    public KieContainer kieContainer() {
        KieServices ks = KieServices.Factory.get();
        KieFileSystem kfs = ks.newKieFileSystem();
        
        // 加載天機(jī)卷軸（規(guī)則文件）
        Resource resource = new ClassPathResource("rules/credit_rule.drl");
        kfs.write(ks.getResources().newInputStreamResource(resource.getInputStream())
                    .setTargetPath("credit_rule.drl"));
        
        KieBuilder kieBuilder = ks.newKieBuilder(kfs).buildAll();
        return ks.newKieContainer(kieBuilder.getKieModule().getReleaseId());
    }
}

// Controller層調(diào)用天尊之力
@PostMapping("/apply")
public Result applyLoan(@RequestBody LoanRequest request) {
    kieSession.insert(request);
    kieSession.fireAllRules(); // 執(zhí)行天機(jī)推演
    return riskService.process(request);
}

rule "特殊時(shí)段放水"
    when
        $req : LoanRequest(hour > 2 && hour < 5)
    then
        $req.setCreditLimit(50000); //給值夜班的兄弟開后門
end