解析SpringBoot自定义参数校验注解

<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-validation</artifactId>
 </dependency>

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.*;
@Documented
@Retention(value = RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER})
@Constraint(validatedBy = OrderCountValidator.class)
public @interface OrderCountValid {
    String message() default "订单数量超出库存";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class OrderCountValidator implements ConstraintValidator<OrderCountValid , Integer> {
    //可以注入mapper、service进来
    @Autowired
    private OrderService orderService;
    @Override
    public boolean isValid(Integer buyCount, ConstraintValidatorContext context) {
        return orderService.OrderCountValid(buyCount);
    }
}

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class OrderCountValidator implements ConstraintValidator<OrderCountValid , Integer> {
    //可以注入mapper、service进来
    @Autowired
    private OrderService orderService;
    @Override
    public boolean isValid(Integer buyCount, ConstraintValidatorContext context) {
        return orderService.OrderCountValid(buyCount);
    }
}

@RestController
@RequestMapping(value = "/order")
public class OrderController {
    @PostMapping("/placeOrder")
    public String placeOrder(@RequestBody @Valid Order order){
        return "success";
    }
}

import org.springframework.stereotype.Component;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import javax.validation.ConstraintViolation;
import javax.validation.ConstraintViolationException;
import java.util.stream.Collectors;
@RestControllerAdvice
@Component
public class GlobalExceptionHandler {
    // 当直接校验具体参数时会出现javax.validation.ConstraintViolationException
    @ExceptionHandler(value = ConstraintViolationException.class)
    public String handleException1(ConstraintViolationException e) {
        // 拼接参数
        String errorMsg = e.getConstraintViolations().stream().map(ConstraintViolation::getMessage).collect(Collectors.joining(", "));
        return errorMsg;
    }
    // 当直接校验具体参数时会出现org.springframework.web.bind
    @ExceptionHandler(value = MethodArgumentNotValidException.class)
    public String handleException2(MethodArgumentNotValidException e) {
        BindingResult exceptions = e.getBindingResult();
        // 判断异常中是否有错误信息，如果存在就使用异常中的消息，否则使用默认消息
        if (exceptions.hasErrors()) {
            // 这里默认错误消息
            return exceptions.getFieldError().getDefaultMessage();
        }
        return "请求参数错误";
    }
}