问题

问题很简单，但我还没有找到解决方法：

我有这个：

@RequestMapping("/example")
public class ExampleController {
    @GetMapping("get")
    public List<WhateverObject> getWhateverObjects(@RequestParam String objectName) {
        
        /* 代码 */
    }
}

我们正在使用Spring Boot，我想要验证"objectName"是否与一组预定义的值匹配（这组值在枚举类型中，但该部分容易更改，所以如果需要手动写下这些值，我也不介意）。关于验证@RequestParam对象，我所看到的只涵盖了基本的内容（@Min(value)、@NotNull等等）。

我知道可以为bean使用CustomValidators，但它不适用于我当前的问题（而且我不能更改参数的类型）。Spring是否有针对此自定义验证的特定功能，还是我需要在/* 代码 */部分直接进行验证？

英文:

Question is easy, but I haven't found a solution for this:

I got this:

@RequestMapping(&quot;/example&quot;)
public class ExampleController {
	@GetMapping(&quot;get&quot;)
    public List&lt;WhateverObject&gt; getWhateverObjects(@RequestParam String objectName) {
		
		/* Code */
    }
}

We are using SpringBoot, and I'm looking to validate "objectName" against a defined list of values (This list is in an enum type, but that part is prone to change, so I wont mind if I need to write the values down by hand). All I've seen regarding validation of @RequestParam objects covers just basic stuff (@Min(value), @NotNull and all that.

I know about CustomValidators for beans, but it does not applies to my current problematic (And I can't change the type of parameter). Does Spring has something specific for this custom validation or do I need to make the validation "directly" in the /* Code */ section?

答案1

得分: 4

你可以创建自己的`ConstraintValidator`，然而你并没有说明你是否需要将你的值与`Enum`的值或其内部属性进行比较。我将在下面的几个部分分别提供这两种情况的示例。
----------
## 与枚举值比较 ##
正如 **greenPadawan** 提到的，你可以通过你的`Enum`来改变参数的类型，如果你能够/只需要这样做，那是最好的选择。
下面的示例将解释如何自定义在这种情况下使用的约束，如果你想保持`String`（甚至在更新它以包含更多/其他检查时），第一步是创建你将用于检查约束的注解：
    /**
     * 被注解的元素必须包含在给定的{@link Enum}的接受值中。
     */
    @Documented
    @Retention(RUNTIME)
    @Target({FIELD, ANNOTATION_TYPE, PARAMETER})
    @Constraint(validatedBy = EnumHasValueValidator.class)
    public @interface EnumHasValue {
      String message() default "必须是以下值之一：{values}";
      Class<?>[] groups() default {};
      Class<? extends Payload>[] payload() default {};
      /**
       * @return 用于检查值的{@link Enum}的{@link Class}
       */
      Class<? extends Enum> enumClass();
      /**
       * @return 如果接受{@code null}作为有效值则返回{@code true}，否则返回{@code false}。
       */
      boolean isNullAccepted() default false;
    }
第二步是创建验证器本身：
    /**
     * 验证给定的{@link String}是否与所提供的{@link Enum}的值匹配
     */
    public class EnumHasValueValidator implements ConstraintValidator<EnumHasValue, String> {
      private static final String ERROR_MESSAGE_PARAMETER = "values";
      List<String> enumValidValues;
      String constraintTemplate;
      private boolean isNullAccepted;
      @Override
      public void initialize(final EnumHasValue hasValue) {
        enumValidValues = Arrays.stream(hasValue.enumClass().getEnumConstants())
                                .map(Enum::name)
                                .collect(Collectors.toList());
        constraintTemplate = hasValue.message();
        isNullAccepted = hasValue.isNullAccepted();
      }
      @Override
      public boolean isValid(String value, ConstraintValidatorContext context) {
        boolean isValid = null == value ? isNullAccepted
                                        : enumValidValues.contains(value);
        if (!isValid) {
          HibernateConstraintValidatorContext hibernateContext = context.unwrap(HibernateConstraintValidatorContext.class);
          hibernateContext.disableDefaultConstraintViolation();
          hibernateContext.addMessageParameter(ERROR_MESSAGE_PARAMETER, enumValidValues)
                          .buildConstraintViolationWithTemplate(constraintTemplate)
                          .addConstraintViolation();
        }
        return isValid;
      }
    }
现在你可以在以下示例中使用它：
    public enum IngredientEnum {
      CHEESE,
      HAM,
      ONION,
      PINEAPPLE,
      BACON,
      MOZZARELLA
    }
以及控制器：
    @AllArgsConstructor
    @RestController
    @RequestMapping("/test")
    @Validated
    public class TestController {
      @GetMapping("/testAgainstEnum")
      public List<WhateverObject> testAgainstEnum(@RequestParam @EnumHasValue(enumClass=IngredientEnum.class) String objectName) {
        ...
      }
    }
你可以在下面的图片中看到一个示例：
[![EnumHasValue示例][1]][1]
（*如你所见，在这种情况下，大小写是被考虑在内的，如果你愿意，你可以在验证器中进行更改*）
----------
## 与枚举内部属性比较 ##
在这种情况下，第一步是定义一种提取这种内部属性的方法：
    /**
     * 用于获取{@link Enum}中的内部属性的值。
     */
    public interface IEnumInternalPropertyValue<T> {
      /**
       * 获取包含在{@link Enum}中的内部属性的值。
       */
      T getInternalPropertyValue();
    }
    public enum PizzaEnum implements IEnumInternalPropertyValue<String> {
      MARGUERITA("Margherita"),
      CARBONARA("Carbonara");
      private String internalValue;
      PizzaEnum(String internalValue) {
        this.internalValue = internalValue;
      }
      @Override
      public String getInternalPropertyValue() {
        return this.internalValue;
      }
    }
所需的注解和相关的验证器与之前的类似：
    /**
     * 被注解的元素必须包含在给定的接受{@link Class}的{@link Enum}的内部{@link String}属性中。
     */
    @Documented
    @Retention(RUNTIME)
    @Target({FIELD, ANNOTATION_TYPE, PARAMETER})
    @Constraint(validatedBy = EnumHasInternalStringValueValidator.class)
    public @interface EnumHasInternalStringValue {
      String message() default "必须是以下值之一：{values}";
      Class<?>[] groups() default {};
      Class<? extends Payload>[] payload() default {};
      /**
       * @return 用于检查值的{@link Enum}的{@link Class}
       */
      Class<? extends Enum<? extends IEnumInternalPropertyValue<String>>> enumClass();
      /**
       * @return 如果接受{@code null}作为有效值则返回{@code true}，否则返回{@code false}。
       */
      boolean isNullAccepted() default false;
    }
验证器：
    /**
     * 验证给定的{@link String}是否与所提供的{@link Enum}的内部{@link String}属性之一匹配
     */
    public class EnumHasInternalStringValueValidator implements ConstraintValidator<EnumHasInternalStringValue, String> {
      private static final String ERROR_MESSAGE_PARAMETER = "values";
      List<String> enumValidValues;
      String constraintTemplate;
      private boolean isNullAccepted;
      @Override
      public void initialize(final EnumHasInternalStringValue hasInternalStringValue) {
        enumValidValues = Arrays.stream(hasInternalStringValue.enumClass().getEnumConstants())
                                .map(e -> ((IEnumInternalPropertyValue<String>)e).getInternalPropertyValue())
                                .collect(Collectors.toList());
        constraintTemplate = hasInternalStringValue.message();
        isNullAccepted = hasInternalStringValue.isNullAccepted();
      }
      @Override
      public boolean isValid(String value, ConstraintValidatorContext context) {
        boolean isValid = null == value ? isNullAccepted
                                        : enumValidValues.contains(value);
        if (!isValid) {
          HibernateConstraintValidatorContext hibernateContext = context.unwrap(HibernateConstraintValidatorContext.class);
          hibernateContext.disableDefaultConstraintViolation();
          hibernateContext.addMessageParameter(ERROR_MESSAGE_PARAMETER, enumValidValues)
<details>
<summary>英文:</summary>
You can create your own `ConstraintValidator`, however you don&#39;t say if you need to compare your value against the values of an `Enum` or with an internal property inside it. I will include an example of both cases in the next sections.
----------
## Compare against enum values ##
As **greenPadawan** mentioned, you can change the type of parameter by your `Enum`, if you can/only need it, that is the best option. 
The following example explains you how to customize that use case if you want to keep the `String` (even updating it to include more/other checks if you want). The first step is create the annotation you will use to check the constraint:
    /**
     * The annotated element must be included in value of the given accepted {@link Class} of {@link Enum}.
     */
    @Documented
    @Retention(RUNTIME)
    @Target({FIELD, ANNOTATION_TYPE, PARAMETER})
    @Constraint(validatedBy = EnumHasValueValidator.class)
    public @interface EnumHasValue {
	  String message() default &quot;must be one of the values included in {values}&quot;;
	  Class&lt;?&gt;[] groups() default {};
	  Class&lt;? extends Payload&gt;[] payload() default {};
	  /**
	   * @return {@link Class} of {@link Enum} used to check the value
	   */
	  Class&lt;? extends Enum&gt; enumClass();
	  /**
	   * @return {@code true} if {@code null} is accepted as a valid value, {@code false} otherwise.
	   */
	  boolean isNullAccepted() default false;
    }
The second is create your validator itself:
    /**
     *    Validates if the given {@link String} matches with one of the values belonging to the
     * provided {@link Class} of {@link Enum}
     */
    public class EnumHasValueValidator implements ConstraintValidator&lt;EnumHasValue, String&gt; {
	  private static final String ERROR_MESSAGE_PARAMETER = &quot;values&quot;;
	  List&lt;String&gt; enumValidValues;
	  String constraintTemplate;
	  private boolean isNullAccepted;
	  @Override
      public void initialize(final EnumHasValue hasValue) {
		enumValidValues = Arrays.stream(hasValue.enumClass().getEnumConstants())
				                .map(Enum::name)
				                .collect(Collectors.toList());
		constraintTemplate = hasValue.message();
		isNullAccepted = hasValue.isNullAccepted();
      }
	  @Override
	  public boolean isValid(String value, ConstraintValidatorContext context) {
		boolean isValid = null == value ? isNullAccepted
				                        : enumValidValues.contains(value);
		if (!isValid) {
			HibernateConstraintValidatorContext hibernateContext = context.unwrap(HibernateConstraintValidatorContext.class);
			hibernateContext.disableDefaultConstraintViolation();
			hibernateContext.addMessageParameter(ERROR_MESSAGE_PARAMETER, enumValidValues)
					        .buildConstraintViolationWithTemplate(constraintTemplate)
					        .addConstraintViolation();
		}
		return isValid;
	  }
    }
Now you can use it in the following example:
    public enum IngredientEnum {
      CHEESE,
      HAM,
      ONION,
      PINEAPPLE,
      BACON,
      MOZZARELLA
    }
And the controller:
    @AllArgsConstructor
    @RestController
    @RequestMapping(&quot;/test&quot;)
    @Validated
    public class TestController {
      @GetMapping(&quot;/testAgainstEnum&quot;)
      public List&lt;WhateverObject&gt; testAgainstEnum(@RequestParam @EnumHasValue(enumClass=IngredientEnum.class) String objectName) {
        ...
      }
    }
You can see an example in the following picture: 
[![EnumHasValue example][1]][1]
(*As you can see, in this case, lower/upper case are taking into account, you can change it in the validator if you want*)
----------
## Compare against internal enum property ##
In this case, the first step is define a way to extract such internal property:
    /**
     * Used to get the value of an internal property in an {@link Enum}.
     */
    public interface IEnumInternalPropertyValue&lt;T&gt; {
      /**
       * Get the value of an internal property included in the {@link Enum}.
       */
      T getInternalPropertyValue();
    }
    public enum PizzaEnum implements IEnumInternalPropertyValue&lt;String&gt; {
      MARGUERITA(&quot;Margherita&quot;),
      CARBONARA(&quot;Carbonara&quot;);
      private String internalValue;
      PizzaEnum(String internalValue) {
        this.internalValue = internalValue;
      }
      @Override
      public String getInternalPropertyValue() {
        return this.internalValue;
      }
    }
The required annotation and related validator are quite similar to the previous ones:
    /**
     *    The annotated element must be included in an internal {@link String} property of the given accepted
     * {@link Class} of {@link Enum}.
     */
    @Documented
    @Retention(RUNTIME)
    @Target({FIELD, ANNOTATION_TYPE, PARAMETER})
    @Constraint(validatedBy = EnumHasInternalStringValueValidator.class)
    public @interface EnumHasInternalStringValue {
	  String message() default &quot;must be one of the values included in {values}&quot;;
	  Class&lt;?&gt;[] groups() default {};
	  Class&lt;? extends Payload&gt;[] payload() default {};
	  /**
	   * @return {@link Class} of {@link Enum} used to check the value
	   */
	  Class&lt;? extends Enum&lt;? extends IEnumInternalPropertyValue&lt;String&gt;&gt;&gt; enumClass();
	  /**
	   * @return {@code true} if {@code null} is accepted as a valid value, {@code false} otherwise.
	   */
	  boolean isNullAccepted() default false;
    }
Validator:
    /**
     *    Validates if the given {@link String} matches with one of the internal {@link String} property belonging to the
     * provided {@link Class} of {@link Enum}
     */
    public class EnumHasInternalStringValueValidator implements ConstraintValidator&lt;EnumHasInternalStringValue, String&gt; {
	  private static final String ERROR_MESSAGE_PARAMETER = &quot;values&quot;;
	  List&lt;String&gt; enumValidValues;
	  String constraintTemplate;
	  private boolean isNullAccepted;
	  @Override
      public void initialize(final EnumHasInternalStringValue hasInternalStringValue) {
		enumValidValues = Arrays.stream(hasInternalStringValue.enumClass().getEnumConstants())
				                .map(e -&gt; ((IEnumInternalPropertyValue&lt;String&gt;)e).getInternalPropertyValue())
				                .collect(Collectors.toList());
		constraintTemplate = hasInternalStringValue.message();
		isNullAccepted = hasInternalStringValue.isNullAccepted();
      }
	  @Override
	  public boolean isValid(String value, ConstraintValidatorContext context) {
		boolean isValid = null == value ? isNullAccepted
				                        : enumValidValues.contains(value);
		if (!isValid) {
			HibernateConstraintValidatorContext hibernateContext = context.unwrap(HibernateConstraintValidatorContext.class);
			hibernateContext.disableDefaultConstraintViolation();
			hibernateContext.addMessageParameter(ERROR_MESSAGE_PARAMETER, enumValidValues)
					        .buildConstraintViolationWithTemplate(constraintTemplate)
					        .addConstraintViolation();
		}
		return isValid;
	  }
    }
And the controller:
    @AllArgsConstructor
    @RestController
    @RequestMapping(&quot;/test&quot;)
    @Validated
    public class TestController {
      @GetMapping(&quot;/testStringInsideEnum&quot;)
      public List&lt;WhateverObject&gt; testStringInsideEnum(@RequestParam @EnumHasInternalStringValue(enumClass=PizzaEnum.class) String objectName) {
        ...
      }
    }
You can see an example in the following picture: 
[![EnumHasValue example][2]][2]
The source code of the last annotation and validator can be found [here][3]
  [1]: https://i.stack.imgur.com/S3s3U.png
  [2]: https://i.stack.imgur.com/YR9rv.png
  [3]: https://github.com/doctore/Spring5Microservices/tree/master/common/src/main/java/com/spring5microservices/common/validator
</details>
# 答案2
**得分**: 2
你可以将枚举用作参数的类型，而不是使用 `String`。
<details>
<summary>英文:</summary>
You can use your enum as the type of your parameter instead of `String`
</details>

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