Java Bean验证:仅当属性不为空时才强制使用@Pattern [英] Java bean validation: Enforce a @Pattern only when the property is not blank

问题描述

我有一个表格，允许用户选择输入他们的邮政编码.我知道如何通过使用@Pattern约束和正则表达式来验证邮政编码的格式.但是，由于这是一个可选字段，因此我不希望格式为空.

I have a form that allows the user to optionally enter their zip code. I know how to validate the format of the zip code, by using a @Pattern constraint and regex. But as this is an optional field, I do not want the format validated if it is blank.

如果该字段为空白，如何告诉系统忽略@Pattern约束?这是一个可选字段，我只想验证它是否为空白.

How can I tell the system to ignore the @Pattern constraint if the field is blank? This is an optional field and I only want to validate it if it is not blank.

public class MyForm {
    String firstName;
    String lastName;

    @Pattern(regex = "^\d{5}(?:[-\s]\d{4})?$")
    String optionalZipCode;      // <- This is an optional field.
}

推荐答案

Hardy的解决方案确实有效，但我希望声明更清晰，因为正则表达式可能需要一段时间才能解密.因此，我最终基于@Pattern创建了自己的验证器@BlankOrPattern.

Hardy's solution does work, but I wanted the declaration to be clearer as regular expressions can take a while to decypher. So I ended up creating my own validator @BlankOrPattern based on @Pattern.

注释:BlankOrPattern.java

@Target( {ElementType.FIELD})
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = BlankOrPatternValidator.class)
public @interface BlankOrPattern {
    String regexp();
    Flag[] flags() default {};
    String message() default "{javax.validation.constraints.Pattern.message}";
    Class<?>[] groups() default { };
    Class<? extends Payload>[] payload() default {};
}

验证者:BlankOrPatternValidator.java

public class BlankOrPatternValidator implements ConstraintValidator<BlankOrPattern, String> {

    private Pattern pattern;

    public void initialize(BlankOrPattern parameters) {
        Flag flags[] = parameters.flags();
        int intFlag = 0;
        for (Flag flag : flags) {
            intFlag = intFlag | flag.getValue();
        }

        try {
            pattern = compile(parameters.regexp(), intFlag);
        } catch (PatternSyntaxException e) {
            throw new IllegalArgumentException("Invalid regular expression.", e);
        }
    }

    public boolean isValid(String value, ConstraintValidatorContext constraintValidatorContext) {
        if (value == null || value.length() == 0) {
            return true;
        }
        Matcher m = pattern.matcher(value);
        return m.matches();
    }
}

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