記錄一個使用Hibernate Validator驗證信息參數化遇到的問題

Hibernate Validator框架支持驗證信息的參數化。

以Length注解為例：

public class User
{
    private String name;

    @Length(message="{MSG_W00001}"，min=1,max=10)
    public String getName(){
    return name;
    }
}

配置信息如下所示：

<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
    <property name="basename" value="messages/message" />
    <property name="useCodeAsDefaultMessage" value="true" />
</bean>
    
<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
    <property name="providerClass" value="org.hibernate.validator.HibernateValidator"/>
    <property name="validationMessageSource" ref="messageSource"/>
</bean>

MessageResource:

MSG_W00001 = length must be between {min} and {max}

當name不滿足Length驗證時，期待的驗證信息應該是：
length must be between 1 and 10
但實際上驗證信息卻是：
length must be between min and max

網上搜索一番也沒找到答案，只好自己動手解決問題。在Hibernate Validator(ver 4.3.2)默認是依賴ResourceBundleMessageInterpolator類來獲得最終的驗證信息，核心函數如下：

private String interpolateMessage(String message, Map<String, Object> annotationParameters, Locale locale) {
    LocalisedMessage localisedMessage = new LocalisedMessage( message, locale );
    String resolvedMessage = null;

    if ( cacheMessages ) {
        resolvedMessage = resolvedMessages.get( localisedMessage );
    }

    // if the message is not already in the cache we have to run 
    //step 1-3 of the message resolution 
    if ( resolvedMessage == null ) {
        ResourceBundle userResourceBundle = userResourceBundleLocator
                .getResourceBundle( locale );
        ResourceBundle defaultResourceBundle = defaultResourceBundleLocator
                .getResourceBundle( locale );

        String userBundleResolvedMessage;
        resolvedMessage = message;
        boolean evaluatedDefaultBundleOnce = false;
        do {
            // search the user bundle recursive (step1)
            userBundleResolvedMessage = replaceVariables(
                    resolvedMessage, userResourceBundle, locale, true
            );

            // exit condition - we have at least tried to validate 
            //against the default bundle and there was no
            // further replacements
            if ( evaluatedDefaultBundleOnce
                    && !hasReplacementTakenPlace( userBundleResolvedMessage, resolvedMessage ) ) {
                break;
            }

            // search the default bundle non recursive (step2)
            resolvedMessage = replaceVariables( userBundleResolvedMessage, 
                defaultResourceBundle, locale, false );
            evaluatedDefaultBundleOnce = true;
        } while ( true );
    }

    // cache resolved message
    if ( cacheMessages ) {
        String cachedResolvedMessage = 
            resolvedMessages.putIfAbsent( localisedMessage, resolvedMessage );
        if ( cachedResolvedMessage != null ) {
            resolvedMessage = cachedResolvedMessage;
        }
    }

    // resolve annotation attributes (step 4)
    resolvedMessage = replaceAnnotationAttributes( resolvedMessage, annotationParameters );

    // last but not least we have to take care of escaped literals
    resolvedMessage = resolvedMessage.replace( "\\{", "{" );
    resolvedMessage = resolvedMessage.replace( "\\}", "}" );
    resolvedMessage = resolvedMessage.replace( "\\\\", "\\" );
    return resolvedMessage;
}

可以看到step 4正是我們期待的把{min}和{max}替換成Length里min和max的處理，可是為什么不起作用呢？
理論上驗證信息應該經歷以下變化:
{MSG_W00001} -> length must be between {min} and {max} -> length must be between 1 and 10

可是通過調試卻發現在step 4處理前驗證信息變成了下面的樣子:
length must be between min and max
這說明step1-3的處理有問題。具體來看step1-3的處理主要通過replaceVariables和resolveParameter方法來實現：

private String replaceVariables(String message, ResourceBundle bundle, Locale locale, boolean recurse) {
    Matcher matcher = MESSAGE_PARAMETER_PATTERN.matcher( message );
    StringBuffer sb = new StringBuffer();
    String resolvedParameterValue;
    while ( matcher.find() ) {
        String parameter = matcher.group( 1 );
        resolvedParameterValue = resolveParameter(
                parameter, bundle, locale, recurse
        );

        matcher.appendReplacement( sb, Matcher.quoteReplacement( resolvedParameterValue ) );
    }
    matcher.appendTail( sb );
    return sb.toString();
}

private String resolveParameter(String parameterName, ResourceBundle bundle, Locale locale, boolean recurse) {
    String parameterValue;
    try {
        if ( bundle != null ) {
            parameterValue = bundle.getString( removeCurlyBrace( parameterName ) );
            if ( recurse ) {
                parameterValue = replaceVariables( parameterValue, bundle, locale, recurse );
            }
        }
        else {
            parameterValue = parameterName;
        }
    }
    catch ( MissingResourceException e ) {
        // return parameter itself
        parameterValue = parameterName;
    }
    return parameterValue;
}

resolveParameter方法里，recurse被設置為ture，所以會遞歸的查找和替換參數。
首先{MSG_W00001}把替換成length must be between {min} and {max}。
然后會繼續在MessageResource中查找min和max。根據resolveParameter方法如果找不到則會被替換。顯然我們
在MessageResource沒有定義min和max，但是問什么{min}和{max}會被替換成min和max呢？
問題出在<property name="useCodeAsDefaultMessage" value="true" />這個設置上，當找不到min和max對應的值時bundle.getString函數
返回了它的參數，而不是拋出MissingResourceException異常，導致{min}和{max}會被替換成min和max。
把配置修改成<property name="useCodeAsDefaultMessage" value="false" />，驗證信息就變成了我們所期待的"length must be between 1 and 10"。

 

至此這個問題就解決了。可是感覺Hibernate Validator在這個問題上處理有很問題，很難會讓人聯想到useCodeAsDefaultMessage這個設定會
對驗證信息的參數化造成影響。ResourceBundleMessageInterpolator應該不依賴於全局的useCodeAsDefaultMessage設定才更合理。