org.springframework.boot.autoconfigure.condition.OnExpressionCondition.java Source code

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Here is the source code for org.springframework.boot.autoconfigure.condition.OnExpressionCondition.java

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/*
 * Copyright 2012-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.autoconfigure.condition;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.config.BeanExpressionContext;
import org.springframework.beans.factory.config.BeanExpressionResolver;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.expression.StandardBeanExpressionResolver;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.core.type.ClassMetadata;

/**
 * A Condition that evaluates a SpEL expression.
 * 
 * @author Dave Syer
 * @see ConditionalOnExpression
 */
public class OnExpressionCondition implements Condition {

    private static Log logger = LogFactory.getLog(OnExpressionCondition.class);

    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {

        String checking = ConditionLogUtils.getPrefix(logger, metadata);

        String value = (String) metadata.getAnnotationAttributes(ConditionalOnExpression.class.getName())
                .get("value");
        if (!value.startsWith("#{")) {
            // For convenience allow user to provide bare expression with no #{} wrapper
            value = "#{" + value + "}";
        }
        if (logger.isDebugEnabled()) {
            StringBuilder builder = new StringBuilder(checking).append("Evaluating expression");
            if (metadata instanceof ClassMetadata) {
                builder.append(" on " + ((ClassMetadata) metadata).getClassName());
            }
            builder.append(": " + value);
            logger.debug(builder.toString());
        }
        // Explicitly allow environment placeholders inside the expression
        value = context.getEnvironment().resolvePlaceholders(value);
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        BeanExpressionResolver resolver = beanFactory.getBeanExpressionResolver();
        BeanExpressionContext expressionContext = (beanFactory != null)
                ? new BeanExpressionContext(beanFactory, null)
                : null;
        if (resolver == null) {
            resolver = new StandardBeanExpressionResolver();
        }
        boolean result = (Boolean) resolver.evaluate(value, expressionContext);
        if (logger.isDebugEnabled()) {
            logger.debug(checking + "Finished matching and result is matches=" + result);
        }
        return result;
    }

}