org.springframework.statemachine.support.AbstractExpressionEvaluator.java Source code

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Here is the source code for org.springframework.statemachine.support.AbstractExpressionEvaluator.java

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/*
 * Copyright 2015 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
 *
 * https://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.statemachine.support;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.core.convert.ConversionService;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

/**
 * Base class providing common functionality for using Spring expression language.
 *
 * @author Mark Fisher
 * @author Dave Syer
 * @author Oleg Zhurakousky
 * @author Artem Bilan
 * @author Gary Russell
 * @author Janne Valkealahti
 *
 */
public abstract class AbstractExpressionEvaluator implements BeanFactoryAware, InitializingBean {

    private volatile StandardEvaluationContext evaluationContext;

    private final ExpressionParser expressionParser = new SpelExpressionParser();

    private final BeanFactoryTypeConverter typeConverter = new BeanFactoryTypeConverter();

    private volatile BeanFactory beanFactory;

    @Override
    public void setBeanFactory(final BeanFactory beanFactory) {
        if (beanFactory != null) {
            this.beanFactory = beanFactory;
            this.typeConverter.setBeanFactory(beanFactory);
            if (this.evaluationContext != null && this.evaluationContext.getBeanResolver() == null) {
                this.evaluationContext.setBeanResolver(new BeanFactoryResolver(beanFactory));
            }
        }
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        getEvaluationContext();
    }

    /**
     * Sets the conversion service.
     *
     * @param conversionService the new conversion service
     */
    public void setConversionService(ConversionService conversionService) {
        if (conversionService != null) {
            this.typeConverter.setConversionService(conversionService);
        }
    }

    /**
     * Gets the evaluation context.
     *
     * @return the evaluation context
     */
    protected StandardEvaluationContext getEvaluationContext() {
        return this.getEvaluationContext(true);
    }

    /**
     * Emits a WARN log if the beanFactory field is null, unless the argument is false.
     * @param beanFactoryRequired set to false to suppress the warning.
     * @return The evaluation context.
     */
    protected final StandardEvaluationContext getEvaluationContext(boolean beanFactoryRequired) {
        if (this.evaluationContext == null) {
            if (this.beanFactory == null && !beanFactoryRequired) {
                this.evaluationContext = ExpressionUtils.createStandardEvaluationContext();
            } else {
                this.evaluationContext = ExpressionUtils.createStandardEvaluationContext(this.beanFactory);
            }
            if (this.typeConverter != null) {
                this.evaluationContext.setTypeConverter(this.typeConverter);
            }
        }
        return this.evaluationContext;
    }

    protected Object evaluateExpression(String expression, Object input) {
        return this.evaluateExpression(expression, input, (Class<?>) null);
    }

    protected <T> T evaluateExpression(String expression, Object input, Class<T> expectedType) {
        return this.expressionParser.parseExpression(expression).getValue(this.getEvaluationContext(), input,
                expectedType);
    }

    protected Object evaluateExpression(Expression expression, Object input) {
        return this.evaluateExpression(expression, input, (Class<?>) null);
    }

    protected <T> T evaluateExpression(Expression expression, Class<T> expectedType) {
        return expression.getValue(this.getEvaluationContext(), expectedType);
    }

    protected Object evaluateExpression(Expression expression) {
        return expression.getValue(this.getEvaluationContext());
    }

    protected <T> T evaluateExpression(Expression expression, Object input, Class<T> expectedType) {
        return expression.getValue(this.getEvaluationContext(), input, expectedType);
    }

}