io.gravitee.el.spel.SpelTemplateEngine Maven / Gradle / Ivy

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/**
 * Copyright (C) 2015 The Gravitee team (http://gravitee.io)
 *
 * 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 io.gravitee.el.spel;

import io.gravitee.el.TemplateContext;
import io.gravitee.el.TemplateEngine;
import io.gravitee.el.exceptions.ExpressionEvaluationException;
import io.gravitee.el.spel.context.SpelTemplateContext;
import io.reactivex.Maybe;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.SpelEvaluationException;

/**
 * @author David BRASSELY (david.brassely at graviteesource.com)
 * @author Jeoffrey HAEYAERT (jeoffrey.haeyaert at graviteesource.com)
 * @author GraviteeSource Team
 */
public class SpelTemplateEngine implements TemplateEngine {

    protected final SpelTemplateContext templateContext;
    private final io.gravitee.el.spel.SpelExpressionParser spelExpressionParser;

    public SpelTemplateEngine(io.gravitee.el.spel.SpelExpressionParser spelExpressionParser) {
        this.spelExpressionParser = spelExpressionParser;
        this.templateContext = new SpelTemplateContext();
    }

    @Override
    public  T getValue(String expression, Class clazz) {
        return eval(spelExpressionParser.parseExpression(expression), templateContext.getContext(), clazz);
    }

    @Override
    public  Maybe eval(String expression, Class clazz) {
        try {
            CachedExpression cachedExpression = spelExpressionParser.parseAndCacheExpression(expression);
            return templateContext
                .evaluationContext(cachedExpression)
                .flatMapMaybe(evaluationContext -> eval(cachedExpression, evaluationContext, clazz));
        } catch (Exception e) {
            return Maybe.error(e);
        }
    }

    @Override
    public TemplateContext getTemplateContext() {
        return templateContext;
    }

    protected  Maybe eval(CachedExpression exp, EvaluationContext evaluationContext, Class clazz) {
        return Maybe.fromCallable(() -> eval(exp.getExpression(), evaluationContext, clazz));
    }

    protected  T eval(Expression expression, EvaluationContext evaluationContext, Class clazz) {
        try {
            return expression.getValue(evaluationContext, clazz);
        } catch (SpelEvaluationException spelEvaluationException) {
            throw new ExpressionEvaluationException(expression.getExpressionString(), spelEvaluationException);
        }
    }
}