org.gerzog.jstataggr.expressions.spel.SpelExpressionHandler.java Source code

Introduction

Here is the source code for org.gerzog.jstataggr.expressions.spel.SpelExpressionHandler.java

Source

/**
 * Copyright (C)2014 - Nikolay Lagutko <nikolay.lagutko@mail.com>
 *
 * 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.gerzog.jstataggr.expressions.spel;

import static org.apache.commons.lang3.Validate.notEmpty;
import static org.apache.commons.lang3.Validate.notNull;

import javax.annotation.PostConstruct;

import org.gerzog.jstataggr.core.expressions.IExpressionHandler;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

/**
 * @author Nikolay Lagutko (nikolay.lagutko@mail.com)
 *
 */
public class SpelExpressionHandler implements IExpressionHandler {

    @Autowired
    private BeanFactory beanFactory;

    private EvaluationContext context;

    private ExpressionParser expressionParser;

    public void setBeanFactory(final BeanFactory beanFactory) {
        this.beanFactory = beanFactory;
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T> T invokeExpression(final String expression, final T originalValue) throws Exception {
        notNull(originalValue, "Context value cannot be null");
        notEmpty(expression, "Expression cannot be null or empty");

        final Expression parsedExpression = expressionParser.parseExpression(expression);

        return (T) parsedExpression.getValue(context, originalValue, originalValue.getClass());
    }

    @PostConstruct
    public void initialize() {
        final StandardEvaluationContext context = new StandardEvaluationContext();
        context.setBeanResolver(new BeanFactoryResolver(beanFactory));

        this.context = context;
        this.expressionParser = new SpelExpressionParser();
    }
}