com.github.hetianyi.common.util.ExpressionParserUtil Maven / Gradle / Ivy

Go to download
package com.github.hetianyi.common.util;


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;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * SpEL parser util.
 *
 * @author Jason He
 * @version 1.0.6
 * @since 1.0.5
 * @date 2019-02-01
 */
public class ExpressionParserUtil {

    /**
     * expression parser.
     */
    private static final ExpressionParser parser = new SpelExpressionParser();
    /**
     * expression cache map.
     */
    private static final Map expressionMap = Collections.synchronizedMap(new HashMap<>());

    /**
     * get singleton expression.
     * @param expression
     * @return
     */
    private static Expression getExpression(String expression) {
        Expression ret = expressionMap.get(expression);
        if (null == ret) {
            synchronized (expressionMap) {
                if (null == ret) {
                    ret = parser.parseExpression(expression);
                    expressionMap.put(expression, ret);
                }
            }
        }
        return ret;
    }

    /**
     * parse SpEL expression using ExpressionParser with default settings.
     * @param expression SpEL expression
     * @param argKey variable name
     * @param args variable value
     * @param resultType result value type
     * @param 
     * @return
     */
    public static  T parse(String expression, String argKey, Object[] args,
                              Class resultType) {
        EvaluationContext ctx = new StandardEvaluationContext();
        ctx.setVariable(argKey, args);
        Expression exp = getExpression(expression);
        return exp.getValue(ctx, resultType);
    }

}