基于JavaScript手写一个简单版的规则表达式

package com.example.demo.mymvel;


import java.util.Map;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;




/**
 * 描述：Mvel表达式执行器 </br>
 * 作者：IT学习道场 </br>
 * 时间：2023/5/6 17:20
 */
public class MvelExpressionEvaluator {
    /**
     * 表达式
     */
    private String expression;


    public MvelExpressionEvaluator(String expression) {
        this.expression = expression;
    }


    /**
     * 执行表达式执行
     * @param variables 表达式入参参数
     * @return object - 表达式返回的值
     * @throws Exception
     */
    public Object evaluate(Map variables) throws Exception {
        String parsedExpression = parseExpressionWithVariables(expression, variables);
        //加载js脚本引擎
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("JavaScript");
        return engine.eval(parsedExpression);
    }


    /**
     * 解析参数表达式
     * @param expression 原表达式
     * @param variables 参数map
     * @return
     */
    private String parseExpressionWithVariables(String expression, Map variables) {
        Pattern pattern = Pattern.compile("\\{(.+?)\\}");
        Matcher matcher = pattern.matcher(expression);
        StringBuffer sb = new StringBuffer();
        while (matcher.find()) {
            String variableName = matcher.group(1).trim();
            if (variables.containsKey(variableName)) {
                Object variableValue = variables.get(variableName);
                matcher.appendReplacement(sb, variableValue.toString());
            }
        }
        matcher.appendTail(sb);
        return sb.toString();
    }
}

package com.example.demo.mymvel;


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


/**
 * 描述：测试 </br>
 * 作者：IT学习道场 </br>
 * 时间：2023/5/6 17:20
 */
public class Test {
    public static void main(String[] args) {
        Map variables = new HashMap<>();
        variables.put("x", 1);
        variables.put("y", 2);
        variables.put("z", 3);
        //String rule = "({x} + {y}) * {z}";
        String rule = "{x} > 1 && {y} > 1";
        MvelExpressionEvaluator evaluator = new MvelExpressionEvaluator(rule);
        try {
            Object result = evaluator.evaluate(variables);
            System.out.println(result);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}