spring ExpressionParser 四则运算表达式解析参数提取

最近接触spring的表达式计算很好用，但是解析表达式参数赋值还需要一些算法，自己写了一个。

代码：

import com.alibaba.fastjson.JSONObject;
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.ArrayList;
import java.util.List;
import java.util.Map;
 
public class ElUtil {
 
    public static Integer pareser(String el, Map<String,String> map){
 
        ExpressionParser parser = new SpelExpressionParser();
        Expression expression = parser.parseExpression(el);
        EvaluationContext context = new StandardEvaluationContext();
        for (String m: map.keySet()
             ) {
            context.setVariable(m, Integer.valueOf(map.get(m)));
        }
       return expression.getValue(context,Integer.class);
 
    }
 
    public static void pick(String el){
 
        List list = new ArrayList<>();
 
        el = el.trim();
 
        for(int i=0;i<el.length();i++)
 
            if(el.charAt(i)=='#'){
 
                int j=i+1;
 
                while(j<el.length()) {
 
                    if (el.charAt(j) == '+' || el.charAt(j) == '-' || el.charAt(j) == '*' || el.charAt(j) == '/' || el.charAt(j) == '(' || el.charAt(j) == ')') {
 
                        String field = el.substring(i + 1, j);
                        list.add(field);
 
 
                        i = j;
                        break;
                    }
                    if(j+1==el.length()){
 
                        String field = el.substring(i + 1);
                        list.add(field);
                        break;
                    }
                    j++;
 
                }
 
            }
 
        System.out.println(JSONObject.toJSONString(list));
 
    }
 
    public static void main(String[] args) {
 
        pick("(#a+#b)/(#c+#d)*(#e+#f)");
    }
}

输出

["a","b","c","d","e","f"]

这样就可以传个map，然后计算了