2021-06-30 检查OGNL表达式是否合法

简单点就是依据括号了。

/**
 * @author eric
 * @date 2021/6/30
 */
public class OgnlCheckUtil {
    /**
     * 左括号 1，右括号 -1，最后总和0则匹配
     *
     * @param ognl
     * @return
     */
    public static void check(String ognl) {
        int top = 0;
        char[] express = ognl.toCharArray();
        for (int i = 0; i < express.length; i++) {
            if (express[i] == '(') {
                top++;
            } else if (express[i] == ')') {
                if (top > 0) {
                    top--;
                } else {
                    //top <= 0,无左括号却有一个右括号，有一个右括号不匹配
                    throw new RuntimeException("多了)");
                }
            }
        }
        if (top > 0) {
            throw new RuntimeException("多了(");
        } else if (top < 0) {
            throw new RuntimeException("多了)");
        }
    }
}