背景是接口导入时，部分字段因为手动录入可能误输空格，所以需去掉前后空格，这些属性为非必填，所以未校验非空，引发空指针异常。

代码类似这样，未判断是否为空，直接trim,导致空指针异常

    @Test
    public void test(){
        String a = "    a    ";
        String b = "    ";
        String c = " ";
        String d = null;
        System.out.println("a: " + StringUtils.isEmpty(a));
        System.out.println("b: " + StringUtils.isEmpty(b));
        System.out.println("c: " + StringUtils.isEmpty(c));
        System.out.println("d: " + StringUtils.isEmpty(d));
        System.out.println("a.trim: " + StringUtils.isEmpty(a.trim()));
        System.out.println("b.trim: " + StringUtils.isEmpty(b.trim()));
        System.out.println("c.trim: " + StringUtils.isEmpty(c.trim()));
        System.out.println("d.trim: " + StringUtils.isEmpty(d.trim()));
    }

trim源码如下

public static String trim(byte[] value) {
        int len = value.length;
        int st = 0;
        while ((st < len) && ((value[st] & 0xff) <= ' ')) {
            st++;
        }
        while ((st < len) && ((value[len - 1] & 0xff) <= ' ')) {
            len--;
        }
        return ((st > 0) || (len < value.length)) ?
            newString(value, st, len - st) : null;
    }

合理的使用应该加上判断

if(!StringUtils.isEmpty(d)){
   System.out.println("d.trim: " + StringUtils.isEmpty(d.trim()));
}