java - MyBatis拼接sql语句，如果判断空格呢？？？？？

Question

是这样，最近有个需求是，如果用户在搜索框里面输入的是一个空格那就搜索值为空的数据，但是我在mybatis里面写if判断，总是不生效求大神帮忙看下，屁话少说，我上代码！

        <if test="orderRemark !=null and orderRemark !=''">
            and a.order_Remark like '%${orderRemark}%'
        </if>

传入一个空字符串（没有空格），翻译出来的sql语句是，and a.order_Remark like '%%'
然后我又改了下

    <if test="orderRemark !=null and orderRemark !=''">
            <choose>
                <when test="orderRemark==' '">
                    and a.order_Remark like ='' or a.order_Remark is null
                </when>
                <otherwise>
                    and a.order_Remark like '%${orderRemark}%'              
                </otherwise>
            </choose>
        </if>

这时候我传进去一个带有空格的字符串
翻译出来的是 and a.order_Remark like '% %'
既然第二个已经有空格了，为什么没进when的判断呢？？？？？
求大神帮忙啊！！！！！！！！！！！！！！！

Answer 1

You can use the trim() method to remove spaces before passing parameters, so there is no need to judge in mybatis

Answer 2

I checked on Baidu and found this issue on Google.
So I tried the solution myself. When I first started testing, I found that if I judged a space (' ') in the when of xml, I couldn't judge it, but I could judge two spaces.
I thought it was strange at the time, so I wondered if it was because of the single quotes. Then I thought about how single quotes represent characters in Java, so how can they be compared with strings. So I added ' ' after a space (toString()), like this <when test="orderRemark==' '.toString()"> and that’s it.
So I guess if there is one space, it defaults to characters, and if there are more than two spaces, it will be converted to a string. My guess, please correct me.

Answer 3

If this is very troublesome, just make a judgment in the java code, or if it is judged to be empty, just use a special character. Don't judge the null character, and be flexible