public class Params {
    private String arr1;
}

比如传参 {arr1: "ss"}

<if test="arr1 != null and arr1 == 'a'"></if>

通过字符串相等arr1 == 'a' 会自动把arr1的数据转化为number,而出现报错

Error querying database.  Cause: java.lang.NumberFormatException: For input string: "ss"

而正确写法应该这样 arr1 == "a"

<if test='arr1 != null and arr1 == "a"'></if>