Mybatis & lt; if test = & quot; & gt; problem, mybatistest

Mybatis <if test = ""> problem, mybatistest

The angel encountered a puzzling problem using mybatis, which is described as follows:

Use <if test = "com. levelId! = Null and com. levelId! = ''"> (The red part is two single quotes). The input value type is Long,

The problem is that when the input value is 0, the statement in the label should be executed but not executed. If other values are input, the tested statements include, 3, and so on, it can be executed as long as it is not 0.

Remove and com. levelId! = ''. I don't know why. I want to learn more. I hope you can give me some advice. Thank you!