Mybatis judges that the string in if is equal to the pit encountered in the comparison

In normal development, we often use

<if test="topicType != null and topicType != ''">
    AND a.topic_type = #{topicType}
</if>

This form of judgment, when I use "==" judgment, there is a strange problem

code show as below:

<if test="createBy != null and topicType == '1'">
    AND a.create_by = #{createBy.id}
</if>

When I meet these two conditions, the query file still cannot be appended.

Change it to:

<if test="createBy != null and topicType == '1'.toString()">
    AND a.create_by = #{createBy.id}
</if>

or

<if test='createBy != null and topicType == "1"'>
    AND a.create_by = #{createBy.id}
</if>

After that, my query conditions can be used normally.

Mybatis is parsed with OGNL expressions. In OGNL expressions, '1' will be parsed as characters, java is strongly typed, char and a string will cause inequality, so the sql in the if tag will not be parsed as a character. Parse. A single character needs to be written in double quotes or use .toString()!