Logback (3) | Could not find Janino library on the class path. Skipping conditional processing.

在做Spring、Mybatis和Logback的集成时候，logback.xml中可以写表达式：

<!-- if-then form -->
<if condition="some conditional expression">
<then>
...
</then>
</if>

<!-- if-then-else form -->
<if condition="some conditional expression">
<then>
...
</then>
<else>
...
</else>
</if>

运行的时候发现报错：

Could not find Janino library on the class path. Skipping conditional processing.

查看Logback Configuration：

Conditional processing of configuration files
Developers often need to juggle between several logback configuration files targeting different environments such as development, testing and production. These configuration files have substantial parts in common differing only in a few places. To avoid duplication, logback supports conditional processing of configuration files with the help of <if>, <then> and <else> elements so that a single configuration file can adequately target several environments. Note that conditional processing requires the Janino library.

参考：https://logback.qos.ch/manual/configuration.html

发现需要引入Janino Library：

Conditional processing and JaninoEventEvaluator require the Janino library

Conditional processing in configuration files requires the Janino library. Moreover, the evaluator examples based on JaninoEventEvaluator require Janino as well. Once you download Janino, simply place commons-compiler.jar and janino.jar on your application’s class path.

DON’T FORGET As of Janino version 2.6.0, in addition to janino.jar, commons-compiler.jar needs to be on the class path as well.

Here is the corresponding Maven dependency declaration for your convenience.

<dependency>
<groupId>org.codehaus.janino</groupId>
<artifactId>janino</artifactId>
<version>3.0.6</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.codehaus.janino/commons-compiler -->
<dependency>
<groupId>org.codehaus.janino</groupId>
<artifactId>commons-compiler</artifactId>
<version>3.0.8</version>
</dependency>

参考：https://logback.qos.ch/setup.html#janino