logback 之encoder和layout

encoder 和 layout 在作用上没有本质区别。但是自0.9.19版本之后，极力推荐使用encoder。

下面是官网解释：

Encoders are responsible for transforming an event into a byte array as well as writing out that byte array into an OutputStream. Encoders were introduced in logback version 0.9.19. In previous versions, most appenders relied on a layout to transform an event into a string and write it out using a java.io.Writer. In previous versions of logback, users would nest a PatternLayout within FileAppender. Since logback 0.9.19, FileAppender and sub-classes expect an encoder and no longer take a layout.

Why the breaking change?

Layouts, as discussed in detail in the next chapter, are only able to transform an event into a String. Moreover, given that a layout has no control over when events get written out, layouts cannot aggregate events into batches. Contrast this with encoders which not only have total control over the format of the bytes written out, but also control when (and if) those bytes get written out.

At the present time (2010-03-08), PatternLayoutEncoder is the only really useful encoder. It merely wraps a PatternLayout which does most of the work. Thus, it may seem that encoders do not bring much to the table except needless complexity. However, we hope that with the advent of new and powerful encoders this impression will change.

 

 

参考网址：

http://logback.qos.ch/manual/encoders.html

http://logback.qos.ch/codes.html#layoutInsteadOfEncoder