RollingFileAppender
RollingFileAppender extends FileAppender with the capability to rollover log files. For example, RollingFileAppender can log to a file named log.txt file and, once a certain condition is met, change its logging target to another file.
There are two important sub-components that interact with RollingFileAppender. The first RollingFileAppender sub-component, namely RollingPolicy, (see below) is responsible for undertaking the actions required for a rollover. A second sub-component of RollingFileAppender, namely TriggeringPolicy, (see below) will determine if and exactly when rollover occurs. Thus, RollingPolicy is responsible for the what and TriggeringPolicy is responsible for the when.
To be of any use, a RollingFileAppender must have both a RollingPolicy and a TriggeringPolicy set up. However, if its RollingPolicy also implements the TriggeringPolicy interface, then only the former needs to be specified explicitly.
Here are the available properties for RollingFileAppender:
| Property Name | Type | Description |
|---|---|---|
file |
String | See FileAppender properties. |
append |
boolean | See FileAppender properties. |
encoder |
Encoder | See OutputStreamAppender properties. |
rollingPolicy |
RollingPolicy | This option is the component that will dictate RollingFileAppender's behavior when rollover occurs. See more information below. |
triggeringPolicy |
TriggeringPolicy | This option is the component that will tell RollingFileAppender when to activate the rollover procedure. See more information below. |
prudent |
boolean | FixedWindowRollingPolicy is not supported in prudent mode. RollingFileAppender supports the prudent mode in conjunction with TimeBasedRollingPolicy albeit with two restrictions. 1. In prudent mode, file compression is not supported nor allowed. (We can't have one JVM writing to a file while another JVM is compressing it.) 2. The file property of FileAppender cannot be set and must be left blank. Indeed, most operating systems do not allow renaming of a file while another process has it opened. See also properties for FileAppender. |