Log4j2.xml中动态读取配置

Posted 2022-08-19 张志翔 ̮

log4j2支持多种方式的获取值添加进入日志中, 由此衍生出多种lookup~~

可以看下org.apache.logging.log4j.core.lookup包下的代码, 基本上就是官方文档中列的方式, 并可以深入了解框架本身是怎么进行数据获取的, 必要时可自行实现!

支持多种方式动态读取配置, 下面写几个我用过的示例:

1. bundle: $bundle:BundleName:BundleKey

bundle: 固定前缀, 标识读取配置文件

BundleName: 配置文件名(如application.properties)

BundleKey: 配置key

eg: $bundle:application:log.path

从application.properties中读取key为log.path的值

return ResourceBundle.getBundle(bundleName).getString(bundleKey)

2. sys: $sys:some.property或$sys:some.property:-default_value

sys: 标识读取系统属性, 基本是通过System.getProperty()可读取的属性, jvm参数等

some.property: 属性的key

default_value: 默认值

eg: $sys:test.log.path:-/opt/logs/

从系统属性中读取test.log.path属性值, 未取到时默认值为/opt/logs/

3. env基本上和sys一致, 不同点在于读取系统环境变量

官方配置如下

Prefix	Context
base64	Base64 encoded data. The format is $base64:Base64_encoded_data. For example: $base64:SGVsbG8gV29ybGQhCg== yields Hello World!.
bundle	Resource bundle. The format is $bundle:BundleName:BundleKey. The bundle name follows package naming conventions, for example: $bundle:com.domain.Messages:MyKey.
ctx	Thread Context Map (MDC)
date	Inserts the current date and/or time using the specified format
env	System environment variables. The formats are $env:ENV_NAME and $env:ENV_NAME:-default_value.
jndi	A value set in the default JNDI Context.
jvmrunargs	A JVM input argument accessed through JMX, but not a main argument; see RuntimeMXBean.getInputArguments(). Not available on android.
log4j	Log4j configuration properties. The expressions $log4j:configLocation and $log4j:configParentLocation respectively provide the absolute path to the log4j configuration file and its parent folder.
main	A value set with MapLookup.setMainArguments(String[])
map	A value from a MapMessage
sd	A value from a StructuredDataMessage. The key "id" will return the name of the StructuredDataId without the enterprise number. The key "type" will return the message type. Other keys will retrieve individual elements from the Map.
sys	System properties. The formats are $sys:some.property and $sys:some.property:-default_value.

参考:

自定义lookup: Log4j2研究之lookup_夫礼者的专栏-CSDN博客

Log4j2 Lookup扩展之支持Spring环境变量解析 - 子达的个人空间 - OSCHINA - 中文开源技术交流社区

Log4j – Configuring Log4j 2