can logback use property defined in spring? - spring

we put properties in a specific place(kept by zooKeeper, and already parsed into spring), not in classpath. Now in logback.xml, I need a DBAppender to log messages into mysql, I don't want to copy a properties into classpath, and I try to use placeholder ${url} directly without importing properties in logback.xml, it does not work.
So is there a way to use configuration in spring for logback?

No logback can only access system properties. And also logback tends to be intialised before spring, although you can cause it to be reconfigured.
Have a look at how spring-boot does it. It copies some (about 3 or 4) properties from spring config into system properties before re-initialising logback. In this way the log file path can be interpolated via spring properties and variable replacement.

Related

logging.path to ${LOG_PATH}

I am setup to use logback with my SpringBoot application and everything is running fine and dandy.
I noticed a property called logging.path in the application.properties file which sets the value for ${LOG_PATH} in logback.xml. How does it do it?
I went through the SpringBoot logging documentation.
Any documentation I could find on property placeholder configurer
Yet I don't understand how logging.path could pass the value for ${LOG_PATH}. Though not a killer issue, I would like to know how this mapping is made.
The magic is spring will transfter logging.path into System propeties LOG_PATH.
Description from spring doc:
To help with the customization some other properties are transferred from the Spring Environment to System properties:
And it also says:
All the logging systems supported can consult System properties when parsing their configuration files. See the default configurations in spring-boot.jar for examples.
Details:
https://docs.spring.io/spring-boot/docs/1.5.6.RELEASE/reference/htmlsingle/#boot-features-custom-log-configuration
For more recent versions of Spring Boot, such as 2.5.x, the logging.file.path maps to LOG_PATH.

Use External properties file

Am looking to pass variables at run time once war file is deployed on tomcat ..
How can i use application.properties whcih is in classplath along with another properties file ex. abcd.properties located at particular directory..Am basically looking to set additional classpath and read value from properties file in that path along with default classpath location for war deployment.
Am using Spring boot .One of the way is to pass all properties to database end , but am looking for a file based i.e properties based workout.
(Having multiple applications on same tomcat instance.)
Spring Boot App --> run as --> run configurations. Now here in VM arguments add Dproperties.location="Path of the properties".
Now, in your Spring Boot application use the annotation #PropertySource("file:${properties.location}/propertiesfileName.properties") just above the class declaration.
Autowire Environment in your class. use env.getProperty("propertyname").
You can access the values from application.properties as usual using #Value annotation. Hope this helps.

Actuator - custom logfile endpoint possible?

I have set up my log configuration using logback.
The configuration sets up my logs in a rolling manner in a custom location. This means that I'm not using either:
"logging.file" or "logging.path" in my application.yml configuration, and as a consequence, the logfile endpoint no longer works.
Does anybody know of a way to customize this endpoint, so that I can point to the location/file specified in my logback.xml configuration?
Reading the two sections on Logging 26 & 74. It looks like it recommends using the logback-spring.xml config file with the base.xml configuration. With that you can still use the logging.file or logging.path application properties within the configuration. That way the /logfile endpoint is still valid for the current log file (probably won't look into the rolling files if that is what you setup).
You can specify the log file source from which the actuator will read.
To do that, try to use this property in your application.properties
endpoints.logfile.external-file=/var/log/app.log
or (based on your springboot version):
management.endpoint.logfile.external-file=/var/log/app.log

No plain text passwords in Spring Boot’s application.properties

Having something like
security.user.password = plainTextPassword
inside Spring Boot’s application.properties is obviously an anti-pattern as it prevents the code from being pushed to a public SCM. In my non-Spring Boot projects I use
security.user.password = ${myPasswordFromMavenSettingsXML}
and put a corresponding <properties/> reference inside my pom.xml.
Using Maven’s resource filter plugin the passwords are replaced at build time so the application have access to actual plain text passwords after it has been build and deployed.
For some reason Maven’s resource filter plugin does not work in this case. Is there a way to not commit plain text passwords to an SCM and let Spring Boot to insert them at build time?
Spring boot has multiple mechanisms to provided externalized configuration. Some examples are command line arguments, environment variables and also application properties outside of your packaged JAR.
What I usually do:
Locally we configured several environment variables. Most (if not all) IDE's allow you to configure environment variables from within the run configuration.
For example if you don't want to expose the spring.datasource.password property you could set an environment variable called SPRING_DATASOURCE_PASSWORD.
When we deploy on another environment, we usually choose to add another application.properties or application.yml file within the same folder as the application JAR/WAR, since Spring boot picks that up as well.
Another solution is to use Spring cloud since it has a config service which can be used as a microservice to provide configuration. The configuration can be versioned using SCM as well, but you can put it on a separate system that is not connected to your source code.

Having spring bean properties refreshed automatically from properties file

I'm using Spring 2.5.6. I have a bean whose properties are being assign from a property file via a PropertyPlaceholderConfigurer. I'm wondering whether its possible to have the property of the bean updated when the property file is modified. There would be for example some periodic process which checks the last modified date of the property file, and if it has changed, reload the bean.
I'm wondering if there is already something that satisfies my requirements. If not, what would be the best approach to solving this problem?
Thanks for your help.
Might also look into useing Spring's PropertyOverrideConfigurer. Could re-read the properties and re-apply it in some polling/schedular bean.
It does depend on how the actual configured beans use these properties. They might, for example, indirectly cache them somewhere themself.
If you want dynamic properties at runtime, perhaps another way to do it is JMX.
One way to do this is to embed a groovy console in your application. Here's some instructions. They were very simple to do, btw - took me very little time even though I'm not that familiar with groovy.
Once you do that you can simply go into the console and change values inside the live application on the fly.
You might try to use a custom scope for the bean that recreates beans on changes of the properties file. See my more extensive answer here.
Spring Cloud Config has facilities to change configuration properties at runtime via the Spring Cloud Bus and using a Cloud Config Server. The configuration or .properties or .yml files are "externalized" from the Spring app and instead retrieved from a Spring Cloud Config Server that the app connects to on startup. That Cloud Config Server retrieves the appropriate configuration .properties or .yml files from a GIT repo (there are other storage solutions, but GIT is the most common). You can then change configuration at runtime by changing the contents of the GIT repo's configuration files--The Cloud Config Server broadcasts the changes to any Client Spring applications via the Spring Cloud Bus, and those applications' configuration is updated without needing a restart of the app. You can find a working simple example here: https://github.com/ldojo/spring-cloud-config-examples

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