How to use property placeholders in .yml file
I am working with Java and spring boot. I was wondering how to add property placeholders to files .yml
. I found some prime example, but I'm not sure where the property placeholders are being created. Is it in system env variables, file, etc.?
Bootstrap.yml
spring:
cloud:
config:
username: ${my.stored.files.username}
password: ${my.stored.files.password}
label: ${spring.cloud.find.label}
uri: ${spring.cloud.config.uri}
enabled: false
failFast: true
The user is using property placeholders, but where did the user declare this? Where is this .yml reading values from? (same question as above) Is there a document explaining the connection?
This web app will be pushed to the cloud foundry using "cf push" which will automatically display the manifest.yml file for customization. If possible, a cloud casting example would be great.
Understanding
app.name=MyApp
app.description=${app.name} is a Spring Boot application
The user was able to use $ {app.name} because it was defined. I am confused about the above example. How and where does the user get "$ {my.stored.files.username}. Where is this defined? I assumed it would be in system.properties or environment variables. Can anyone confirm?"
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After intensive research, I was able to find that when using placeholders in .yml files, these values are read from environment variables. Which was part of my theory in the beginning, but nobody confirmed.
Answer
spring:
cloud:
config:
username: ${my.stored.files.username}
password: ${my.stored.files.password}
label: ${spring.cloud.find.label}
uri: ${spring.cloud.config.uri}
enabled: false
failFast: true
* In environment variables *
set key as: my.stored.files.username
set value as: UsernameSample
Then
When you run the application the yml will look like this.
config:
username: ${my.stored.files.username}
//gets replaced with UsernameSample
This is the link that solved my problem link
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SpringApplication loads properties from application.properties files in the following locations and adds them to the Spring framework:
- The / config subdirectory of the current directory
- Current directory
- Classpath / config package
- The root of the classpath
The list is ordered by priority (properties defined in locations higher in the list override properties defined in lower locations).
You can also use YAML files ('.yml') as an alternative to '.properties'.
If you don't like application.properties as the configuration file name, you can switch to a different file name by specifying the spring.config.name environment property. You can also refer to an explicit location using the spring.config.location environment property (which is a comma separated list of directory locations or file paths). The following example shows how to specify a different filename:
$ java -jar myproject.jar --spring.config.name=myproject
The following example shows how to specify two locations:
$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties
spring.config.name and spring.config.location are used very early to determine which files should be loaded. They must be defined as an environment property (usually an OS environment variable, system property, or command line argument).
If spring.config.location contains directories (as opposed to files), they must end with / (and, at runtime, be appended with names generated from spring.config.name before boot, including profile-specific file names). The files specified in spring.config.location are used as-is, with no support for profile-specific options, and are overridden by any profile-specific properties.
Location configurations are searched in reverse order. The default locations configured are classpath: /, classpath: / config /, file: ./, file: ./ config /. The resulting search order is as follows:
file:./config/
file:./
classpath:/config/
classpath:/
When custom config locations are configured using spring.config.location, they override the default locations. For example, if your spring.config.location file specifies classpath: / custom-config /, file: ./ custom-config /, the search order will be as follows:
file:./custom-config/
classpath:custom-config/
In addition, when custom configuration locations are configured using spring.config.additional-location, they are used in addition to the default locations. Additional locations are searched before default locations. For example, if additional classpath locations are configured: / custom-config /, file: ./ custom-config /, the search order becomes:
file:./custom-config/
classpath:custom-config/
file:./config/
file:./
classpath:/config/
classpath:/
This search order allows you to specify default values in one configuration file and then selectively override these values in another. You can provide default values for your application in application.properties (or whatever base name you choose with spring.config.name) in one of the default locations. These defaults can be overridden at runtime with a different file located in one of the custom locations.
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