CommandLineArgumentsinSpringBoot
We can use command-line arguments to configure our application, override application properties or pass custom arguments.
2. Maven Command-Line Arguments
First, let"s see how we can pass arguments while running our application using Maven Plugin.
Later, we"ll see how to access the arguments in our code.
2.1. Spring Boot 1.x
For Spring Boot 1.x, we can pass the arguments to our application using -Drun.arguments:
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mvn spring-boot:run -Drun.arguments=--customArgument=custom
We can also pass multiple parameters to our app:
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mvn spring-boot:run -Drun.arguments=--spring.main.banner-mode=off,--customArgument=custom
Note that:
- Arguments should be comma separated
- Each argument should be prefixed with —
- We can also pass configuration properties, like spring.main.banner-mode shown in the example above
2.2. Spring Boot 2.x
For Spring Boot 2.x, we can pass the arguments using -Dspring-boot.run.arguments:
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mvn spring-boot:run -Dspring-boot.run.arguments=--spring.main.banner-mode=off,--customArgument=custom
3. Gradle Command-Line Arguments
Next, let"s discover how to pass arguments while running our application using Gradle Plugin.
We"ll need to configure our bootRun task in build.gradle file:
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bootRun {
if
(project.hasProperty(
"args"
)) {
args project.args.split(
","
)
}
}
Now, we can pass the command-line arguments as follows:
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.
/gradlew
bootRun -Pargs=--spring.main.banner-mode=off,--customArgument=custom
4. Overriding System Properties
Other than passing custom arguments, we can also override system properties.
For example, here"s our application.properties file:
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server.port=8081
spring.application.name=SampleApp
To override the server.port value, we need to pass the new value in the following manner (for Spring Boot 1.x):
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mvn spring-boot:run -Drun.arguments=--server.port=8085
Similarly for Spring Boot 2.x:
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mvn spring-boot:run -Dspring-boot.run.arguments=--server.port=8085
Note that:
- Spring Boot converts command-line arguments to properties and adds them as environment variables
- We can use short command-line arguments –port=8085 instead of –server.port=8085 by using a placeholder in our application.properties:
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server.port=${port:8080} - Command-line arguments take precedence over application.properties values
If needed, we can stop our application from converting command-line arguments to properties:
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@SpringBootApplication
public
class
Application
extends
SpringBootServletInitializer {
public
static
void
main(String[] args) {
SpringApplication application =
new
SpringApplication(Application.
class
);
application.setAddCommandLineProperties(
false
);
application.run(args);
}
}
5. Accessing Command-Line Arguments
Let"s see how we can access the command-line arguments from our application"s main() method:
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@SpringBootApplication
public
class
Application
extends
SpringBootServletInitializer {
public
static
void
main(String[] args) {
for
(String arg:args) {
System.out.println(arg);
}
SpringApplication.run(Application.
class
, args);
}
}
This will print the arguments we passed to our application from command-line, but we could also use them later in our application.
6. Passing Command-Line Arguments to the SpringBootTest
With the release of Spring Boot 2.2, we gained the possibility to inject command-line arguments during testing using @SpringBootTest and its args attribute:
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@SpringBootTest
(args =
"--spring.main.banner-mode=off"
)
public
class
ApplicationTest {
@Test
public
void
whenUsingSpringBootTestArgs_thenCommandLineArgSet(
@Autowired
Environment env) {
Assertions.assertThat(env.getProperty(
"spring.main.banner-mode"
)).isEqualTo(
"off"
);
}
}
7. Conclusion
In this article, we learned how to pass arguments to our Spring Boot application from command-line, and how to do it using both Maven and Gradle.
We"ve also shown how you can access those arguments from your code, in order to configure your application.
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