java - How to externalize Spring Boot application.properties to tomcat/lib folder

Question

I need a configuration free, deployable war, myapp1.war that can retrieve the configuration files from the tomcat/lib folder. As I have other web applications coexisting on the same Tomcat: myapp2.war, myapp3.war, I need this layout:

tomcat/lib/myapp1/application.properties
tomcat/lib/myapp2/application.properties
tomcat/lib/myapp3/application.properties

This way I can build the war files without any properties files inside the war and deploy on any server.

I have read the Spring documentation but it explains how to set the location when running as a jar:

java -jar myapp.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties

I cannot figure out how to do this for the case of multiple coexisting war files.

I would like to know if this is possible or should I give up on Spring Boot and go back to the traditional Spring MVC applications.

Answer 1

A solution could be to load application-{profile}.properties as @PropertySource annotations as this question suggests, but then the logging system wont work, as you can see in the documentation.

The logging system is initialized early in the application lifecycle and as such logging properties will not be found in property files loaded via @PropertySource annotations.

This means that your logging properties in application-{profiles}.properties like:

logging.config=classpath:myapp1/logback.xml
logging.path = /path/to/logs
logging.file = myapp1.log

will be ignored and the logging system wont work.

To solve this I have used the SpringApplicationBuilder.properties() method to load properties at the beginning, when the application is configured. There I set the 'spring.config.location' used by Spring Boot to load all the application-{profiles}.properties:

public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder springApplicationBuilder) {
        return springApplicationBuilder
                .sources(Application.class)
                .properties(getProperties());
    }

    public static void main(String[] args) {

        SpringApplicationBuilder springApplicationBuilder = new SpringApplicationBuilder(Application.class)
                .sources(Application.class)
                .properties(getProperties())
                .run(args);
    }

   static Properties getProperties() {
      Properties props = new Properties();
      props.put("spring.config.location", "classpath:myapp1/");
      return props;
   }
}

Then I have moved the properties files from src/main/resources to src/main/resources/myapp1

.
├src
| └main
|   └resources
|     └myapp1
|       └application.properties
|       └application-development.properties
|       └logback.xml
└─pom.xml

In the pom.xml I have to set the scope of embedded tomcat libraries as "provided". Also, to exclude all properties files in src/main/resources/myapp1 from the final war and generate a configuration free, deployable war:

    <plugin>
        <artifactId>maven-war-plugin</artifactId>
        <version>2.6</version>
        <configuration>
            <failOnMissingWebXml>false</failOnMissingWebXml>
            <packagingExcludes>
              **/myapp1/
            </packagingExcludes>
        </configuration>
    </plugin>

Then in Tomcat I have

├apache-tomcat-7.0.59
 └lib
   ├─myapp1
   |  └application.properties        
   |  └logback.xml
   └─myapp2
     └application.properties
     └logback.xml

Now I can generate the configuration free war and drop it into the apache-tomcat-7.0.59/webapps folder. Properties files will be resolved using the classpath, independently for each webapp:

   apache-tomcat-7.0.59/lib/myapp1
   apache-tomcat-7.0.59/lib/myapp2
   apache-tomcat-7.0.59/lib/myapp3