How to access Configuration objects in Spring Boot

Question

Spring Boot has a mechanism for accessing the contents of .properties (or YAML) files that one might want to include in an application. I currently have a dbase.properties file (residing in src/main/resources) that contains the following information:

app.dbase.name=MyDbase
app.dbase.connect=jdbc:postgresql://localhost:5432
app.dbase.user=auser
app.dbase.password=mypassword

As described in various Spring Boot documents and examples, I have a configuration class that is defined below:

@Configuration
@PropertySource("dbase.properties")
@ConfigurationProperties(prefix = "app.dbase")
public class DbInfo
{
   private String name;
   private String connect;
   private String user;
   private String password;

   // Getters and setters left out for brevity
}

Unfortunately, while the various documents and examples give good information on how to define a configuration class, I have been unable to find any description on how to use it! Apparently, a Spring Boot web application creates an instance of a configuration class upon startup (and it looks like it also initializes them with the values from the properties file) but my attempts to guess how to access its contents when I need to have failed. The method of doing so is probably simple, but no one seems to want to describe this method anywhere.

So: how does one access and use one of these configuration classes once they are instantiated?

Answer 1

Note that @ConfigurationProperties would require all of the properties in your file to be prefixed with 'app.dbase', as in 'app.dbase.username' and 'app.dbase.password'. If that's the case, the class you have now should work. You would call it like this:

@Component 
public class Component {

   @Autowired DbInfo dbInfo;

   public method() {
      String username = dbInfo.username();
   }
}

If you are having issues, you may be required to add this to a Configuration class:

@Configuration
public class Config {

   @Bean
   public static PropertySourcesPlaceholderConfigurer propertyConfigurer() {
       return new PropertySourcesPlaceholderConfigurer();
   }

   ...
}

You may also need to add 'classpath:' inside your annotation, as in: @PropertySource("classpath:dbase.properties"), assuming your properties file is in your src/main/resources.