spring settings repository

问题:

many of my application-properties are provided by the database i would like to inject them via a repository. I wonder if this is doable with spring. I would be happy if someone could suggest a solution. The code i'm thinking about looks something liek this:

    @Component
    public class ExampleService implements Service {

        private PlatformSetting setting1;

        @Required
        @Qualifier("setting1")
        public void setSetting1(PlatformSetting setting1) {
            this.setting1 = setting1;
        }

        public String getMessage() {
            return "Hello world!" + setting1.getValue();    
        }

    }


    @Repository
    public class PlatformSettingRepository {


        private HashMap<String, PlatformSetting> settings;
        {
            settings = new HashMap<String, PlatformSetting>();
            settings.put("setting1", new PlatformSetting("bla1"));
            settings.put("setting2", new PlatformSetting("bla2"));

        }

        @Bean
        public PlatformSetting findSetting(@Qualifier String qual) {
            return settings.get(qual);
        }
    }

i know i could just inject the PlatformSettingRepositoy into the service to look it up. But i don't want to make these lookups at invocation time i want the spring container to do them on startup.

回答1:

Use Spring expression language.

Step 1: Expose your settings hashmap using @Bean, lets say with id ="appSettings"

Step 2: Now where you want settings 1 injected, just use the annotation :

@Value("#{ appSettings['setting1'] }")
private PlatformSetting setting1;

Note: This works with plain values, and it should work in your case as well. Though I haven't tried it. If this doesn't work, you could directly use a expression parser in your method since you are already using java config way of initializing beans.

回答2:

PropertyPlaceholderConfigurer combined with CommonsConfigurationFactory is your answer. Please take a look at this post.

回答3:

You can use InitializingBean:

 @Component
 public class Config implements InitializingBean {

    /**
     * Used to hold app properties.
     */
     private Properties properties = new Properties();

     //Getters, setters and filling properties from where you need

     public void afterPropertiesSet() throws Exception {
         //Initialize some static properties of other objects here.
     }
}

than inject Config to your other classes.