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I have a very simple Spring Boot app that I'm trying to get working with some externalised configuration. I've tried to follow the information on the spring boot documentation however I'm hitting a road block.

When I run the app below the external configuration in the application.properties file does not get populated into the variable within the bean. I'm sure I'm doing something stupid, thanks for any suggestions.

MyBean.java (located in /src/main/java/foo/bar/)

package foo.bar; import org.springframework.beans.factory.annotation.Value; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.stereotype.Component; @Component public class MyBean { @Value("${some.prop}") private String prop; public MyBean() { System.out.println("================== " + prop + "================== "); } }

Application.java (located in /src/main/java/foo/)

package foo; import foo.bar.MyBean; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.boot.autoconfigure.EnableAutoConfiguration; import org.springframework.boot.SpringApplication; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; @Configuration @ComponentScan @EnableAutoConfiguration public class Application { @Autowired private MyBean myBean; public static void main(String[] args) { SpringApplication.run(Application.class, args); } }

application.properties (located in /src/main/resources/)

some.prop=aabbcc

Log output when executing the Spring Boot app:

grb-macbook-pro:properties-test-app grahamrb$ java -jar ./build/libs/properties-test-app-0.1.0.jar . ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v1.1.5.RELEASE) 2014-09-10 21:28:42.149 INFO 16554 --- [ main] foo.Application : Starting Application on grb-macbook-pro.local with PID 16554 (/Users/grahamrb/Dropbox/dev-projects/spring-apps/properties-test-app/build/libs/properties-test-app-0.1.0.jar started by grahamrb in /Users/grahamrb/Dropbox/dev-projects/spring-apps/properties-test-app) 2014-09-10 21:28:42.196 INFO 16554 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@67e38ec8: startup date [Wed Sep 10 21:28:42 EST 2014]; root of context hierarchy 2014-09-10 21:28:42.828 INFO 16554 --- [ main] o.s.b.f.s.DefaultListableBeanFactory : Overriding bean definition for bean 'beanNameViewResolver': replacing [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration.class]] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter.class]] 2014-09-10 21:28:43.592 INFO 16554 --- [ main] .t.TomcatEmbeddedServletContainerFactory : Server initialized with port: 8080 2014-09-10 21:28:43.784 INFO 16554 --- [ main] o.apache.catalina.core.StandardService : Starting service Tomcat 2014-09-10 21:28:43.785 INFO 16554 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/7.0.54 2014-09-10 21:28:43.889 INFO 16554 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2014-09-10 21:28:43.889 INFO 16554 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1695 ms 2014-09-10 21:28:44.391 INFO 16554 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/] 2014-09-10 21:28:44.393 INFO 16554 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*] ================== null================== 2014-09-10 21:28:44.606 INFO 16554 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2014-09-10 21:28:44.679 INFO 16554 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest) 2014-09-10 21:28:44.679 INFO 16554 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[text/html],custom=[]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest) 2014-09-10 21:28:44.716 INFO 16554 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2014-09-10 21:28:44.716 INFO 16554 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2014-09-10 21:28:44.902 INFO 16554 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup 2014-09-10 21:28:44.963 INFO 16554 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080/http 2014-09-10 21:28:44.965 INFO 16554 --- [ main] foo.Application : Started Application in 3.316 seconds (JVM running for 3.822) ^C2014-09-10 21:28:54.223 INFO 16554 --- [ Thread-2] ationConfigEmbeddedWebApplicationContext : Closing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@67e38ec8: startup date [Wed Sep 10 21:28:42 EST 2014]; root of context hierarchy 2014-09-10 21:28:54.225 INFO 16554 --- [ Thread-2] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown
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  • 5
    And how should @Value be replaced before a bean is constructed? Your way of "detecting" if the value is set is wrong. At that moment it always be null as @Value will be processed AFTER object construction. Commented Sep 10, 2014 at 11:49

13 Answers 13

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229

The way you are performing the injection of the property will not work, because the injection is done after the constructor is called.

You need to do one of the following:

Better solution

@Component public class MyBean { private final String prop; @Autowired public MyBean(@Value("${some.prop}") String prop) { this.prop = prop; System.out.println("================== " + prop + "================== "); } }

Solution that will work but is less testable and slightly less readable

@Component public class MyBean { @Value("${some.prop}") private String prop; public MyBean() { } @PostConstruct public void init() { System.out.println("================== " + prop + "================== "); } }

Also note that is not Spring Boot specific but applies to any Spring application

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19 Comments

I had to add an @Autowired annotation to the constructor to make it work
@SébastienTromp You're talking about the first solution, correct?
Thanks for the tip. This should be in the Spring documentation where it talks about the @Value annotation - but those guys don't seem to be interested in feedback on their documentation :(
@geoand What if you have over 10 values, would you have to type all 10 just the way you did it? Or is there a cleaner way
@Jackie Indeed there is a cleaner way! Check out @ConfigurationProperties and @EnableConfigurationProperties annotations
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8

The user "geoand" is right in pointing out the reasons here and giving a solution. But a better approach is to encapsulate your configuration into a separate class, say SystemContiguration java class and then inject this class into what ever services you want to use those fields.

Your current way(@grahamrb) of reading config values directly into services is error prone and would cause refactoring headaches if config setting name is changed.

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2 Comments

How wouldn't there be any less headaches if you had a separate class for that property? You'll still have a string that needs to be remembered when refactoring
There is only one place you need to "remember", not N number. The scalar values that exist on SystemContiguration give you strong typing. Also, if there is business logic that has "forks" ~~~based on values coming from the configuration~~~.....it is better to inject something into the class/businessLogic that needs the values. Aka, it is much easier to mock SystemContiguration then trying to get @Value working all over the place.
6

This answer may or may not be applicable to your case ... Once I had a similar symptom and I double checked my code many times and all looked good but the @Value setting was still not taking effect. And then after doing File > Invalidate Cache / Restart with my IntelliJ (my IDE), the problem went away ...

This is very easy to try so may be worth a shot

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5

Moved no argument constructor code to PostConstruct has done the trick for me. As it'll keep default bean loading workflow intact.

@Component public class MyBean { @Value("${some.prop}") private String prop; @PostConstruct public void init() { System.out.println("================== " + prop + "================== "); } }
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3

Actually, For me below works fine.

@Component public class MyBean { public static String prop; @Value("${some.prop}") public void setProp(String prop) { this.prop= prop; } public MyBean() { } @PostConstruct public void init() { System.out.println("================== " + prop + "================== "); }

}

Now whereever i want, just invoke

MyBean.prop

it will return value.

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3

Simplest solution that solved this issue for me:

Add @PropertySource annotation to the Component/Service that needs to populate @Value field:

@Service @PropertySource("classpath:myproperties.properties") public class MyService { @Value("${some.prop}") private String someProperty; // some logic... }

Make sure to add the properties file to the resource folder of the same module as your Service/Component.

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2

Using Environment class we can get application. Properties values

@Autowired,

private Environment env;

and access using 

String password =env.getProperty(your property key);
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2 Comments

Never autowire fields.
why "Nevet autowire fields"
1

You are getting this error because you are initializing the class with new keyword. To solve this, first you need to create the configuration class and under this class you need to create the bean of this class. When you will call it by using bean then it will work..

package ca.testing; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.context.annotation.AnnotationConfigApplicationContext; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.PropertySource; import org.springframework.stereotype.Component; import javax.annotation.PostConstruct; import java.sql.Connection; import java.sql.DriverManager; @Component @PropertySource("db.properties") public class ConnectionFactory { @Value("${jdbc.user}") private String user; @Value("${jdbc.password}") private String password; @Value("${jdbc.url}") private String url; Connection connection; public Connection getConnection(){ try { connection = DriverManager.getConnection(url, user, password); System.out.println(connection.hashCode()); }catch (Exception e){ System.out.println(e); } return connection; } public static void main(String[] args) { AnnotationConfigApplicationContext context= new AnnotationConfigApplicationContext(Config.class); ConnectionFactory connectionFactory= context.getBean(ConnectionFactory.class); connectionFactory.getConnection(); } }
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0

follow these steps. 1:- create your configuration class like below you can see

import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.beans.factory.annotation.Value; @Configuration public class YourConfiguration{ // passing the key which you set in application.properties @Value("${some.pro}") private String somePro; // getting the value from that key which you set in application.properties @Bean public String getsomePro() { return somePro; } }

2:- when you have a configuration class then inject in the variable from a configuration where you need.

@Component public class YourService { @Autowired private String getsomePro; // now you have a value in getsomePro variable automatically. }
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0

If you're working in a large multi-module project, with several different application.properties files, then try adding your value to the parent project's property file.

If you are unsure which is your parent project, check your project's pom.xml file, for a <parent> tag.

This solved the issue for me.

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0

You can use Environment Class to get data :

@Autowired private Environment env; String prop= env.getProperty('some.prop');
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0

Do not use the new keyword to create instances of MyBean e.g. MyBean myBean = new MyBean() is incorrect. Always rely on Spring to inject the dependencies using @Autowired.

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0

Not really.your problem but if you have a transcription error in the names of your properties and their references in @Value annotations you will often get an error about a dependency injection failure when you try to run the code.

The grimness of the message makes it seem as if something more fundamental is broken.

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