Spring automagic, #Autowired - spring

Question

#Autowired
Environment env;
#Value("${jdbcConnectionString}")
private String jdbcConnectionString;
The above works automagically in certain classes, however is null in similar classes in same package and with same annotations #Configuration/#Component.
I am trying to find out the proper approach to understand what spring does when while configuring various artifacts.
I am able to run stuff every now and then but any good resource to understand the magic is well appreciated.
PS. I am only interested in java-config based approach now.
Working :
package a.b.c;
#Configuration
public class AppConfig {
#Autowired
Environment env;
package a.b.d;
#Configuration
#EnableBatchProcessing
public class JobConfiguration {
#Autowired
private Environment env;
package a.b.L;
public class BatchJobListener implements Ordered, JobExecutionListener {
#Autowired
public Environment env;
Not working inside
package a.b.u
Tried to annotate classes with #Component/#Configuration

Answer 1

In order to autowire a bean, you need first to defined it in a Context.
#Configuration
public class ConfigOne {
#Bean
public String myBean(){
return "my bean";
}
}
The bean that you want to inject and the bean where the bean will be injected need to be in the same context. You can do it with:
JavaConfigApplicationContext context =
new JavaConfigApplicationContext(ConfigOne.class, ConfigTwo.class);
Or you can use #import to import one configuration class into another.
#Configuration
#Import(ConfigTwo.class)
public class ConfigOne {
UPDATE
What I meant was that probably you're not making the configuration in the ringht way. So all your beans where you're injecting the enviroment are not in the same context.
However, if you have configured well everything, it's possible that some classes are loading before enviroment. In this case you can use EnvironmentAware
#Configuration
#PropertySource("classpath:myProperties.properties")
public class MyConfiguration implements EnvironmentAware {
private Environment environment;
#Override
public void setEnvironment(final Environment environment) {
this.environment = environment;
}
public void myMethod() {
final String myPropertyValue = environment.getProperty("myProperty");
// ...
}
}

Answer 2

In your main class where you are initializing the spring boot application, do you have similar configuration:
#Configuration
#SpringBootApplication
#EnableAutoConfiguration
#ComponentScan("a.b") //Note that this scans the components where you have configured spring container backed objects
#PropertySource({
"classpath:someProperty1.properties",
"classpath:someProperty2.properties"
})
public class Main{
public static void main(String[] args) {
SpringApplication.run(Main.class, args);
}
}
What this basically does is, it tells spring that this is a configuration class, and indicates this configuration class that it also triggers auto-configuration and component scanning (scan only these specific packages (a.b) and check if there are any annotations present for automatic bean detection, like: #Component, #Service, #Controller, #Repository). On detecting any class which have these stereotypes spring would create object(s) depending on the configuration. On creating these objects one may have autowired some objects or one could refer to some property defined in properties file. The config #PropertySource does this.
The package declaration in #ComponentScan should be the base package.