What is the best way to read environment variables in SpringBoot?
In Java I did it using:
String foo = System.getenv("bar");
Is it possible to do it using #Value annotation?
Quoting the documentation:
Spring Boot allows you to externalize your configuration so you can work with the same application code in different environments. You can use properties files, YAML files, environment variables and command-line arguments to externalize configuration. Property values can be injected directly into your beans using the #Value annotation, accessed via Spring’s Environment abstraction or bound to structured objects via #ConfigurationProperties.
So, since Spring boot allows you to use environment variables for configuration, and since Spring boot also allows you to use #Value to read a property from the configuration, the answer is yes.
For example, the following will give the same result:
#Component
public class TestRunner implements CommandLineRunner {
#Value("${bar}")
private String bar;
private final Logger logger = LoggerFactory.getLogger(getClass());
#Override
public void run(String... strings) throws Exception {
logger.info("Foo from #Value: {}", bar);
logger.info("Foo from System.getenv(): {}", System.getenv("bar")); // Same output as line above
}
}
You can do it with the #Value annotation:
#Value("${bar}")
private String myVariable;
You can also use colon to give a default value if not found:
#Value("${bar:default_value}")
private String myVariable;
Here are three "placeholder" syntaxes that work for accessing a system environment variable named MY_SECRET:
#Value("${MY_SECRET:aDefaultValue}")
private String s1;
#Value("#{environment.MY_SECRET}")
private String s2;
#Value("${myApp.mySecretIndirect:aDefaultValue}") // via application property
private String s3;
In the third case, the placeholder references an application property that has been initialized from the system environment in a properties file:
myApp.mySecretIndirect=${MY_SECRET:aDefaultValue}
For #Value to work, it must be used inside a live #Component (or similar). There are extra gochas if you want this to work during unit testing -- see my answer to Why is my Spring #Autowired field null?
Alternatively, you can use the org.springframework.core.env.Environment interface to access environment variables:
import org.springframework.core.env.Environment;
#Autowired
private Environment env;
//...
System.out.println(env.getProperty("bar"));
Read more...
Yes, you can. However, most answer didn't mention, the ordering is very important, please check this https://docs.spring.io/spring-boot/docs/1.5.6.RELEASE/reference/html/boot-features-external-config.html
Your OS environment variables will overwrite the value come from Application properties packaged inside your jar (application.properties and YAML variants)., so basically, your environment variables has higher priority.
you can use it with The #Value annotation for the #Components and #service class
Some times it won't work if it is a normal class
Example:
#Component
public class Testclass{
#Value("${MY_SECRET:aDefaultValue}")
private String test1;
#Value("#{environment.MY_SECRET}")
private String test1;
#Value("${myApp.mySecretIndirect:aDefaultValue}")
private String test1;
//to get the properties list whih are in "," seperated
#Value("${my.list.of.strings}")
private List<String> myList;
}
You can place your environment variable in an application.yml/application.properties file and then you can fetch the value using the #Value annotation.
But in order to use #Value annotation your class should be a bean and should be annotated with #Component annnotation.
You can also provide a default value for the variable.
#Component
#NoArgsConstructor
#Scope(BeanDefinition.SCOPE_PROTOTYPE)
public class MyClass {
#Value("${something.variable:<default-value>}")
private String myEnvVariable;
}
First, you have to define the relevant field information in the properties configuration file, and then use # value to obtain and use
example:
#Value("${abc}")
private String abc;
Related
Given:
application.yml --> content
kafka:
topicA: topic-a
topicB: topic-b
public enum KafkaTopicBeanMapping {
TOPICA(#Value("${kafka.topicA}", "ratelimiterABean"));
TOPICB(#Value("${kafka.topicB}", "ratelimiterBBean"));
private final String topicName;
private final String ratelimiterBeanName;
}
But in the above case, I am getting error that #Value("${kafka.topicA}") cannot be used here.
I don't want to put ratelimiterBeanName as part of application.yml.
Is there a way to achieve this?
Java Enums are static in nature, they can be initialized only once. #Value in Spring makes values dynamic in nature which enums are not capable of.
I'm using a properties file with the value:
com.abc.cpuUtilization.okThreshold = 0.5
I want to use the following configuration class:
#Component
#ConfigurationProperties(prefix="com.abc")
public class SystemConfiguration{
#Value("${cpuUtilization.okThreshold}")
private Double cpuUtilizationOkThreshold;
// getters and setters of cpuUtilizationOkThreshold
}
}
But I get an exception of Could not resolve placeholder 'cpuUtilization.okThreshold'
When setting #Value to be: "${com.abc.cpuUtilization.okThreshold}" it works, but it makes the code look ugly and cumbersome.
Is there a way to configure this class, so I will not have to write the whole prefix for the #Value annotation?
Spring configuration properties scanning works like package scanning.
The #Value annotation works with the full property name, or a raw string value. And so the value you set should be.
Assume to have the com.abc.cpu-utilization.okThreshold=0.5 property.
Solution 1: your SystemConfiguration modify the prefix and delete the #Value:
#Getter
#Setter
#Configuration
#ConfigurationProperties(prefix = "com.abc.cpu-utilization")
public class SystemConfiguration {
private Double okThreshold;
}
Solution 2: your SystemConfiguration could point to com.abc and contain an inner configuration for the cpu-utilization intermediate package:
#Getter
#Setter
#Configuration
#ConfigurationProperties(prefix = "com.abc")
public class SystemConfiguration {
private CpuUtilizationConfig cpuUtilization;
}
#Data
public class CpuUtilizationConfig {
private Double okThreshold;
}
Note that okThreshold and cpuUtilization directly reflect the property naming we have prior defined. Then, Spring will do the magic :-)
See:
Baeldung - Guide to #ConfigurationProperties in Spring Boot
Baeldung - A Quick Guide to Spring #Value
As thepaoloboi said, The #ConfigurationProperties(prefix="com.abc") annotation will allow you to bind fields via their name. If you specify a prefix of "com.abc" and you have a variable named "cpuUtilization", the value of the variable will be that of the "com.abc.cpuUtilization" property.
The #Value annotation fetches the property with the exact same name. #Value("${cpuUtilization.threshold}") will fetch the property with that exact name. It does not take the prefix into account.
For congiuation propertiestion you just need to add the values in proeprties file with the same key with the variable.
in application.properties.
com.abc.cpuUtilization.okThreshold=123
Your class should be:
#Component
#ConfigurationProperties(prefix="com.abc.cpuUtilization")
public class SystemConfiguration{
private Double okThreshold;
}
}
The #ConfigurationProperties(prefix="com.abc") annotation will allow you to bind fields via their name. As #Olgun YILDIZ stated, if you specify a prefix of "com.abc" and you have a variable named "cpuUtilization" , the value of the variable will be that of the "com.abc.cpuUtilization" property. (In fact, you could even name your variable "cpuutilization" , "cpu_utilization" , "cpu-utilization" or "CPU_UTILIZATION" because of Spring's relaxed rules for binding properties).
The #Value annotation fetches the property with the exact same name. #Value("${cpuUtilization.threshold}") will fetch the property with that exact name. It does not take the prefix into account.
Either you do as #Olgun suggested (prefix of "com.abc.cpuUtilization" and variable name "okThreshold" ) or you set the whole property name in the #Value.
#ConfigurationProperties works best with hierarchical properties that all have the same prefix therefore, you add a prefix of com.abc.cpuUtilization.Your POJO class Should be like
#Configuration
#ConfigurationProperties(prefix="com.abc.cpuUtilization")
public class SystemConfiguration{
private Double okThreshold;
public Double getOkThreshold() {
return okThreshold;
}
public void setOkThreshold(Double okThreshold) {
this.okThreshold = okThreshold;
}
}
}
If you don't use #Configuration in the POJO, then you need to add #EnableConfigurationProperties(ConfigProperties.class) in the main Spring application class to bind the properties into the POJO.
Then you can set value in application.properties
com.abc.cpuUtilization.okThreshold=0.5
Refer:https://www.baeldung.com/configuration-properties-in-spring-boot
First of all, change your "cpuUtilization.okThreshold" value to com.abc.cpuUtilization-okThreshold = 0.5
Then in the config class:
#Component
#ConfigurationProperties("com.abc")
public class SystemConfiguration{
private Double cpuUtilizationOkThreshold;
// getters and setters of cpuUtilizationOkThreshold
}
}
Try to configure without using "prefix" and without using the #Value annotation, it worked for me.
I know that I can create objects from properties file line properties.
I'd like to get a dynamic array of objects, something like this.
application.properties
heroes.hero1=1,superman,kent
heroes.hero2=2,batman,wayne
Let's say that sometime somebody will add another hero to the file. Is it possible for spring to automatically understand additions to array of heroes? Is there a solution to this? Or is it just easier to read and construct such objects from txt files.
You can actually implement this using Spring Boot Core Functionality:
Create for instance a new Java Class (with use of Lombok for Getters/ Setters now)
#ConfigurationProperties(prefix = "heroes")
#Getter
#Setter
public class HeroesProperties {
private Map<String, List<String>> heroesMapping;
}
And in your application.properties you can add dynamically more heroes in your way.
E.g.
heroes.hero1=1,superman,kent
heroes.hero2=2,xx,aa
heroes.hero3=3,yy,bb
heroes.heroN=4,zz,cc
inject Environment and call getProperty :
import org.springframework.core.env.Environment;
#Autowired
private Environment env;
public String[] getHero() {
return env.getProperty("heroes",String[].class);
}
Yes, you can. Use following code for injecting these properties:
#Value("${heroes.hero1}")
private String[] heroes1;
#Value("${heroes.hero2}")
private String[] heroes2;
I would like to have properties, that I can reference via #Value in spring beans, that can only be created dependend on other properties.
In particular I am having a property, that describes the file system location of a directory.
myDir=/path/to/mydir
And by convention, there is a file in that directory, that is always called myfile.txt.
Now i want to have access to both, the directory and the file, via #Value annotations inside my beans. And sometimes I want to access them as Strings, sometimes as java.io.Files and sometimes as org.springframework.core.io.FileSystemResource (which by the way works very well out of the box!). But because of that concatenating Strings on demand is not an option.
So what I of course could do is just declare both, but I would end up with
myDir=/path/to/mydir
myFile/path/to/mydir/myfile.txt
and I would like to avoid that.
So I came up with an #Configuration class, that takes the property and adds it as new PropertySource:
#Autowired
private ConfigurableEnvironment environment;
#Value("${myDir}")
private void addCompleteFilenameAsProperty(Path myDir) {
Path absoluteFilePath = myDir.resolve("myfile.txt");
Map<String, Object> props = new HashMap<>();
props.put("myFile, absoluteFilePath.toString());
environment.getPropertySources().addFirst(new MapPropertySource("additional", props));
}
As you can see, in my context I even created a PropertyEditor, that can convert to java.nio.file.Paths.
Now the problem is, that for some reason, this "works on my machine" (in my IDE), but does not run on the intended target environment. There I get
java.lang.IllegalArgumentException: Could not resolve placeholder 'myFile' in string value "${myFile}"
Spring can combine properties
myDir=/path/to/mydir
myFile=${myDir}/myfile.txt
You can also use a default value without defining your myFile in the properties at first:
Properties file
myDir=/path/to/mydir
In class:
#Value("#{myFile:${myDir}/myfile.txt}")
private String myFileName;
Spring expressions can be used to refer the properties.
In my example it was
query-parm=QueryParam1=
query-value=MyParamaterValue
Now while binding them in Spring Bean.
#Configuration
public class MyConfig {
#Value("${query-param}${query-value}")
private String queryString;
}
Above code will inject QueryParam1=MyParamaterValue to the variable queryString.
Consider this example
#Stateless
public class UniqueIdGenerator {
private static final String COLON = ":";
private String serverPrivateKey;
#SuppressWarnings("UnusedDeclaration")
public UniqueIdGenerator() {
}
#Inject
public UniqueIdGenerator(#Nonnull final String serverPrivateKey) {
this.serverPrivateKey = serverPrivateKey;
}
...
}
I would like to #Inject value of serverPrivateKey based on an environment variable available in different environments.
What is the best way to inject it here?
To inject values from the environment, rather than writing your own producer methods, you may want to have a look at the Configuration API of Apache DeltaSpike.
Using a #ConfigProperty qualifier, you can inject values from a number of different property sources, like system properties, environment variables or JNDI.
Example:
#Inject
#ConfigProperty(name = "SERVER_PRIVATE_KEY")
private String serverPrivateKey;
We use the following pattern: There is a bean which gives us the value which we need. The bean knows how to get the value (environment, System property, whatever). To make things easier later, the type of the bean should be an interface (in your case that might be IPrivateKeyProvider).
The UniqueIdGenerator is then created and we inject the first bean. The setup then decides which bean this will be (some kind of mock for tests and a real implementation for production code).
You will have to use producer Method :
According to related oracle documentation :
A producer method generates an object that can then be injected. Typically, you use producer
methods in the following situations:
[...]
When the concrete type of the object to be injected may vary at runtime
See an example here