I've never worked with Spring before, and I've run into a configuration object that looks somewhat like this
public class Config {
#Value("${app.module.config1}")
private String config1;
#Value("${app.module.config2}")
private String config2
...
public String getConfig1() {
return config1;
}
...
Can anyone explain what is happening here? I'm assuming this is some type of code injection, but I can't find where these values are coming from!
They allow you to direct inject a Value from a properties file (system or declared property) in the variable. Using the util:properties tag you can add something like this in your applicationContext.xml
<util:properties id="message" location="classpath:com/your/program/resources/message.properties" />
Pointing for a properties file named "message.properties" with some content:
application.hello.message = Hello World!
And then, in your java source file, inject a direct value from this properties file using the #Value annotation:
#Value("#{message['application.hello.message']}")
private String helloWorldMessage;
#Value("${app.module.config1}")
This is part of the spring expression language where the spring framework would look for app.module.config1 JVM property from System.getProperties() and injects the value of that property into config1 attribute in that class. Please see this reference for more details in Spring 3.0.x and this reference for the current docs.
Related
I have a situation where we are reading one property from properties file and now we have been asked to point to another endpoint and for some time we have to manage both these endpoints unless this new endpoint is tested and validated throughly.
I wanted to handle this situation by adding this newer property in properties file and in the actual class were we are reading this property with #Value Annotation the old one can be passed as default with its key as value something like
#Value("${backend.endpoint:${older.endpoint}}"). is it possible ?
Yes you can do it, I have tested it, my sample code
code:
#Value("#{ ${spring.myapp.usenewval} ? '${spring.myapp.newval}' : '${spring.myapp.oldval}}'}")
private String message;
Properties
spring:
myapp:
usenewval: false
newval: hello
oldval: world.....
You can always set spring.myapp.usenewval from outside like
java -jar -Dspring.myapp.usenewval=true myapp.jar
You can use it like this. (I've personally never done it, so forgive me if I'm wrong)
#Configuration
public class PropertyConfiguration {
#Value("{'${backend.endpoint:${older.endpoint:}}'}")
private String myValue;
}
This #Value annotation uses backend.endpoint, if it is provided and defaults to older.endpoint, if backend.endpoint is not provided.
If neither is provided, the property must be set null.
There are other ways to handle this as well. Probably, use #Value for both the property and handle in code.
Here is quick fix for you. Kindly refer it.
You can set default value to #Value annotation of spring as following.
#Controller
#RequestMapping(value = "/your path")
public class MyController {
#Value("${key:true}")
private boolean booleanWithDefaultValue;
}
Here, I take Boolean variable and set default value as "true".
Hope this solution works.
I am trying to populate Custom class with properties. following is my Custom Properties class:
#Configuration
#ConfigurationProperties(prefix = "foo.bar")
public class CustomProperties{
private String PROPERTY_ONE;
private String propertyTwo;
//setters
//getters
}
and my properties in application.properties are:
foo.bar.PROPERTY_ONE=some text
foo.bar.PROPERTY_TWO=some other text
When I am trying to use value from CustomProperties this is what I gets:
customProperties.getPROPERTY_ONE() = null
customProperties.getPopertyTwo() = some other text
So I observed that if I have variable name with underscore(_) in it not populating the property value.
is there any way to get the value with variable having underscore?
Yes, it is 100% possible to get your configuration values.
It's all about the casing! Inside of CustomProperties simply name your first property propertyOne ... and refactor your getters/setters appropriately ... and you'll be good to go!
Spring's got the camel casing going on when translating the configuration fields to your Configuration classes/properties. So instead of matching the casing of your properties, follow the camel casing equivalent of the property name found in your configuration file.
Example: PROPERTY_ONE translates to propertyOne
I have read pretty much everything I can find on StackOverflow and other sites and I don't see a definitive answer anywhere.
I have a class that implements #Condition that I use in a #Configuration file to conditionally load some beans. I am doing something like this:
public class MyCondition implements Condition {
#Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metdata) {
String property = context.getEnvironment().getProperty("some.prop.from.file");
boolean enable = Boolean.parseBoolean(property);
return enable;
}
}
When debugging I see that getting the property from the environment always returns null, even though the property is injected in other beans using #Value.
So my question can you or can't you attempt to get a property value from a file within a #Condition class? Can you only get System properties? I would think that this is a common use case that I would think Spring could handle.
Had to add the property to application.properties and not the other property files that are loaded during startup.
I am trying to find a way to do the following in my spring boot 1.5 application.
I have a variable who's value is dynamic meaning it comes in from an external system.
String name = "abc"; //gets set externally
I want to try and use the name's value to lookup my property file and see if there is a matching property defined. something like..
#Value("#{myClassName.name.concat('something')}")
String propertyValue;
Now my application.property file has the following property set
assume name has the value "abc"
property file contents:
abc.something:abcValue
Now, when i try to access the value of the variable propertyValue it gets set to the value abc.something and not abcValue.
I probably think I cannot use #Value with #{} to get to that, I was wondering if there was a way to to use #{} inside ${} so that I goes and fetches the property value after calculating the name of the property using #{}.
Let me know if you need more details please.
A bean life-cycle requires properties to be resolved at compile time. So, #Value requires constant parameter.
You can use Environment bean to access your properties programmatically.
import org.springframework.core.env.Environment;
#Service
public class Serivce {
#Autowired
private Environment environment;
public String getProperty(final String keyPart) {
String key = "build.your." + keyPart;
return environment.getProperty(key)
}
}
By the way you can use #('${spring.some.property}') in SpEL to access placeholder.
// This is valid access to property
#Value("#('${spring.some.property}')")
private String property;
I read a post about authentication with facebook, http://www.jasha.eu/blogposts/2013/09/retrieve-facebook-profile-data-java-spring-social.html
he use autowired to inject 3 arguments to the constructor. which gives me SpelEvaluationException.
My project, I add a config.properties under /src/
facebook.clientId=237473571343
facebook.clientSecret=9iuwijig[sa[w90u2tjgjgj
application.host=http://localhost:8080
and the constructor
#Controller
public class FacebookSpringSocialAuthenticator {
public static final String STATE = "state";
private String applicationHost;
private FacebookConnectionFactory facebookConnectionFactory;
#Autowired
public FacebookSpringSocialAuthenticator(
#Value("#{properties['facebook.clientId']}")
String clientId,
#Value("#{properties['facebook.clientSecret']}")
String clientSecret,
#Value("#{properties['application.host']}")
String applicationHost) {
this.applicationHost = applicationHost;
facebookConnectionFactory =
new FacebookConnectionFactory(clientId, clientSecret);
}
}
after search and reading discussions and docs, I still don't figure out what to do.
the #{} is spring EL support, don't know how to use it, and don't know the difference to ${}
if I change to #Value("${facebook.clientId}"), there will be no exception, then I use debug mode to read the value of clientId, it does not show 237473571343, it shows ${facebook.clientId}, is that working correctly?
#Value("#{properties['facebook.clientId']}")
In your #Value annotation you are using a SpEL expression. In your case it is going to look for a Map or Properties object named properties and try to find a property with the key facebook.clientId.
To make it work you need to add the following
<util:properties id="properties" location="config.properties" />
Although this works I would strongly suggest to use a *PlaceHolderConfigurer instead of using SpEL.First add atag to your configuration, next change your#Value` to simply use properties.
<context:property-placeholder location="config.properties" />
Then your #Value can be like
#Value("${facebook.clientId}")
The added advantage of this is that you could also use system or environment properties to do some configuration (or override parts of your configuration).