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Not able to pass config values in #HystrixProperty annotation

I am trying to pass properties values in #HystrixProperty annotation like below
#HystrixProperty(name="circuitBreaker.requestVolumeThreshold", value="${requestVolumeThreshold}")
Also Tried this
#HystrixProperty(name="circuitBreaker.requestVolumeThreshold", value="#{${requestVolumeThreshold}}")
However its giving me exception "IllegalArgumentException"; bad property value
Where Am I going wrong ?

Spring Expression Language condtional application properties

I'm trying to get a value from the application properties file with condtional. If property a doesn't exits take property b.
But I can't get it to work. I have read about "SPEL" but cannot really understand it. I have tried this
#Value("'${api.path}' ?: '${api.backuppath}'")
private String path;
This doesnt work because it needs value on both property to work. In my case the first property can be null or the second can be null.

Why in the annotation-based Spring app #Value default value is getting resolved to null?

In my class, I have 2 private fields that are pre-populated via #Value annotation. Although the value is getting read correctly from .properties file, its default value is never applied if in .properties file it's not set.
I have tried with creating PropertySourcesPlaceholderConfigurer bean and specifying location to the file: "classpath:application.properties". These are my properties:
#Value("${year:2019}")
private Integer year;
resources/application.properties:
year=
When the year is set, Integer year receives the right value. If it remains empty, I expect default value (2019) to be set, but it remains null.
Spring version: 5.1.8.RELEASE

It is null because your properties file sets it to blank. If you remove the year= from the properties file you should get the default value.

Reading empty string from consul using spring-cloud-consul

I'm migrating from file based .properties file to consul based configuration in my spring application. I'm using spring-cloud-consul. Earlier in my property file I had a property like following
test.key=
In spring application class corresponding field is like this
#Value("${test.key:defaultVal}")
private String testConsul;
In the runtime, the value of testConsul string is an empty string. But when using the consul, whenever I put key test.key without a value, in the runtime it gets resolved to a null.
Is there anyway I can pass an empty string value through consul ?

This is the work around we're using. use a default value which is not exist
${no.such.key:}
Hope this helps.

Spring 4 #Value where property default is a java system property

In Spring 4, using the #Value annotation, what is the right way to specify a system property as a default if a specified property does not exists?
Whereas this works for the no-default case:
#Value("${myapp.temp}")
private String tempDirectory;
This doesn't work when I need a default:
#Value("#{myapp.temp ?: systemProperties.java.io.tmpdir}")
private String tempDirectory;
Nor does this:
#Value("#{myapp.temp ?: systemProperties(java.io.tmpdir)}")
private String tempDirectory;
Both of these give me an exception at the time Spring is trying to create the bean:
org.springframework.beans.factory.BeanCreationException: Error creating bean
with name 'configurationService': Invocation of init method failed;
nested exception is java.lang.NullPointerException
Can this be done?

I tried the following and it worked for me:
#Value("${myapp.temp:#{systemProperties['java.io.tmpdir']}}")
private String tempDirectory;
The missing parts for you I believe was not using ?: and needing the #{}. According to this answer:
${...} is the property placeholder syntax. It can only be used to dereference properties.
#{...} is SpEL syntax, which is far more capable and complex. It can also handle property placeholders, and a lot more besides.
So basically what is happening is we are telling Spring to first interpret myapp.temp as property placeholder syntax by using the ${} syntax. We then use : instead of ?: (which is called the Elvis operator) since the elvis operator only applies to Spring Expression Language expressions, not property placeholder syntax. The third part of our statement is #{systemProperties['java.io.tmpdir']} which is telling Spring to interpret the next expression as a Spring Expression and allows us to get system properties.

Try systemProperties['java.io.tmpdir'].
It's a map, so if the key has a dot in the name, you should use [..]

For me it only works with different property-names (being property.name.a a key with a value in my application.properties and property.name.b a Environment-Variable) like:
#Value("${property.name.a:${property.name.b}}")
The same names didn´t work for me like expected (loading the default, when the first property isn´t present), e.g.:
#Value("${property.name.a:${property.name.a}}")