SpEL (Spring) syntax for default value when property non-existant or equal to 0

user_4426091 0
Viewed 7004

I'm trying to set an Integer property to a default value of 1 if it either does not exist or if its current value is 0 and I can't for the life of me get the 0 comparison to work properly.

The original value (if set) will come in via the command line.

Here are the relevant line in my class:

@Configuration
public class AppConfig {

    @Value("${${instance.procmultiplier} == 0 ? Integer.parseInt('1') : ${instance.procmultiplier}}")
    public Integer procMultiplier;
}

I have tried numerous variations of the @Value annotation and at one point, I swear it recognized the 0 value, and I can't get back to that state. I was first trying to simply get it to recognize the 0 value and default to 1 and I was then going to try and insert a null-check.

Is there a way to do both all in the same annotation? One idea I had was to split the null-check and 0-check into two different properties, basically have procmultiplier=${instance.procmultiplier:1} in a properties file and then change the annotation to @Value("${${procmultiplier} == 0 ? Integer.parseInt('1') : ${procmultiplier}}") but nothing I try works.

My command is: mvn clean package && java -Dspring.profiles.active=json -Dinstance.procmultiplier=0 -jar target/MyApp-0.0.1-SNAPSHOT.jar.

The property ends up just being equal to whatever I set it to on the command line.

Any ideas on how to check for both non-existent and 0 and default to 1 if either is true, otherwise set to whatever comes in via command line?

spring-el spring-boot spring java
3 Answers

It appears my problem was using ${...} instead of #{...}. Here is my solution using two different properties:

bootstrap.properties

procmultiplier=${instance.procmultiplier:1}

AppConfig.java

@Configuration
public class AppConfig {

    @Value("#{${procmultiplier} == 0 ? 1 : ${procmultiplier}}")
    public Integer procMultiplier;
}

Command Line: mvn clean package && java -Dspring.profiles.active=json -Dinstance.procmultiplier=0 -jar target/MyApp-0.0.1-SNAPSHOT.jar

Also allows for a missing instance.procmultiplier parameter.

I still don't know how to do it all in one shot with 1 property though...

user_44260910

According to this post you should try 

@Value("#{someBean.someProperty != null ? someBean.someProperty : 'default'}")
private String ternary;
user_55728690

This works for me in xml:

<bean id="myBean" class="myClass" >
    <property name="myProp" value="#{systemProperties['a.b'] ?: '${a.b}'}"/>
</bean>

This will take from system properties if exist, otherwise from property file

user_154166960
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