CODEWITHSUNDEEP
javaspringspring-mvcproperties
Atharva
Atharva

Reputation: 6969

How to access property value from JVM options in Spring with some default values set in applicationContext.xml?

I want to access some property value passed from JVM in Spring's applicationContext.xml. One way I know to achieve this is by #{systemProperties.myProperty} for some -DmyProperty=xyz according to Spring's Expression Language feature.

But I am interested in having a default value for each such property that I assign through JVM, in case the user doesn't set the value from JVM options of the server. How can I achieve this in any context xml file for Spring? Please help.

Upvotes: 4

Views: 8244

Answers (3)

fahran
fahran

Reputation: 163

Using annotation-based config, you can provide a default in Spring EL using the Elvis Operator:

 @Value("#{systemProperties['hostname'] ?: 'default-hostname'}")
 private String hostname;

Based on atrain's helpful answer. I can't comment yet, or I'd have put the syntax correction there :(

Upvotes: 1

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136042

You can make a bean which takes a map parameter from context with default values and initializes system properties

<bean class="test.B1">
    <constructor-arg>
        <map>
            <entry key="p1" value="v1" />
            <entry key="p2" value="v2" />
                                 ....
        </map>
    </constructor-arg>
</bean>

.

public B1(Map<String, String> defaultProperties) {
    for (Map.Entry<String, String> e : defaultProperties.entrySet()) {
        if (System.getProperty(e.getKey()) == null) {
            System.setProperty(e.getKey()
                    , e.getValue());
        }
    }
}

B1 definition in the context should be before any bean using #{systemProperties.myProperty} so that properties are initialized first

UPDATE

That was about overriding system properties. But if you only need to override Spring placeholders like here

<bean class="test.B1">
    <property name="prop1" value="${xxx}" />
</bean>

it's enough to set property-placeholder's local-override attr to "true" 

<context:property-placeholder location="classpath:/app.properties" local-override="true" />

Upvotes: 3

atrain
atrain

Reputation: 9255

In Spring EL, you can add in a default value. In your case:

#{systemProperties.myProperty:MyDefaultValue}

Upvotes: 1

Related Questions