How do I create a spring bean for a Java double primitive?
Question
I'd like to create a spring bean that holds the value of a double. Something like:
<bean id="doubleValue" value="3.7"/>
Solution
Declare it like this:
<bean id="doubleValue" class="java.lang.Double">
<constructor-arg index="0" value="3.7"/>
</bean>
And use like this:
<bean id="someOtherBean" ...>
<property name="value" ref="doubleValue"/>
</bean>
OTHER TIPS
It's also worth noting that depending on your need defining your own bean may not be the best bet for you.
<util:constant static-field="org.example.Constants.FOO"/>
is a good way to access a constant value stored in a class and default binders also work very well for conversions e.g.
<bean class="Foo" p:doubleValue="123.00"/>
I've found myself replacing many of my beans in this manner, coupled with a properties file defining my values (for reuse purposes). What used to look like this
<bean id="d1" class="java.lang.Double">
<constructor-arg value="3.7"/>
</bean>
<bean id="foo" class="Foo">
<property name="doubleVal" ref="d1"/>
</bean>
gets refactored into this:
<bean
id="propertyFile"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
p:location="classpath:my.properties"
/>
<bean id="foo" class="Foo" p:doubleVal="${d1}"/>
Why don't you just use a Double? any reason?
Spring 2.5+
You can define bean like this in Java config:
@Configuration
public class BeanConfig {
@Bean
public Double doubleBean(){
return new Double(3.7);
}
}
You can use this bean like this in your program:
@Autowired
Double doubleBean;
public void printDouble(){
System.out.println(doubleBean); //sample usage
}
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