Java Spring bean with private constructor - Stack Overflow

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Spring bean with private constructor

up vote4down votefavorite 1	Is possible in Spring that class for bean doesn't have public constructor but only private ? Will this private constructor invoked when bean is created? Thanks. java spring constructor javabeans private share|improve this question asked Aug 31 '11 at 8:36 user710818 2,47911340 77% accept rate
	3   How about giving it a try and then posting the results? – dm3 Aug 31 '11 at 8:38 It is difficult - I don't have all source. – user710818 Aug 31 '11 at 8:40 feedback

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Yes, Spring can invoke private constructors. If it finds a constructor with the right arguments, regardless of visibility, it will use reflection to set its constructor to be accessible. share|improve this answer edited Aug 31 '11 at 9:13 answered Aug 31 '11 at 8:48 Kevin Stembridge 2,271720

Could you please give me the reference to docs? Constructor has parameters, and in xml file to this arguments assigned values. – user710818 Aug 31 '11 at 8:52 you mean if a bean has specifically something like private bean() { ... } spring can invoke that? How is that possible, that defies the whole purpose of "private". – Ashkan Aryan Aug 31 '11 at 8:56 Sorry, I'm probably wrong about it only being no-arg constructors. I'm just going by what I've noticed on my own projects. I can't say I've ever seen it in the Spring documentation anywhere. But this is the javadoc for the class that is responsible for doing the instantiation. static.springsource.org/spring/docs/3.0.x/javadoc-api/org/…...) – Kevin Stembridge Aug 31 '11 at 9:01 4   @Ashkan It is possible using reflection. In particular, the Spring BeanUtils class uses a class called ReflectionUtils to make the constructor accessible. See javadocs for Constructor.setAccessible(). – Kevin Stembridge Aug 31 '11 at 9:03 @Kevin Stembridge you are correct, it is possible using Reflection. – Ashkan Aryan Aug 31 '11 at 9:07 show 2 more comments feedback

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You can always use a factory method to create beans rather than relying on a default constructor, fromThe IoC container: Instantiation using an instance factory method: <!-- the factory bean, which contains a method called createInstance() --> <bean id="serviceLocator" class="com.foo.DefaultServiceLocator"> <!-- inject any dependencies required by this locator bean --> </bean> <!-- the bean to be created via the factory bean --> <bean id="exampleBean" factory-bean="serviceLocator" factory-method="createInstance"/> This has the advantage that you can use non-default constructors for your bean, and the dependencies for the factory method bean can be injected as well. share|improve this answer edited Aug 31 '11 at 9:08 answered Aug 31 '11 at 8:51 Matthew Farwell 20.9k52964

interesting, but I cannot find factory. May be exists another way? – user710818 Aug 31 '11 at 9:08 1   You can't find factory? I don't understand what you are saying. – Matthew Farwell Aug 31 '11 at 9:09 @Matthew: He appears to be retrofitting Spring around some fugly third-party code. That's just bound to be messy. – Donal Fellows Aug 31 '11 at 9:29 1   @Donal, no I didn't understand what he said in the comment. – Matthew Farwell Aug 31 '11 at 9:52

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