How to scan multiple paths using the @ComponentScan annotation?

Question

I'm using Spring 3.1 and bootstrapping an application using the @Configuration and @ComponentScan attributes.

The actual start is done with

new AnnotationConfigApplicationContext(MyRootConfigurationClass.class);

This Configuration class is annotated with

@Configuration
@ComponentScan("com.my.package")
public class MyRootConfigurationClass

and this works fine. However I'd like to be more specific about the packages I scan so I tried.

@Configuration
@ComponentScan("com.my.package.first,com.my.package.second")
public class MyRootConfigurationClass

However this fails with errors telling me it can't find components specified using the @Component annotation.

What is the correct way to do what I'm after?

Thanks

Two correct answers given at about the same time as far as I can tell. I'll give the accept to hage just because he has less points, but thank you both. — Programming Guy, May 31 '12 at 01:26
If you are wondering the same thing for **kotlin** version check this one https://stackoverflow.com/a/62818187/7747942 — Sylhare, Jul 09 '20 at 15:21

hage · Accepted Answer · 2017-12-11T08:20:01.047

183

@ComponentScan uses string array, like this:

@ComponentScan({"com.my.package.first","com.my.package.second"})

When you provide multiple package names in only one string, Spring interprets this as one package name, and thus can't find it.

edited Dec 11 '17 at 08:20

answered May 29 '12 at 07:21

hage

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score 51 · Answer 2 · answered Jan 24 '14 at 12:55

51

There is another type-safe alternative to specifying a base-package location as a String. See the API here, but I've also illustrated below:

@ComponentScan(basePackageClasses = {ExampleController.class, ExampleModel.class, ExmapleView.class})

Using the basePackageClasses specifier with your class references will tell Spring to scan those packages (just like the mentioned alternatives), but this method is both type-safe and adds IDE support for future refactoring -- a huge plus in my book.

Reading from the API, Spring suggests creating a no-op marker class or interface in each package you wish to scan that serves no other purpose than to be used as a reference for/by this attribute.

IMO, I don't like the marker-classes (but then again, they are pretty much just like the package-info classes) but the type safety, IDE support, and drastically reducing the number of base packages needed to include for this scan is, with out a doubt, a far better option.

answered Jan 24 '14 at 12:55

Prancer

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1

Could someone explain why @ComponentScan({"com.app", "com.controllers"}) doesn't work for me but @ComponentScan(basePackageClasses ={"com.controllers"}) does work nice ? I find it boring writing every class name – xaverras Oct 08 '15 at 14:19
3

You only have to specify one class in the package, for the package you want to scan. This is known as a marker class. If you need to scan a package higher in the hierarchy that has no classes, spring suggests a technique using a "spring marker" interface or final class defined in that package solely for the purpose of package scanning. – Prancer Oct 12 '15 at 11:54
Thank you. I am so sick of tracking down #wheresWaldo with string-magic/magic-strings. – granadaCoder Mar 29 '21 at 21:30

score 21 · Answer 3 · answered May 29 '12 at 07:23

21

Provide your package name separately, it requires a String[] for package names.

Instead of this:

@ComponentScan("com.my.package.first,com.my.package.second")

Use this:

@ComponentScan({"com.my.package.first","com.my.package.second"})

answered May 29 '12 at 07:23

mprabhat

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Java's "when is a comma-separated", "when is it a string-array", "when is it a string varargs" jigsaw puzzle drives me nuts sometimes. – granadaCoder Mar 30 '21 at 18:22

shashwatZing · Answer 4 · 2020-01-27T15:28:43.387

Another way of doing this is using the basePackages field; which is a field inside ComponentScan annotation.

@ComponentScan(basePackages={"com.firstpackage","com.secondpackage"})

If you look into the ComponentScan annotation .class from the jar file you will see a basePackages field that takes in an array of Strings

public @interface ComponentScan {
String[] basePackages() default {};
}

Or you can mention the classes explicitly. Which takes in array of classes

Class<?>[]  basePackageClasses

score 5 · Answer 5 · answered Nov 24 '16 at 07:07

5

You use ComponentScan to scan multiple packages using

@ComponentScan({"com.my.package.first","com.my.package.second"})

answered Nov 24 '16 at 07:07

ksw

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Farouk.ch · Answer 6 · 2019-02-21T07:20:03.450

3

You can also use @ComponentScans annotation:

@ComponentScans(value = { @ComponentScan("com.my.package.first"),
                          @ComponentScan("com.my.package.second") })

edited Feb 21 '19 at 07:20

answered Feb 16 '19 at 20:48

Farouk.ch

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4

Please consider adding explanation to your answer – yeya Feb 16 '19 at 21:06

score 2 · Answer 7 · edited Mar 21 '20 at 16:26

2

I use:

@ComponentScan(basePackages = {"com.package1","com.package2","com.package3", "com.packagen"})

edited Mar 21 '20 at 16:26

Dharman

30,962
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answered Mar 21 '20 at 11:38

Yann

21
1

score 1 · Answer 8 · answered Feb 01 '19 at 10:20

1

make sure you have added this dependency in your pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

answered Feb 01 '19 at 10:20

Amirtha Krishnan

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Thanks after spending close to half an hour this was the missing dependency – DvixExtract Jul 21 '19 at 11:19
Spring Context is the only required dependency for those annotations. – A_X Jan 22 '22 at 14:35

score 1 · Answer 9 · edited Dec 23 '22 at 05:40

1

Use

 @ComponentScan(basePackages = {"package1", "package2"})

define it at top before class.

Edit: the brackets must be around all the base packages, not a pair of brackets per package

edited Dec 23 '22 at 05:40

geanakuch

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answered Dec 16 '22 at 11:57

vaibhav

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Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Dec 19 '22 at 10:28

How to scan multiple paths using the @ComponentScan annotation?

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