Scanning Multiple Paths Or Packages with @ComponentScan Annotation in Spring Boot

1. Introduction

in this article, You'll learn how to scan multiple packages in spring boot application with @ComponentScan annotation.

All the classes and sub-packages will be scanned automatically under Spring Boot main class package. During the scan, it will detect @Component, @Configurations, @Bean annotated classes, and methods.

If you have many packages or paths in your application and all of them are outside the spring boot main class will not be scanned automatically.

By using @ComponentScan annotation, we can autowire the classes from another project or another jar.

2. Adding Single Package Package to @ComponentScan in Spring Boot

Creating a new class EmployeeOne in "com.javaprogramto.packagee.one". This is not under the main boot application.

How to Scan Multiple Packages with @ComponentScan Annotation

package com.javaprogramto.packagee.one;

import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Component

public class EmployeeOne {

    private int id;
    private String name;

}

By default, this class will not be scanned. So, you must tell to spring that scan this class.

To tell spring, use @ComponentScan with the argument that takes String value. as below

Note:

When you add @ComponentScan explicitly then-new package and current spring boot main application package will be scanned recursively.

package com.javaprogramto.springboot.SpringBootCofigurations;

import com.javaprogramto.packagee.one.EmployeeOne;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ComponentScan;

import java.util.HashMap;
import java.util.Map;

@SpringBootApplication
@ComponentScan("com.javaprogramto.packagee.one")

public class SpringBootCofigurationsApplication {

    public static void main(String[] args) {

        SpringApplication app = new SpringApplication(SpringBootCofigurationsApplication.class);


        ApplicationContext context =  app.run(args);
        EmployeeOne e = (EmployeeOne)context.getBean("employeeOne");
        System.out.println("Employee bean : "+e);

    }


}

Output:

2020-05-08 20:47:23.666  INFO 7798 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''

2020-05-08 20:47:23.670  INFO 7798 --- [           main] j.s.S.SpringBootCofigurationsApplication : Started SpringBootCofigurationsApplication in 1.458 seconds (JVM running for 1.893)

Employee beab : com.javaprogramto.packagee.one.Employee@2fb69ff6

3. Scanning Multiple Packages in Spring Boot

Next, Create another class in the different packages as below.

package com.javaprogramto.packagee.two;

import org.springframework.stereotype.Component;

@Component
public class EmployeeTwo {

    private int id;
    private String name;
}

To add many packages to Component Scan, you should pass the String[] array to the @ComponentScan annotation.

package com.javaprogramto.springboot.SpringBootCofigurations;

import com.javaprogramto.packagee.one.EmployeeOne;
import com.javaprogramto.packagee.two.EmployeeTwo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ComponentScan;

import java.util.HashMap;
import java.util.Map;

@SpringBootApplication
@ComponentScan({"com.javaprogramto.packagee.one", "com.javaprogramto.packagee.two"})

public class SpringBootCofigurationsApplication {

    public static void main(String[] args) {

        SpringApplication app = new SpringApplication(SpringBootCofigurationsApplication.class);

        Map<String, Object> customConfig = new HashMap<>();
        customConfig.put("server.port", "9009");

        ApplicationContext context =  app.run(args);
        EmployeeOne e = (EmployeeOne)context.getBean("employeeOne");
        System.out.println("EmployeeOne bean : "+e);

        EmployeeTwo e2 = (EmployeeTwo) context.getBean("employeeTwo");
        System.out.println("EmployeeTwo bean : "+e2);

    }

}

Output:

EmployeeOne bean : com.javaprogramto.packagee.one.EmployeeOne@41c89d2f

EmployeeTwo bean : com.javaprogramto.packagee.two.EmployeeTwo@410e94e

4. Scan with @ComponentScan with basePackages Attribute

There is another way to define the package scanning with basePackages attribute in @ComponentScan annotation.

You need not add the @ComponetScan annotation on the main class. Define this annotation in any class.

@ComponentScan(basePackages = "com.javaprogramto.packagee.three")
@Component
public class EmployeeTwo {

    private int id;
    private String name;
}

Next, create a new class in package three as below.

package com.javaprogramto.packagee.three;

import org.springframework.stereotype.Component;

@Component
public class EmployeeThree {
}

Now, run the main class with the below code.

EmployeeThree e3 = (EmployeeThree) context.getBean("employeeThree");
System.out.println("EmployeeThree bean : "+e3);

Output:

[EmployeeThree bean : com.javaprogramto.packagee.three.EmployeeThree@c7a977f]

5. Conclusion

In this article, you've seen how to add multiple packages to be scanned by the Spring Boot applications with @ComponentScan annotation with arguments and with basePackages attribute.

All the code is shown in this article is over GitHub.

You can download the project directly and can run in your local without any errors.

View on GitHub 

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If you have any queries please post in the comment section.