Primary

we use @Primary to give higher preference to a bean when there are multiple beans of the same type.

Example

@Configuration
public class Config {

    @Bean
    public Employee JohnEmployee() {
        return new Employee("John");
    }

    @Bean
    public Employee TonyEmployee() {
        return new Employee("Tony");
    }
}

Spring throws NoUniqueBeanDefinitionException if we try to run this code. To access beans with the same type we usually use @Qualifier(“beanName”) annotation.
We apply it at the injection point along with Autowired. In our case, we select the beans at the configuration phase so Qualifier can't be applied here.

Using @Primary with Beans

@Configuration
public class Config {

    @Bean
    public Employee JohnEmployee() {
        return new Employee("John");
    }

    @Bean
    @Primary
    public Employee TonyEmployee() {
        return new Employee("Tony");
    }
}

Now, let's start the application context and get the Employee bean from it:

AnnotationConfigApplicationContext context
  = new AnnotationConfigApplicationContext(Config.class);

Employee employee = context.getBean(Employee.class);
System.out.println(employee);

When we run the applcation, it will print:

Employee{name='Tony'}