How to load all beans lazily with @ComponentScan in Spring?

Question

I am using Java-based config to set up my Spring application context like this:

@Configuration
@Lazy
@ComponentScan(basePackageClasses = {MyProject.class, OtherProject.class})
public class MyAppConfig {
    ...
}

Beans defined explicitly in the config are loaded lazily, like you would expect. However, scanned classes annotated with @Named are always loaded eagerly. How can I solve this?

Any help is appreciated.

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Note that for classes in the MyProject package, I can work around this by annotating them with @Lazy as well. But the other project does not have a dependency to Spring and I want to keep it like that (hence @Named and not @Component ).

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Note also that this does not seam to be a problem in XML-based config. There, setting default-lazy-init="true" in the <beans> tag seams to do what I want (although I haven't tested that).

Answer 1

As of version 4.1 RC2, this bug is fixed, and you can accomplish lazy loading on component scan with:

@ComponentScan(basePackages = ["..."], lazyInit = true)

https://jira.spring.io/browse/SPR-10459

Answer 2

As you said before there is no direct way to handle that (using @Lazy in the configuration class). But you can try with this approach:

I suppose that OtherProject is a project that is not using Spring, and imagine that these classes are not annotated.

Then you should define in Myproject a configuration that looks like that:

@Configuration
// Avoid use this line if classes aren't annotated @ComponentScan("com.otherProject")
public class MyProjectConfig {

    @Bean(name = "lazyBean")
    @Lazy
    public LazyBean lazyBean(){
        System.out.println("Loading LazyBean bean");
        return new LazyBean(); // Or use a static method factory, this is only an example
    }
}

Using this, the bean "lazyBean" will be created when some instance inject it or when you explicity call it, but never at init time.

Please note that you need to define a new bean per class that you want to use, so this is not good if you have tons of classes but good to minimize the accessibility of classes of your other project (perhaps not all your classes are necessary).

I hope this helps.

Answer 3

从Spring Boot 2.2开始 ，您可以将属性设置为true （默认为false ）以启用延迟初始化：

spring.main.lazy-initialization=true