ResourceLoader, ResourcePatternResolver, ApplicationContext and Resources Paths

ResourceLoader #

This is a technology used to access Resources within a Spring project. -> It uses Resource implementations.

It is fundamentally implemented within the ApplicationContext.

It is utilized when there's a need to access files within the project (primarily files under the classpath).

Most predefined files are loaded automatically. However, it's used when additional files are needed.

@Service
public class ResourceService {
    @Autowired //Automatically receives dependency. Injects itself.
    ApplicationContext ctx;

    public void setResource() {
        Resource myTemplate = ctx.getResource("classpath:some/resource/path/myTemplate.txt");
            //ctx.getResource("file:/some/resource/path/myTemplae.txt);
            //ctx.getResource("http://myhost.com/resource/path/myTemplate.txt);
        
        //use myTemplate
    }
}

ResourcePatternResolver #

An interface used to load ResourceLoader from the Spring ApplicationContext.

It automatically selects the ResourceLoader implementation based on location specifier patterns (classpath:, file:, http:).

public interface ApplicationContext extends EnvironmentCapable, ListableBeanFactory, MierachicalBeanFactory, MessageSource, ApplicationEvenPublisher, ResourcePatternResolver {
    //Spring ApplicationContext interface
}

ResourcePatternResolver is extended by ApplicationContext.

ApplicationContext and Resource Paths #

Methods for retrieving configuration values that make up the ApplicationContext (Spring's core configuration).

//create applicationContext
ApplicationContext ctx = new ClassPathXmlApplicationContext("conf/appContext.xml");

ApplicationContext ctx = new FileSystemXmlApplicationContext("conf/appContext.xml");

ApplicationContext ctx = new FileSystemXmlApplicationContext("classpath:conf/appContext.xml");

//then use
Bear bear = (Bear) ctx.getBean("bear");

Using XML is all in the past. Nowadays, configuration values are set based on annotations.