Allow property binding of resource to be defined as a raw string / resource content

[nightswimmings]

I am not sure this is more suited for Spring-Boot or Spring Core, but I think it would be beneficial to allow resources to be defined as plain strings.

The idea of Resource is abstracting a resource, whether it comes from a file, an url, etc.. so why not plain text? That way we allow the user passing a file with "foobar" but also the content itself, which would be impossible now

Perhaps something like
my-resource-binded-property: "raw:file_content"
(where "raw" could be a keyword prefix like "classpath:", or "bare:" or "string:")

[wilkinsona]

Thanks for the suggestion, @nightswimmings. You can achieve this today without too much code by plugging in your own ProtocolResolver. Here's an example that shows a configuration properties bound Resource that's configured using a string with a custom prefix:

package com.example.demo;

import java.io.IOException;
import java.nio.charset.StandardCharsets;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.ProtocolResolver;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.StreamUtils;

@SpringBootApplication
@ConfigurationProperties("example")
public class Gh28714Application {

    private Resource resource;
    
    public Resource getResource() {
        return resource;
    }

    public void setResource(Resource resource) {
        this.resource = resource;
    }

    public static void main(String[] args) throws IOException {
        SpringApplication app = new SpringApplication(Gh28714Application.class);
        app.addInitializers((context) -> context.addProtocolResolver(new StringProtocolResolver()));
        Resource resource = app.run("--example.resource=string:a resource configured via a string").getBean(Gh28714Application.class).getResource();
        System.out.println(StreamUtils.copyToString(resource.getInputStream(), StandardCharsets.UTF_8));
    }

    static class StringProtocolResolver implements ProtocolResolver {

        private static final String STRING_PROTOCOL_PREFIX = "string:";

        @Override
        public Resource resolve(String location, ResourceLoader resourceLoader) {
            if (location.startsWith(STRING_PROTOCOL_PREFIX)) {
                return new ByteArrayResource(
                        location.substring(STRING_PROTOCOL_PREFIX.length()).getBytes(StandardCharsets.UTF_8));
            }
            return null;
        }

    }

}

An ApplicationContextInitializer can be registered via spring.factories so this could be implemented in a way that's largely transparent to the application. We'll keep this open to consider adding something like this to Boot itself. In the meantime, hopefully the above will be of use.

[nightswimmings]

Amazing, thanks @wilkinsona !

[sysmat]

It is amazing