Injection of List<Resource> is inconsistent with Resource[]

Normally it’s safe to change type from array to list, but it’s not for Resource.

@Value("${resources:file:/tmp/*.text}")
Resource[] resourceArray;  // multiple FileSystemResource

@Value("${resources:file:/tmp/*.text}")
List<Resource> resourceList; // only one FileUrlResource

here is the full test

import static org.junit.Assert.assertEquals;

import java.io.File;
import java.io.IOException;
import java.util.List;

import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.Resource;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.TestPropertySource;
import org.springframework.test.context.junit4.SpringRunner;

import test.ResourceInjectionTest.TestConfiguration;

@RunWith(SpringRunner.class)
@TestPropertySource(properties = { "resources=file:/tmp/*.text" })
@ContextConfiguration(classes = TestConfiguration.class)
public class ResourceInjectionTest {

	private static File[] files;

	@Autowired
	private TestConfiguration testConfiguration;

	@BeforeClass
	public static void setup() throws IOException {
		files = new File[2];
		files[0] = new File("/tmp", "a.text");
		files[1] = new File("/tmp", "b.text");
		for (File f : files)
			f.createNewFile();
	}

	@AfterClass
	public static void cleanup() {
		for (File f : files)
			f.delete();
	}

	@Test
	public void testInjection() {
		assertEquals(2, testConfiguration.resourceArray.length); // two FileSystemResource
		assertEquals(2, testConfiguration.resourceList.size()); // one FileUrlResource
	}

	static class TestConfiguration {
		
		@Value("${resources}")
		Resource[] resourceArray;

		@Value("${resources}")
		List<Resource> resourceList;
		
	}
}

[sbrannen]

Indeed, the difference is that a ResourceArrayPropertyEditor is used to handle the array case; whereas, a CustomCollectionEditor is used to handle the list case.

The former internally uses a ResourcePatternResolver to expand the pattern into the 2 files in the filesystem; whereas, the latter simply treats the pattern as a simple string without expansion.

[sbrannen]

Team Decision: Assigned to 5.x backlog as a potential enhancement.