cloud.piranha.resource.impl.MultiReleaseResource Maven / Gradle / Ivy
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package cloud.piranha.resource.impl;
import cloud.piranha.resource.api.Resource;
import java.io.IOException;
import java.io.InputStream;
import static java.lang.System.Logger.Level.WARNING;
import java.net.URL;
import java.util.Objects;
import java.util.jar.Attributes;
import java.util.jar.Manifest;
import java.util.stream.IntStream;
import java.util.stream.Stream;
/**
* A resource wrapper that loads the versioned entries from META-INF/versions if
* the resource contains a main attribute named "Multi-Release" in the
* META-INF/MANIFEST.MF
*
*
* A multi-release resource is a resource that contains a set of "base" entries
* and a set of "versioned" entries contained in subdirectories of
* "META-INF/versions" directory
*
* The versioned entries are partitioned by the major version of the Java
* release. A versioned entry, with a version {@code n}, {@code 8 < n}, in the
* "META-INF/versions/{n}" directory overrides the base entry as well as any
* entry with a version number {@code i} where {@code 8 < i < n}
*/
public final class MultiReleaseResource implements Resource {
/**
* Stores the logger.
*/
private static final System.Logger LOGGER = System.getLogger(MultiReleaseResource.class.getName());
/**
* Stores the META-INF constant
*/
private static final String META_INF = "META-INF";
/**
* Stores the META-INF/versions/ constant
*/
private static final String META_INF_VERSIONS = META_INF + "/versions/";
/**
* Stores the current version of the runtime
*/
private static final int CURRENT_VERSION = Runtime.version().feature();
/**
* Stores the base release version
*/
private static final int BASE_RELEASE_VERSION = 8;
/**
* Stores the resource
*/
private final Resource resource;
/**
* Stores if the resource if a multi release
*/
private final boolean isMultiRelease;
/**
* Constructor
*
* @param resource the resource
*/
public MultiReleaseResource(Resource resource) {
this.resource = resource;
boolean isMultiReleaseTemp = false;
try ( InputStream resourceAsStream = resource.getResourceAsStream("META-INF/MANIFEST.MF")) {
if (resourceAsStream != null) {
isMultiReleaseTemp = Boolean.parseBoolean(new Manifest(resourceAsStream).getMainAttributes().getValue(Attributes.Name.MULTI_RELEASE));
}
} catch (IOException ioe) {
LOGGER.log(WARNING, "I/O error occurred while getting manifest for multi release resource", ioe);
}
isMultiRelease = isMultiReleaseTemp;
}
@Override
public URL getResource(String location) {
if (!isMultiRelease) {
return resource.getResource(location);
}
return versionedEntry(location);
}
/**
* Searches in the META-INF/versions for a versioned entry of some resource.
*
*
* It performs a search in META-INF/versions from the current Java release
* until the 9 version (the first version supporting multi-release
* resources).
*
* @param location the location of a resource
* @return the URL of the versioned entry if present otherwise the base
* entry
*/
private URL versionedEntry(String location) {
if (location.startsWith(META_INF)) {
return resource.getResource(location);
}
return IntStream.iterate(CURRENT_VERSION, version -> version > BASE_RELEASE_VERSION, version -> --version)
.mapToObj(version -> resource.getResource(META_INF_VERSIONS + version + "/" + location))
.filter(Objects::nonNull)
.findFirst()
.orElseGet(() -> resource.getResource(location));
}
@Override
public InputStream getResourceAsStream(String location) {
if (!isMultiRelease) {
return resource.getResourceAsStream(location);
}
try {
URL url = versionedEntry(location);
if (url != null) {
return url.openStream();
}
} catch (IOException ioe) {
LOGGER.log(WARNING, "I/O error occurred while getting multi release resource", ioe);
}
return null;
}
@Override
public Stream getAllLocations() {
return resource.getAllLocations();
}
@Override
public String getName() {
return resource.getName();
}
@Override
public String toString() {
return getName() + " " + super.toString();
}
}