de.larssh.utils.io

Class Resources

java.lang.Object

de.larssh.utils.io.Resources

public final class Resources
extends Object

This class contains helper methods for loading and handling resources.

The commonly used methods to load resources might differ when running from JAR instead of running from local file system. These methods make sure behavior is the same and code works in both situations.

Method Summary

Modifier and Type	Method and Description
static Optional<Path>	getPathToClass(Class<?> clazz) Determine the class file that clazz is defined in.
static Optional<Path>	getPathToJar(Class<?> clazz) Determine the JAR file that clazz is loaded from.
static Optional<Path>	getResource(ClassLoader classLoader, Path resource) Finds the path to resource using the class loader's resource lookup algorithm.
static Optional<Path>	getResourceRelativeTo(Class<?> clazz, Path resource) Finds the path to resource relative to clazz.
static Stream<Path>	getResources(ClassLoader classLoader, Path resource) Finds the paths to resource using the class loader's resource lookup algorithm.
static Stream<Path>	getResourcesRelativeTo(Class<?> clazz, Path resource) Finds the paths to resource relative to clazz.
static Optional<Manifest>	readManifest(Class<?> clazz) Reads the Manifest of the JAR file that clazz has been loaded from.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getPathToClass

public static Optional<Path> getPathToClass(Class<?> clazz)

Determine the class file that clazz is defined in. Classes with no own class file result in Optional.empty().

This method might load (without closing) a FileSystem to handle a JAR archive.

Attention: https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8131067

Parameters:

clazz - class

Returns:

path to the the class file

getPathToJar

public static Optional<Path> getPathToJar(Class<?> clazz)

Determine the JAR file that clazz is loaded from.

Classes outside of a JAR or with no own class file result in Optional.empty().

Parameters:

clazz - class

Returns:

path to the the JAR file

getResource

public static Optional<Path> getResource(ClassLoader classLoader,
                                         Path resource)

Finds the path to resource using the class loader's resource lookup algorithm.

The commonly used method ClassLoader.getResource(String) might differ when running from JAR instead of running from local file system. This method makes sure behavior is the same and code works in both situations.

Calling this might load the FileSystem that is registered for handling JAR files. If no file or folder is found Optional.empty() is returned.

Parameters:

classLoader - class loader to use for resource lookup

resource - path to the resource to find

Returns:

the path to the resource

getResourceRelativeTo

public static Optional<Path> getResourceRelativeTo(Class<?> clazz,
                                                   Path resource)

Finds the path to resource relative to clazz.

The commonly used method Class.getResource(String) might differ when running from JAR instead of running from local file system. This method makes sure behavior is the same and code works in both situations.

Calling this might load the FileSystem that is registered for handling JAR files. If no file or folder is found Optional.empty() is returned.

Parameters:

clazz - class to use for resource lookup

resource - relative path to the resource to find

Returns:

the path to the resource

getResources

public static Stream<Path> getResources(ClassLoader classLoader,
                                        Path resource)

Finds the paths to resource using the class loader's resource lookup algorithm. Instead of getResource(ClassLoader, Path) this method returns not only the first matching resource, but also the shadowed resources based on the class loaders hierarchy.

The commonly used method ClassLoader.getResources(String) might differ when running from JAR instead of running from local file system. This method makes sure behavior is the same and code works in both situations.

Calling this might load the FileSystem that is registered for handling JAR files. If no file or folder is found Optional.empty() is returned.

Parameters:

classLoader - class loader to use for resource lookup

resource - path to the resource to find

Returns:

the paths of the found resources

getResourcesRelativeTo

public static Stream<Path> getResourcesRelativeTo(Class<?> clazz,
                                                  Path resource)

Finds the paths to resource relative to clazz. Instead of getResourceRelativeTo(Class, Path) this method returns not only the first matching resource, but also the shadowed resources based on the class loaders hierarchy.

Calling this might load the FileSystem that is registered for handling JAR files. If no file or folder is found Optional.empty() is returned.

Parameters:

clazz - class to use for resource lookup

resource - path to the resource to find

Returns:

the paths of the found resources

readManifest

public static Optional<Manifest> readManifest(Class<?> clazz)
                                       throws IOException

Reads the Manifest of the JAR file that clazz has been loaded from.

Classes outside of a JAR or with no own class file or JARs with no manifest result in Optional.empty().

Parameters:

clazz - class

Returns:

manifest

Throws:

IOException - if an I/O error occurs