com.bbn.parliament.util.JavaResource Maven / Gradle / Ivy
// Copyright (c) 2019, 2020 RTX BBN Technologies Corp.
package com.bbn.parliament.util;
import java.io.IOException;
import java.io.InputStream;
import java.io.UncheckedIOException;
import java.nio.charset.StandardCharsets;
import java.util.MissingResourceException;
/**
* A utility class for loading a Java resource into memory.
*
* Since Java resources are usually considered part of the code base in which
* they reside, exceptions generally only happen as the result of programming
* errors, and should therefore be detected during implementation and testing.
* Thus, we convert them to runtime exceptions (UncheckedIOException) under the
* assumption that they won't happen in practice in a real deployment.
*
* @author iemmons
*/
public class JavaResource {
private JavaResource() {} // Prevent instantiation
/**
* Opens an InputStream on the resource of the given name in the package of the
* given class.
*
* @param resourceName The name of the resource to open
* @param cls A class whose package is the resource's location
* @return An InputStream for the indicated resource. If the resource cannot be
* found, the method throws.
*/
@SuppressWarnings("resource")
public static InputStream getAsStream(String resourceName, Class cls) {
InputStream result = cls.getResourceAsStream(resourceName); // NOPMD - CloseResource
return requireNonNull(result, cls, resourceName);
}
/**
* Opens an InputStream on the resource of the given name.
*
* @param resourceName The name of the resource to open
* @return An InputStream for the indicated resource. If the resource cannot be
* found, the method throws.
*/
@SuppressWarnings("resource")
public static InputStream getAsStream(String resourceName) {
ClassLoader cl = Thread.currentThread().getContextClassLoader();
InputStream result = cl.getResourceAsStream(resourceName); // NOPMD - CloseResource
return requireNonNull(result, null, resourceName);
}
private static InputStream requireNonNull(InputStream stream, Class cls, String resourceName) {
if (stream == null) {
String message = String.format("Unable to locate resource '%1$s'", resourceName);
String clsName = (cls == null) ? null : cls.getCanonicalName();
throw new MissingResourceException(message, clsName, resourceName);
}
return stream;
}
/**
* Reads into memory the resource of the given name in the package of the given
* class. The resource is assumed to be encoded as UTF-8 text.
*
* @param resourceName The name of the resource to open
* @param cls A class whose package is the resource's location
* @return A String representing the indicated resource. If the resource cannot
* be found, the method throws.
*/
public static String getAsString(String resourceName, Class cls) {
try (InputStream is = getAsStream(resourceName, cls)) {
return new String(is.readAllBytes(), StandardCharsets.UTF_8);
} catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
/**
* Reads into memory the resource of the given name.
*
* @param resourceName The name of the resource to open
* @return A String representing the indicated resource. If the resource cannot
* be found, the method throws.
*/
public static String getAsString(String resourceName) {
try (InputStream is = getAsStream(resourceName)) {
return new String(is.readAllBytes(), StandardCharsets.UTF_8);
} catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
}