Resource utility.

src/main/java/com/falsepattern/lib/util/ResourceUtil.java

@@ -0,0 +1,139 @@
+package com.falsepattern.lib.util;
+
+import lombok.val;
+
+import java.io.ByteArrayOutputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * A utility class for reading resources in many ways.
+ */
+public class ResourceUtil {
+
+    /**
+     * Reads a resource as a string, using the {@link StandardCharsets#UTF_8} charset, from a specific jar file. See {@link #getResourceFromJar(String, Class)}.
+     * @param resourcePath The resource to read
+     * @param referenceClass The class, from whose jar to get the resource from
+     * @return The string from the resource
+     * @throws IOException From {@link #readBytes(InputStream)}
+     */
+    public static String getResourceStringFromJar(String resourcePath, Class<?> referenceClass) throws IOException {
+        return getResourceStringFromJar(resourcePath, referenceClass, StandardCharsets.UTF_8);
+    }
+
+
+    /**
+     * Reads a resource as a string from a specific jar file. See {@link #getResourceFromJar(String, Class)}.
+     * @param resourcePath The resource to read
+     * @param referenceClass The class, from whose jar to get the resource from
+     * @param charset The charset to decode the raw bytes with
+     * @return The string from the resource
+     * @throws IOException From {@link #readBytes(InputStream)}
+     */
+    public static String getResourceStringFromJar(String resourcePath, Class<?> referenceClass, Charset charset) throws IOException {
+        return new String(getResourceBytesFromJar(resourcePath, referenceClass), charset);
+    }
+
+
+    /**
+     * Reads a resource as a string, using the {@link StandardCharsets#UTF_8} charset.
+     * @param resourcePath The resource to read
+     * @return The string from the resource
+     * @throws IOException From {@link #readBytes(InputStream)}
+     */
+    public static String getResourceString(String resourcePath) throws IOException {
+        return getResourceString(resourcePath, StandardCharsets.UTF_8);
+    }
+
+    /**
+     * Reads a resource as a string.
+     * @param resourcePath The resource to read
+     * @param charset The charset to decode the raw bytes with
+     * @return The string from the resource
+     * @throws IOException From {@link #readBytes(InputStream)}
+     */
+    public static String getResourceString(String resourcePath, Charset charset) throws IOException {
+        return new String(getResourceBytes(resourcePath), charset);
+    }
+
+    /**
+     * Reads the raw bytes of a resource in a specific jar file. See {@link #getResourceFromJar(String, Class)}.
+     * @param resourcePath The resource to read
+     * @param referenceClass The class, from whose jar to get the resource from
+     * @return The bytes of the resource
+     * @throws IOException From {@link #readBytes(InputStream)}
+     */
+    public static byte[] getResourceBytesFromJar(String resourcePath, Class<?> referenceClass) throws IOException {
+        return readBytesSafe(getResourceFromJar(resourcePath, referenceClass), resourcePath);
+    }
+
+    /**
+     * Reads the raw bytes of a resource.
+     * @param resourcePath The resource to read
+     * @return The bytes of the resource
+     * @throws IOException From {@link #readBytes(InputStream)}
+     */
+    public static byte[] getResourceBytes(String resourcePath) throws IOException {
+        return readBytesSafe(ResourceUtil.class.getResourceAsStream(resourcePath), resourcePath);
+    }
+
+    private static byte[] readBytesSafe(InputStream stream, String resourcePath) throws IOException {
+        if (stream == null) {
+            throw new FileNotFoundException("Could not find resource at " + resourcePath);
+        }
+        return readBytes(stream);
+    }
+
+    /**
+     * Fully reads a stream into a byte array.
+     * @param stream The stream to read
+     * @return The data from the stream
+     * @throws IOException From {@link InputStream#read(byte[])}
+     */
+    public static byte[] readBytes(InputStream stream) throws IOException {
+        val out = new ByteArrayOutputStream();
+        val buf = new byte[4096];
+        int read;
+        while ((read = stream.read(buf)) >= 0) {
+            out.write(buf, 0, read);
+        }
+        return out.toByteArray();
+    }
+
+    /**
+     * Retrieves a resource from the jar file of a specific class.
+     * Falls back to {@link Class#getResourceAsStream(String)} if the resource is not found in the jar, or the class is
+     * not from a jar file.
+     * @param resourcePath The resource to retrieve
+     * @param referenceClass The class, from whose jar to get the resource from
+     * @return The resource, or null if it was not found.
+     */
+    public static InputStream getResourceFromJar(String resourcePath, Class<?> referenceClass) {
+        URL classFile = referenceClass.getResource('/' + referenceClass.getName().replace('.', '/') + ".class");
+        lookup:
+        {
+            if (classFile == null)
+                break lookup;
+            String file = classFile.getFile();
+            int id = file.indexOf("!");
+            if (!classFile.getProtocol().equals("jar") || id < 0)
+                break lookup;
+            //Loading from a jar
+            try {
+                URL resource = new URL("jar:" + file.substring(0, id) + "!" + resourcePath);
+                return resource.openStream();
+            } catch (IOException e) {
+                System.err.println("Failed to load resource " + resourcePath + " from jar " + file.substring(0, id));
+                e.printStackTrace();
+            }
+        }
+        //Fallback logic
+        System.out.println("Using fallback resource loading logic for " + resourcePath + " with reference to " + referenceClass.getName());
+        return referenceClass.getResourceAsStream(resourcePath);
+    }
+}