Backport LoaderUtil updates

Most of what's changed in 3.0 minus the JPMS-specific code.

Signed-off-by: Matt Sicker <[email protected]>

Author: jvz

log4j-api/src/main/java/org/apache/logging/log4j/util/Cast.java

@@ -0,0 +1,40 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.logging.log4j.util;
+
+@InternalApi
+public final class Cast {
+
+    /**
+     * Returns the provided object cast to the generic parameter type or null when the argument is null.
+     *
+     * @param o   object to cast
+     * @param <T> the type to cast
+     * @return object after casting or null if the object was null
+     * @throws ClassCastException if the object cannot be cast to the provided type
+     */
+    public static <T> T cast(final Object o) {
+        if (o == null) {
+            return null;
+        }
+        @SuppressWarnings("unchecked") final T t = (T) o;
+        return t;
+    }
+
+    private Cast() {
+    }
+}

log4j-api/src/main/java/org/apache/logging/log4j/util/InternalException.java

@@ -0,0 +1,54 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.logging.log4j.util;
+
+/**
+ * Exception thrown when an error occurs while accessing internal resources. This is generally used to
+ * convert checked exceptions to runtime exceptions.
+ */
+public class InternalException extends RuntimeException {
+
+    private static final long serialVersionUID = 6366395965071580537L;
+
+    /**
+     * Construct an exception with a message.
+     *
+     * @param message The reason for the exception
+     */
+    public InternalException(final String message) {
+        super(message);
+    }
+
+    /**
+     * Construct an exception with a message and underlying cause.
+     *
+     * @param message The reason for the exception
+     * @param cause The underlying cause of the exception
+     */
+    public InternalException(final String message, final Throwable cause) {
+        super(message, cause);
+    }
+
+    /**
+     * Construct an exception with an underlying cause.
+     *
+     * @param cause The underlying cause of the exception
+     */
+    public InternalException(final Throwable cause) {
+        super(cause);
+    }
+}