--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/java/util/spi/ToolProvider.java Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.util.spi;
+
+import java.io.PrintStream;
+import java.io.PrintWriter;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.ServiceLoader;
+import java.util.stream.StreamSupport;
+
+/**
+ * An interface for command-line tools to provide a way to
+ * be invoked without necessarily starting a new VM.
+ *
+ * <p>Tool providers are normally located using the service-provider
+ * loading facility defined by {@link ServiceLoader}.
+ * Each provider must provide a name, and a method to run
+ * an instance of the corresponding tool. When a tool is run,
+ * it will be provided with an array of string arguments, and a
+ * pair of streams: one for normal (or expected) output and the other
+ * for reporting any errors that may occur.
+ * The interpretation of the string arguments will normally be defined by
+ * each individual tool provider, but will generally correspond to the
+ * arguments that could be provided to the tool when invoking the tool
+ * from the command line.
+ *
+ * @since 9
+ */
+public interface ToolProvider {
+ /**
+ * Returns the name of this tool provider.
+ *
+ * @apiNote It is recommended that the name be the same as would be
+ * used on the command line: for example, "javac", "jar", "jlink".
+ *
+ * @return the name of this tool provider
+ */
+ String name();
+
+ /**
+ * Runs an instance of the tool, returning zero for a successful run.
+ * Any non-zero return value indicates a tool-specific error during the
+ * execution.
+ *
+ * Two streams should be provided, for "expected" output, and for any
+ * error messages. If it is not necessary to distinguish the output,
+ * the same stream may be used for both.
+ *
+ * @apiNote The interpretation of the arguments will be specific to
+ * each tool.
+ *
+ * @param out a stream to which "expected" output should be written
+ *
+ * @param err a stream to which any error messages should be written
+ *
+ * @param args the command-line arguments for the tool
+ *
+ * @return the result of executing the tool.
+ * A return value of 0 means the tool did not encounter any errors;
+ * any other value indicates that at least one error occurred
+ * during execution.
+ *
+ * @throws NullPointerException if any of the arguments are {@code null},
+ * or if there are any {@code null} values in the {@code args}
+ * array
+ */
+ int run(PrintWriter out, PrintWriter err, String... args);
+
+ /**
+ * Runs an instance of the tool, returning zero for a successful run.
+ * Any non-zero return value indicates a tool-specific error during the
+ * execution.
+ *
+ * Two streams should be provided, for "expected" output, and for any
+ * error messages. If it is not necessary to distinguish the output,
+ * the same stream may be used for both.
+ *
+ * @apiNote The interpretation of the arguments will be specific to
+ * each tool.
+ *
+ * @implNote This implementation wraps the {@code out} and {@code err}
+ * streams within {@link PrintWriter}s, and then calls
+ * {@link #run(PrintWriter, PrintWriter, String[])}.
+ *
+ * @param out a stream to which "expected" output should be written
+ *
+ * @param err a stream to which any error messages should be written
+ *
+ * @param args the command-line arguments for the tool
+ *
+ * @return the result of executing the tool.
+ * A return value of 0 means the tool did not encounter any errors;
+ * any other value indicates that at least one error occurred
+ * during execution.
+ *
+ * @throws NullPointerException if any of the arguments are {@code null},
+ * or if there are any {@code null} values in the {@code args}
+ * array
+ */
+ default int run(PrintStream out, PrintStream err, String... args) {
+ Objects.requireNonNull(out);
+ Objects.requireNonNull(err);
+ for (String arg : args) {
+ Objects.requireNonNull(args);
+ }
+
+ PrintWriter outWriter = new PrintWriter(out);
+ PrintWriter errWriter = new PrintWriter(err);
+ try {
+ try {
+ return run(outWriter, errWriter, args);
+ } finally {
+ outWriter.flush();
+ }
+ } finally {
+ errWriter.flush();
+ }
+ }
+
+ /**
+ * Returns the first instance of a {@code ToolProvider} with the given name,
+ * as loaded by {@link ServiceLoader} using the system class loader.
+ *
+ * @param name the name of the desired tool provider
+ *
+ * @return an {@code Optional<ToolProvider>} of the first instance found
+ *
+ * @throws NullPointerException if {@code name} is {@code null}
+ */
+ static Optional<ToolProvider> findFirst(String name) {
+ Objects.requireNonNull(name);
+ ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
+ return AccessController.doPrivileged(
+ (PrivilegedAction<Optional<ToolProvider>>) () -> {
+ ServiceLoader<ToolProvider> sl =
+ ServiceLoader.load(ToolProvider.class, systemClassLoader);
+ return StreamSupport.stream(sl.spliterator(), false)
+ .filter(p -> p.name().equals(name))
+ .findFirst();
+ });
+ }
+}
+