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8306112: Implementation of JEP 445: Unnamed Classes and Instance Main…
… Methods (Preview) 8308613: javax.lang.model updates for JEP 445 (preview) 8308913: Update core reflection for JEP 445 (preview) Co-authored-by: Maurizio Cimadamore <mcimadamore@openjdk.org> Co-authored-by: Joe Darcy <darcy@openjdk.org> Co-authored-by: Jan Lahoda <jlahoda@openjdk.org> Co-authored-by: Jim Laskey <jlaskey@openjdk.org> Co-authored-by: Adam Sotona <asotona@openjdk.org> Reviewed-by: mcimadamore, vromero, darcy
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169 changes: 169 additions & 0 deletions
169
src/java.base/share/classes/jdk/internal/misc/MainMethodFinder.java
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|---|---|---|
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| /* | ||
| * Copyright (c) 2023, 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. | ||
| */ | ||
|
|
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| package jdk.internal.misc; | ||
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|
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| import java.lang.reflect.Method; | ||
| import java.lang.reflect.Modifier; | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
|
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| public class MainMethodFinder { | ||
| private static boolean correctArgs(Method method) { | ||
| int argc = method.getParameterCount(); | ||
|
|
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| return argc == 0 || argc == 1 && method.getParameterTypes()[0] == String[].class; | ||
| } | ||
|
|
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| /** | ||
| * Gather all the "main" methods in the class hierarchy. | ||
| * | ||
| * @param refc the main class or super class | ||
| * @param mains accumulated main methods | ||
| * @param isMainClass the class is the main class and not a super class | ||
| */ | ||
| private static void gatherMains(Class<?> refc, List<Method> mains, boolean isMainClass) { | ||
| if (refc != null && refc != Object.class) { | ||
| for (Method method : refc.getDeclaredMethods()) { | ||
| int mods = method.getModifiers(); | ||
| // Must be named "main", public|protected|package-private, not synthetic (bridge) and either | ||
| // no arguments or one string array argument. Only statics in the Main class are acceptable. | ||
| if ("main".equals(method.getName()) && | ||
| !method.isSynthetic() && | ||
| !Modifier.isPrivate(mods) && | ||
| correctArgs(method) && | ||
| (isMainClass || !Modifier.isStatic(mods))) | ||
| { | ||
| mains.add(method); | ||
| } | ||
| } | ||
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| gatherMains(refc.getSuperclass(), mains, false); | ||
| } | ||
| } | ||
|
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| /** | ||
| * Comparator for two methods. | ||
| * Priority order is; | ||
| * sub-class < super-class. | ||
| * static < non-static, | ||
| * string arg < no arg and | ||
| * | ||
| * @param a first method | ||
| * @param b second method | ||
| * | ||
| * @return -1, 0 or 1 to represent higher priority. equals priority or lesser priority. | ||
| */ | ||
| private static int compareMethods(Method a, Method b) { | ||
| Class<?> aClass = a.getDeclaringClass(); | ||
| Class<?> bClass = b.getDeclaringClass(); | ||
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| if (aClass != bClass) { | ||
| if (bClass.isAssignableFrom(aClass)) { | ||
| return -1; | ||
| } else { | ||
| return 1; | ||
| } | ||
| } | ||
|
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| int aMods = a.getModifiers(); | ||
| int bMods = b.getModifiers(); | ||
| boolean aIsStatic = Modifier.isStatic(aMods); | ||
| boolean bIsStatic = Modifier.isStatic(bMods); | ||
|
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| if (aIsStatic && !bIsStatic) { | ||
| return -1; | ||
| } else if (!aIsStatic && bIsStatic) { | ||
| return 1; | ||
| } | ||
|
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| int aCount = a.getParameterCount(); | ||
| int bCount = b.getParameterCount(); | ||
|
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| if (bCount < aCount) { | ||
| return -1; | ||
| } else if (aCount < bCount) { | ||
| return 1; | ||
| } | ||
|
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| return 0; | ||
| } | ||
|
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| /** | ||
| * Return the traditional main method or null if not found. | ||
| * | ||
| * @param mainClass main class | ||
| * | ||
| * @return main method or null | ||
| */ | ||
| private static Method getTraditionalMain(Class<?> mainClass) { | ||
| try { | ||
| Method traditionalMain = mainClass.getMethod("main", String[].class); | ||
| int mods = traditionalMain.getModifiers(); | ||
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| if (Modifier.isStatic(mods) && Modifier.isPublic(mods) && traditionalMain.getReturnType() == void.class) { | ||
| return traditionalMain; | ||
| } | ||
| } catch (NoSuchMethodException ex) { | ||
| // not found | ||
| } | ||
|
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| return null; | ||
| } | ||
|
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| /** | ||
| * {@return priority main method if none found} | ||
| * | ||
| * @param mainClass main class | ||
| * | ||
| * @throws NoSuchMethodException when not preview and no method found | ||
| */ | ||
| public static Method findMainMethod(Class<?> mainClass) throws NoSuchMethodException { | ||
| boolean isTraditionMain = !PreviewFeatures.isEnabled(); | ||
| if (isTraditionMain) { | ||
| return mainClass.getMethod("main", String[].class); | ||
| } | ||
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| List<Method> mains = new ArrayList<>(); | ||
| gatherMains(mainClass, mains, true); | ||
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| if (mains.isEmpty()) { | ||
| throw new NoSuchMethodException("No main method found"); | ||
| } | ||
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| if (1 < mains.size()) { | ||
| mains.sort(MainMethodFinder::compareMethods); | ||
| } | ||
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| Method mainMethod = mains.get(0); | ||
| Method traditionalMain = getTraditionalMain(mainClass); | ||
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| if (traditionalMain != null && !traditionalMain.equals(mainMethod)) { | ||
| System.err.println("WARNING: \"" + mains.get(0) + "\" chosen over \"" + traditionalMain + "\""); | ||
| } | ||
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| return mains.get(0); | ||
| } | ||
| } |
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