ModuleLoaderMap.java

/*
 * Copyright (c) 2015, 2017, 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
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package jdk.internal.module;

import java.lang.module.Configuration;
import java.lang.module.ResolvedModule;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import jdk.internal.loader.ClassLoaders;

/**
 * Supports the mapping of modules to class loaders.
 * The set of modules mapped to the boot and platform class loaders is generated at build time from this source file.
 */
// 为加载模块的内置类加载器映射系统模块
public final class ModuleLoaderMap {
    
    /**
     * Returns the names of the modules defined to the boot loader.
     */
    // 返回BootClassLoader映射的所有系统module名称
    public static Set<String> bootModules() {
        // The list of boot modules generated at build time.
        String[] BOOT_MODULES = new String[] {
            "java.base",
            "java.datatransfer",
            "java.desktop",
            "java.instrument",
            "java.logging",
            "java.management",
            "java.management.rmi",
            "java.naming",
            "java.prefs",
            "java.rmi",
            "java.security.sasl",
            "java.xml",
            "jdk.internal.vm.ci",
            "jdk.jfr",
            "jdk.management",
            "jdk.management.agent",
            "jdk.management.jfr",
            "jdk.naming.rmi",
            "jdk.net",
            "jdk.sctp",
            "jdk.unsupported"
        };
        Set<String> bootModules = new HashSet<>(BOOT_MODULES.length);
        bootModules.addAll(Arrays.asList(BOOT_MODULES));
        return bootModules;
    }
    
    /**
     * Returns the names of the modules defined to the platform loader.
     */
    // 返回PlatformClassLoader映射的所有系统module名称
    public static Set<String> platformModules() {
        // The list of platform modules generated at build time.
        String[] PLATFORM_MODULES = new String[] {
            "java.compiler",
            "java.net.http",
            "java.scripting",
            "java.se",
            "java.security.jgss",
            "java.smartcardio",
            "java.sql",
            "java.sql.rowset",
            "java.transaction.xa",
            "java.xml.crypto",
            "jdk.accessibility",
            "jdk.aot",
            "jdk.charsets",
            "jdk.crypto.cryptoki",
            "jdk.crypto.ec",
            "jdk.crypto.mscapi",
            "jdk.dynalink",
            "jdk.httpserver",
            "jdk.internal.vm.compiler",
            "jdk.internal.vm.compiler.management",
            "jdk.jsobject",
            "jdk.localedata",
            "jdk.naming.dns",
            "jdk.scripting.nashorn",
            "jdk.security.auth",
            "jdk.security.jgss",
            "jdk.xml.dom",
            "jdk.zipfs"
        };
        Set<String> platformModules = new HashSet<>(PLATFORM_MODULES.length);
        platformModules.addAll(Arrays.asList(PLATFORM_MODULES));
        return platformModules;
    }
    
    /**
     * Returns the function to map modules in the given configuration to the
     * built-in class loaders.
     */
    // 将模块图中的module映射到PlatformClassLoader和AppClassLoader（过滤了BootClassLoader）
    static Function<String, ClassLoader> mappingFunction(Configuration cf) {
        Set<String> bootModules = bootModules();
        Set<String> platformModules = platformModules();
        
        ClassLoader platformClassLoader = ClassLoaders.platformClassLoader();
        ClassLoader appClassLoader = ClassLoaders.appClassLoader();
        
        Map<String, ClassLoader> map = new HashMap<>();
        
        // 遍历当前模块所在的模块图
        for (ResolvedModule resolvedModule : cf.modules()) {
            String mn = resolvedModule.name();
    
            // 忽略bootModules
            if(bootModules.contains(mn)) {
                continue;
            }
    
            if(platformModules.contains(mn)) {
                map.put(mn, platformClassLoader);
            } else {
                map.put(mn, appClassLoader);
            }
        }
        
        return new Mapper(map);
    }
    
    /**
     * Maps the system modules to the built-in class loaders.
     */
    public static final class Mapper implements Function<String, ClassLoader> {
        private final Map<String, ClassLoader> map;
        
        Mapper(Map<String, ClassLoader> map) {
            this.map = map; // defensive copy not needed
        }
        
        @Override
        public ClassLoader apply(String name) {
            return map.get(name);
        }
    }
}