org.springframework.cloud.function.deployer.ApplicationBootstrap.java Source code

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Here is the source code for org.springframework.cloud.function.deployer.ApplicationBootstrap.java

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/*
 * Copyright 2012-2019 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.cloud.function.deployer;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.jar.JarFile;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.boot.SpringApplication;
import org.springframework.util.StringUtils;

/**
 * Utility class to launch a Spring Boot application (optionally) in an isolated class
 * loader. The class loader is created in such a way that it is mostly a copy of the
 * current class loader (i.e. the one that loaded this class), but has a parent containing
 * reactor-core (if present). It can then share the reactor dependency with other class
 * loaders that the app itself creates, without any other classes being shared, other than
 * the core JDK.
 *
 * @author Mark Fisher
 * @author Dave Syer
 */
public class ApplicationBootstrap {

    private static Log logger = LogFactory.getLog(ApplicationBootstrap.class);

    private ApplicationRunner runner;

    private URLClassLoader classLoader;

    private static boolean isolated(String[] args) {
        for (String arg : args) {
            if (arg.equals("--function.runner.isolated=false")) {
                return false;
            }
        }
        return true;
    }

    /**
     * Run the provided main class as a Spring Boot application with the provided command
     * line arguments.
     * @param mainClass the main class
     * @param args the command line arguments
     */
    public void run(Class<?> mainClass, String... args) {
        if (ApplicationBootstrap.isolated(args)) {
            runner(mainClass).run(args);
        } else {
            SpringApplication.run(mainClass, args);
        }
    }

    /**
     * Clean up the resources used by this instance, if any. Called automatically on a
     * runtime shutdown hook.
     */
    public void close() {
        if (this.runner != null) {
            this.runner.close();
            this.runner = null;
        }
        if (this.classLoader != null) {
            try {
                this.classLoader.close();
            } catch (IOException e) {
                throw new IllegalStateException("Cannot close ClassLoader", e);
            } finally {
                this.classLoader = null;
            }
        }
    }

    public ApplicationRunner getRunner() {
        return this.runner;
    }

    private ApplicationRunner runner(Class<?> mainClass) {
        if (this.runner == null) {
            synchronized (this) {
                if (this.runner == null) {
                    this.classLoader = createClassLoader(mainClass);
                    this.runner = new ApplicationRunner(this.classLoader, mainClass.getName());
                    Runtime.getRuntime().addShutdownHook(new Thread(this::close));
                }
            }
        }
        return this.runner;
    }

    private URLClassLoader createClassLoader(Class<?> mainClass) {
        URL[] urls = findClassPath(mainClass);
        if (urls.length == 1) {
            URL[] classpath = extractClasspath(urls[0]);
            if (classpath != null) {
                urls = classpath;
            }
        }
        List<URL> child = new ArrayList<>();
        List<URL> parent = new ArrayList<>();
        for (URL url : urls) {
            child.add(url);
        }
        for (URL url : urls) {
            if (isRoot(StringUtils.getFilename(clean(url.toString())))) {
                parent.add(url);
                child.remove(url);
            }
        }
        logger.debug("Parent: " + parent);
        logger.debug("Child: " + child);
        ClassLoader base = getClass().getClassLoader();
        if (!parent.isEmpty()) {
            base = new URLClassLoader(parent.toArray(new URL[0]), base.getParent());
        }
        return new URLClassLoader(child.toArray(new URL[0]), base);
    }

    private URL[] findClassPath(Class<?> mainClass) {
        ClassLoader base = mainClass.getClassLoader();
        if (!(base instanceof URLClassLoader)) {
            try {
                // Guess the classpath, based on where we can resolve existing resources
                List<URL> list = Collections.list(mainClass.getClassLoader().getResources("META-INF"));
                List<URL> result = new ArrayList<>();
                result.add(mainClass.getProtectionDomain().getCodeSource().getLocation());
                for (URL url : list) {
                    String path = url.toString();
                    path = path.substring(0, path.length() - "/META-INF".length()) + "/";
                    result.add(new URL(path));
                }
                return result.toArray(new URL[result.size()]);
            } catch (IOException e) {
                throw new IllegalStateException("Cannot find class path", e);
            }
        } else {
            @SuppressWarnings("resource")
            URLClassLoader urlClassLoader = (URLClassLoader) base;
            return urlClassLoader.getURLs();
        }
    }

    private boolean isRoot(String file) {
        return file.startsWith("reactor-core") || file.startsWith("reactive-streams");
    }

    private String clean(String jar) {
        // This works with fat jars like Spring Boot where the path elements look like
        // jar:file:...something.jar!/.
        return jar.endsWith("!/") ? jar.substring(0, jar.length() - 2) : jar;
    }

    private URL[] extractClasspath(URL url) {
        // This works for a jar indirection like in surefire and IntelliJ
        if (url.toString().endsWith(".jar")) {
            JarFile jar;
            try {
                jar = new JarFile(new File(url.toURI()));
                String path = jar.getManifest().getMainAttributes().getValue("Class-Path");
                if (path != null) {
                    List<URL> result = new ArrayList<>();
                    for (String element : path.split(" ")) {
                        result.add(new URL(element));
                    }
                    return result.toArray(new URL[0]);
                }
            } catch (Exception e) {
            }
        }
        return null;
    }

}