hadoop1.x作业提交过程分析（源码分析第二篇）
/** Run a Hadoop job jar.If the main class is not in the jar's manifest,* then it must be provided on the command line. */
public static void main(String[] args) throws Throwable {
String usage = "RunJar jarFile args...";
if (args.length < 1) {
System.err.println(usage);
System.exit(-1);
}
int firstArg = 0;
String fileName = args;
File file = new File(fileName);
String mainClassName = null;
JarFile jarFile;
try {
jarFile = new JarFile(fileName);
} catch(IOException io) {
throw new IOException("Error opening job jar: " + fileName)
.initCause(io);
}
Manifest manifest = jarFile.getManifest();
if (manifest != null) {
mainClassName = manifest.getMainAttributes().getValue("Main-Class");
}
jarFile.close();
if (mainClassName == null) {
if (args.length < 2) {
System.err.println(usage);
System.exit(-1);
}
mainClassName = args;
}
//进行相应的一些目录处理工作
mainClassName = mainClassName.replaceAll("/", ".");
File tmpDir = new File(new Configuration().get("hadoop.tmp.dir"));
tmpDir.mkdirs();
if (!tmpDir.isDirectory()) {
System.err.println("Mkdirs failed to create " + tmpDir);
System.exit(-1);
}
final File workDir = File.createTempFile("hadoop-unjar", "", tmpDir);
workDir.delete();
workDir.mkdirs();
if (!workDir.isDirectory()) {
System.err.println("Mkdirs failed to create " + workDir);
System.exit(-1);
}
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
try {
FileUtil.fullyDelete(workDir);
} catch (IOException e) {
}
}
});
unJar(file, workDir);//解压jar包
ArrayList classPath = new ArrayList();
classPath.add(new File(workDir+"/").toURL());
classPath.add(file.toURL());
classPath.add(new File(workDir, "classes/").toURL());
File[] libs = new File(workDir, "lib").listFiles();
if (libs != null) {
for (int i = 0; i < libs.length; i++) {
classPath.add(libs.toURL());
}
}
ClassLoader loader =
new URLClassLoader(classPath.toArray(new URL));
Thread.currentThread().setContextClassLoader(loader);
Class mainClass = Class.forName(mainClassName, true, loader);
Method main = mainClass.getMethod("main", new Class[] {
Array.newInstance(String.class, 0).getClass()
});
String[] newArgs = Arrays.asList(args)
.subList(firstArg, args.length).toArray(new String);
try {
main.invoke(null, new Object[] { newArgs });
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
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