带注释的 Bootstrap.java
带注释的 Bootstrap.java ，配合文章"Tomcat 8（七）解读Bootstrap"使用
带注释的Bootstrap.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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
*
* http://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.apache.catalina.startup;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.catalina.Globals;
import org.apache.catalina.security.SecurityClassLoad;
import org.apache.catalina.startup.ClassLoaderFactory.Repository;
import org.apache.catalina.startup.ClassLoaderFactory.RepositoryType;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
/**
* Bootstrap loader for Catalina. This application constructs a class loader
* for use in loading the Catalina internal classes (by accumulating all of the
* JAR files found in the "server" directory under "catalina.home"), and
* starts the regular execution of the container. The purpose of this
* roundabout approach is to keep the Catalina internal classes (and any
* other classes they depend on, such as an XML parser) out of the system
* class path and therefore not visible to application level classes.
*
* @author Craig R. McClanahan
* @author Remy Maucherat
*/
public final class Bootstrap {
private static final Log log = LogFactory.getLog(Bootstrap.class);
/**
* Daemon object used by main.
*/
private static Bootstrap daemon = null;
private static final File catalinaBaseFile;
private static final File catalinaHomeFile;
private static final Pattern PATH_PATTERN = Pattern.compile("(\".*?\")|(([^,])*)");
static {
// Will always be non-null
//System.getProperty("user.dir")，获取当前目录
//由于是在$CATALINA_HOME\bin下运行的Bootstrap，所以userDir为$CATALINA_HOME\bin
String userDir = System.getProperty("user.dir");
// Home first
//Globals是存放全局常量的类
//Globals.CATALINA_HOME_PROP = "catalina.home"
//catalina.home在运行Bootstrap时已设置(Tomcat的根目录)
String home = System.getProperty(Globals.CATALINA_HOME_PROP);
File homeFile = null;
//获取Tomcat的绝对路径
if (home != null) {
File f = new File(home);
try {
homeFile = f.getCanonicalFile();
} catch (IOException ioe) {
homeFile = f.getAbsoluteFile();
}
}
if (homeFile == null) {
// First fall-back. See if current directory is a bin directory
// in a normal Tomcat install
File bootstrapJar = new File(userDir, "bootstrap.jar");
if (bootstrapJar.exists()) {
File f = new File(userDir, "..");
try {
homeFile = f.getCanonicalFile();
} catch (IOException ioe) {
homeFile = f.getAbsoluteFile();
}
}
}
if (homeFile == null) {
// Second fall-back. Use current directory
File f = new File(userDir);
try {
homeFile = f.getCanonicalFile();
} catch (IOException ioe) {
homeFile = f.getAbsoluteFile();
}
}
//设置catalinaHomeFile
catalinaHomeFile = homeFile;
System.setProperty(
Globals.CATALINA_HOME_PROP, catalinaHomeFile.getPath());
// Then base
String base = System.getProperty(Globals.CATALINA_BASE_PROP);
//设置catalinaBaseFile
if (base == null) {
catalinaBaseFile = catalinaHomeFile;
} else {
File baseFile = new File(base);
try {
baseFile = baseFile.getCanonicalFile();
} catch (IOException ioe) {
baseFile = baseFile.getAbsoluteFile();
}
catalinaBaseFile = baseFile;
}
System.setProperty(
Globals.CATALINA_BASE_PROP, catalinaBaseFile.getPath());
}
// -------------------------------------------------------------- Variables
/**
* Daemon reference.
*/
private Object catalinaDaemon = null;
protected ClassLoader commonLoader = null;
protected ClassLoader catalinaLoader = null;
protected ClassLoader sharedLoader = null;
// -------------------------------------------------------- Private Methods
private void initClassLoaders() {
try {
//创建commonLoader
commonLoader = createClassLoader("common", null);
if( commonLoader == null ) {
// no config file, default to this loader - we might be in a 'single' env.
commonLoader=this.getClass().getClassLoader();
}
//创建catalinaLoader、sharedLoader
catalinaLoader = createClassLoader("server", commonLoader);
sharedLoader = createClassLoader("shared", commonLoader);
} catch (Throwable t) {
handleThrowable(t);
log.error("Class loader creation threw exception", t);
System.exit(1);
}
}
private ClassLoader createClassLoader(String name, ClassLoader parent)
throws Exception {
//CatalinaProperties解析$CATALINA_HOME\conf\catalina.properties，
//并将catalina.properties内的属性存为系统属性
//catalina.properties内common.loader="${catalina.base}/lib",
//"${catalina.base}/lib/*.jar","${catalina.home}/lib","${catalina.home}/lib/*.jar"
//读取common.loader
String value = CatalinaProperties.getProperty(name + ".loader");
if ((value == null) || (value.equals("")))
return parent;
//将${catalina.base},${catalina.home}替换为Tomcat的绝对路径
value = replace(value);
List<Repository> repositories = new ArrayList<>();
String[] repositoryPaths = getPaths(value);
for (String repository : repositoryPaths) {
// Check for a JAR URL repository
try {
@SuppressWarnings("unused")
URL url = new URL(repository);
repositories.add(
new Repository(repository, RepositoryType.URL));
continue;
} catch (MalformedURLException e) {
// Ignore
}
// Local repository
if (repository.endsWith("*.jar")) {
repository = repository.substring
(0, repository.length() - "*.jar".length());
repositories.add(
new Repository(repository, RepositoryType.GLOB));
} else if (repository.endsWith(".jar")) {
repositories.add(
new Repository(repository, RepositoryType.JAR));
} else {
repositories.add(
new Repository(repository, RepositoryType.DIR));
}
}
//ClassLoaderFactory依据repositories的内容创建ClassLoader
return ClassLoaderFactory.createClassLoader(repositories, parent);
}
/**
* System property replacement in the given string.
*
* @param str The original string
* @return the modified string
*/
protected String replace(String str) {
// Implementation is copied from ClassLoaderLogManager.replace(),
// but added special processing for catalina.home and catalina.base.
String result = str;
int pos_start = str.indexOf("${");
if (pos_start >= 0) {
StringBuilder builder = new StringBuilder();
int pos_end = -1;
while (pos_start >= 0) {
builder.append(str, pos_end + 1, pos_start);
pos_end = str.indexOf('}', pos_start + 2);
if (pos_end < 0) {
pos_end = pos_start - 1;
break;
}
String propName = str.substring(pos_start + 2, pos_end);
String replacement;
if (propName.length() == 0) {
replacement = null;
} else if (Globals.CATALINA_HOME_PROP.equals(propName)) {
replacement = getCatalinaHome();
} else if (Globals.CATALINA_BASE_PROP.equals(propName)) {
replacement = getCatalinaBase();
} else {
replacement = System.getProperty(propName);
}
if (replacement != null) {
builder.append(replacement);
} else {
builder.append(str, pos_start, pos_end + 1);
}
pos_start = str.indexOf("${", pos_end + 1);
}
builder.append(str, pos_end + 1, str.length());
result = builder.toString();
}
return result;
}
/**
* Initialize daemon.
*/
public void init() throws Exception {
//创建commonLoader、catalinaLoader、sharedLoader
initClassLoaders();
//为当前线程设置ClassLoader
Thread.currentThread().setContextClassLoader(catalinaLoader);
//设置SecurityClassLoad。具体作用还不清楚。。。
SecurityClassLoad.securityClassLoad(catalinaLoader);
// Load our startup class and call its process() method
if (log.isDebugEnabled())
log.debug("Loading startup class");
//通过反射实例化Catalina
Class<?> startupClass =
catalinaLoader.loadClass
("org.apache.catalina.startup.Catalina");
Object startupInstance = startupClass.newInstance();
// Set the shared extensions class loader
if (log.isDebugEnabled())
log.debug("Setting startup class properties");
String methodName = "setParentClassLoader";
Class<?> paramTypes[] = new Class[1];
paramTypes[0] = Class.forName("java.lang.ClassLoader");
Object paramValues[] = new Object[1];
paramValues[0] = sharedLoader;
//通过反射设置Catalina的parentClassLoader
Method method =
startupInstance.getClass().getMethod(methodName, paramTypes);
method.invoke(startupInstance, paramValues);
//将实例化的Catalina赋值给catalinaDaemon
catalinaDaemon = startupInstance;
}
/**
* Load daemon.
*/
private void load(String[] arguments)
throws Exception {
// Call the load() method
//调用catalinaDaemon的load方法，并传递参数"start"
String methodName = "load";
Object param[];
Class<?> paramTypes[];
if (arguments==null || arguments.length==0) {
paramTypes = null;
param = null;
} else {
paramTypes = new Class[1];
paramTypes[0] = arguments.getClass();
param = new Object[1];
param[0] = arguments;
}
Method method =
catalinaDaemon.getClass().getMethod(methodName, paramTypes);
if (log.isDebugEnabled())
log.debug("Calling startup class " + method);
method.invoke(catalinaDaemon, param);
}
/**
* getServer() for configtest
*/
private Object getServer() throws Exception {
String methodName = "getServer";
Method method =
catalinaDaemon.getClass().getMethod(methodName);
return method.invoke(catalinaDaemon);
}
// ----------------------------------------------------------- Main Program
/**
* Load the Catalina daemon.
*/
public void init(String[] arguments)
throws Exception {
init();
load(arguments);
}
/**
* Start the Catalina daemon.
*/
public void start()
throws Exception {
if( catalinaDaemon==null ) init();
//调用catalinaDaemon的start方法
Method method = catalinaDaemon.getClass().getMethod("start", (Class [] )null);
method.invoke(catalinaDaemon, (Object [])null);
}
/**
* Stop the Catalina Daemon.
*/
public void stop()
throws Exception {
Method method = catalinaDaemon.getClass().getMethod("stop", (Class [] ) null);
method.invoke(catalinaDaemon, (Object [] ) null);
}
/**
* Stop the standalone server.
*/
public void stopServer()
throws Exception {
Method method =
catalinaDaemon.getClass().getMethod("stopServer", (Class []) null);
method.invoke(catalinaDaemon, (Object []) null);
}
/**
* Stop the standalone server.
*/
public void stopServer(String[] arguments)
throws Exception {
Object param[];
Class<?> paramTypes[];
if (arguments==null || arguments.length==0) {
paramTypes = null;
param = null;
} else {
paramTypes = new Class[1];
paramTypes[0] = arguments.getClass();
param = new Object[1];
param[0] = arguments;
}
Method method =
catalinaDaemon.getClass().getMethod("stopServer", paramTypes);
method.invoke(catalinaDaemon, param);
}
/**
* Set flag.
*/
public void setAwait(boolean await)
throws Exception {
//通过反射，设置catalinaDaemon的await
Class<?> paramTypes[] = new Class[1];
paramTypes[0] = Boolean.TYPE;
Object paramValues[] = new Object[1];
paramValues[0] = Boolean.valueOf(await);
Method method =
catalinaDaemon.getClass().getMethod("setAwait", paramTypes);
method.invoke(catalinaDaemon, paramValues);
}
public boolean getAwait()
throws Exception
{
Class<?> paramTypes[] = new Class[0];
Object paramValues[] = new Object[0];
Method method =
catalinaDaemon.getClass().getMethod("getAwait", paramTypes);
Boolean b=(Boolean)method.invoke(catalinaDaemon, paramValues);
return b.booleanValue();
}
/**
* Destroy the Catalina Daemon.
*/
public void destroy() {
// FIXME
}
/**
* Main method and entry point when starting Tomcat via the provided
* scripts.
*
* @param args Command line arguments to be processed
*/
public static void main(String args[]) {
if (daemon == null) {
// Don't set daemon until init() has completed
//***2.1***
Bootstrap bootstrap = new Bootstrap();
try {
//***2.2***
bootstrap.init();
} catch (Throwable t) {
handleThrowable(t);
t.printStackTrace();
return;
}
//***2.3***
daemon = bootstrap;
} else {
// When running as a service the call to stop will be on a new
// thread so make sure the correct class loader is used to prevent
// a range of class not found exceptions.
Thread.currentThread().setContextClassLoader(daemon.catalinaLoader);
}
//***2.4***
try {
String command = "start";
if (args.length > 0) {
command = args[args.length - 1];
}
if (command.equals("startd")) {
args[args.length - 1] = "start";
daemon.load(args);
daemon.start();
} else if (command.equals("stopd")) {
args[args.length - 1] = "stop";
daemon.stop();
} else if (command.equals("start")) {
//***2.5***
daemon.setAwait(true);
//***2.6***
daemon.load(args);
//***2.7***
daemon.start();
} else if (command.equals("stop")) {
daemon.stopServer(args);
} else if (command.equals("configtest")) {
daemon.load(args);
if (null==daemon.getServer()) {
System.exit(1);
}
System.exit(0);
} else {
log.warn("Bootstrap: command \"" + command + "\" does not exist.");
}
} catch (Throwable t) {
// Unwrap the Exception for clearer error reporting
if (t instanceof InvocationTargetException &&
t.getCause() != null) {
t = t.getCause();
}
handleThrowable(t);
t.printStackTrace();
System.exit(1);
}
}
/**
* Obtain the name of configured home (binary) directory. Note that home and
* base may be the same (and are by default).
*/
public static String getCatalinaHome() {
return catalinaHomeFile.getPath();
}
/**
* Obtain the name of the configured base (instance) directory. Note that
* home and base may be the same (and are by default). If this is not set
* the value returned by {@link #getCatalinaHome()} will be used.
*/
public static String getCatalinaBase() {
return catalinaBaseFile.getPath();
}
/**
* Obtain the configured home (binary) directory. Note that home and
* base may be the same (and are by default).
*/
public static File getCatalinaHomeFile() {
return catalinaHomeFile;
}
/**
* Obtain the configured base (instance) directory. Note that
* home and base may be the same (and are by default). If this is not set
* the value returned by {@link #getCatalinaHomeFile()} will be used.
*/
public static File getCatalinaBaseFile() {
return catalinaBaseFile;
}
// Copied from ExceptionUtils since that class is not visible during start
private static void handleThrowable(Throwable t) {
if (t instanceof ThreadDeath) {
throw (ThreadDeath) t;
}
if (t instanceof VirtualMachineError) {
throw (VirtualMachineError) t;
}
// All other instances of Throwable will be silently swallowed
}
// Protected for unit testing
protected static String[] getPaths(String value) {
List<String> result = new ArrayList<>();
Matcher matcher = PATH_PATTERN.matcher(value);
while (matcher.find()) {
String path = value.substring(matcher.start(), matcher.end());
path = path.trim();
if (path.startsWith("\"") && path.length() > 1) {
path = path.substring(1, path.length() - 1);
path = path.trim();
}
if (path.length() == 0) {
continue;
}
result.add(path);
}
return result.toArray(new String[result.size()]);
}
}
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