Tomcat源码分析(一)--初始化init(Bootstrap启动)

程序员文章站 2022-03-22 16:57:33

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下载tomcat 8.0源码可以到tomcat官网去下载 source code distributions 选择zip,下载完新建一个pom.xml就可以导入到eclipse中了。其实知道Tomcat源码就可以把spring Web项目整个运行流程就可以想明白。

一、Tomcat总体结构

Tomcat源码分析(一)--初始化init(Bootstrap启动)

一个Tomcat中只有一个Server,一个Server可以包含多个Service,一个Service只有一个Cotainer,但可以有多个Connectors,

(因为一个服务可以有多个连接，如同时提供http和https连接，也可以提供相同协议不同端口的接口)

Tomcat最顶层的容器就叫Server,代表整个服务器,Server包含一个或多个的Service.

Service包括了Connector和Container.

Tomcat里的Server由org.apache,catalina.startup.Catalina来管理。Catalina类的三个方法start,stop,load分别管理整个服务器的生命周期。

load方法用于根据conf/server.xml文件创建Server并调用Server的init方法进行初始化,

---》 Catalina类的load()方法详细解释在（Tomcat源码分析(二)）

start方法用于启动服务器，stop方法用于停止服务器，start和stop都调用了Server的start和stop方法。load方法内部调用了Server的init方法。

Server的start方法--->所有的Service中的start方法-->调用所有包含Connector和Container的start方法-》启动了服务器

init和stop方法也是一样。

  /**
     * Await and shutdown.
     */
    public void await() {

        getServer().await();

    }

Catalina的await方法--》Server的await方法作用是进入一个循环，让主线程不会退出。

二、Tomcat的启动入口

Catalina类主要负责具体的管理类，而Bootstrap类是启动的入口(main方法)。

Bootstrap类main方法：

  /**
     * 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
            Bootstrap bootstrap = new Bootstrap();
            try {
                bootstrap.init();
            } catch (Throwable t) {
                handleThrowable(t);
                t.printStackTrace();
                return;
            }
            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);
        }

        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")) {
                daemon.setAwait(true);
                daemon.load(args);
                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);
        }

    }

如果args参数为空，默认执行start。

main方法内：

bootstrap.init();

具体的实现init()方法：

  /**
     * Initialize daemon.
     */
    public void init() throws Exception {

        initClassLoaders();

        Thread.currentThread().setContextClassLoader(catalinaLoader);

        SecurityClassLoad.securityClassLoad(catalinaLoader);

        // Load our startup class and call its process() method
        if (log.isDebugEnabled())
            log.debug("Loading startup class");
        Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
        Object startupInstance = startupClass.getConstructor().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;
        Method method =
            startupInstance.getClass().getMethod(methodName, paramTypes);
        method.invoke(startupInstance, paramValues);

        catalinaDaemon = startupInstance;

    }

1、初始化ClassLoader（initClassLoaders）

创建commonLoader、catalinaLoader和sharedLoader;

代码如下:

   private void initClassLoaders() {
        try {
            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();
            }
            catalinaLoader = createClassLoader("server", commonLoader); //这里如果获取不到server.loader对应的value值就会返回commonLoader。
            sharedLoader = createClassLoader("shared", commonLoader);
        } catch (Throwable t) {
            handleThrowable(t);
            log.error("Class loader creation threw exception", t);
            System.exit(1);
        }
    }

createClassLoader方法

代码如下:

private ClassLoader createClassLoader(String name, ClassLoader parent)
        throws Exception {

        String value = CatalinaProperties.getProperty(name + ".loader");
        if ((value == null) || (value.equals("")))
            return parent;

        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));
            }
        }

        return ClassLoaderFactory.createClassLoader(repositories, parent);
    }

ClassLoaderFactory类的ClassLoaderFactory.createClassLoader(repositories, parent);具体实现代码如下：

  /**
     * Create and return a new class loader, based on the configuration
     * defaults and the specified directory paths:
     *
     * @param repositories List of class directories, jar files, jar directories
     *                     or URLS that should be added to the repositories of
     *                     the class loader.
     * @param parent Parent class loader for the new class loader, or
     *  <code>null</code> for the system class loader.
     *
     * @exception Exception if an error occurs constructing the class loader
     */
    public static ClassLoader createClassLoader(List<Repository> repositories,
                                                final ClassLoader parent)
        throws Exception {

        if (log.isDebugEnabled())
            log.debug("Creating new class loader");

        // Construct the "class path" for this class loader
        Set<URL> set = new LinkedHashSet<>();

        if (repositories != null) {
            for (Repository repository : repositories)  {
                if (repository.getType() == RepositoryType.URL) {
                    URL url = buildClassLoaderUrl(repository.getLocation());
                    if (log.isDebugEnabled())
                        log.debug("  Including URL " + url);
                    set.add(url);
                } else if (repository.getType() == RepositoryType.DIR) {
                    File directory = new File(repository.getLocation());
                    directory = directory.getCanonicalFile();
                    if (!validateFile(directory, RepositoryType.DIR)) {
                        continue;
                    }
                    URL url = buildClassLoaderUrl(directory);
                    if (log.isDebugEnabled())
                        log.debug("  Including directory " + url);
                    set.add(url);
                } else if (repository.getType() == RepositoryType.JAR) {
                    File file=new File(repository.getLocation());
                    file = file.getCanonicalFile();
                    if (!validateFile(file, RepositoryType.JAR)) {
                        continue;
                    }
                    URL url = buildClassLoaderUrl(file);
                    if (log.isDebugEnabled())
                        log.debug("  Including jar file " + url);
                    set.add(url);
                } else if (repository.getType() == RepositoryType.GLOB) {
                    File directory=new File(repository.getLocation());
                    directory = directory.getCanonicalFile();
                    if (!validateFile(directory, RepositoryType.GLOB)) {
                        continue;
                    }
                    if (log.isDebugEnabled())
                        log.debug("  Including directory glob "
                            + directory.getAbsolutePath());
                    String filenames[] = directory.list();
                    if (filenames == null) {
                        continue;
                    }
                    for (int j = 0; j < filenames.length; j++) {
                        String filename = filenames[j].toLowerCase(Locale.ENGLISH);
                        if (!filename.endsWith(".jar"))
                            continue;
                        File file = new File(directory, filenames[j]);
                        file = file.getCanonicalFile();
                        if (!validateFile(file, RepositoryType.JAR)) {
                            continue;
                        }
                        if (log.isDebugEnabled())
                            log.debug("    Including glob jar file "
                                + file.getAbsolutePath());
                        URL url = buildClassLoaderUrl(file);
                        set.add(url);
                    }
                }
            }
        }

        // Construct the class loader itself
        final URL[] array = set.toArray(new URL[set.size()]);
        if (log.isDebugEnabled())
            for (int i = 0; i < array.length; i++) {
                log.debug("  location " + i + " is " + array[i]);
            }

        return AccessController.doPrivileged(
                new PrivilegedAction<URLClassLoader>() {
                    @Override
                    public URLClassLoader run() {
                        if (parent == null)
                            return new URLClassLoader(array);
                        else
                            return new URLClassLoader(array, parent);
                    }
                });
    }

把从catalina.properties文件中拿到的xx.loader对应的value值，组装成URLClassLoader对象。

具体的new URLClassLoader(array);实现如下：

 public URLClassLoader(URL[] urls) {
        super();
        // this is to make the stack depth consistent with 1.1
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkCreateClassLoader();
        }
        this.acc = AccessController.getContext();
        ucp = new URLClassPath(urls, acc);
    }

CatalinaProperties类的getProperty方法获取 loader.

 /**
     * Return specified property value.
     */
    public static String getProperty(String name) {
        return properties.getProperty(name);
    }

CatalinaProperties类在在类初次被加载的时候调用了loadProperties();

 static {
        loadProperties();
    }

 /**
     * Load properties.加载配置信息 
     */
    private static void loadProperties() {

        InputStream is = null;
        Throwable error = null;

        try { //从系统变量中查找
            String configUrl = System.getProperty("catalina.config");
            if (configUrl != null) {
                is = (new URL(configUrl)).openStream();
            }
        } catch (Throwable t) {
            handleThrowable(t);
        }

        if (is == null) { //从tomcat的conf目录下找到catalina.properties文件加载
            try {
                File home = new File(Bootstrap.getCatalinaBase());
                File conf = new File(home, "conf");
                File propsFile = new File(conf, "catalina.properties");
                is = new FileInputStream(propsFile);
            } catch (Throwable t) {
                handleThrowable(t);
            }
        }

        if (is == null) { //从类路径中加载
            try {
                is = CatalinaProperties.class.getResourceAsStream
                    ("/org/apache/catalina/startup/catalina.properties");
            } catch (Throwable t) {
                handleThrowable(t);
            }
        }

        if (is != null) { //如果已经找到则加载
            try {
                properties = new Properties();
                properties.load(is);
            } catch (Throwable t) {
                handleThrowable(t);
                error = t;
            } finally {
                try {
                    is.close();
                } catch (IOException ioe) {
                    log.warn("Could not close catalina.properties", ioe);
                }
            }
        }

        if ((is == null) || (error != null)) {
            // Do something
            log.warn("Failed to load catalina.properties", error);
            // That's fine - we have reasonable defaults.
            properties = new Properties();
        }

        // Register the properties as system properties
        //将这些配置变量注册为系统变量
        Enumeration<?> enumeration = properties.propertyNames();
        while (enumeration.hasMoreElements()) {
            String name = (String) enumeration.nextElement();
            String value = properties.getProperty(name);
            if (value != null) {
                System.setProperty(name, value);
            }
        }
    }

System.getProperty("catalina.config"):

System.getProperty 就是从系统的变量中获取值。

序号	属性	说明
1	java.version	Java 运行时环境版本
2	java.vendor	Java 运行时环境供应商
3	java.vendor.url	Java 供应商的 URL
4	java.home	Java 安装目录
5	java.vm.specification.version	Java 虚拟机规范版本
6	java.vm.specification.vendor	Java 虚拟机规范供应商
7	java.vm.specification.name	Java 虚拟机规范名称
8	java.vm.version	Java 虚拟机实现版本
9	java.vm.vendor	Java 虚拟机实现供应商
10	java.vm.name	Java 虚拟机实现名称
11	java.specification.version	Java 运行时环境规范版本
12	java.specification.vendor	Java 运行时环境规范供应商
13	java.specification.name	Java 运行时环境规范名称
14	java.class.version	Java 类格式版本号
15	java.class.path	Java 类路径
16	java.library.path	加载库时搜索的路径列表
17	java.io.tmpdir	默认的临时文件路径
18	java.compiler	要使用的 JIT 编译器的名称
19	java.ext.dirs	一个或多个扩展目录的路径
20	os.name	操作系统的名称
21	os.arch	操作系统的架构
22	os.version	操作系统的版本
23	file.separator	文件分隔符（在 UNIX 系统中是“/”）
24	path.separator	路径分隔符（在 UNIX 系统中是“:”）
25	line.separator	行分隔符（在 UNIX 系统中是“/n”）
26	user.name	用户的账户名称
27	user.home	用户的主目录
28	user.dir	用户的当前工作目录

System.out.println("Java运行环境的版本:" + System.getProperty("java.version"));

System.out.println("Java运行环境的生产商:" + System.getProperty("java.vendor"));

System.out.println("Java的安装路径：" + System.getProperty("java.home"));

System.out.println("虚拟机实现的版本：" + System.getProperty("java.vm.version"));

System.out.println("虚拟机实现的生产商：" + System.getProperty("java.vm.vendor"));

System.out.println("默认的临时文件路径：" + System.getProperty("java.io.tmpdir"));

System.out.println("用户的账户名称：" + System.getProperty("user.name"));

System.out.println("当前用户工作目录：" + System.getProperty("user.dir"));

System.out.println("用户的home路径：" + System.getProperty("user.home"));

System.out.println("操作系统的名称:" + System.getProperty("os.name"));

System.out.println("操作系统的版本：" + System.getProperty("os.version"));

System.out.println("操作系统的架构：" + System.getProperty("os.arch"));

System.out.println("运行环境规范的名称:" + System.getProperty("java.specification.name"));

System.out.println("Java类格式化的版本号：" + System.getProperty("java.class.version"));

System.out.println("类所在的路径：" + System.getProperty("java.class.path"));

当然还可以通过System.setProperty方法set值，如：System.setProperty("jdbc.drivers","aaa.bbb.ccc");

System.setProperty(name, value);

如果从tomcat的conf目录下找到加载：代码如下：

    if (is == null) { //从tomcat的conf目录下找到catalina.properties文件加载
            try {
                File home = new File(Bootstrap.getCatalinaBase());
                File conf = new File(home, "conf");
                File propsFile = new File(conf, "catalina.properties");
                is = new FileInputStream(propsFile);
            } catch (Throwable t) {
                handleThrowable(t);
            }
        }

那么catalina.properties文件内容如下:

# 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.

#
# List of comma-separated packages that start with or equal this string
# will cause a security exception to be thrown when
# passed to checkPackageAccess unless the
# corresponding RuntimePermission ("accessClassInPackage."+package) has
# been granted.
package.access=sun.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.tomcat.
#
# List of comma-separated packages that start with or equal this string
# will cause a security exception to be thrown when
# passed to checkPackageDefinition unless the
# corresponding RuntimePermission ("defineClassInPackage."+package) has
# been granted.
#
# by default, no packages are restricted for definition, and none of
# the class loaders supplied with the JDK call checkPackageDefinition.
#
package.definition=sun.,java.,org.apache.catalina.,org.apache.coyote.,\
org.apache.jasper.,org.apache.naming.,org.apache.tomcat.

#
#
# List of comma-separated paths defining the contents of the "common"
# classloader. Prefixes should be used to define what is the repository type.
# Path may be relative to the CATALINA_HOME or CATALINA_BASE path or absolute.
# If left as blank,the JVM system loader will be used as Catalina's "common"
# loader.
# Examples:
#     "foo": Add this folder as a class repository
#     "foo/*.jar": Add all the JARs of the specified folder as class
#                  repositories
#     "foo/bar.jar": Add bar.jar as a class repository
#
# Note: Values are enclosed in double quotes ("...") in case either the
#       ${catalina.base} path or the ${catalina.home} path contains a comma.
#       Because double quotes are used for quoting, the double quote character
#       may not appear in a path.
common.loader="${catalina.base}/lib","${catalina.base}/lib/*.jar","${catalina.home}/lib","${catalina.home}/lib/*.jar"

#
# List of comma-separated paths defining the contents of the "server"
# classloader. Prefixes should be used to define what is the repository type.
# Path may be relative to the CATALINA_HOME or CATALINA_BASE path or absolute.
# If left as blank, the "common" loader will be used as Catalina's "server"
# loader.
# Examples:
#     "foo": Add this folder as a class repository
#     "foo/*.jar": Add all the JARs of the specified folder as class
#                  repositories
#     "foo/bar.jar": Add bar.jar as a class repository
#
# Note: Values may be enclosed in double quotes ("...") in case either the
#       ${catalina.base} path or the ${catalina.home} path contains a comma.
#       Because double quotes are used for quoting, the double quote character
#       may not appear in a path.
server.loader=

#
# List of comma-separated paths defining the contents of the "shared"
# classloader. Prefixes should be used to define what is the repository type.
# Path may be relative to the CATALINA_BASE path or absolute. If left as blank,
# the "common" loader will be used as Catalina's "shared" loader.
# Examples:
#     "foo": Add this folder as a class repository
#     "foo/*.jar": Add all the JARs of the specified folder as class
#                  repositories
#     "foo/bar.jar": Add bar.jar as a class repository
# Please note that for single jars, e.g. bar.jar, you need the URL form
# starting with file:.
#
# Note: Values may be enclosed in double quotes ("...") in case either the
#       ${catalina.base} path or the ${catalina.home} path contains a comma.
#       Because double quotes are used for quoting, the double quote character
#       may not appear in a path.
shared.loader=

# Default list of JAR files that should not be scanned using the JarScanner
# functionality. This is typically used to scan JARs for configuration
# information. JARs that do not contain such information may be excluded from
# the scan to speed up the scanning process. This is the default list. JARs on
# this list are excluded from all scans. The list must be a comma separated list
# of JAR file names.
# The list of JARs to skip may be over-ridden at a Context level for individual
# scan types by configuring a JarScanner with a nested JarScanFilter.
# The JARs listed below include:
# - Tomcat Bootstrap JARs
# - Tomcat API JARs
# - Catalina JARs
# - Jasper JARs
# - Tomcat JARs
# - Common non-Tomcat JARs
# - Test JARs (JUnit, Cobertura and dependencies)
tomcat.util.scan.StandardJarScanFilter.jarsToSkip=\
bootstrap.jar,commons-daemon.jar,tomcat-juli.jar,\
annotations-api.jar,el-api.jar,jsp-api.jar,servlet-api.jar,websocket-api.jar,\
catalina.jar,catalina-ant.jar,catalina-ha.jar,catalina-storeconfig.jar,\
catalina-tribes.jar,\
jasper.jar,jasper-el.jar,ecj-*.jar,\
tomcat-api.jar,tomcat-util.jar,tomcat-util-scan.jar,tomcat-coyote.jar,\
tomcat-dbcp.jar,tomcat-jni.jar,tomcat-websocket.jar,\
tomcat-i18n-en.jar,tomcat-i18n-es.jar,tomcat-i18n-fr.jar,tomcat-i18n-ja.jar,\
tomcat-juli-adapters.jar,catalina-jmx-remote.jar,catalina-ws.jar,\
tomcat-jdbc.jar,\
tools.jar,\
commons-beanutils*.jar,commons-codec*.jar,commons-collections*.jar,\
commons-dbcp*.jar,commons-digester*.jar,commons-fileupload*.jar,\
commons-httpclient*.jar,commons-io*.jar,commons-lang*.jar,commons-logging*.jar,\
commons-math*.jar,commons-pool*.jar,\
jstl.jar,taglibs-standard-spec-*.jar,\
geronimo-spec-jaxrpc*.jar,wsdl4j*.jar,\
ant.jar,ant-junit*.jar,aspectj*.jar,jmx.jar,h2*.jar,hibernate*.jar,httpclient*.jar,\
jmx-tools.jar,jta*.jar,log4j*.jar,mail*.jar,slf4j*.jar,\
xercesImpl.jar,xmlParserAPIs.jar,xml-apis.jar,\
junit.jar,junit-*.jar,ant-launcher.jar,\
cobertura-*.jar,asm-*.jar,dom4j-*.jar,icu4j-*.jar,jaxen-*.jar,jdom-*.jar,\
jetty-*.jar,oro-*.jar,servlet-api-*.jar,tagsoup-*.jar,xmlParserAPIs-*.jar,\
xom-*.jar

# Default list of JAR files that should be scanned that overrides the default
# jarsToSkip list above. This is typically used to include a specific JAR that
# has been excluded by a broad file name pattern in the jarsToSkip list.
# The list of JARs to scan may be over-ridden at a Context level for individual
# scan types by configuring a JarScanner with a nested JarScanFilter.
tomcat.util.scan.StandardJarScanFilter.jarsToScan=\
log4j-web*.jar,log4j-taglib*.jar,log4javascript*.jar,slf4j-taglib*.jar

# String cache configuration.
tomcat.util.buf.StringCache.byte.enabled=true
#tomcat.util.buf.StringCache.char.enabled=true
#tomcat.util.buf.StringCache.trainThreshold=500000
#tomcat.util.buf.StringCache.cacheSize=5000

# This system property is deprecated. Use the relaxedPathChars relaxedQueryChars
# attributes of the Connector instead. These attributes permit a wider range of
# characters to be configured as valid.
# Allow for changes to HTTP request validation
# WARNING: Using this option may expose the server to CVE-2016-6816
#tomcat.util.http.parser.HttpParser.requestTargetAllow=|

其中包含了 common.loader,

server.loader,

shared.loader,

tomcat.util.scan.StandardJarScanFilter.jarsToSkip,

tomcat.util.scan.StandardJarScanFilter.jarsToScan,

tomcat.util.buf.StringCache.byte.enabled,

这些key值，在调用loadProperties方法的时候都会加载存储在Properties properties里。

${catalina.base}:

catalina.home指向公用信息的位置，就是bin和lib的父目录。
catalina.base指向每个Tomcat目录私有信息的位置，就是conf、logs、temp、webapps和work的父目录。

而设置 catalina.base的值和catalina.home的值是在 tomcat\bin\catalina.bat文件中catalina.base设置方法。

catalina.bat文件里面设置catalina.base部分代码如下：

rem Guess CATALINA_HOME if not defined
set "CURRENT_DIR=%cd%"
if not "%CATALINA_HOME%" == "" goto gotHome
set "CATALINA_HOME=%CURRENT_DIR%"
if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome
cd ..
set "CATALINA_HOME=%cd%"
cd "%CURRENT_DIR%"
:gotHome

if exist "%CATALINA_HOME%\bin\catalina.bat" goto okHome
echo The CATALINA_HOME environment variable is not defined correctly
echo This environment variable is needed to run this program
goto end
:okHome

2、Thread.currentThread().setContextClassLoader(catalinaLoader);

主要作用是把catalinaLoader设置为Tomcat主线程的上下文类加载器。

3、SecurityClassLoad.securityClassLoad(catalinaLoader);线程安全的加载class(类)

SecurityClassLoad类：

  public static void securityClassLoad(ClassLoader loader) throws Exception {
        securityClassLoad(loader, true);
    }

    static void securityClassLoad(ClassLoader loader, boolean requireSecurityManager) throws Exception {

        if (requireSecurityManager && System.getSecurityManager() == null) {
            return;
        }

        loadCorePackage(loader);
        loadCoyotePackage(loader);
        loadLoaderPackage(loader);
        loadRealmPackage(loader);
        loadServletsPackage(loader);
        loadSessionPackage(loader);
        loadUtilPackage(loader);
        loadValvesPackage(loader);
        loadWebResourcesPackage(loader);
        loadJavaxPackage(loader);
        loadConnectorPackage(loader);
        loadTomcatPackage(loader);
    }

  private static final void loadCorePackage(ClassLoader loader) throws Exception {
        final String basePackage = "org.apache.catalina.core.";
        loader.loadClass(basePackage + "AccessLogAdapter");
        loadAnonymousInnerClasses(loader, basePackage + "ApplicationContextFacade");//加载匿名内部类
        loader.loadClass(basePackage + "ApplicationDispatcher$PrivilegedForward");
        loader.loadClass(basePackage + "ApplicationDispatcher$PrivilegedInclude");
        loader.loadClass(basePackage + "AsyncContextImpl");
        loader.loadClass(basePackage + "AsyncContextImpl$DebugException");
        loadAnonymousInnerClasses(loader, basePackage + "AsyncContextImpl");
        loader.loadClass(basePackage + "AsyncListenerWrapper");
        loader.loadClass(basePackage + "ContainerBase$PrivilegedAddChild");
        loadAnonymousInnerClasses(loader, basePackage + "DefaultInstanceManager");
        loader.loadClass(basePackage + "DefaultInstanceManager$AnnotationCacheEntry");
        loader.loadClass(basePackage + "DefaultInstanceManager$AnnotationCacheEntryType");
        loader.loadClass(basePackage + "ApplicationHttpRequest$AttributeNamesEnumerator");
    }

loadCorePackage 加载org.apache.catalina.core.路径下的类包括 AccessLogAdapter，ApplicationContextFacade...

4.使用反射调用了org.apache.catalina.startup.Catalina类的构造方法。

  // Load our startup class and call its process() method
        if (log.isDebugEnabled())
            log.debug("Loading startup class");
        Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
        Object startupInstance = startupClass.getConstructor().newInstance();

5.使用Method反射调用org.apache.catalina.startup.Catalina类的setParentClassLoader方法并且参数是sharedLoader。

  // 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;
        Method method =
            startupInstance.getClass().getMethod(methodName, paramTypes);
        method.invoke(startupInstance, paramValues);

Tomcat源码分析(一)--初始化init(Bootstrap启动)

一、Tomcat总体结构

二、Tomcat的启动入口

Tomcat源码分析（六）----- Tomcat 启动过程(一)

Bootstrap初始化过程源码分析--netty客户端的启动

Tomcat初始化源码流程分析(图解及源码注释) (一)

SpringBoot内置tomcat启动原理、以及SpringBoot初始化Servlet的源码分析

Tomcat8源码分析系列-启动分析(一) Lifecycle

Tomcat源码分析三：Tomcat启动加载过程（一）的源码解析

Tomcat源码分析（六）----- Tomcat 启动过程(一)

Bootstrap初始化过程源码分析--netty客户端的启动