package org.apache.catalina.startup;
src file:http://svn.apache.org/repos/asf/tomcat/tc6.0.x/tags/TOMCAT_6_0_42/java/org/apache/catalina/startup/Bootstrap.java
goal:了解tomcat启动的大致流程
欢迎各位指正其中的错误和不足
入口main方法
1 public static void main(String args[]) {
2
3 if (daemon == null) {
4 daemon = new Bootstrap();
5 try {
6 daemon.init();//init(完成了加载环境变量和类加载器的工作)
7 } catch (Throwable t) {
8 t.printStackTrace();
9 return;
10 }
11 }
12
13 try {
14 String command = "start";
15 if (args.length > 0) {
16 command = args[args.length - 1];
17 }
18
19 if (command.equals("startd")) {
20 args[args.length - 1] = "start";
21 daemon.load(args);
22 daemon.start();
23 } else if (command.equals("stopd")) {
24 args[args.length - 1] = "stop";
25 daemon.stop();
26 } else if (command.equals("start")) {// 默认没有参数会进入这里
27 // 设置挂起标志
28 daemon.setAwait(true);
29 // 信息: Initialization processed in 3024454 ms
30 daemon.load(args);
31 // 启动server
32 daemon.start();
33 } else if (command.equals("stop")) {
34 daemon.stopServer(args);
35 } else {
36 log.warn("Bootstrap: command \"" + command + "\" does not exist.");
37 }
38 } catch (Throwable t) {
39 t.printStackTrace();
40 }
41
42 }
以上是bootstrap类的main方法,里边逐步调用了一些用于初始化的方法.下面一一解读:
init()方法:
1 /**
2 * Initialize daemon.
3 */
4 public void init() throws Exception {
5
6 // Set Catalina path
7 setCatalinaHome();// 加载Catalina.Home环境变量(catalina.home)
8 setCatalinaBase();// 加载Catalina.Base环境变量(catalina.base)
9
10 initClassLoaders();// 初始化类加载器
11
12 Thread.currentThread().setContextClassLoader(catalinaLoader);
13
14 SecurityClassLoad.securityClassLoad(catalinaLoader);
15
16 // Load our startup class and call its process() method
17 if (log.isDebugEnabled()) {
18 log.debug("Loading startup class");
19 }
20 Class startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
21 Object startupInstance = startupClass.newInstance();
22
23 // Set the shared extensions class loader
24 if (log.isDebugEnabled()) {
25 log.debug("Setting startup class properties");
26 }
27 String methodName = "setParentClassLoader";
28 Class paramTypes[] = new Class[1];
29 paramTypes[0] = Class.forName("java.lang.ClassLoader");
30 Object paramValues[] = new Object[1];
31 paramValues[0] = sharedLoader;
32 // 找到org.apache.catalina.startup.Catalina#setParentClassLoader方法
33 Method method = startupInstance.getClass().getMethod(methodName, paramTypes);
34 // 设置java.lang.ClassLoader为父类加载器
35 method.invoke(startupInstance, paramValues);
36
37 catalinaDaemon = startupInstance;// 设置Catalina进程
38 }
init()方法
- 对环境变量的读取,主要是读取 catalina.home\catalina.base
- 初始化类加载器,默认使用当前类的类加载器 this.getClass().getClassLoader();
- 加载了Catalina类 classLoader.loadClass("org.apache.catalina.startup.Catalina")
- 反射设置父类加载器 org.apache.catalina.startup.Catalina#setParentClassLoader设置java.lang.ClassLoader为ParentClassLoader
daemon.setAwait(true)方法:
1 /**
2 * Set flag.
3 */
4 public void setAwait(boolean await) throws Exception {
5
6 Class paramTypes[] = new Class[1];
7 paramTypes[0] = Boolean.TYPE;
8 Object paramValues[] = new Object[1];
9 paramValues[0] = new Boolean(await);
10 // 获取Catalina类(其实是其父类Embedded)中的setAwait方法
11 Method method = catalinaDaemon.getClass().getMethod("setAwait", paramTypes);
12 // 使用await参数调用
13 method.invoke(catalinaDaemon, paramValues);
14
15 }
setAwait方法
- 这个方法并没有具体的深入研究,不过从字面意义上来看,应该是设置了一个锁.欢迎各位指正.
daemon.load(args)方法:
1 /**
2 * Load daemon.
3 */
4 private void load(String[] arguments) throws Exception {
5
6 // Call the load() method
7 String methodName = "load";
8 Object param[];
9 Class paramTypes[];
10 if (arguments==null || arguments.length==0) {
11 paramTypes = null;
12 param = null;
13 } else {
14 paramTypes = new Class[1];
15 paramTypes[0] = arguments.getClass();
16 param = new Object[1];
17 param[0] = arguments;
18 }
19 // 获取Catalina的load方法
20 Method method = catalinaDaemon.getClass().getMethod(methodName, paramTypes);
21 if (log.isDebugEnabled())
22 log.debug("Calling startup class " + method);
23 // 调用(启动一个新的服务器实例)
24 method.invoke(catalinaDaemon, param);
25
26 }
daemon.load方法
通过反射调用Catalina的load方法
1 /**
2 * Start a new server instance.
3 */
4 public void load() {
5
6 long t1 = System.nanoTime();
7
8 initDirs();// 读取环境变量
9
10 // Before digester - it may be needed
11
12 initNaming();
13
14 // Create and execute our Digester
15 Digester digester = createStartDigester();
16
17 InputSource inputSource = null;
18 InputStream inputStream = null;
19 File file = null;
20 try {
21 file = configFile();//获取server.xml位置
22 inputStream = new FileInputStream(file);
23 inputSource = new InputSource("file://" + file.getAbsolutePath());
24 } catch (Exception e) {
25 ;
26 }
27 // 如果不能获取server.xml,则使用ClassLoader再查找一次
28 if (inputStream == null) {
29 try {
30 inputStream = getClass().getClassLoader().getResourceAsStream(getConfigFile());
31 inputSource = new InputSource(getClass().getClassLoader().getResource(getConfigFile()).toString());
32 } catch (Exception e) {
33 ;
34 }
35 }
36
37 // This should be included in catalina.jar
38 // Alternative: don‘t bother with xml, just create it manually.
39 if( inputStream==null ) {
40 try {
41 inputStream = getClass().getClassLoader()
42 .getResourceAsStream("server-embed.xml");
43 inputSource = new InputSource
44 (getClass().getClassLoader()
45 .getResource("server-embed.xml").toString());
46 } catch (Exception e) {
47 ;
48 }
49 }
50
51
52 if ((inputStream == null) && (file != null)) {
53 log.warn("Can‘t load server.xml from " + file.getAbsolutePath());
54 if (file.exists() && !file.canRead()) {
55 log.warn("Permissions incorrect, read permission is not allowed on the file.");
56 }
57 return;
58 }
59
60 try {
61 inputSource.setByteStream(inputStream);
62 digester.push(this);
63 digester.parse(inputSource);// 加载server.xml
64 inputStream.close();
65 } catch (Exception e) {
66 log.warn("Catalina.start using "
67 + getConfigFile() + ": " , e);
68 return;
69 }
70
71 // Stream redirection
72 initStreams();// 设置log
73
74 // Start the new server
75 if (getServer() instanceof Lifecycle) {
76 try {
77 getServer().initialize();
78 } catch (LifecycleException e) {
79 if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE"))
80 throw new java.lang.Error(e);
81 else
82 log.error("Catalina.start", e);
83
84 }
85 }
86
87 long t2 = System.nanoTime();
88 if(log.isInfoEnabled())
89 log.info("Initialization processed in " + ((t2 - t1) / 1000000) + " ms");
90
91 }
Catalina.load方法
- #initDirs()完成了读取环境变量
- #initNaming()设置命名空间catalina.useNaming\java.naming.factory.url.pkgs\java.naming.factory.initial 这几个命名空间没有具体研究作用,同样欢迎补充
- 创建Digester
- 读取server.xml文件
- #digester.push(this)
- #digester.parse(inputSource)使用digester解析server.xml并按照配置创建Server对象
- #initStreams()设置log
- 调用#getServer().initialize()启动server
daemon.start()方法:
1 /**
2 * Start the Catalina daemon.
3 */
4 public void start() throws Exception {
5 if (catalinaDaemon == null)
6 init();
7
8 Method method = catalinaDaemon.getClass().getMethod("start", (Class[]) null);
9 method.invoke(catalinaDaemon, (Object[]) null);
10
11 }
daemon.start方法
通过反射调用Catalina的start方法
1 /**
2 * Start a new server instance.
3 */
4 public void start() {
5
6 if (getServer() == null) {
7 load();
8 }
9
10 if (getServer() == null) {
11 log.fatal("Cannot start server. Server instance is not configured.");
12 return;
13 }
14
15 long t1 = System.nanoTime();
16
17 // Start the new server
18 if (getServer() instanceof Lifecycle) {
19 try {
20 ((Lifecycle) getServer()).start();
21 } catch (LifecycleException e) {
22 log.error("Catalina.start: ", e);
23 }
24 }
25
26 long t2 = System.nanoTime();
27 if(log.isInfoEnabled())
28 log.info("Server startup in " + ((t2 - t1) / 1000000) + " ms");
29
30 try {
31 // Register shutdown hook
32 if (useShutdownHook) {
33 if (shutdownHook == null) {
34 shutdownHook = new CatalinaShutdownHook();
35 }
36 Runtime.getRuntime().addShutdownHook(shutdownHook);
37
38 // If JULI is being used, disable JULI‘s shutdown hook since
39 // shutdown hooks run in parallel and log messages may be lost
40 // if JULI‘s hook completes before the CatalinaShutdownHook()
41 LogManager logManager = LogManager.getLogManager();
42 if (logManager instanceof ClassLoaderLogManager) {
43 ((ClassLoaderLogManager) logManager).setUseShutdownHook(
44 false);
45 }
46 }
47 } catch (Throwable t) {
48 // This will fail on JDK 1.2. Ignoring, as Tomcat can run
49 // fine without the shutdown hook.
50 }
51
52 if (await) {
53 await();
54 stop();
55 }
56
57 }
Catalina.start方法
- 逐步启动server的生命周期
时间： 2024-08-02 21:13:32