使用idea开发工具调试代码的时候，如果是java的web项目，使用的是tomcat作为web容器，打断点debug调试跟踪，当跟踪到org.apache.catalina包下的时候，则无法进入，这是因为idea运行的tomcat是通过插件的方式集成的，tomcat里面的lib包不再项目的依赖路径中，所以不能跟踪进去

首先在自己项目中被tomcat回调的接口实现类中，标记一个断点信息，通过idea启动web项目，当出现如图所示的断点信息的时候，因为断点位置标记的是tomcat回调的接口类，所以按照调用堆栈网上则是tomcat内部代码，但此时双击org.apache.catalina包下面的类名，是没有任何反应的，因为我们还没有将tomcat对应的依赖文件添加到classpath下面

添加依赖

<dependency>
 <groupId>org.apache.tomcat</groupId>
 <artifactId>tomcat-catalina</artifactId>
 <version>8.5.55</version>
 <scope>provided</scope>
</dependency>

因为运行时使用的是tomcat的lib目录下面的jar文件，所以此处的scope使用provided方式

下面就可以进入到tomcat源码调试了

tomcat启动日志是怎么执行打出来的？

03-Jun-2020 10:31:30.929 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Server.服务器版本: Apache Tomcat/8.5.55
03-Jun-2020 10:31:30.938 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 服务器构建:    May 5 2020 22:10:54 UTC
03-Jun-2020 10:31:30.938 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 服务器版本号(:   8.5.55.0
03-Jun-2020 10:31:30.938 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 操作系统名称:   Windows 10
03-Jun-2020 10:31:30.938 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log OS.版本:      10.0
03-Jun-2020 10:31:30.938 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 架构:       amd64
03-Jun-2020 10:31:30.939 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Java 环境变量:   C:\Program Files\Java\jdk1.8.0_212\jre
03-Jun-2020 10:31:30.939 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log Java虚拟机版本:  1.8.0_212-b10
03-Jun-2020 10:31:30.939 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log JVM.供应商:    Oracle Corporation
03-Jun-2020 10:31:30.939 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_BASE:   C:\Users\Administrator\.IntelliJIdea2018.3\system\tomcat\Unnamed_spring-shiro-training
03-Jun-2020 10:31:30.939 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_HOME:   D:\tomcat8.5.55\apache-tomcat-8.5.55

通过定位到 VersionLoggerListener 日志可以查看到

private void log() {
 log.info(sm.getString("versionLoggerListener.serverInfo.server.version",
  ServerInfo.getServerInfo()));
 log.info(sm.getString("versionLoggerListener.serverInfo.server.built",
  ServerInfo.getServerBuilt()));
 log.info(sm.getString("versionLoggerListener.serverInfo.server.number",
  ServerInfo.getServerNumber()));
 log.info(sm.getString("versionLoggerListener.os.name",
  System.getProperty("os.name")));
 log.info(sm.getString("versionLoggerListener.os.version",
  System.getProperty("os.version")));
 log.info(sm.getString("versionLoggerListener.os.arch",
  System.getProperty("os.arch")));
 log.info(sm.getString("versionLoggerListener.java.home",
  System.getProperty("java.home")));
 log.info(sm.getString("versionLoggerListener.vm.version",
  System.getProperty("java.runtime.version")));
 log.info(sm.getString("versionLoggerListener.vm.vendor",
  System.getProperty("java.vm.vendor")));
 log.info(sm.getString("versionLoggerListener.catalina.base",
  System.getProperty("catalina.base")));
 log.info(sm.getString("versionLoggerListener.catalina.home",
  System.getProperty("catalina.home")));


 if (logArgs) {
 List<String> args = ManagementFactory.getRuntimeMXBean().getInputArguments();
 for (String arg : args) {
  log.info(sm.getString("versionLoggerListener.arg", arg));
 }
 }


 if (logEnv) {
 SortedMap<String, String> sortedMap = new TreeMap<>(System.getenv());
 for (Map.Entry<String, String> e : sortedMap.entrySet()) {
  log.info(sm.getString("versionLoggerListener.env", e.getKey(), e.getValue()));
 }
 }


 if (logProps) {
 SortedMap<String, String> sortedMap = new TreeMap<>();
 for (Map.Entry<Object, Object> e : System.getProperties().entrySet()) {
  sortedMap.put(String.valueOf(e.getKey()), String.valueOf(e.getValue()));
 }
 for (Map.Entry<String, String> e : sortedMap.entrySet()) {
  log.info(sm.getString("versionLoggerListener.prop", e.getKey(), e.getValue()));
 }
 }
}

发现是通过键值对的方式获取的，再通过字符串全局搜索发现

但是匹配的是英文，那么中文是怎么打出来的呢？

最后通过调试发现找的是这个

类似上面的东西,调试的时候发现tocmat的东西启动还是相当多的
且看下面这个

idea tomcat启动后的数据

03-Jun-2020 10:31:30.939 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Djava.util.logging.config.file=C:\Users\Administrator\.IntelliJIdea2018.3\system\tomcat\Unnamed_spring-shiro-training\conf\logging.properties
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-agentlib:jdwp=transport=dt_socket,address=127.0.0.1:52290,suspend=y,server=n
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-javaagent:C:\Users\Administrator\.IntelliJIdea2018.3\system\captureAgent\debugger-agent.jar
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dfile.encoding=UTF-8
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcom.sun.management.jmxremote=
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcom.sun.management.jmxremote.port=1099
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcom.sun.management.jmxremote.ssl=false
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcom.sun.management.jmxremote.password.file=C:\Users\Administrator\.IntelliJIdea2018.3\system\tomcat\Unnamed_spring-shiro-training\jmxremote.password
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcom.sun.management.jmxremote.access.file=C:\Users\Administrator\.IntelliJIdea2018.3\system\tomcat\Unnamed_spring-shiro-training\jmxremote.access
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Djava.rmi.server.hostname=127.0.0.1
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Djdk.tls.ephemeralDHKeySize=2048
03-Jun-2020 10:31:30.940 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Djava.protocol.handler.pkgs=org.apache.catalina.webresources
03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dignore.endorsed.dirs=
03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcatalina.base=C:\Users\Administrator\.IntelliJIdea2018.3\system\tomcat\Unnamed_spring-shiro-training
03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Dcatalina.home=D:\tomcat8.5.55\apache-tomcat-8.5.55
03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.startup.VersionLoggerListener.log 命令行参数：-Djava.io.tmpdir=D:\tomcat8.5.55\apache-tomcat-8.5.55\temp

以上还只是基本的环境配置等启动
然后是准备链接到tomcat服务

03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.core.AprLifecycleListener.lifecycleEvent 使用APR版本[1.7.0]加载了基于APR的Apache Tomcat本机库[1.2.24]。
03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.core.AprLifecycleListener.lifecycleEvent APR功能：IPv6[true]、sendfile[true]、accept filters[false]、random[true]。
03-Jun-2020 10:31:30.941 信息 [main] org.apache.catalina.core.AprLifecycleListener.lifecycleEvent APR/OpenSSL配置：useAprConnector[false]，useOpenSSL[true]
03-Jun-2020 10:31:30.944 信息 [main] org.apache.catalina.core.AprLifecycleListener.initializeSSL OpenSSL成功初始化 [OpenSSL 1.1.1g  21 Apr 2020]
03-Jun-2020 10:31:31.032 信息 [main] org.apache.coyote.AbstractProtocol.init 初始化协议处理器 ["http-nio-8080"]
03-Jun-2020 10:31:31.046 信息 [main] org.apache.tomcat.util.net.NioSelectorPool.getSharedSelector Using a shared selector for servlet write/read
03-Jun-2020 10:31:31.055 信息 [main] org.apache.catalina.startup.Catalina.load Initialization processed in 175489 ms
03-Jun-2020 10:31:31.080 信息 [main] org.apache.catalina.core.StandardService.startInternal 正在启动服务[Catalina]
03-Jun-2020 10:31:31.080 信息 [main] org.apache.catalina.core.StandardEngine.startInternal Starting Servlet Engine: Apache Tomcat/8.5.55
03-Jun-2020 10:31:31.089 信息 [main] org.apache.coyote.AbstractProtocol.start 开始协议处理句柄["http-nio-8080"]
03-Jun-2020 10:31:31.102 信息 [main] org.apache.catalina.startup.Catalina.start Server startup in 47 ms

tomat启动主要是在Catalina中

然后是

启动

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

 getServer().await();


}

其实tomcat启动本质上就是socket的服务器罢了

@Override
public void await() {
 // Negative values - don't wait on port - tomcat is embedded or we just don't like ports
 if (port == -2) {
 // undocumented yet - for embedding apps that are around, alive.
 return;
 }
 if (port==-1) {
 try {
  awaitThread = Thread.currentThread();
  while(!stopAwait) {
  try {
   Thread.sleep( 10000 );
  } catch( InterruptedException ex ) {
   // continue and check the flag
  }
  }
 } finally {
  awaitThread = null;
 }
 return;
 }


 // Set up a server socket to wait on
 try {
 awaitSocket = new ServerSocket(port, 1,
  InetAddress.getByName(address));
 } catch (IOException e) {
 log.error("StandardServer.await: create[" + address
    + ":" + port
    + "]: ", e);
 return;
 }


 try {
 awaitThread = Thread.currentThread();


 // Loop waiting for a connection and a valid command
 while (!stopAwait) {
  ServerSocket serverSocket = awaitSocket;
  if (serverSocket == null) {
  break;
  }


  // Wait for the next connection
  Socket socket = null;
  StringBuilder command = new StringBuilder();
  try {
  InputStream stream;
  long acceptStartTime = System.currentTimeMillis();
  try {
   socket = serverSocket.accept(); //一旦accecpt后面就开始执行了
   socket.setSoTimeout(10 * 1000); // Ten seconds
   stream = socket.getInputStream();
  } catch (SocketTimeoutException ste) {
   // This should never happen but bug 56684 suggests that
   // it does.
   log.warn(sm.getString("standardServer.accept.timeout",
    Long.valueOf(System.currentTimeMillis() - acceptStartTime)), ste);
   continue;
  } catch (AccessControlException ace) {
   log.warn(sm.getString("standardServer.accept.security"), ace);
   continue;
  } catch (IOException e) {
   if (stopAwait) {
   // Wait was aborted with socket.close()
   break;
   }
   log.error(sm.getString("standardServer.accept.error"), e);
   break;
  }


  // Read a set of characters from the socket
  int expected = 1024; // Cut off to avoid DoS attack
  while (expected < shutdown.length()) {
   if (random == null)
   random = new Random();
   expected += (random.nextInt() % 1024);
  }
  while (expected > 0) {
   int ch = -1;
   try {
   ch = stream.read();
   } catch (IOException e) {
   log.warn(sm.getString("standardServer.accept.readError"), e);
   ch = -1;
   }
   // Control character or EOF (-1) terminates loop
   if (ch < 32 || ch == 127) {
   break;
   }
   command.append((char) ch);
   expected--;
  }
  } finally {
  // Close the socket now that we are done with it
  try {
   if (socket != null) {
   socket.close();
   }
  } catch (IOException e) {
   // Ignore
  }
  }


  // Match against our command string
  boolean match = command.toString().equals(shutdown);
  if (match) {
  log.info(sm.getString("standardServer.shutdownViaPort"));
  break;
  } else
  log.warn(sm.getString("standardServer.invalidShutdownCommand", command.toString()));
 }
 } finally {
 ServerSocket serverSocket = awaitSocket;
 awaitThread = null;
 awaitSocket = null;


 // Close the server socket and return
 if (serverSocket != null) {
  try {
  serverSocket.close();
  } catch (IOException e) {
  // Ignore
  }
 }
 }
}

tomcat容器启动之后，下面就是Springmvc模块的内容了