//springBoot中默認(rèn)的配置文件為"application.yml"或者"application.perties"文件，也就是說server是其中的一個(gè)配置參數(shù)。
@ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)
public class ServerProperties
  implements EmbeddedServletContainerCustomizer, EnvironmentAware, Ordered {
//代碼
}

@Override
public void customize(ConfigurableEmbeddedServletContainer container) {
 //多個(gè)參數(shù)判斷，如果在application中沒配置的情況下都是null
 if (getPort() != null) {
  container.setPort(getPort());
 }
 ...//n多個(gè)參數(shù)判斷，
 //以下的代碼就是重點(diǎn)，因?yàn)槭莟omcat容器，所以以下條件為“真”，經(jīng)過一系列的查找父類或者實(shí)現(xiàn)接口即可找到抽象類“AbstractConfigurableEmbeddedServletContainer”
 //public class TomcatEmbeddedServletContainerFactory extends AbstractEmbeddedServletContainerFactory implements ResourceLoaderAware
 //public abstract class AbstractEmbeddedServletContainerFactory extends AbstractConfigurableEmbeddedServletContainer implements EmbeddedServletContainerFactory 
 if (container instanceof TomcatEmbeddedServletContainerFactory) {
  getTomcat().customizeTomcat(this,
   (TomcatEmbeddedServletContainerFactory) container);
 }
//以上代碼執(zhí)行完成之后，實(shí)際上已經(jīng)有對(duì)應(yīng)的session所有的默認(rèn)參數(shù)，之后通過下面方法，將所有參數(shù)放入對(duì)應(yīng)的容器中。第3、4步就是設(shè)置過程
 container.addInitializers(new SessionConfiguringInitializer(this.session));
}

//重要代碼
//45行
private static final int DEFAULT_SESSION_TIMEOUT = (int) TimeUnit.MINUTES
  .toSeconds(30);
//66行
private int sessionTimeout = DEFAULT_SESSION_TIMEOUT;
 
@Override
public void setSessionTimeout(int sessionTimeout) {
 this.sessionTimeout = sessionTimeout;
}
//171-188行
@Override
public void setSessionTimeout(int sessionTimeout, TimeUnit timeUnit) {
 Assert.notNull(timeUnit, "TimeUnit must not be null");
 this.sessionTimeout = (int) timeUnit.toSeconds(sessionTimeout);
}

/**
 * Return the session timeout in seconds.
 * @return the timeout in seconds
 */
public int getSessionTimeout() {
 return this.sessionTimeout;
}

public static class Session {

 /**
 * Session timeout in seconds.
 */
 private Integer timeout;

 public Integer getTimeout() {
  return this.timeout;
 }
//將session超時(shí)時(shí)間設(shè)置進(jìn)來
 public void setTimeout(Integer sessionTimeout) {
  this.timeout = sessionTimeout;
 }

//以下代碼
private void configureSession(Context context) {
 long sessionTimeout = getSessionTimeoutInMinutes();
 context.setSessionTimeout((int) sessionTimeout);
 Manager manager = context.getManager();
 if (manager == null) {
  manager = new StandardManager();
  //此處即為設(shè)置相應(yīng)的參數(shù)的位置。之后會(huì)調(diào)用StandardContext類的setManger（Manager）方法，在setManger中會(huì)調(diào)用"manager.setContext(this)"
  context.setManager(manager);
 }
}
//計(jì)算超時(shí)時(shí)間為分鐘（注意：此處會(huì)將之前的1800秒，轉(zhuǎn)換為30分鐘）?？梢钥闯鲎罱K的時(shí)間結(jié)果是個(gè)整數(shù)的分鐘類型，也就是說如果設(shè)置的超時(shí)時(shí)間（單位為秒）不是60的倍數(shù)，也會(huì)最終轉(zhuǎn)換為60的倍數(shù)，并且最小超時(shí)時(shí)間設(shè)置的是60秒。
private long getSessionTimeoutInMinutes() {
 long sessionTimeout = getSessionTimeout();
 if (sessionTimeout > 0) {
  sessionTimeout = Math.max(TimeUnit.SECONDS.toMinutes(sessionTimeout), 1L);
 }
 return sessionTimeout;
}

//以下代碼
@Override
public void setContext(Context context) {
 //省略其余設(shè)置代碼，直接重新設(shè)置Session超時(shí)時(shí)間，此時(shí)又將上面的分鐘單位轉(zhuǎn)為秒。此時(shí)終于給Sesseion設(shè)置了默認(rèn)超時(shí)時(shí)間。
 if (this.context != null) {
  setMaxInactiveInterval(this.context.getSessionTimeout() * 60);
  this.context.addPropertyChangeListener(this);
 }
}

/**
 * Get the session timeout.
 * @return the session timeout
 * @deprecated since 1.3.0 in favor of {@code session.timeout}.
 */
@Deprecated
@DeprecatedConfigurationProperty(replacement = "server.session.timeout")
public Integer getSessionTimeout() {
 return this.session.getTimeout();
}

//判斷是否超時(shí)
@Override
public boolean isValid() {
 //省略多個(gè)條件判斷
 if (maxInactiveInterval > 0) {
  //判斷此session空閑時(shí)間是否比maxInactiveInterval大，如果大的情況下，session就超時(shí)
  int timeIdle = (int) (getIdleTimeInternal() / 1000L);
  if (timeIdle >= maxInactiveInterval) {
   expire(true);
  }
 }
 return this.isValid;
}
//將上次訪問時(shí)間和當(dāng)前時(shí)間比較，拿到空閑時(shí)間值
@Override
public long getIdleTimeInternal() {
 long timeNow = System.currentTimeMillis();
 long timeIdle;
 if (LAST_ACCESS_AT_START) {
  timeIdle = timeNow - lastAccessedTime;
 } else {
  timeIdle = timeNow - thisAccessedTime;
 }
 return timeIdle;
}

 @Bean
 public EmbeddedServletContainerCustomizer containerCustomizer(){
  return new EmbeddedServletContainerCustomizer() {
   @Override
   public void customize(ConfigurableEmbeddedServletContainer container) {
     container.setSessionTimeout(600);//單位為S
   }
  };
 }