部署某个旧项目时候，发现启动特别慢，要等好几分钟。然后每次部署都停留在

At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.

jdk环境是1.8，tomcat版本是8.0.

上下文日志：

securerandom.source=file:/dev/./urandom

15-Nov-2018 09:56:13.331 INFO [localhost-startStop-1] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
15-Nov-2018 09:59:29.043 WARNING [localhost-startStop-1] org.apache.catalina.util.SessionIdGeneratorBase.createSecureRandom Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [195,690] milliseconds.

可以看到，就是这个：

Creation of SecureRandom instance

导致了启动时间变长。

解决方案有两个：

1）在Tomcat环境中解决

可以通过配置JRE使用非阻塞的Entropy Source。

在catalina.sh中加入这么一行：

-Djava.security.egd=file:/dev/./urandom

即可。

2）在JVM环境中解决

打开$JAVA_PATH/jre/lib/security/java.security这个文件，找到下面的内容：

securerandom.source=file:/dev/urandom

替换成

securerandom.source=file:/dev/./urandom