让Tomcat启动时，打印出更多信息

前言

在启动Tomcat时，有时候因为一些错误启动不起来，但log信息又非常少，如何能让Tomcat打印出更多的信息呢？

正文

方法就是：

修改{catalina_home}/conf/logging.properties 文件。

大家在启动时可能常会看到下面的信息：

26-Dec-2016 21:45:31.293 信息 [RMI TCP Connection(2)-127.0.0.1] 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.

　　上面的信息是说“有一些Jar里没有找到TLD文件”，其实这个信息没有什么大问题。但如果想看一下“到底在哪些Jar里没有找到TLD文件”的话，应该怎么做呢？
　　看上面的信息中，意思是说org.apache.jasper.servlet.TldScanner 类的scanJars方法，在扫描时没有找到TLD文件。那么我们就在logging.properties 文件中加入下面的配置：

org.apache.jasper.servlet.TldScanner.level = FINE

说明：
1，org.apache.jasper.servlet.TldScanner 是刚才说的类。
2，level=FINE 是配置这个类的信息打印级别，我们这里设置成Fine，也可以设置成更低一些，例如：Debug。

设置完后，我们再启动一下Tomcat，就会看到下面的信息。这样详细的信息（哪个Jar有TLD文件，哪个Jar没有）都列出来了。

26-Dec-2016 23:07:59.245 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner.scanResourcePaths No TLD files were found in resource path [/WEB-INF/view/].
26-Dec-2016 23:07:59.245 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner.scanResourcePaths No TLD files were found in resource path [/WEB-INF/].
26-Dec-2016 23:07:59.248 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner TldScannerCallback.scanNoTLDfileswerefoundin[file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework−Chapter3/target/chapter3−1.0.0/WEB−INF/lib/jackson−core−2.5.1.jar].ConsideraddingtheJARtothetomcat.util.scan.StandardJarScanFilter.jarsToSkippropertyinCATALINABASE/conf/catalina.propertiesfile.26−Dec−201623:07:59.248详细[RMITCPConnection(4)−127.0.0.1]org.apache.jasper.servlet.TldScanner TldScannerCallback.scan No TLD files were found in [file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework-Chapter3/target/chapter3-1.0.0/WEB-INF/lib/commons-dbutils-1.6.jar]. Consider adding the JAR to the tomcat.util.scan.StandardJarScanFilter.jarsToSkip property in CATALINA_BASE/conf/catalina.properties file.
26-Dec-2016 23:07:59.253 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner TldScannerCallback.scanTLDfileswerefoundinJAR[file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework−Chapter3/target/chapter3−1.0.0/WEB−INF/lib/smart−plugin−security−1.0.0.jar].26−Dec−201623:07:59.264详细[RMITCPConnection(4)−127.0.0.1]org.apache.jasper.servlet.TldScanner TldScannerCallback.scan TLD files were found in JAR [file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework-Chapter3/target/chapter3-1.0.0/WEB-INF/lib/shiro-web-1.2.3.jar].
26-Dec-2016 23:07:59.265 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner TldScannerCallback.scanNoTLDfileswerefoundin[file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework−Chapter3/target/chapter3−1.0.0/WEB−INF/lib/shiro−core−1.2.3.jar].ConsideraddingtheJARtothetomcat.util.scan.StandardJarScanFilter.jarsToSkippropertyinCATALINABASE/conf/catalina.propertiesfile.26−Dec−201623:07:59.266详细[RMITCPConnection(4)−127.0.0.1]org.apache.jasper.servlet.TldScanner TldScannerCallback.scan No TLD files were found in [file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework-Chapter3/target/chapter3-1.0.0/WEB-INF/lib/jackson-annotations-2.5.0.jar]. Consider adding the JAR to the tomcat.util.scan.StandardJarScanFilter.jarsToSkip property in CATALINA_BASE/conf/catalina.properties file.
26-Dec-2016 23:07:59.267 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner TldScannerCallback.scanNoTLDfileswerefoundin[file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework−Chapter3/target/chapter3−1.0.0/WEB−INF/lib/smart−framework−1.0.0.jar].ConsideraddingtheJARtothetomcat.util.scan.StandardJarScanFilter.jarsToSkippropertyinCATALINABASE/conf/catalina.propertiesfile.26−Dec−201623:07:59.320详细[RMITCPConnection(4)−127.0.0.1]org.apache.jasper.servlet.TldScanner TldScannerCallback.scan TLD files were found in JAR [file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework-Chapter3/target/chapter3-1.0.0/WEB-INF/lib/jstl-1.2.jar].
26-Dec-2016 23:07:59.321 详细 [RMI TCP Connection(4)-127.0.0.1] org.apache.jasper.servlet.TldScanner TldScannerCallback.scanNoTLDfileswerefoundin[file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework−Chapter3/target/chapter3−1.0.0/WEB−INF/lib/mysql−connector−java−5.1.39.jar].ConsideraddingtheJARtothetomcat.util.scan.StandardJarScanFilter.jarsToSkippropertyinCATALINABASE/conf/catalina.propertiesfile.26−Dec−201623:07:59.322详细[RMITCPConnection(4)−127.0.0.1]org.apache.jasper.servlet.TldScanner TldScannerCallback.scan No TLD files were found in [file:/Users/shijiapeng/IdeaProjects/Smart4jFramework/Smart4jFramework-Chapter3/target/chapter3-1.0.0/WEB-INF/lib/jackson-databind-2.5.2.jar]. Consider adding the JAR to the tomcat.util.scan.StandardJarScanFilter.jarsToSkip property in CATALINA_BASE/conf/catalina.properties file.
26-Dec-2016 23:07:59.323 信息 [RMI TCP Connection(4)-127.0.0.1] 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.