1 Tomcat异常

1.1 起步内存溢出问题Exception in thread   http-bio-8080

1.1.1异常现象

现象如下：
Tomcat7启动后，后台抛出如下异常，前台一直无法登陆

Exception in thread ""http-bio-8080"-exec-6" java.lang.OutOfMemoryError: PermGen space
Exception in thread ""http-bio-8080"-exec-9" java.lang.OutOfMemoryError: PermGen space
Exception in thread "schedulerFactory_Worker-3" java.lang.OutOfMemoryError: PermGen space
Exception in thread ""http-bio-8080"-exec-2" java.lang.OutOfMemoryError: PermGen space
Exception in thread "Timer-0" java.lang.OutOfMemoryError: PermGen space

1.1.2解决方案

给 tomcat指定的 jdk加大启动的内存参数

-Xms128m -Xmx512m -XX:PermSize=128m -XX:MaxPermSize=128m

1.2 At least one JAR was scanned for TLDs yet contained no TLDs解决办法

在尝试以下操作前，请先关闭杀毒软件，确保不是受杀毒软件的影响；
部署的系统报如下错误，就是百度杀毒引起的。
报错内容：

Jun 03, 2013 1:09:49 PM org.apache.jasper.compiler.TldLocationsCache tldScanJar
INFO: 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.

这样的问题是你的页面中含有``的注释，去掉就好了，tomcat7.0.20.

tomcat 7对 EL表达式的语法要求比较严格，例如 "${owner.new}"因包含关键字 new就会导致解析出错。
问题是出来了，怎么解决呢？有三种，如下：

1. 严格遵守 java规范，修改对象的属性名称，要求不包含 java关键字;
2. 修改 EL表达式，例如 "${owner.new}"可以修改为 "${owner['new']}";
3. 修改 tomcat属性，忽略对 EL表达式的关键字检查。修改 $CATALINA_BASE/conf/catalina.properties文件，添加 org.apache.el.parser.SKIP_IDENTIFIER_CHECK=true选项。

1.3 tomcat HTTP Status 405

出现 HTTP Status 405 - HTTP method GET is not supported by this URL原因是：

1. 继承自 Httpservlet的 Servlet没有重写对于请求和响应的处理方法： doGet或doPost等方法，默认调用父类的 doGet或doPost等方法。
2. 父类 HttpServlet的doGet或doPost等方法覆盖了你写的到 doGet或doPost等方法。

不管是1或2，父类 HttpServlet的doGet或doPost等方法默认实现是返回状态码是 405的Http错误表示  对于指定资源请求方法不被允许。
解决方法：

1. 子类重写 doGet或doPost等方法。
2. 在扩张的 Servlet中重写 doGet或doPost等方法来处理请求和响应时，不要调用父类的 doGet或doPost等方法即去掉 supper.doGet(request,response)和super.doPost(request,response);

1.4 java.lang.IllegalStateException；Cannot forward after response has been committe

当发生在如下错误的时候，有一个方案可行，
java.lang.IllegalStateException: Cannot forward after response has been committed
当你有多个跳转的页面的语句时候，好好检查一下，当 转发 或者 重定向的时候，需要在后加一个 retrun 即可。
服务器中不允许多次跳转，否则会下面这个错误。

因为服务器端使用 sendRedirect跳转到客户端的时候,不能在使用 req.getRequestDispatcher("跳转的页面").forward(req, reqs);跳转;
所以在跳转之后， return就不会往下执行。

protected void login(HttpServletRequest req, HttpServletResponse reqs) throws ServletException, IOException {  
    // TODO Auto-generated method stub  
    if(req.getUserPrincipal()!=null){  
        String userID = req.getRemoteUser();  
        boolean bol = req.isUserInRole(USER_ROLE_ADMIN);  
        UserModel userModel =connectionDao.getUserModelByUserID(userID);  
        if(bol){  
            req.getSession().setAttribute("user",userModel);  
            reqs.sendRedirect(req.getContextPath()+"/admin/main.jsp");  
            return;  
        }else{  
            reqs.sendRedirect(req.getContextPath()+"/index.jsp");  
            return;  
        }  
    }  }

1.5 tomcat奇怪错误之A child container failed during start

错误详情：

严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/SimpleLogin]]
at java.util.concurrent.FutureTask StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/SimpleLogin]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
... 7 more
Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> * in servlet mapping
at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3217)
at org.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3192)
at org.apache.catalina.deploy.WebXml.configureContext(WebXml.java:1302)
at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1323)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:855)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:346)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5173)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
2012-8-23 14:28:31 org.apache.catalina.core.ContainerBase startInternal
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
at java.util.concurrent.FutureTask StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1131)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:785)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
2012-8-23 14:28:31 org.apache.catalina.startup.Catalina start
严重: Catalina.start:
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.startup.Catalina.start(Catalina.java:675)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:451)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 9 more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1131)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 11 more
2012-8-23 14:28:31 org.apache.catalina.startup.Catalina start
信息: Server startup in 984 ms

错误原因：
已经发布到 tomcat上的某个项目的 servlet过滤器配置错误。
如在 web.xml下，将过滤规则定为 *就是一种错误，需要更正为 /*或者其他（但是必须要有 /开头，表示当前项目）