1，检查是否将classpath设置错误：正确的为.;%java_home%/lib/rt.jar;%java_home%/lib/tools.jar  <!--java_home is your jdk directory-->

2，This   can   usually   be   solved   by   copying   manually   $JAVA_HOME/lib/tools.jar   from   the   JDK    
  to   the   common/lib   directory   of   the   Tomcat   server,   followed   by   a   Tomcat   restart.       
  看到了吗？  
  把jdk安装目录下的lib/tools.jar拷贝到tomcat安装目录下的common/lib目录下，然后重启tomcat，试试   。

3,设置tomcat的字符集为GBK，预防乱码的产生：F:/Tomcat 5.0/conf目录下的server.xml中增加一个参数URIEncoding="GBK"

for example:    <Connector  URIEncoding="GBK"
port="8080"      maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
               enableLookups="false" redirectPort="8443" acceptCount="100"
               debug="0" connectionTimeout="20000"
               disableUploadTimeout="true" />

4,增大tomcat的jvm内存使用参数：在F:/Tomcat 5.0/bin目录下的catalina.bat文件中增加set JAVA_OPTS=-Xms256m -Xmx512m

for example:  the first word is added by us.

set JAVA_OPTS=-Xms384m -Xmx768m
set _EXECJAVA=%_RUNJAVA%
set MAINCLASS=org.apache.catalina.startup.Bootstrap
set ACTION=start
set SECURITY_POLICY_FILE=
set DEBUG_OPTS=
set JPDA=