javax.servlet jar是专为开发者打造的一款java依融包，javax.servlet.jar包可以解决找不到javax.servlet.*等问题，如果在提示的时候提示不存，可以在知识兔下载然后放到指定的目录后就可以正常应用了，需要此款jar包的朋友们欢迎前来下载应用。
常见问题
编译时错误：软件包 javax.servlet.http 不存在import javax.servlet.http.HttpServletRequest;
解决办法：
1、 把servlet-api.jar加到classpath中，如
把%CATALINA_HOME%\lib;%CATALINA_HOME%\lib\servlet-api.jar;%CATALINA_HOME%\lib\jsp-api.jar 加到classpath变量的后面。
2、 把Tomcat目录下的 tomcat\lib\servlet-api.jar 拷贝到 Java\jdk1.6.0_22\jre\lib\ext 目录下。
3、 javac时把相关的类没有加到-classpath选项中去，如：
编译时应用：javac -classpath ./test.jar TestJar.java
运行时应用：java -cp .:./test.jar TestJar 才可以运行。
请问这里为什么javac应用-classpath，java应用-cp?难道classpath不等价于cp? 没有区别，除了一个是缩写，一个是全称之外，功能是一模一样的。
包括：
javax.servlet.Filter
javax.servlet.Servlet
javax.servlet.FilterChain
javax.servlet.http.Cookie
javax.servlet.jsp.JspPage
javax.servlet.FilterConfig
javax.servlet.ServletConfig
javax.servlet.jsp.ErrorData
javax.servlet.jsp.JspWriter
javax.servlet.GenericServlet
javax.servlet.ServletContext
javax.servlet.ServletRequest
javax.servlet.http.HttpUtils
javax.servlet.jsp.JspContext
javax.servlet.jsp.JspFactory
javax.servlet.jsp.tagext.Tag
javax.servlet.ServletResponse
javax.servlet.jsp.HttpJspPage
javax.servlet.jsp.PageContext
javax.servlet.ServletException
javax.servlet.http.HttpServlet
javax.servlet.http.HttpSession
javax.servlet.jsp.JspException
javax.servlet.RequestDispatcher
javax.servlet.SingleThreadModel
javax.servlet.jsp.JspEngineInfo
javax.servlet.jsp.el.Expression
javax.servlet.jsp.tagext.JspTag
javax.servlet.ServletInputStream
javax.servlet.jsp.el.ELException
javax.servlet.jsp.tagext.BodyTag
javax.servlet.jsp.tagext.TagData
javax.servlet.jsp.tagext.TagInfo
javax.servlet.ServletContextEvent
javax.servlet.ServletOutputStream
javax.servlet.ServletRequestEvent
javax.servlet.http.NoBodyResponse
javax.servlet.jsp.JspTagException
javax.servlet.jsp.tagext.PageData
javax.servlet.UnavailableException
javax.servlet.jsp.tagext.SimpleTag
javax.servlet.ServletRequestWrapper
javax.servlet.http.HttpSessionEvent
javax.servlet.jsp.SkipPageException
javax.servlet.jsp.el.FunctionMapper
javax.servlet.jsp.tagext.TagAdapter
javax.servlet.jsp.tagext.TagSupport
javax.servlet.ServletContextListener
javax.servlet.ServletRequestListener
javax.servlet.ServletResponseWrapper
javax.servlet.jsp.tagext.BodyContent
javax.servlet.jsp.tagext.JspFragment
javax.servlet.jsp.tagext.TagFileInfo
javax.servlet.http.HttpServletRequest
javax.servlet.http.HttpSessionContext
javax.servlet.http.NoBodyOutputStream
javax.servlet.jsp.el.ELParseException
javax.servlet.jsp.el.VariableResolver
javax.servlet.jsp.tagext.FunctionInfo
javax.servlet.jsp.tagext.IterationTag
javax.servlet.jsp.tagext.TagExtraInfo
javax.servlet.jsp.tagext.VariableInfo
javax.servlet.http.HttpServletResponse
javax.servlet.http.HttpSessionListener
javax.servlet.jsp.tagext.BodyTagSupport
javax.servlet.jsp.tagext.TagLibraryInfo
javax.servlet.jsp.el.ExpressionEvaluator
javax.servlet.jsp.tagext.TagVariableInfo
javax.servlet.jsp.tagext.TryCatchFinally
javax.servlet.jsp.tagext.SimpleTagSupport
javax.servlet.jsp.tagext.TagAttributeInfo
javax.servlet.ServletContextAttributeEvent
javax.servlet.ServletRequestAttributeEvent
javax.servlet.http.HttpSessionBindingEvent
javax.servlet.jsp.tagext.DynamicAttributes
javax.servlet.jsp.tagext.ValidationMessage
javax.servlet.http.HttpServletRequestWrapper
javax.servlet.jsp.tagext.TagLibraryValidator
javax.servlet.ServletContextAttributeListener
javax.servlet.ServletRequestAttributeListener
javax.servlet.http.HttpServletResponseWrapper
javax.servlet.http.HttpSessionBindingListener
javax.servlet.http.HttpSessionAttributeListener
javax.servlet.http.HttpSessionActivationListener
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