org.apache.jasper.JasperException: Unable to compile class for JSP解决方法

org.apache.jasper.JasperException: Unable to compile class for JSP
An   error   occurred   at   line:   6   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
BookDetails   cannot   be   resolved   to   a   type

An   error   occurred   at   line:   6   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
cart   cannot   be   resolved

An   error   occurred   at   line:   22   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
cart   cannot   be   resolved

An   error   occurred   at   line:   31   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
ListIterator   cannot   be   resolved   to   a   type

An   error   occurred   at   line:   31   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
BookDetails   cannot   be   resolved   to   a   type

An   error   occurred   at   line:   31   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
BookDetails   cannot   be   resolved   to   a   type


org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:84)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:328)
org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:409)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:297)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:276)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:264)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:563)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:303)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


An   error   occurred   at   line:   6   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
BookDetails   cannot   be   resolved   to   a   type

An   error   occurred   at   line:   6   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
cart   cannot   be   resolved

An   error   occurred   at   line:   22   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
cart   cannot   be   resolved

An   error   occurred   at   line:   31   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
ListIterator   cannot   be   resolved   to   a   type

An   error   occurred   at   line:   31   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error:
BookDetails   cannot   be   resolved   to   a   type

An   error   occurred   at   line:   31   in   the   jsp   file:   /bookcatalog.jsp
Generated   servlet   error: