無法將類java.lang.String的＃{ad.userid}轉換爲類javax.faces.component.UIComponent

Question

我正在獲取主頁，但是當轉到具有h:inputText的JSP頁面時，我得到以下錯誤：

 
root cause 
javax.servlet.ServletException: javax.servlet.jsp.JspException: org.apache.jasper.el.JspELException: /login.jsp(21,0) '#{ad.userid}' Cannot convert #{ad.userid} of type class java.lang.String to class javax.faces.component.UIComponent 
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858) 
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791) 
org.apache.jsp.login_jsp._jspService(login_jsp.java:83) 
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377) 
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) 
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 
com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:542) 
com.sun.faces.application.view.JspViewHandlingStrategy.executePageToBuildView(JspViewHandlingStrategy.java:359) 
com.sun.faces.application.view.JspViewHandlingStrategy.buildView(JspViewHandlingStrategy.java:150) 
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:96) 
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97) 
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:135) 
javax.faces.webapp.FacesServlet.service(FacesServlet.java:309) 

root cause 

org.apache.jasper.el.JspELException: /login.jsp(21,0) '#{ad.userid}' Cannot convert #{ad.userid} of type class java.lang.String to class javax.faces.component.UIComponent 
org.apache.jasper.el.JspValueExpression.getValue(JspValueExpression.java:107) 
com.sun.faces.application.ApplicationImpl.createComponentApplyAnnotations(ApplicationImpl.java:1878) 
com.sun.faces.application.ApplicationImpl.createComponent(ApplicationImpl.java:443) 
javax.faces.webapp.UIComponentELTag.createComponent(UIComponentELTag.java:218) 
javax.faces.webapp.UIComponentClassicTagBase.createChild(UIComponentClassicTagBase.java:483) 
javax.faces.webapp.UIComponentClassicTagBase.findComponent(UIComponentClassicTagBase.java:667) 
javax.faces.webapp.UIComponentClassicTagBase.doStartTag(UIComponentClassicTagBase.java:1139) 
com.sun.faces.taglib.html_basic.InputTextTag.doStartTag(InputTextTag.java:424) 
org.apache.jsp.login_jsp._jspx_meth_h_005finputText_005f0(login_jsp.java:253) 
org.apache.jsp.login_jsp._jspx_meth_h_005fform_005f0(login_jsp.java:168) 
org.apache.jsp.login_jsp._jspx_meth_f_005fview_005f0(login_jsp.java:113) 
org.apache.jsp.login_jsp._jspService(login_jsp.java:76) 
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377) 
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) 
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 
com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:542) 
com.sun.faces.application.view.JspViewHandlingStrategy.executePageToBuildView(JspViewHandlingStrategy.java:359) 
com.sun.faces.application.view.JspViewHandlingStrategy.buildView(JspViewHandlingStrategy.java:150) 
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:96) 
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97) 
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:135) 
javax.faces.webapp.FacesServlet.service(FacesServlet.java:309) 

Answer 1

在線路的login.jsp 21，替換

<h:inputText binding="#{ad.userid}" /> 

通過

<h:inputText value="#{ad.userid}" /> 

要了解爲什麼binding屬性適用於head here。