f：来自CommandButton的param没有得到参数

Question

我有一个pdf下载servlet的问题（它在上传的同一个bean中）。如果我指定文件的路径，如C:/..工作正常，但如果我尝试传递参数ruta我得到：#{fileUploadController.downLoad}: java.lang.NullPointerException

FileUploadController.java

@ManagedBean(name = "fileUploadController")
@SessionScoped
public class FileUploadController implements Serializable {    

private static final long serialVersionUID = 1L;
 //tama�o del buffer
private static final int DEFAULT_BUFFER_SIZE = 10240;
private byte[] archi= new byte[0];
private String nombre;
public String ruta;   

public byte[] getArchi(){
    return archi;
}
public void setArchi(byte[] archi){
    this.archi= archi;
}

// Nombre del Archivo
public String getNombre() {
    return nombre;
}

public void setNombre(String nombre) {
    this.nombre= nombre;
}

public String getRuta() {
    return ruta;
}

public void setRuta(String ruta) {
    this.ruta= ruta;
}

// ruta fisica del archivo
public String getRealPath() {       
    FacesContext aFacesContext = FacesContext.getCurrentInstance();
    ServletContext context = (ServletContext) aFacesContext.getExternalContext().getContext();

    return context.getRealPath("/");
}

/* subida del archivo con sus atributos */
public void fileUpload(FileUploadEvent event, String type, String directorio) {
    try {       
        this.nombre = new java.util.Date().getTime() + type;
        this.ruta = directorio + getNombre();
        this.archi =getFileContents(event.getFile().getInputstream());          

        File file = new File(directorio);

        // Crea el directorio, incluidos subdirectorios q no existan

        if(!file.exists())          
            file.mkdirs();
    } catch (Exception ex) {
        System.out.println("Error en la subida " + ex);
    }
}

private byte[] getFileContents(InputStream in) {
    byte[] bytes = null;
    try {            
        // write the inputStream to a FileOutputStream            
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        int read = 0;
        bytes = new byte[1024];

        while ((read = in.read(bytes)) != -1) {
            bos.write(bytes, 0, read);
        }
        bytes = bos.toByteArray();
        in.close();
        in = null;
        bos.flush();
        bos.close();
        bos = null;    
    } catch (IOException e) {
        System.out.println(e.getMessage());
    }
    return bytes;
}    

// Guardar el archivo
public void guardar() {
    try {
        FileOutputStream out;

        out = new FileOutputStream(ruta);
        System.out.print("out"+ out);

        out.write(archi);
        System.out.print(archi);
        out.close();
    } catch (Exception ex) {
        System.out.println(ex);
    }
}

/*-------------------- Servlet Descarga Archivos----------------------------------------------*/     
public void  downLoad() throws IOException, ServletException{
    FacesContext contexto = FacesContext.getCurrentInstance();
    this.ruta = getRutaParam(contexto);

    /*yo*/
    HttpServletResponse  response = (HttpServletResponse) contexto .getExternalContext().getResponse(); 
    //ruta de los archivos

    File file = new File(ruta); 

    //Validacion 
    if (!file.exists()) {  
        System.out.println("El archivo no existe!");
        response.sendError(HttpServletResponse.SC_NOT_FOUND);  
        return;  
    } 

    response.reset();  
    response.setBufferSize(DEFAULT_BUFFER_SIZE);  
    response.setContentType("application/pdf");  
    response.setHeader("Content-Length", String.valueOf(file.length())); 
    response.setHeader("Content-Disposition", "attachment;Nombre del Archivo=\""  + file.getName() + "\"");

    //inicializo el input y el output
    BufferedInputStream input = null;  
    BufferedOutputStream output = null;  

    try {  
        input = new BufferedInputStream(new FileInputStream(file), DEFAULT_BUFFER_SIZE);                
        output = new BufferedOutputStream(response.getOutputStream(),  DEFAULT_BUFFER_SIZE);  

        byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];  
        int length;  
        while ((length = input.read(buffer)) > 0) {  
            output.write(buffer, 0, length);  
        }  
    } finally {  
        //cierro
        input.close();  
        output.close();  
    }  
    contexto.responseComplete();  
}    

//get value from "f:param"
public String getRutaParam(FacesContext contexto){
    Map<String,String> params = contexto.getExternalContext().getRequestParameterMap();
    return params.get("ruta");
}       
}

Page2.xhtml

<h:body>
  <h2>Acceso Alumno</h2>
  <h1>Alumnos registrados </h1> 
  <h:form>
    <h:dataTable id="tabla" value="#{alumno.getListaAlumno()}" var="var" border="1">
      <h:column>
        <f:facet name="header">Id </f:facet>
        <h:outputText value = "#{var.id}"/>
      </h:column>
      <h:column>
        <f:facet name="header">Nombre y Apellidos </f:facet>
        <h:outputText value = "#{var.nombreApellidos}"/>
      </h:column>
      <h:column>
        <f:facet name="header">Matricula </f:facet>
        <h:outputText value = "#{var.matricula}"/>
      </h:column>
      <h:column>
        <f:facet name="header">ProductBox </f:facet>
        <h:commandButton value="Guardar Archivo"  
                         action="#{fileUploadController.downLoad}">
          <f:param name="rutaArchivo" value="#{fileUploadController.ruta}" />
        </h:commandButton>                                 
      </h:column>           
    </h:dataTable>
  </h:form>      
  <h:form>
    <h:commandButton action="home?faces-redirect=true"
                     value="Home" />         
  </h:form>
  <!-- Cerrar Sesion -->
  <a href="logout">Cerrar Sesion</a>       
</h:body>

堆栈跟踪

Advertencia: #{fileUploadController.downLoad}: java.lang.NullPointerException
javax.faces.FacesException: #{fileUploadController.downLoad}: java.lang.NullPointerException
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIData.broadcast(UIData.java:1108)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:70)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at 

org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    ... 61 more
Caused by: java.lang.NullPointerException
    at java.io.File.<init>(File.java:277)
    at proyecto.upload.FileUploadController.downLoad(FileUploadController.java:161)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:273)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
    ... 62 more

Hibernate: 
    select
        alumno0_.ID as ID0_,
        alumno0_.NOMBREAPELLIDOS as NOMBREAP2_0_,
        alumno0_.MATRICULA as MATRICULA0_,
        alumno0_.PDF as PDF0_ 
    from
        test.file alumno0_
sep 03, 2014 4:10:29 PM com.sun.faces.context.ExceptionHandlerImpl log
1100: JSF1073: se ha interceptado javax.faces.FacesException durante el procesamiento de INVOKE_APPLICATION 5 : UIComponent-ClientId=, Mensaje=#{fileUploadController.downLoad}: java.lang.NullPointerException
sep 03, 2014 4:10:29 PM com.sun.faces.context.ExceptionHandlerImpl log
1100: #{fileUploadController.downLoad}: java.lang.NullPointerException
javax.faces.FacesException: #{fileUploadController.downLoad}: java.lang.NullPointerException
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:89)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:70)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javax.faces.FacesException: #{fileUploadController.downLoad}: java.lang.NullPointerException
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:118)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIData.broadcast(UIData.java:1108)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    ... 56 more
Caused by: javax.faces.el.EvaluationException: java.lang.NullPointerException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    ... 61 more
Caused by: java.lang.NullPointerException
    at java.io.File.<init>(File.java:277)
at proyecto.upload.FileUploadController.downLoad(FileUploadController.java:161)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:273)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 62 more

Answer 1

在page2.xhtml中，在h：命令按钮中，我使用f：setPropertyActionListener而不是f：param，它工作正常。示例：

<h:commandButton action="#{fileUploadController.downLoad}" value="Guardar Archivo"  > 

               <f:setPropertyActionListener target="#{updownload.ruta}" value="#{var.nombrepdf}" />             

           </h:commandButton>