FileDownload Exception in JAVA

StackOverflow https://stackoverflow.com/questions/22144469

  •  19-10-2022
  •  | 
  •  

Question

I have a Java-Web-Application which reads the local Log-Files of the Tomcat Server, and writes it in a table. There should be a Download-Button, so I can download each log.

First I choose a Log-File, which the Application should read. This works. Now the DownloadController should know, which file I want to download.

But I always get the Error, that the class can not be instantiated. Where is the Problem?

Here my Code:

index.xhtml:

    <?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
        xmlns:h="http://java.sun.com/jsf/html"
        xmlns:f="http://java.sun.com/jsf/core"
        xmlns:p="http://primefaces.org/ui">
    <h:head>
        <title>LogReader</title>

        <style type="text/css">
            .info {
                background-color: #F2F5A9 !important;
                background-image: none !important;
                color: #000000 !important;
            }
            .warn {
                background-color: #FFCC00 !important;
                background-image: none !important;
                color: #000000 !important;
            }            
            .error {
                background-color: #FF6600 !important;
                background-image: none !important;
                color: #000000 !important;
            }
            .fatal {
                background-color: #FF0000 !important;
                background-image: none !important;
                color: #000000 !important;
            }
        </style>

        <p:dialog modal="true" widgetVar="statusDialog" header="Load Log-File"   
            draggable="false" closable="false">  
            <p:graphicImage value="/design/ajaxloadingbar.gif" />  
        </p:dialog>  

    </h:head>

    <h:body>

        <h:form id="logReader">

            <p:accordionPanel dynamic="true" cache="true" widgetVar="accordion" activeIndex="-1" multiple="false">              
                <p:tab title="Select File">  
                    <h:panelGrid>  
                        <p:dataList id="folder" var="file" value="#{fileUploadController.tableBean.listFolder}" itemType="disc"> 
                            <p:commandLink id="ajax" update=":logReader:logs" actionListener="#{fileUploadController.readFile(file)}" style="margin-right:20px;" onstart="PF('statusDialog').show();" onsuccess="PF('statusDialog').hide();" onclick="accordion.select(-1);">  
                                    <h:outputText value="#{file}" />  
                                </p:commandLink>                             
                        </p:dataList>                          
                    </h:panelGrid>  
                </p:tab> 

                <p:tab title="Download File">  
                    <h:panelGrid>  
                        <p:commandButton id="downloadLink" value="Download" ajax="false" onclick="PrimeFaces.monitorDownload(start, stop)"   
                        icon="ui-icon-arrowthichk-s">  
                            <p:fileDownload value="#{fileDownloadController.tableBean.fileDownload}" />  
                        </p:commandButton> 
                    </h:panelGrid>  
                </p:tab>  

            </p:accordionPanel>

            <br />        
            <p:outputPanel id="logs">

                <p:dataTable id="dataTable" var="log" value="#{fileUploadController.tableBean.logsSmall}" widgetVar="dataTable" rowStyleClass="#{log.level eq 'ERROR' ? 'error' : log.level eq 'INFO' ? 'info' : log.level eq 'WARN' ? 'warn' : log.level eq 'FATAL' ? 'fatal' : null}"  
                             emptyMessage="No Log found with given criteria" filteredValue="#{tableBean.filteredLogs}" 
                             rowKey="#{log.datetime}" paginator="true" rows="20" paginatorTemplate="{CurrentPageReport}  {FirstPageLink} {PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}" rowsPerPageTemplate="5,10,15,20,50,100" selection="#{tableBean.selectedLog}" selectionMode="single">  

                    <f:facet name="header">  
                       <p:outputPanel>  
                           <h:outputText value="Search all fields:" />  
                           <p:inputText id="globalFilter" onkeyup="dataTable.filter();" style="width:150px" />  
                       </p:outputPanel>  
                   </f:facet>  

                   <p:column id="datetimeColumn" filterBy="datetime" sortBy="datetime"   
                           headerText="DateTime" footerText=""  
                           filterMatchMode="contains">  
                       <h:outputText value="#{log.datetime}" />
                   </p:column>  

                   <p:column id="levelColumn" filterBy="level"   
                           headerText="LogLevel" footerText=""  
                           filterOptions="#{tableBean.levelOptions}"  
                           filterMatchMode="exact" sortBy="level">  
                       <h:outputText value="#{log.level}" />
                   </p:column>  

                   <p:column id="categoryColumn" filterBy="category" sortBy="category" 
                           headerText="Category" footerText=""  
                           filterMatchMode="contains">  
                       <h:outputText value="#{log.category}" /> 
                   </p:column>  

                   <p:column id="messageColumn" filterBy="message" sortBy="message"  
                           headerText="Message" footerText="" filterMatchMode="contains">  
                       <h:outputText value="#{log.message}" /> 
                   </p:column>  

                </p:dataTable> 
            </p:outputPanel>
        </h:form>

    </h:body>
</html>

the TableBean:

    package com.rausch.logreader;  

import java.io.Serializable;  
import java.util.List;  
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import javax.faces.model.SelectItem;

import org.apache.log4j.Logger;
import org.primefaces.model.StreamedContent;

@ViewScoped
@ManagedBean(name = "tableBean")

public class TableBean implements Serializable {  

    transient Logger logging = Logger.getLogger("com.rausch.logreader.TableBean");

    private final static String[] level;

    private SelectItem[] levelOptions;  

    private List<Log> filteredLogs;  

    public List<Log> logsSmall;

    private List<String> listFolder;

    private Log selectedLog;  

    private Log[] selectedLogs;

    private StreamedContent fileDownload; 

    private String logFile;

    public String getLogFile() {
        return logFile;
    }

    public void setLogFile(String logFile) {
        this.logFile = logFile;
    }

    static {         
        level = new String[5];
        level[0] = "DEBUG";
        level[1] = "INFO";
        level[2] = "WARN";
        level[3] = "ERROR";
        level[4] = "FATAL";
    }  


    public TableBean() {  
       levelOptions = createLevelOptions(level); 
    }  

    public StreamedContent getFileDownload() {
        return fileDownload;
    }

    public void setFileDownload(StreamedContent fileDownload) {
        this.fileDownload = fileDownload;
    }

    public Log getSelectedLog() {  
        return selectedLog;  
    }  

    public void setSelectedLog(Log selectedLog) {  
        this.selectedLog = selectedLog;  
    }  

    public List<Log> getFilteredLogs() {  
        return filteredLogs;  
    }  

    public void setFilteredLogs(List<Log> filteredCars) {  
        this.filteredLogs = filteredCars;  
    }  

    public void setLogsSmall(List<Log> logsSmall) {  
        this.logsSmall = logsSmall;  
    } 

    public List<Log> getLogsSmall(){
        return logsSmall;
    }

    public void setListFolder(List<String> listFolder) {  
        this.listFolder = listFolder;  
    } 

    public List<String> getListFolder(){
        return listFolder;
    }

    private SelectItem[] createLevelOptions(String[] data)  {  
        SelectItem[] options = new SelectItem[data.length + 1];  

        options[0] = new SelectItem("", "Select");  
        for(int i = 0; i < data.length; i++) {  
            options[i + 1] = new SelectItem(data[i], data[i]);  
        }  

        return options;  
    }  

    public SelectItem[] getLevelOptions() {  
        return levelOptions;  
    }     
}

the FileUploadController:

package com.rausch.logreader;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import org.apache.log4j.Logger;  

@ManagedBean(name = "fileUploadController")
@SessionScoped

public class FileUploadController {  
    //implement log4j
    Logger logging = Logger.getLogger("com.rausch.logreader.FileUploadController");
    TableBean tableBean = new TableBean();

    public TableBean getTableBean() {
        return tableBean;
    }

    public void setTableBean(TableBean tableBean) {
        this.tableBean = tableBean;
    }


    private String directory = System.getProperty("catalina.base") + "/logs";
    private File f = new File(directory);

    public FileUploadController(){
        getFolderContent();
    }

    public final void getFolderContent(){
        List<String> listFolder = new ArrayList<String>();
        File[] files = f.listFiles();
        if (files != null) { 
            for (int i = 0; i < files.length; i++) {
                if (!(files[i].isDirectory())) {
                   listFolder.add(files[i].getName());    
                }
            }
            tableBean.setListFolder(listFolder);
        }

    }

    public void readFile(String file){
        try
        {
            String filePath = System.getProperty("catalina.base") + "/logs/" +  file;
            List<Log> logsSmall = new ArrayList<Log>();
            String sCurrentLine;            
            BufferedReader br = new BufferedReader(new FileReader(filePath));            
            //String output = "";
            String datetime = "";
            String level = "";
            String category = "";
            String message = "";

            while ((sCurrentLine = br.readLine()) != null) { 

               //Diverse uninteresting Parsing


                    //Add to the table-list
                    logsSmall.add(new Log(datetime, level, category, message));
                    //System.out.println(output);
                }                  

            }           
            tableBean.setLogsSmall(logsSmall);
            tableBean.setLogFile(file);
        } catch (IOException e) {
            logging.error(e.getMessage());
        }    
    }    

}

And the FileDownloadController:

package com.rausch.logreader;  

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;  
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;  
import javax.servlet.ServletContext;  

import org.primefaces.model.DefaultStreamedContent;  
import org.primefaces.model.StreamedContent;  

@ManagedBean(name = "fileDownloadController")
@SessionScoped
public class FileDownloadController {  


    TableBean tableBean = new TableBean();

    public TableBean getTableBean() {
        return tableBean;
    }

    public void setTableBean(TableBean tableBean) {
        this.tableBean = tableBean;
    }

    private StreamedContent fileDownload;  

    String logFile = tableBean.getLogFile();

    public String getLogFile() {
        return logFile;
    }

    public void setLogFile(String logFile) {
        this.logFile = logFile;
    }

    public void setDownload(DefaultStreamedContent download) {
        this.fileDownload = download;
        tableBean.setFileDownload(fileDownload); 
    }


    public FileDownloadController() throws FileNotFoundException {          
        File file = new File(logFile);
        InputStream input = new FileInputStream(file);
        ExternalContext externalContext = FacesContext.getCurrentInstance().getExternalContext();
        setDownload(new DefaultStreamedContent(input, externalContext.getMimeType(file.getName()), file.getName()));
    } 


    public StreamedContent getFile() {  
        return fileDownload;          
    }    

    public void setFile(String file){
        this.logFile = file;

    }
}

The Exception is:

    com.sun.faces.mgbean.ManagedBeanCreationException: Klasse com.rausch.logreader.FileDownloadController kann nicht instanziiert werden.
    at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:191)
    at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:100)
    at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:409)
    at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:269)
    at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244)
    at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116)
    at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
    at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
    at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:72)
    at org.apache.el.parser.AstValue.getValue(AstValue.java:161)
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:185)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
    at org.primefaces.component.filedownload.FileDownloadActionListener.processAction(FileDownloadActionListener.java:53)
    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:818)
    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
    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:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    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:724)
Caused by: java.lang.NullPointerException
    at java.io.File.<init>(File.java:277)
    at com.rausch.logreader.FileDownloadController.<init>(FileDownloadController.java:50)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at java.lang.Class.newInstance(Class.java:374)
    at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:186)
    ... 41 more

No correct solution

OTHER TIPS

I think that the problem is in the FileDownloadController:

TableBean tableBean = new TableBean();
// [...]
String logFile = tableBean.getLogFile();
// [...]
public FileDownloadController() throws FileNotFoundException {          
    File file = new File(logFile);

You create an new TableBean and never call setLogFile() on it. So, tableBean.getLogFile()returns null, and when you create your file, logFile will be null and you will have a NullPointerException in the File constructor.

Try to cut the code inside your FileDownloadController constructor and paste it in another method with a @PostContruct annotation.

@PostContruct
public void initBean()
{
File file = new File(logFile);
InputStream input = new FileInputStream(file);
ExternalContext externalContext = FacesContext.getCurrentInstance().getExternalContext();
setDownload(new DefaultStreamedContent(input, externalContext.getMimeType(file.getName()), file.getName()));
}
Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top