java.lang.NullPointerException bei FileUploadBean.uploadFile

Question

Ich bekomme , nicht sicher, warum, wie ich Daten in meiner Liste der Zeichenfolge fileData haben.

Java-Code:

private List<String> fileData; 

public void uploadFile(FileEntryEvent event) { 
    System.out.println("Event: " + event.getSource()); 
    System.out.println("Test"); 
    FileEntry fileEntry = (FileEntry) event.getSource(); 
    FileEntryResults results = fileEntry.getResults(); 
    for (FileEntryResults.FileInfo fileInfo : results.getFiles()) { 
     if (fileInfo.isSaved()) { 
      System.out.println("File is saved sucessfully"); 
      fileData.add("FileName: " + fileInfo.getFileName()); 
      fileData.add("FileSize: " + fileInfo.getSize()); 
      fileData.add("FileStatus: " + fileInfo.getStatus()); 
     } 
    } 
} 

public List<String> getFileData() { 
    System.out.println("inside getFileData"); 
    List<String> data = fileData; 
    return fileData; 
} 

public void setFileData(List<String> fileData) { 
    this.fileData = fileData; 
} 

Ausnahme:

Caused by: java.lang.NullPointerException 
     at FileUploadBean.uploadFile(FileUploadBean.java:54) 
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
     at java.lang.reflect.Method.invoke(Method.java:597) 
     at org.apache.el.parser.AstValue.invoke(AstValue.java:264) 
     at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278) 
     at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105) 
     at org.icefaces.ace.component.fileentry.FileEntry.broadcast(FileEntry.java:306) 
     ... 28 more 

Answer 1

fileData ist null, da Sie es noch nicht erstellt haben. Fügen Sie den follwing zu Ihrer uploadFile Methode:

fileData = new ArrayList<String>(); 

PS: Die setFileData Methode, die Sie nicht benötigen.