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IV-2. Konkretes Implementierungsbeispiel
IV-2-3. JSP-Programmierbeispiel
Markieren Sie im Web-Browser den folgenden grau hinterlegten
Quelltext und speichern Sie ihn in der neu anzulegenden Datei:
Falls Sie einen anderen Dateinamen wählen, passen Sie bitte die
Zeile '<form action="index.jsp" ...>'an. Tragen Sie bei 'String sUploadDir = "/upload/"'den von Ihnen gewünschten Verzeichnisnamen für die Upload-Dateienein. Dieser Eintrag muss mit einem Schrägstrich '/' beginnen undenden und das entsprechende Verzeichnis muss im JSP-Web-Servervorher angelegt werden. In diesem Beispiel wird davon ausgegangen, dass nur Bilddateienzum Upload erlaubt sein sollen. Nach dem Upload werden sie in dieWebseite eingebettet und sofort angezeigt. Falls Sie andere Dateienuploaden wollen, müssen die entsprechenden einschränkenden Zeilenentfernt werden, z.B.:
'if(!ii.check())', 'if(!sImgFormat.equals("..."))'und '<img src="...">'.
<%--
Uses Jason Pell's MultipartRequest to upload a file:
https://www.geocities.com/jasonpell/programs.html
Uses Marco Schmidt's ImageInfo to get image file information:
https://www.geocities.com/marcoschmidt.geo/image-info.html
--%>
<%@ page import = "java.io.*, torstenhorn.upload.*" %>
<%!
// Adapt the following string for your upload directory.
// Tomcat local : sUploadDir = "/upload/";
// MyJavaServer.com : sUploadDir = "/~torstenhorn/upload/";
final String sUploadDir = "/upload/";
final String sErrMsg
= "<h2>Fehler: Keine gültige Bilddatei (JPG, PNG, GIF)!</h2>";
String readAndShowImage( HttpServletRequest request )
throws FileNotFoundException, IOException
{
String sRet = "";
// Check for valid parameter data:
if( !request.getMethod().equals( "POST" ) )
return "";
MultipartRequest parser
= new ServletMultipartRequest( request, 1*1024*1024 ); // < 1 MB
if( null == parser ||
null == parser.getFileContents( "myFile" ) )
return "";
// Check for valid image file:
ImageInfo ii = new ImageInfo();
if( null == ii )
return "";
ii.setInput( parser.getFileContents( "myFile" ) );
if( !ii.check() )
return sErrMsg;
// Note: Parameters are in the parser and not in request:
String myComment = parser.getURLParameter( "myComment" );
String sFileName = parser.getFileSystemName( "myFile" );
String sImgFormat = ii.getFormatName().toLowerCase();
// Show image data:
if( null == sImgFormat )
sImgFormat = "Unbekanntes Format";
if( sImgFormat.equals( "jpeg" ) )
sImgFormat = "jpg";
sRet = "<h2>" + sFileName + ":</h2>"
+ sImgFormat.toUpperCase() + ", "
+ ii.getWidth() + " x " + ii.getHeight() + " pixels, "
+ ii.getBitsPerPixel() + " bpp, "
+ parser.getFileSize( "myFile" ) + " Bytes<br>\n";
// Check if image format is suitable for inserting into HTML page:
if( !sImgFormat.equals( "jpg" ) &&
!sImgFormat.equals( "png" ) &&
!sImgFormat.equals( "gif" ) )
return sRet + sErrMsg;
// Generate valid file name. Different operating systems or
// browsers may return the file name with or without path
// and the path may contain '/' (Unix) or '\' (Windows):
if( null == sFileName || 0 >= sFileName.length() )
sFileName = "MyFile";
char c = sFileName.charAt( sFileName.length() - 1 );
if( '/' == c || '\\' == c )
sFileName = sFileName.substring( 0, sFileName.length() - 1 );
int i;
if( 0 <= (i = sFileName.lastIndexOf( '/' )) )
sFileName = sFileName.substring( i + 1 );
if( 0 <= (i = sFileName.lastIndexOf( '\\' )) )
sFileName = sFileName.substring( i + 1 );
if( !sFileName.toLowerCase().endsWith( "." + sImgFormat ) )
sFileName += "." + sImgFormat;
// Different file pathes for HTML page and for storing:
String sFilePathAndNameHtml = sUploadDir + sFileName;
String sFilePathAndNameStore
= getServletContext().getRealPath( sFilePathAndNameHtml );
// Store file:
BufferedInputStream is = null;
BufferedOutputStream os = null;
long sum=0;
try {
is = new BufferedInputStream( parser.getFileContents( "myFile" ) );
os = new BufferedOutputStream(
new FileOutputStream( sFilePathAndNameStore ) );
byte[] buff = new byte[8192];
int len;
while( 0 < (len = is.read( buff )) ) {
os.write( buff, 0, len );
sum += len;
}
} finally {
if( is != null )
is.close();
if( os != null ) {
os.flush();
os.close();
}
}
sRet += "Gespeichert: " + sum + " Bytes<br>\n";
if( null != myComment && 0 < myComment.length() )
sRet += "Kommentar: " + myComment + "<br>\n";
sRet += "<br><img src='" + sFilePathAndNameHtml + "'"
+ " alt='" + sFileName + "'"
+ " height=" + ii.getHeight()
+ " width=" + ii.getWidth() + "><br>\n"
+ "<br>\n sFilePathAndNameHtml = " + sFilePathAndNameHtml
+ "<br>\n sFilePathAndNameStore = " + sFilePathAndNameStore
+ "<br>\n getRealPath(request.getRequestURI()) = "
+ getServletConfig().getServletContext().
getRealPath(request.getRequestURI());
return sRet;
}
%>
<html>
<head>
<title>Bilddatei-Upload</title>
</head>
<body>
<h2>Upload einer Bilddatei vom Client zum Server</h2>
<form action="index.jsp" enctype="multipart/form-data" method="POST">
<table>
<tr>
<td>Kommentar (optional):</td>
<td><input type="text" name="myComment" size=40 maxlength=255></td>
</tr>
<tr>
<td>Bilddatei (JPG, PNG, GIF):</td>
<td><input type="file" name="myFile" size=40 maxlength=255>
<input type="submit" value="Upload"></td>
</tr>
</table>
</form>
<br>
<%= readAndShowImage( request ) %>
</body>
</html>
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DIENSTE
