I want to know how can I use java to confirm a file is a picture file.
I have tried the following code:
public static void main(String[] args) {
// get image format in a file
File file = new File("C:/Users/dell、/Desktop/4.xlsx");
// create an image input stream from the specified fileDD
ImageInputStream iis = null;
try {
iis = ImageIO.createImageInputStream(file);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// get all currently registered readers that recognize the image format
Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);
if (!iter.hasNext()) {
System.out.println("Not a picture file");
throw new RuntimeException("No readers found! Unable to read the uploaded file");
}
// get the first reader
ImageReader reader = iter.next();
try {
System.out.println("Format: " + reader.getFormatName());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// close stream
if (iis != null){
try {
iis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
try {
iis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
But it doesn't work perfectly! It shows an exception once the file is not a picture file, so I want to find a better way.
There are too many image extensions. Maybe the best way to validate if a file is an image, is using Regular Expressions. Something like this...
([^\s]+(\.(?i)(jpg|png|gif|bmp|MORE|IMAGE|EXTENSIONS))$)
Here is a complete example of the implementation.
Use ImageIO#read.
public static boolean isPictureFile(File file){
try{
return ImageIO.read(file) != null;
}catch(Exception ex){
return false;
}
}
Basically, the method ImageIO.read(File) will return a BufferedImage object when it successfully read the image file, a null otherwise. All we have to do is to let ImageIO read the file and check if it returns a null or not, and if there it throws an exception for whatever reason, we can safely assume the file is not a picture file.
Related
I'm trying to modify a doc with Apache POI in Java.
At first the test.doc cannot be read with a exception raised up :
"org.apache.poi.poifs.filesystem.NotOLE2FileException: Invalid header signature; read 0x6576206C6D783F3C, expected 0xE11AB1A1E011CFD0 - Your file appears not to be a valid OLE2 document
"
So I saved the doc as "word 97 - 03" format,and then POI can read the doc properly.
But when I try to rewrite the content to a new file with nothing changed, the file output.doc cannot be opened by MS Office.
When I make a new doc myself with MS Office, the POI works well, everything goes right.
So the problem is "test.doc".
The test.doc is generated by some sort of a program which I can't access the code,so I don't know what goes wrong.
My question is :
1.As test.doc can be read by MS Office why can't POI without saving as a new format doc?
2.As the POI can read the doc, why it cannot write back to a new file(MS Office can't open)?
Here is my code:
FileInputStream fis = null;
try {
fis = new FileInputStream("test.doc");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
POIFSFileSystem pfs = null;
try {
pfs = new POIFSFileSystem(fis);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
HWPFDocument hwdf = null;
try {
hwdf = new HWPFDocument(pfs);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
FileOutputStream fos = null;
try {
fos = new FileOutputStream(new File("output.doc"));
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
hwdf.write(fos);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
}
try {
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
fis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
pfs.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
The HEX stuff read as ASCII and read little-endian converts to <?xml ve, which indicates that test.doc is some other format than actually .doc/.docx.
Word will open other data-formats gracefully sometimes, upon saving it will be saved correctly in the Word-Format.
Therefore you will need to use a hex-editor to take a look at the contents of test.doc and if it is really in some broken format you need to find out where it is coming from and how the creation of that file can be fixed.
i would like to handle a a properties file in my android app. The Properties-File is in the main-Folder, in the folder with the other jar-files. I know, that´s not best.
Code:
InputStream propStream=MainActivity.class.getResourceAsStream("data.properties");
Log.d("propStreamOutput",propStream.toString());
File data = new File(propStream.toString());
Reader reader;
try {
reader = new FileReader(data);
dataProp = new Properties();
dataProp.load( reader );
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
so, the log at line 2 says:
libcore.net.url.JarURLConnectionImpl$JarURLConnectionInputStream#421302e8
in this form logcat calls a System.err :
java.io.FileNotFoundException/libcore.net.url.JarURLConnectionImpl$JarURLConnectionInputStream#42097218: open failed: ENOENT (No such file or directory)
but when I comment like this:
InputStream propStream=MainActivity.class.getResourceAsStream("data.properties");
Log.d("propStreamOutput",propStream.toString());
File data = new File(propStream.toString());
// Reader reader;
// try {
// reader = new FileReader(data);
// dataProp = new Properties();
// dataProp.load( reader );
// } catch (FileNotFoundException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
//
// catch (IOException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
then there is no system.err ! Of course the log call at line 2 says the same.
If you really wanna use the getResourceAsStream() then you have to put the file on the "src" folder, together with your .java files.
This is usually the way for standard Java applications, but on Android the most usual way to perform such things is to put the file in the 'assets' folder, via AssetsManager, which is accessible from your Activity or any Context. like shown below:
InputStream is = null;
try {
is = context.getAssets().open("data.properties");
} catch (final IOException e) {
e.printStackTrace();
} finally {
closeStreamGracefully(is);
}
getRessourceAsStream return an InputStream. When you call toString on this it will return a string representation of the object. Then when you create your data file and try to read it will try to open a file like #sdqzeffdfsf. If you whant to read the properties from this file use Properties
Properties properties = new Properties();
properties.load(propStream);
This is for standard java. However in android you usualy use AssetManager
This question already has answers here:
Loading html file to webview on android from assets folder using Android Studio
(3 answers)
Closed 5 years ago.
try {
File f = new File( "file:///android_asset/[2011]011TAXMANN.COM00167(PATNA)") ;
FileInputStream fis= new FileInputStream(f);
System.out.println("_______YOUR HTML CONTENT CODE IS BELLOW WILL BE PRINTED IN 2 SECOND _______");
Thread.sleep(2000);
int ch;
while((ch=fis.read())!=-1)
{
fileContent=fileContent+(char)ch; // here i stored the content of .Html file in fileContent variable
}
System.out.print(fileContent);
//}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
This is my code. I want to read html content from asstes folder my file is available in asstes folder But it gives exception FileNotFoundException. So plz any one tell me how to read html content from asstes folder in android?
File f = new File( "file:///android_asset/[2011]011TAXMANN.COM00167(PATNA)") ;
when i debug f gives= file:/android_asset/[2011]011TAXMANN.COM00167(PATNA)
plz tell me how to get corrct directory and where i m doing wrong it shud me coming file:///android_asset/[2011]011TAXMANN.COM00167(PATNA)
This is the way to load HTML file from assets in WebView
webview.loadUrl("file:///android_asset/Untitled-1.html");
Untitled-1.html---File name that should be save first as .html extension
Edited
try this link
http://developer.android.com/reference/android/content/res/AssetManager.html
there is method from this doc
public final String[] list (String path)
You cat get InputStream by this code:
getResources().getAssets().open("you_file_name_goes_here");
you don't want to use
webview.loadUrl('file:///android_asset/htmlFile.html');
right?
try this i found it in a blog:
static String getHTMLDataBuffer(String url,Context context) {
InputStream htmlStream;
try {
if (Utils.isReferExternalMemory() && url.contains("sdcard")) {
String tempPath = url.substring(7, url.length());//remove file:// from the url
File file = new File(tempPath);
htmlStream = new FileInputStream(file);
}else{
String tempPath = url.replace("file:///android_asset/", "");
htmlStream = context.getAssets().open(tempPath);
}
Reader is = null;
try {
is = new BufferedReader(new InputStreamReader(htmlStream, "UTF8"));
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// read string from reader
final char[] buffer = new char[1024];
StringBuilder out = new StringBuilder();
int read;
do {
read = is.read(buffer, 0, buffer.length);
if (read>0) {
out.append(buffer, 0, read);
}
} while (read>=0);
return out.toString();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
usage:
String data = getHTMLDataBuffer("file:///android_asset/yourHtmlFile",this);
webview.loadDataWithBaseURL("http://example.com", data, "text/html", "utf-8", null);
Sorry for my bad english :)
I am getting the occassional error message when I try to read a serialized object from a file. It works fine 9 times out of 10, but for some reason I get lots of these error message sin the catlog:
06-01 23:57:50.824: ERROR/MemoryFile(16077): MemoryFile.finalize() called while ashmem
still open
and
06-01 23:57:57.664: ERROR/MemoryFile(16077): java.io.IOException: munmap failed
The second message comes with no indication where the exception is caused. (Clearly when I'm loading the file, but I already have a try/catch around it.)
My loadfile method looks like this:
public TGame loadSavedGame(){
TGame g=null;
InputStream instream = null;
BufferedReader br=null;
InputStreamReader inputreader=null;
try {
File sdCard = Environment.getExternalStorageDirectory();
instream = new
FileInputStream(sdCard.getAbsolutePath()+"/egyptica/serializationtest");
// inputreader = new InputStreamReader(instream);
// br= new BufferedReader(inputreader);
} catch (FileNotFoundException e) {
e.printStackTrace();
return null;
}
try {
ObjectInputStream ois = new ObjectInputStream(instream);
try {
g= (TGame) ois.readObject();
try {
instream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return g;
} catch (ClassNotFoundException ex) {
// TODO Auto-generated catch block
android.util.Log.e("DESERIALIZATION FAILED (CLASS NOT
FOUND):"+ex.getMessage(), "ex");
ex.printStackTrace();
return null;
}
} catch (StreamCorruptedException ex) {
android.util.Log.e("DESERIALIZATION FAILED (CORRUPT):"+ex.getMessage(),
"ex");
// TODO Auto-generated catch block
ex.printStackTrace();
return null;
} catch (IOException ex) {
android.util.Log.e("DESERIALIZATION FAILED (IO
EXCEPTION):"+ex.getMessage(), "ex");
// TODO Auto-generated catch block
ex.printStackTrace();
return null;
}
}
One possibility I have thought of is using a BufferedReader to rea the file. However I'm not sure how to go about doing this. Any help would be appreciated.
Try to put finally block after try and put there closing statements for your streams and also useful thing is to use:
FileInputStream.getFD().sync();
It makes sure that file really received your close/flush
I asked a question earlier about extracting RAR archives in Java and someone pointed me to JUnrar. The official site is down but it seems to be quite widely used as I found a lot of discussions about it online.
Could someone show me how to use JUnrar to extract all the files in an archive? I found a little snippet online but it doesn't seem to work. It shows each item in the archive to be a directory even if it is a file.
Archive rar = new Archive(new File("C://Weather_Icons.rar"));
FileHeader fh = rar.nextFileHeader();
while(fh != null){
if (fh.isDirectory()) {
logger.severe("directory: " + fh.getFileNameString() );
}
//File out = new File(fh.getFileNameString());
//FileOutputStream os = new FileOutputStream(out);
//rar.extractFile(fh, os);
//os.close();
fh=rar.nextFileHeader();
}
Thanks.
May be you should also check this snippet code. A copy of which can be found below.
public class MVTest {
/**
* #param args
*/
public static void main(String[] args) {
String filename = "/home/rogiel/fs/home/movies/vp.mp3.part1.rar";
File f = new File(filename);
Archive a = null;
try {
a = new Archive(new FileVolumeManager(f));
} catch (RarException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (a != null) {
a.getMainHeader().print();
FileHeader fh = a.nextFileHeader();
while (fh != null) {
try {
File out = new File("/home/rogiel/fs/test/"
+ fh.getFileNameString().trim());
System.out.println(out.getAbsolutePath());
FileOutputStream os = new FileOutputStream(out);
a.extractFile(fh, os);
os.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (RarException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
fh = a.nextFileHeader();
}
}
}
}