My program has a function that read/write file from resource. This function I have tested smoothly.
For example, I write something to file, restart and loading again, I can read that data again.
But after I export to jar file, I faced problems when write file. Here is my code to write file:
URL resourceUrl = getClass().getResource("/resource/data.sav");
File file = new File(resourceUrl.toURI());
FileOutputStream output = new FileOutputStream(file);
ObjectOutputStream writer = new ObjectOutputStream( output);
When this code run, I has notice error in Command Prompt:
So, My data cannot saved. (I know it because after I restarted app, nothing changed !!!)
Please help me solve this problem.
Thanks :)
You simply can't write files into a jar file this way. The URI you get from getResource() isn't a file:/// URI, and it can't be passed to java.io.File's constructor. The only way to write a zip file is by using the classes in java.util.zip that are designed for this purpose, and those classes are designed to let you write entire jar files, not stream data to a single file inside of one. In a real installation, the user may not even have permission to write to the jar file, anyway.
You're going to need to save your data into a real file on the file system, or possibly, if it's small enough, by using the preferences API.
You need to read/write file as an input stream to read from jar file.
public static String getValue(String key)
{
String _value = null;
try
{
InputStream loadedFile = ConfigReader.class.getClassLoader().getResourceAsStream(configFileName);
if(loadedFile == null) throw new Exception("Error: Could not load the file as a stream!");
props.load(loadedFile);
}
catch(Exception ex){
try {
System.out.println(ex.getMessage());
props.load(new FileInputStream(configFileName));
} catch (FileNotFoundException e) {
ExceptionWriter.LogException(e);
} catch (IOException e) {
ExceptionWriter.LogException(e);
}
}
_value = props.getProperty(key);
if(_value == null || _value.equals("")) System.out.println("Null value supplied for key: "+key);
return _value;
}
Related
I am trying to create a temporary file and then rename it to a usable file. The temp file is getting created in %temp% but not getting renamed:-
static void writeFile() {
try {
File tempFile = File.createTempFile("TEMP_FAILED_MASTER", "");
PrintWriter pw = new PrintWriter(tempFile);
for (String record : new String[] {"a","b"}) {
pw.println(record);
}
pw.flush();
pw.close();
System.out.println(tempFile.getAbsolutePath());
File errFile = new File("C:/bar.txt");
tempFile.renameTo(errFile);
System.out.println(errFile.getAbsolutePath());
System.out.println("Check!");
} catch (Exception e) {
e.printStackTrace();
}
}
There are a few reasons why a rename can fail. The common ones are:
You don't have write permission for the source or destination directory.
The file you are renaming is open (on Windows)
You are attempting to rename across different file systems.
It can be difficult to diagnose these (and other) failure reasons if you are using File.renameTo because all you get is a boolean return value.
I recommend using Files.move instead. It can cope with moving files between file systems, and will throw an exception if the file cannot be renamed.
I am attempting to display PDFs to the user in their browser using a web service. Once they pass in the URL containing the variables needed. My program first downloads the PDF to local storage then proceeds to copy it to the stream and displays it. Once the viewer is able to view the PDF we wish to delete the file locally so that we do not wind up storing every file searched for. I have managed to accomplish most of this task however I am having issues deleting the file once it is displayed to the user.
Even when I attempt to manually delete the file I receive the "Currently in use in the Java SE Binary" message
Code below:
File testFile = new File("C:\\Users\\stebela\\workspace\\my-app\\invoice"+invNum+".pdf");
try
{
ServletOutputStream os = res.raw().getOutputStream();
FileInputStream inputStr = new FileInputStream(testFile);
IOUtils.copy(inputStr, os);
os.close();
inputStr.close();
//finished settings
res.status(200);
testFile.delete();
} catch (IOException e)
{
System.out.println(e.getMessage());
}
If you don't write to the file, you'r code should work.
If you call inputStr.close(); the file is no longer used by java and it can be deleted.
Pleace check, if your file is not used by any other programm. It's the best if you reboot your PC.
If it still not works, it would be interessting to know, what res is and if your file get's sendet.
I've read this part of the documentation and i think this should solve your problem.
It reads the file into a String and change the header for png images. As the http Body it uses the String of the file.
Make sure, if you change the response type, you have to change the line res.type("image/png"); to the new one.
Here you find the most common ones
File testFile = null;
try {
testFile = new File("C:\\Users\\stebela\\workspace\\my-app\\invoice"+invNum+".png");
FileInputStream fin = new FileInputStream(testFile);
int charAsInt = 0;
String httpBody = "";
while((charAsInt = fin.read()) != -1){
httpBody +=(char)charAsInt;
}
fin.close();
res.body(httpBody);
res.type("image/png");
res.status(200);
testFile.delete();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Currently I'm developing a java application to carry out a survey. I want to read/write to a .txt file, creating a .csv to store inputted data. Below is code I have used so far to write data - Of course this makes the JAR file not portable as it has an absolute path.
File file = new File("C:/Files/JavaApp/src/text.text/");
FileWriter fw = null;
BufferedWriter bw = null;
try {
fw = new FileWriter(file, true);
} catch (IOException e) {
System.out.println(e.getMessage());
}
bw = new BufferedWriter(fw);
try {
bw.write("blah" + ",");
} catch (IOException e) {
System.out.println(e.getMessage());
}
try {
bw.newLine();
} catch (IOException e) {
System.out.println(e.getMessage());
}
try {
bw.close();
} catch (IOException e) {
System.out.println(e.getMessage());
}
I have tried several methods such as ClassName.class.getResource("Text.text"); but it will always return a Reflection or a NullPointer error.
I know that writing to a file within the JAR does pose some problems, meaning I would have to point to a file outside to read/write. However I don't know how to preform this in code. I need the JAR file to be completely portable. Even if that means it must be kept within a directory, so the JAR can search for the .txt file within that directory. Or, is there another way?
If anyone can help me out, I would be very grateful.
To read from the Jar file: How to read a file from jar in Java?
The file is an archive file. It is a zip file with a .jar extension. You shouldn't be writing to it. If the jar file has been signed (security projected) you cannot write to it. Changing a single bit in the file will invalidate it.
What you should do is store a default file in Jar and load that to the "user.home" folder if it is not already there.
I am trying to write some message to text file. The text file is in the server path. I am able to read content from that file. But i am unable to write content to that file. I am getting FileNotFoundException: \wastServer\apps\LogPath\message.txt (Access Denied).
Note: File has a read and write permissions.
But where i am doing wrong. Please find my code below.
Code:
String FilePath = "\\\\wastServer\\apps\\LogPath\\message.txt";
try {
File fo = new File(FilePath);
FileWriter fw=new FileWriter(fo);
BufferedWriter bw=new BufferedWriter(fw);
bw.write("Hello World");
bw.flush();
bw.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
Please help me on this?
Please check whether you can access the apps and LogPath directory.
Type these on Run (Windows Key + R)
\\\\wastServer\\apps\\
\\\\wastServer\\apps\\LogPath\\
And see whether you can access those directories from the machine and user you are executing the above code.
You don't have write access to the share, one of the directories, or the file itself. Possibly the file is already open.
After this line
File fo = new File(FilePath);
try to print the absolute path
System.out.println( fo.getAbsolutePath() );
And then check whether the file exists in that location, instead of directly checking at
\\\\wastServer\\apps\\LogPath\\message.txt
So , you will know, where the compiler is searching for the file.
in my android app I'm using an own java library that extracts a .db-file from jar. In Java desktop it works well, but when I try to do it on android, the inputstream blocks forever. The copy method looks like this:
InputStream in = classloader.getResourceAsStream(...);
OutputStream out = new FileOutputStream(new File(...));
try {
while ((read = in.read()) != -1) {
out.write(read);
}
} finally {
try {
in.close();
} catch (final Exception e) {
LOGGER.debug("Error", e);
}
try {
out.close();
} catch (final Exception e) {
LOGGER.debug("Error", e);
}
}
I want to copy this file to the external files dir and android.permission.WRITE_EXTERNAL_STORAGE is granted.
Is there a way to access the file in /data/app/...apk? If not, how can I detect that it can not be accessed without blocking forever?
You should put the database-file in the /assets-folder and copy it to the /databases-folder on first run. A tutorial on this can be found here.
However, if you only want to create the tables and some sample-entry's, you might want to use the onCreate()-method from the SQLiteOpenHelper to do so.
Maybe you should store your data in the raw folder, you access it then :)
http://developer.android.com/guide/topics/resources/index.html
Answering to the question : we can only extract the class files from the apk that we have got, we will not get the layout/xml files or any other files.
There are ways by which we can extract the class files from the apk.