Develop Reference

JAVA: FileInputStream and FileOutputStream

I have this strange thing with input and output streams, whitch I just can't understand.
I use inputstream to read properties file from resources like this:
Properties prop = new Properties();
InputStream in = getClass().getResourceAsStream( "/resources/SQL.properties" );
rop.load(in);
return prop;
It finds my file and reds it succesfully. I try to write modificated settings like this:
prop.store(new FileOutputStream( "/resources/SQL.properties" ), null);
And I getting strange error from storing:
java.io.FileNotFoundException: \resources\SQL.properties (The system cannot find the path specified)
So why path to properties are changed? How to fix this?
I am using Netbeans on Windows

The problem is that getResourceAsStream() is resolving the path you give it relative to the classpath, while new FileOutputStream() creates the file directly in the filesystem. They have different starting points for the path.
In general you cannot write back to the source location from which a resource was loaded, as it may not exist in the filesystem at all. It may be in a jar file, for instance, and the JVM will not update the jar file.

May be it works
try
{
java.net.URL url = this.getClass().getResource("/resources/SQL.properties");
java.io.FileInputStream pin = new java.io.FileInputStream(url.getFile());
java.util.Properties props = new java.util.Properties();
props.load(pin);
}
catch(Exception ex)
{
ex.printStackTrace();
}
and check the below url
getResourceAsStream() vs FileInputStream

Please see this question: How can I save a file to the class path
And this answer https://stackoverflow.com/a/4714719/239168
In summary: you can't always trivially save back a file your read from the classpath (e.g. a file in a
jar)
However if it was indeed just a file on the classpath, the above answer has a nice approach

Unable to open properties file in servlet via a helper class

I have a class,in which ther is a func,which opens a properties file. When i write main in the same class & call that function,i am able to open the properties file n read. but, when i am tying to call the same func in my servlet by creating instance to that class, i get file not found exception.
This is the function, which i have written in my class to read properties file. And both my class and servlet are in src folder. I am using eclipse IDE.
Code:
private void readPropertiesFileAndFieldListData() {
String PROP_FILE = "./src/fields.properties";
try {
FileReader reader = new FileReader(PROP_FILE);
BufferedReader br = new BufferedReader(reader);
ArrayList<String> field = new ArrayList<String>();
while ((str = br.readLine()) != null) {
if (!str.startsWith("#") && str.trim().length() > 0) {
// System.out.println(str);
field.add(str);
count++;
}
}
}

You're relying on the current working directory of the disk file system path. The current working directory is dependent on how the application is started and is not controllable from inside your application. Relying on it is a very bad idea.
The normal practice is to put that file in the classpath or to add its path to the classpath. Your file is apparently already in the classpath (you placed it in the src folder), so you don't need to change anything else. You should should just get it from the classpath by the class loader. That's more portable than a disk file system path can ever be.
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("fields.properties");
// ...
See also:
getResourceAsStream() vs FileInputStream
Unrelated to the concrete problem, you're basically reinventing the java.util.Properties class. Don't do that. Use the following construct:
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("fields.properties");
Properties properties = new Properties();
properties.load(input);
// ...

PLease write a small test, for printing the file path of "PROP_FILE" to the log or console.
it seems, that you relativ path is incorrect.
Your relative path starting point can change, depending on where your *.exe file is started.
Your test should print
File tFile = new File(PROP_FILE);
// print tFile.getAbsolutePath()
Its better to get a special class by calling
SomeClass.class.getResource(name)
Eclipse RCP from the Bundle
Bundle.getResource(ResourcePathString)
EDIT:
Please check, whether the resource is part of your *.jar. It could be, that you missed to add it to the build.properties file.
Check whether the file is existing, before you read the properties file.

Unable to read Java File from JSF

The directory structure of my application is as follows:-
My App
++++++ src
++++++++com
++++++++++readProp.java
++++++++resource
++++++++++message.properties
I am trying to read the file as follows:-
public Static final string FilePath="resource.message.properties"
Here the code to read the file. I tried using the following two techniques but to no use...
File accountPropertiesFile = new File(FacesContext.getCurrentInstance()
.getExternalContext().getRequestContextPath()
+ FilePath);
properties.load(externalContext.getResourceAsStream(FilePath));
But none yeild any sucess while reading through the Bean class. please help...

Your properties file is in the classpath. The java.io.File only understands the local disk file system structure. This is not going to work. You need to get it straight from the classpath by the classloader.
Here's a kickoff example:
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("/resources/messages.properties");
if (input != null) {
Properties properties = new Properties();
try {
properties.load(input);
} finally {
input.close();
}
}

I don't know if this is your problem, but you should try using slashes instead of periods, since they're stored as actual folders in the filesystem.

How to read file from relative path in Java project? java.io.File cannot find the path specified

I have a project with 2 packages:
tkorg.idrs.core.searchengines
tkorg.idrs.core.searchengines
In package (2) I have a text file ListStopWords.txt, in package (1) I have a class FileLoadder. Here is code in FileLoader:
File file = new File("properties\\files\\ListStopWords.txt");
But I have this error:
The system cannot find the path specified
Can you give a solution to fix it?

If it's already in the classpath, then just obtain it from the classpath instead of from the disk file system. Don't fiddle with relative paths in java.io.File. They are dependent on the current working directory over which you have totally no control from inside the Java code.
Assuming that ListStopWords.txt is in the same package as your FileLoader class, then do:
URL url = getClass().getResource("ListStopWords.txt");
File file = new File(url.getPath());
Or if all you're ultimately after is actually an InputStream of it:
InputStream input = getClass().getResourceAsStream("ListStopWords.txt");
This is certainly preferred over creating a new File() because the url may not necessarily represent a disk file system path, but it could also represent virtual file system path (which may happen when the JAR is expanded into memory instead of into a temp folder on disk file system) or even a network path which are both not per definition digestable by File constructor.
If the file is -as the package name hints- is actually a fullworthy properties file (containing key=value lines) with just the "wrong" extension, then you could feed the InputStream immediately to the load() method.
Properties properties = new Properties();
properties.load(getClass().getResourceAsStream("ListStopWords.txt"));
Note: when you're trying to access it from inside static context, then use FileLoader.class (or whatever YourClass.class) instead of getClass() in above examples.

The relative path works in Java using the . specifier.
. means same folder as the currently running context.
.. means the parent folder of the currently running context.
So the question is how do you know the path where the Java is currently looking?
Do a small experiment
File directory = new File("./");
System.out.println(directory.getAbsolutePath());
Observe the output, you will come to know the current directory where Java is looking. From there, simply use the ./ specifier to locate your file.
For example if the output is
G:\JAVA8Ws\MyProject\content.
and your file is present in the folder "MyProject" simply use
File resourceFile = new File("../myFile.txt");
Hope this helps.

The following line can be used if we want to specify the relative path of the file.
File file = new File("./properties/files/ListStopWords.txt");

InputStream in = FileLoader.class.getResourceAsStream("<relative path from this class to the file to be read>");
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line = null;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (Exception e) {
e.printStackTrace();
}

try .\properties\files\ListStopWords.txt

I could have commented but I have less rep for that.
Samrat's answer did the job for me. It's better to see the current directory path through the following code.
File directory = new File("./");
System.out.println(directory.getAbsolutePath());
I simply used it to rectify an issue I was facing in my project. Be sure to use ./ to back to the parent directory of the current directory.
./test/conf/appProperties/keystore

While the answer provided by BalusC works for this case, it will break when the file path contains spaces because in a URL, these are being converted to %20 which is not a valid file name. If you construct the File object using a URI rather than a String, whitespaces will be handled correctly:
URL url = getClass().getResource("ListStopWords.txt");
File file = new File(url.toURI());

Assuming you want to read from resources directory in FileSystem class.
String file = "dummy.txt";
var path = Paths.get("src/com/company/fs/resources/", file);
System.out.println(path);
System.out.println(Files.readString(path));
Note: Leading . is not needed.

I wanted to parse 'command.json' inside src/main//js/Simulator.java. For that I copied json file in src folder and gave the absolute path like this :
Object obj = parser.parse(new FileReader("./src/command.json"));

For me actually the problem is the File object's class path is from <project folder path> or ./src, so use File file = new File("./src/xxx.txt"); solved my problem

For me it worked with -
String token = "";
File fileName = new File("filename.txt").getAbsoluteFile();
Scanner inFile = null;
try {
inFile = new Scanner(fileName);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
while( inFile.hasNext() )
{
String temp = inFile.next( );
token = token + temp;
}
inFile.close();
System.out.println("file contents" +token);

If text file is not being read, try using a more closer absolute path (if you wish
you could use complete absolute path,) like this:
FileInputStream fin=new FileInputStream("\\Dash\\src\\RS\\Test.txt");
assume that the absolute path is:
C:\\Folder1\\Folder2\\Dash\\src\\RS\\Test.txt

String basePath = new File("myFile.txt").getAbsolutePath();
this basepath you can use as the correct path of your file

if you want to load property file from resources folder which is available inside src folder, use this
String resourceFile = "resources/db.properties";
InputStream resourceStream = ClassLoader.getSystemClassLoader().getResourceAsStream(resourceFile);
Properties p=new Properties();
p.load(resourceStream);
System.out.println(p.getProperty("db"));
db.properties files contains key and value db=sybase

If you are trying to call getClass() from Static method or static block, the you can do the following way.
You can call getClass() on the Properties object you are loading into.
public static Properties pathProperties = null;
static {
pathProperties = new Properties();
String pathPropertiesFile = "/file.xml";
// Now go for getClass() method
InputStream paths = pathProperties.getClass().getResourceAsStream(pathPropertiesFile);
}

How I can specify directories in war file?

I am new to servlet . I use the following code in servlet.then deployed to Jboss 4.1 . backup_database_configuration_location is location of properties file.But it can't be find. how I can specify directories in war file ?
Thanks all in advance
try {
backupDatabaseConfiguration = new Properties();
FileInputStream backupDatabaseConfigurationfile = new FileInputStream(backup_database_configuration_location));
backupDatabaseConfiguration.load(backupDatabaseConfigurationfile);
backupDatabaseConfigurationfile.close();
} catch (Exception e) {
log.error("Exception while loading backup databse configuration ", e);
throw new ServletException(e);
}

If it is placed in the webcontent, then use ServletContext#getResourceAsStream():
InputStream input = getServletContext().getResourceAsStream("/WEB-INF/file.properties"));
The getServletContext() method is inherited from HttpServlet. Just call it as-is inside servlet.
If it is placed in the classpath, then use ClassLoader#getResourceAsStream():
InputStream input = Thread.currentThread().getContextClassLoader().getResourceAsStream("file.properties");
The difference with Class#getResourceAsStream() is that you're not dependent on the classloader which loaded the class (which might be a different one than the thread is using, if the class is actually for example an utility class packaged in a JAR and the particular classloader might not have access to certain classpath paths).

Where is your properties file located? Is it directly somewhere in your hard drive, or packaged in a JAR file?
You can try to retrieve the file using the getResourceAsStream() method:
configuration = new Properties();
configuration.load(MyClass.class.getResourceAsStream(backup_database_configuration_location));
(or course, replace MyClass by your current class name)