Develop Reference

Find place for dedicated application folder

I'm sorry if this title is badly named, I can't think of a better way to phrase it and so edits would be welcomed.
Most applications I've seen that require hard drive file storage create a folder in a suitable place depending on the operating system. On Windows these folders lie in \Users\[current user]\AppData\[etc], on Mac these folders lie in /Users/[current user]/Library/Application Support/[etc], Ubuntu has a similar thing that I can't think of right now.
I would like to know, how are these file paths consistently found in differing operating systems with different users, and is there, at least in java, a simple way to achieve this?
Thank you.

There should be, but there isn't. I even submitted a bug/RFE about it, but as far as I know, it was never accepted. Here's what I use:
public class ApplicationDirectories {
private static final Logger logger =
Logger.getLogger(ApplicationDirectories.class.getName());
private static final Path config;
private static final Path data;
private static final Path cache;
static {
String os = System.getProperty("os.name");
String home = System.getProperty("user.home");
if (os.contains("Mac")) {
config = Paths.get(home, "Library", "Application Support");
data = config;
cache = config;
} else if (os.contains("Windows")) {
String version = System.getProperty("os.version");
if (version.startsWith("5.")) {
config = getFromEnv("APPDATA", false,
Paths.get(home, "Application Data"));
data = config;
cache = Paths.get(home, "Local Settings", "Application Data");
} else {
config = getFromEnv("APPDATA", false,
Paths.get(home, "AppData", "Roaming"));
data = config;
cache = getFromEnv("LOCALAPPDATA", false,
Paths.get(home, "AppData", "Local"));
}
} else {
config = getFromEnv("XDG_CONFIG_HOME", true,
Paths.get(home, ".config"));
data = getFromEnv("XDG_DATA_HOME", true,
Paths.get(home, ".local", "share"));
cache = getFromEnv("XDG_CACHE_HOME", true,
Paths.get(home, ".cache"));
}
}
/** Prevents instantiation. */
private ApplicationDirectories() {
}
/**
* Retrieves a path from an environment variable, substituting a default
* if the value is absent or invalid.
*
* #param envVar name of environment variable to read
* #param mustBeAbsolute whether enviroment variable's value should be
* considered invalid if it's not an absolute path
* #param defaultPath default to use if environment variable is absent
* or invalid
*
* #return environment variable's value as a {#code Path},
* or {#code defaultPath}
*/
private static Path getFromEnv(String envVar,
boolean mustBeAbsolute,
Path defaultPath) {
Path dir;
String envDir = System.getenv(envVar);
if (envDir == null || envDir.isEmpty()) {
dir = defaultPath;
logger.log(Level.CONFIG,
envVar + " not defined in environment"
+ ", falling back on \"{0}\"", dir);
} else {
dir = Paths.get(envDir);
if (mustBeAbsolute && !dir.isAbsolute()) {
dir = defaultPath;
logger.log(Level.CONFIG,
envVar + " is not an absolute path"
+ ", falling back on \"{0}\"", dir);
}
}
return dir;
}
/**
* Returns directory where the native system expects an application
* to store configuration files for the current user. No attempt is made
* to create the directory, and no checks are done to see if it exists.
*
* #param appName name of application
*/
public static Path configDir(String appName)
{
return config.resolve(appName);
}
/**
* Returns directory where the native system expects an application
* to store implicit data files for the current user. No attempt is made
* to create the directory, and no checks are done to see if it exists.
*
* #param appName name of application
*/
public static Path dataDir(String appName)
{
return data.resolve(appName);
}
/**
* Returns directory where the native system expects an application
* to store cached data for the current user. No attempt is made
* to create the directory, and no checks are done to see if it exists.
*
* #param appName name of application
*/
public static Path cacheDir(String appName)
{
return cache.resolve(appName);
}
}
Some notes:
I'm not sure the code for older Windows versions is even necessary, as Java 8 doesn't run on Windows XP.
The XDG Directory Specification says “All paths set in these environment variables must be absolute. If an implementation encounters a relative path in any of these variables it should consider the path invalid and ignore it.”

The directory can be found with the method
static String defaultDirectory() {
String os = System.getProperty("os.name").toLowerCase();
if (OS.contains("win"))
return System.getenv("APPDATA");
else if (OS.contains("mac"))
return System.getProperty("user.home") + "/Library/Application Support";
else if (OS.contains("nux"))
return System.getProperty("user.home");
else
return System.getProperty("user.dir");
}
It is worth noting that on Linux any such folders should be hidden by beginning their name with .
(Answer found from users CodeBunny and Denis Tulskiy on this post)

Android: Reading a file using InputStream character by character

Solved: The code I originally posted is fine, I just tried reading a txt file from a directory in assets without adding the directory's name in the "path" string under the false assumption "getAssets()" gets all assets from all subdirectories in assets.
I am making a game that uses cards with a name and description, the name and description are read from a .txt file in the assets folder. The method is made so it reads everything between '$' and '#' as the name, and '#' and '#' as the description. I wrote the original method in Eclipse (console application) and it worked like a charm. Then I transferred it to Android Studio, added context (since the method is in a class file) and AssetManager, etc and followed instructions from other similar stackoverflow questions but for some reason it just won't work.
Here is the code:
public void readFile(String p) throws IOException {
// Path of the directory
String path = new String(p);
// AssetManager opens assets
AssetManager am = con.getAssets();
// Open file
InputStream i_s = am.open(path);
// StringBuilders store the text read for specific members
StringBuilder _name = new StringBuilder(""); // Records name of card from file
StringBuilder _desc = new StringBuilder(""); // Records description of card from file
// "c" stores each character at a time
char c;
// Main loop that reads entire file
while(i_s.available() > 0) {
c = (char) i_s.read();
if(c=='$') {
c = (char) i_s.read(); // Sends to next character so it doesn't save '$'
while(c!='#') // Loop saves everything between '$' and '#'
{_name.append(c); c = (char) i_s.read();}
}
else if(c=='#') {
c = (char) i_s.read(); // Sends to next character so it doesn't save '#'
while(c!='#') // Loop saves everything between '#' and '#'
{_desc.append(c); c = (char) i_s.read();}
}
}
i_s.close();
// Sets read info into Class properties
this.setName(_name);
this.setDesc(_desc);
}
The method is in CardAction card,a subclass of Card. The set methods are in the Card class.
public void setName(StringBuilder sb) {
this.name = sb.toString();
}
public void setDesc(StringBuilder sb) {
this.desc = sb.toString();
}
Every time I test this (by calling the get methods for name and desc) it return empty strings. What am I doing wrong here?
Additional info: All the Card subclasses inherit the context "con" from Card superclass which passes the context from the main activity as a parameter in the Card constructor, so I am 100% sure Context and AssetManager are working fine.
Edit: Code that calls the readFile method from main activity
String str;
Turn t = new Turn(3, 40, t_o_d, names, true, 1, con);
// chooseFile returns String of randomly chosen file
// name from the assets folder (randomly "draw" card), works
str = t.chooseFile(1);
CardAction ca = new CardAction(con); //Passes context as parameter for constructor
try {ca.readFile(str);}
catch(IOException e1) {}
// cardName and cardDesc are TextViews I set just for testing the readFile method
cardName.setVisibility(View.VISIBLE);
cardDesc.setVisibility(View.VISIBLE);
cardName.setText(ca.getName());
cardDesc.setText(ca.getDesc());

Solved. the method is fine, what my problem was that I tried to open txt files located in their own folders in assets, so I just added another String parameter to the method (for the directory) and concatenated them (adding "/" between them).
Well, considering this was a solution for a completely other problem, I'm still glad this works so anyone struggling with reading files character by character can refer to the code I originally posted :)

Check if a resource already exists with a different case

In a wizard I am creating a package and trying to check if a resource already exists with a different case to avoid ResourceException thrown by org.eclipse.core.internal.resources.Resource#checkDoesNotExist. For example I get this exception when I try to create a package com.Example.test while com.example.test already exist. So I would like to make a check for the every segment of the package name. The case for existing com.Example.test is already handled in my code.
Since the method checkDoesNotExist is in the internal class and not declared by IResource it's not in the public API and I cannot use it to make the check before calling IFolder#create. The method IResource#exists is useless in this case because it's case sensitive.
Currently I have the following solution:
/**
* This method checks if a package or its part exists in the given source folder with a different case.
*
* #param pfr A source folder where to look package in.
* #param packageName Name of the package, e.g. "com.example.test"
* #return A String containing path of the existing resource relative to the project, null if the package name has no conflicts.
* #throws CoreException
* #throws IOException
*/
public static String checkPackageDoesExistWithDifferentCase(IPackageFragmentRoot pfr, String packageName)
throws CoreException, IOException
{
IPath p = pfr.getResource().getLocation();
String[] packagePathSegments = packageName.split("\\.");
for (int i = 0; i < packagePathSegments.length; i++)
{
p = p.append(packagePathSegments[i]);
File f = new File(p.toString());
String canonicalPath = f.getCanonicalPath();
if (f.exists() && !canonicalPath.equals(p.toOSString()))
return canonicalPath.substring(pfr.getJavaProject().getResource().getLocation().toOSString().length() + 1);
}
return null;
}
The issue about this solution is that it would work only on Windows, since f.exists() would return false on case-sensitive filesystems.

As you pointed out, there is not API, but you can check the parent resource if it has a member with the same (case-insensitive) name like this:
IContainer parent = newFolder.getParent();
IResource[] members = parent.members();
for( IResource resource : members ) {
if( resource.getName().equalsIgnoreCase( newFolder.getName() ) ) {
...
}
}

Save Excel file with OLE, Java on Eclipse RCP Application

I try to Save an Excel file. The Excel file is a template with makros (*.xltm). I can open the file and edit the content, but if i try to save the destination Excel file is corrupt.
I try to save the file with:
int id = _workbook.getIDsOfNames(new String[] {"Save"})[0];
_workbook.invoke(id);
or/and
_xlsClientSite.save(_file, true);

You might try specifying a file format in your Save call.
If you're lucky, you can find the file format code you need in the Excel help. If you can't find what you need there, you'll have to get your hands dirty using the OLEVIEW.EXE program. There's likely a copy of it sitting on your hard drive somewhere, but if not, it's easy enough to find a copy with a quick Google search.
To use OLEVIEW.EXE:
Run it
Crack open the 'Type Libraries' entry
Find the version of Excel that you're using
Open that item
Search the enormous pile of text that's displayed for the string 'XlFileFormat'
Examine the XLFileFormat enum for a code that seems promising
If you are using Office2007 ("Excel12") like I am, you might try one of these values:
xlOpenXMLWorkbookMacroEnabled = 52
xlOpenXMLTemplateMacroEnabled = 53
Here's a method that I use to save Excel files using OLE:
/**
* Save the given workbook in the specified format.
*
* #param controlSiteAuto the OLE control site to use
* #param filepath the file to save to
* #param formatCode XlFileFormat code representing the file format to save as
* #param replaceExistingWithoutPrompt true to replace an existing file quietly, false to ask the user first
*/
public void saveWorkbook(OleAutomation controlSiteAuto, String filepath, Integer formatCode, boolean replaceExistingWithoutPrompt) {
Variant[] args = null;
Variant result = null;
try {
// suppress "replace existing?" prompt, if necessary
if (replaceExistingWithoutPrompt) {
setPropertyOnObject(controlSiteAuto, "Application", "DisplayAlerts", "False");
}
// if the given formatCode is null, for some reason, use a reasonable default
if (formatCode == null) {
formatCode = 51; // xlWorkbookDefault=51
}
// save the workbook
int[] id = controlSiteAuto.getIDsOfNames(new String[] {"SaveAs", "FileName", "FileFormat"});
args = new Variant[2];
args[0] = new Variant(filepath);
args[1] = new Variant(formatCode);
result = controlSiteAuto.invoke(id[0], args);
if (result == null || !result.getBoolean()) {
throw new RuntimeException("Unable to save active workbook");
}
// enable alerts again, if necessary
if (replaceExistingWithoutPrompt) {
setPropertyOnObject(controlSiteAuto, "Application", "DisplayAlerts", "True");
}
} finally {
cleanup(args);
cleanup(result);
}
}
protected void cleanup(Variant[] variants) {
if (variants != null) {
for (int i = 0; i < variants.length; i++) {
if (variants[i] != null) {
variants[i].dispose();
}
}
}
}

Java reflection and manifest file in jar

I would like to (and I don't know if it's possible) do something if jarA is in my classpath and do something else if jarB is in my classpath. I am NOT going to be specifying these jars in the Netbeans project library references because I don't know which of the jars will be used.
Now including the jar in my Netbeans project library references works when I try to use the jar's classes through reflection. But when I remove the netbeans project library reference but add the jar to my classpath the reflection does not work.
My question is really 1) can this be done? 2) Am I thinking about it correctly 3) How come when I specify -cp or -classpath to include the directory containing the jar it doesn't work? 4) How come when I specify the directory in my manifest.mf in the jar file it doesn't work?
Please let me know. This is really bothering me.
Thanks,
Julian

on point 3 - you should include the fully qualified jar name in your classpath, not just the directory.

I believe so!
ClassLoader.getSystemClassLoader()getURLs();
This will tell you which Jar files are in your classpath. Then do X or Y as you please.

A classpath can reference a directory that contains .class files, or it can reference a .jar file directly. If it references a directory that contains .jar files, they will not be included.
java -help says this about -classpath: "list of directories, JAR archives,
and ZIP archives to search for class files." This is very clear that a directory on the classpath is searched for class files, not JAR archives.

This is how I'm doing it. The inner class encapsulates the singleton instance of the logger and its trace method (heh - I know - a singleton inside a singleton). The outer class only uses it if the special class can be loaded, otherwise we go on without it. Hopefully you can modify this to suit your needs. And any suggestions as to better code are always appreciated! :-) HTH
import java.lang.reflect.Method;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
* Provides centralized access to standardized output formatting. Output is sent to System.out and,
* if the classpath allows it, to the Cisco CTIOS LogManager. (This is NOT a dependency, however.)
*
*/
public class LogWriter
{
protected static LogWriter me = null;
private SimpleDateFormat dateFormat = null;
private StringBuffer line = null;
CLogger ciscoLogger = null;
/*
* The following 2 methods constitute the thread-safe singleton pattern.
*/
private static class LogWriterHolder
{
public static LogWriter me = new LogWriter();
}
/**
* Returns singleton instance of the class. Thread-safe. The only way to get one is to use this.
*
* #return an instance of LogWriter
*/
public static LogWriter sharedInstance()
{
return LogWriterHolder.me;
}
#SuppressWarnings("unchecked")
LogWriter()
{
dateFormat = new SimpleDateFormat("yyyyMMddHHmmss ");
line = new StringBuffer();
try {
Class x = Class.forName("com.cisco.cti.ctios.util.LogManager");
if( x != null ) {
java.lang.reflect.Method m = x.getMethod("Instance", new Class[0]);
java.lang.reflect.Method n = x.getMethod("Trace", int.class, String.class );
if( m != null ) {
Object y = m.invoke( x , new Object[0] );
if( n != null ) {
ciscoLogger = new CLogger();
ciscoLogger.target = y;
ciscoLogger.traceImpl = n ;
}
}
}
} catch(Throwable e )
{
System.err.println( e.getMessage() ) ;
e.printStackTrace();
}
}
/**
* Formats a line and sends to System.out. The collection and formatting of the text is
* thread safe.
*
* #param message The human message you want to display in the log (required).
* #param hostAddress Host address of server (optional)
* #param hostPort Port on hostAddresss (optional) - also used for className in object-specific logs.
*/
public void log( String message, String hostAddress, String hostPort )
{
if ( message == null || message.length() < 3 ) return;
synchronized( this )
{
try {
line.delete(0, line.length());
line.append(dateFormat.format(new Date()));
line.append(hostAddress);
line.append(":");
line.append(hostPort);
line.append(" ");
while (line.length() < 28)
line.append(" ");
line.append(message);
this.write( line.toString() );
} catch (Exception e) {
e.printStackTrace();
}
}
}
private void write(String line )
{
System.out.println( line ) ;
}
/**
* Write a simple log message to output delegates (default is System.out).
* <p>
* Will prepend each line with date in yyyyMMddHHmmss format. there will be a big space
* after the date, in the spot where host and port are normally written, when {#link LogWriter#log(String, String, String) log(String,String,String)}
* is used.
*
* #param message What you want to record in the log.
*/
public void log( String message )
{
if( ciscoLogger != null ) ciscoLogger.trace(0x01, message );
this.log( message, "", "");
}
class CLogger
{
Object target;
Method traceImpl;
#SuppressWarnings("boxing")
public void trace( int x, String y )
{
try {
traceImpl.invoke( target, x, y) ;
} catch( Throwable e ) {
// nothing to say about this
}
}
}
}