I have for example .pdf file (path to that file). How to open this file in default application (probably Acrobat Reader) from SWT application (for example on Button click) ?
You should be able to use:
Program.launch(file);
to open the file (using the default application or creator). From the javadoc:
Launches the operating system executable associated with the file or URL (http:// or https://). If the file is an executable then the executable is launched. Note that a Display must already exist to guarantee that this method returns an appropriate result.
Note that there are some peculiarities in Program.launch() (or at least there were, though these may have been fixed in more recent versions of the runtime.) I don't really remember the specifics of the bugs, but we do some checks to work around some issues:
If you're on a Unix platform, and you're specifying an absolute path, there may be trouble opening that file. We prefix absolute paths with /. - so that /tmp/foo would be translated to /./tmp/foo - although I don't really remember the specifics of this bug any more than that.
On Windows, if you're trying to open a UNC path - for example \\server\bar - you need to wrap the string in double-quotes. For example: Program.open("\"\\server\bar\"");
Try Desktop.open:
Desktop.getDesktop().open(file);
Maybe this can help to find a decision: we ran into PermGen space trouble upon call Desktop.open() - which is in AWTpackage - out of our SWT application.
So I would prefer Program.launch() over Desktop.open() in a SWT-environment.
Related
I have Jar file which dependency on another project jar. Both are thin jars and are at same location. 1st jar has manifest file which list second jar in its class-path property.
In 1st jar I am launching second jar as a process using ProcesBuilder class in java. To do so I need absolute path of second jar. In 1st jar i have class XClient
If I do XClient.class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath();
i am getting absolute path of 1st jar. Then I can split and add the name of second jar(hard-coded) to build the absolute path
In second jar I have class XServer
If I do
XServer .class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath();
Its throws exception
I am not sure if I am doing the right approach but my goal is very clear I wanted to get the absolute path to the dependent jar.
Please help
I tried to use the same approach (but used File file=new File(this.getClass().getProtectionDomain().getCodeSource().toUri()) instead of getPath()) but this can fail in different ways:
when the class is inside a jar the File object points to the jar instead the folder the jar is in - so an if(file.isFile()) file=file.getParentFile(); is needed to get the directory instead of the jar file
when the jar file is loaded by something other than the usual URLClassLoader (last time I tried was back in 1.8 - and I only know that since Jigsaw the main classloader can't be cast to an URLClassLoader anymore) this may will return some unspecified result, if at all, so actual behaviour depends on the very system setup - wich can make it difficult to debug when used on a remote system not under your control
UNC paths (Windows shares) are error prone by themselfs - adding another layer on top of it (java) just add a lot of potential other pitfalls you all have to test and debug - wich often ends up you tell the client what to use and how to setup instead of design your code to follow the java principle: "write once, compile once, run everywhere" (btw: this also applies even if you "mount" a network share so you can address it by a local drive letter instead of a remote network path - but this even causes problems when you try to link two machines where one is a clone of the other)
as already mentioned as comment: "it doesn'T work" is not a usefull or meaningfull description - if you get an error message (in this case as you mentioned an exception stacktrace) post it along with the code wich produced it (if accessible)
How I solved my problem? I just ask the user for the directory / file by a swing JFileChooser. Yes, this isn't fool proof and maybe not the best way - but it works as swing still ships with SE JVM (instead of FX).
If you want to find a path use Class.getResource() and let java do the work, pretty much like crypto: don'T do your own.
Aside from all that: Your mentioned "usecase" doesn'T require what you try to do. You said that the server is already in the classpath - so it gets loaded on startup and you can access the XServer class. The easiest way instead of forking another process is to just run it in another thread. If you know wich class has the main (the manifest of the server.jar will tell you) and you can access it in classpath just do something like this:
Thread serverThread=new Thread(new Runnable()
{
public void run()
{
String[] args=Arrays.asList("required", "parameters");
XServer.main(args);
}
});
serverThread.start();
If no paramters required you can just pass an empty String array. As main() should not throw Exceptions (at least no checked ones) no exception should be needed.
Before all those comments are thrown at me: Yes, I am very well aware of possible issues with such approach like classpath issues (same classname in same packagename but different versions) and such it may be more feasible than try to figure out the absolute path and launch a fork / sub process.
Also: Starting another process may require to interact with its streams (provide required input into child process inputstream and read the child process outputstream and errorstream - otherwise the forked process may can "hang" as it waits for the pipelines to get cleared. It's a pain in the but to debug that kind of issue if it's not your own code and you can have a profiler and debugger attached to it to figure out why all just suddenly stopped to work.
If you really want to (I don't think there's any requirement forcing a "you need to") launch your server along with the client do it with a launch script outside of java but with os level stuff.
I developed a software in netbeans + Ubuntu and then converted the runnable .jar file of netbeans to .exe file using a converter software.
I used:
File f = new File("./dir/fileName");
which works fine in Ubuntu but it gives an error in Windows, because the directory pattern of both OSs are different.
Absolute paths should not be hardcoded. They should be read e.g. from a config file or user input.
Then you can use the NIO.2 File API to create your file paths: Paths.get(...) (java.io.File is a legacy API).
In your case it could be:
Path filePath = Paths.get("dir", "fileName");
I used: File f = new File("./dir/fileName") which works fine in Ubuntu but it gives error in Windows, bcz the directory pattern of both os are different.
It is presumably failing because that file doesn't exist at that path. Note that it is a relative path, so the problem could have been that the the path could not be resolved from the current directory ... because the current directory was not what the application was expecting.
In fact, it is perfectly fine to use forward slashes in pathnames in Java on Window. That's because at the OS level, Windows accepts both / and \ as path separators. (It doesn't work in the other direction though. UNIX, Linux and MacOS do not accept backslash as a pathname separator.)
However Puce's advice is mostly sound:
It is inadvisable to hard-code paths into your application. Put them into a config file.
Use the NIO2 Path and Paths APIs in preference to File. If you need to assemble paths from their component parts, these APIs offer clean ways to do it while hiding the details of path separators. The APIs are also more consistent than File, and give better diagnostics.
But: if you do need to get the pathname separator, File.separator is an acceptable way to get it. Calling FileSystem.getSeparator() may be better, but you will only see a difference if your application is using different FileSystem objects for different file systems with different separators.
You can use File.separator as you can see in api docs:
https://docs.oracle.com/javase/8/docs/api/java/io/File.html
I'd like to pass a file path argument to my application in a relative form, e.g ~/test.conf or ../test.conf, but i can't get a proper full file path, though i've tried it with old java.io and new java.nio Files/Paths. Is there a general way to get a resolved file path without large amount of code? It would be fine for the solution to work only in unix envs like OsX or Debian.
Update
With a provided argument like ~/test.conf
in case of getAbsolutePath it returns a path with a prefixed current folder - /Users/currentUser/Projects/Personal/TestProject/~/text.conf. Canonical path returns the same.
The hard bit here is dealing with POSIX home directories, and sure you deal with ~otheruser/dir/test.conf too (if you want to do it properly).
Luckily that's covered in How to handle ~ in file paths.
TL;DR - use something like:
path.replace("~/", System.getProperty("user.home") + "/");
Once you've done that, and as others have commented, you can just use standard java.io methods (including getCanonicalPath()).
How would I access a picture in a different folder in Java? I have a series of pictures and they change based on user input, which is what x is for.
picture.setIcon(new ImageIcon("\\resources\\icons\\pictures\\"+x+".png"));
The images are located (from the .class files) in resources/icons/pictures, but the above code doesn't work. The value of x isn't the problem since it works as it should. Am I calling the pictures the right way?
Am I calling the pictures the right way?
Probably not. If they are (embedded) application resources they will typically be in a Jar and unavailable via the String based constructor of the ImageIcon (which expects the String equates to a File path).
For an embedded resources, access them by URL.
URL urlToImg = this.getClass().
getResource("/resources/icons/pictures/"+x+".png");
picture.setIcon(new ImageIcon(urlToImg));
You should be using forward slashes instead of backslashes I believe.
new ImageIcon("/resources/icons/pictures/"+x+".png")
This is the standard Java cross-platform way of denoting resource file paths. It still works on Windows - the Java runtime library handles the transaltion for you.
The images are located (from the .class files) in resources/icons/pictures
That's a problem. The system isn't interested in where the class file is, but from where you invoke a program.
Specifying a resource folder via command line,
java -jar myJar.jar C:\\home\\of\\the\\images
or via a property
java -jar myJar.jar -DImageHome=/foo/bar/images
or from a properties file is most flexible.
If you like to put the images into the jar, use Andrews suggestion, getClass ().getRessource ("...");
Btw: I know for sure, that forward slashes are portable. Backslashes, afaik, aren't.
I am trying to use IM4J (a Java wrapper for ImageMagick) to create thumbnails of JPEGs and it is my first experience (ever) with both libraries. Please note that this is a hard requirement handed to me by my tech lead (so please don't suggest to use anything other than an IM4J/ImageMagick) solution - my hands are tied on the technology choice here!
I am getting a FileNotFoundException on the and convert command which tells me I don't have one of these libraries (or both) setup correctly.
On my computer, here is my directory structure:
C:/
myApp/
images/ --> where all of my JPEGs are
thumbnails/ --> where I want ImageMagick to send the converted thumbnails to
imageMagickHome/ --> Where I downloaded the DLL to
ImageMagick-6.7.6-1-Q16-windows-dll.exe
...
In my Java project, I make sure that the IM4J JAR (im4java-1.2.0.jar) is on the classpath at runtime. Although I am required to use the 1.2.0 version of IM4J, I have the liberty to use any version of ImageMagick that I want. I simply chose this version because it seemed like the most current/stable version for my Windows 7 (32-bit) machine. If I should use a different version, please send me a link to it from the ImageMagick downloads page in your answer!
As for ImageMagick, I just downloaded that EXE from here and placed it in the folder mentioned above - I didn't do any installation, wizard, MSI, environment variable configuration, etc.
Then, in my Java code:
// In my driver...
File currentFile = new File("C:/myApp/images/test.jpg"); --> exists and is sitting at this location
File thumbFile = new File("C:/myApp/thumbnails/test-thumb.jpg"); --> doesnt exist yet! (destination file)
Thumbnailer myThumbnailer = new Thumbnailer();
myThumbnailer.generateThumbnail(currentFile, thumbFile);
// Then the Thumbnailer:
public class Thumbnailer
{
// ... omitted for brevity
public void generateThumbnail(File originalFile, File thumbnailFile)
{
// Reads appConfig.xml from classpath, validates it against a schema,
// and reads the contents of an element called <imPath> into this
// method's return value. See below
String imPath = getIMPathFromAppConfigFile();
org.im4java.core.IMOperation op = new Operation();
op.colorspace(this.colorSpace);
op.addImage(originalFile.getAbsolutePath());
op.flatten();
op.addImage(thumbnailFile.getAbsolutePath());
ConvertCmd cmd = new ConvertCmd();
cmd.setSearchPath(imPath);
// This next line is what throws the FileNotFoundException
cmd.run(op);
}
}
The section of my appConfig.xml file that contains the imPath:
<imPath>C:/myApp/imageMagickHome</imPath>
Please note - if this appConfig.xml is not well-formed, our schema validator will catch it. Since we are not getting schema validation errors, we can rule this out as a culprit. However, notice my file path delimiters; they are all forward slashes. I did this because I was told that, on Windows systems, the forward slash is treated the same as a *nix backslash, in reference to file paths. Believe it or not, we are developing on Windows
machines, but deploying to linux servers, so this was my solution (again, not my call!).
IM4J even acknowledges that Windows users can have trouble sometimes and explains in this article that Windows developers might have to set an IM4JAVA_TOOLPATH env var to get this library to work. I tried this suggestion, created a new System-wide environmental variable of the same name and set its value to C:\myApp\imageMagickHome. Still no difference. But notice here I am using backslashes. This is because this env var is local to my machine, whereas the appConfig.xml is a config descriptor that gets deployed to the linux servers.
From what I can tell, the culprit is probably one (or more) of the following:
I didn't "install" the ImageMagick EXE correctly and should have used an installer/MSI; or I need to add some other environmental variables for ImageMagick (not IM4J) itself
Perhaps I still don't have IM4J configured correctly and need to add more environmental variables
Could be the Windows/*nix "/" vs. "" issue from my appConfig.xml file as mentioned above
I'm also perplexed as to why I'm getting a FileNotFoundException on a file named "convert":
java.io.FileNotFoundException: convert
I assume this is a batch/shell file living somewhere inside the IM4J jar (since the only thing I downloaded for ImageMagick was the EXE). However, if I extract the IM4J jar I only see classes inside of it. I see "script generator" classes, so I assume these kick off before my cmd.run(op) call and create the convert file, and maybe that's what I'm missing (perhaps I need to manually kick off one of these generators, like CmdScriptGenerator prior to executing my Thumbnailer methods. . Or, maybe my download is incomplete.
Either way, I'm just not versed enough with either library to know where to start.
Thanks for any help with this.
Run the 'ImageMagick-6.7.6-1-Q16-windows-dll.exe' installer first to install the imagemagick libraries. Then make sure your environment path includes the location of the installed binaries ('convert.exe', 'mogrify.exe', etc)
Make sure u have Set the environment-variable IM4JAVA_TOOLPATH.