What is the best way to store and load application level properties in Java.
Is there anything simulare to .net where I would just put something in the app.config
<appSettings>
<add key="emailAddress" value="me#example.com" />
</appSettings>
And then retrieve it like this:
string AdminEmail = ConfigurationManager.AppSettings["emailAddress"];
Do I have to load properties files into file streams and such? seems like unnecessary work.
I have tried this:
Properties props = new Properties();
FileInputStream fis = new FileInputStream("myProps.properties");
props.load(fis);
fis.close();
But this is give me a java.io.FileNotFoundException exception. Where does the properties file need to go to in relation to the class?
The Preferences API provides this functionality. It has many warts, but if you are looking to do this in an OS-agnostic fashion, this is the only way to accomplish this using the standard Java runtime libraries. You can of course always write your own OS-specific code to meet your needs. Yes, you can write simple code to load a properties file, but the location of that file can become a problem across multiple operating systems. I assume since you are writing a desktop app in Java, you care about OS portability. Otherwise Java might not be the best choice for a desktop app.
If you use a FileInputStream like that, your path is relative to the current directory of the OS, which usually is the startup directory.
If you instead use the Java built in resources mechanism (as described in the API, getResourceAsStream() et al), the path will be relative to the location of your class. With this approach you can also load resources from within jars and even over networks (for Applets for instance). The concept which is used is a sort of virtual filesystem, which is called the 'classpath' in Java jargon. There is a devx article covering it a litte more in detail.
In short, this sort of code works well:
Properties prop = new Properties();
//with properties in the same dir as current class
prop.load(getClass().getResourceAsStream("my.properties"));
//with properties in the root dir of your jar, or in base of classpath
prop.load(getClass().getResourceAsStream("/my.properties"));
You will need to add error handling...
Typically it will attempt to load from the application's current directory, which can vary depending on how you run it. You should be able to determine this at runtime by doing:
String currentFolder = System.getProperty("user.dir");
The file path it would be looking for in that case is relative to where you started your java application from. This is not where the main class is or the jar file but where you called Java from. If you are starting your application with a script that calls Java, then it is that directory.
Say for example, you application is bundled in a jar file 'app.jar'. Put 'myProps.properties' in the same directory and run 'java -jar app.jar' from that directory. It should find your properties file that way.
You can use Properties with a ResourceBundle. I use this in a application to store labels, buttons and messages in different languages
First you create a properties file, like test.properties. It´s a text file and inside it you put your information like this:
propertyname=value
In your case
emailAddress=me#example.com
email2=blablabla#example.com
and so on...
To get this properties in the code, create a ResourceBundle object with the name of your property file to call the properties.
ResourceBundle rb = ResourceBundle.getBundle("test");
To get an specific value from a properties file, just call the ResourceBundle
String value = rb.getString("emailAddress");
This way, the String named value contains the value of the property named "emailAddress", located in the test.properties file
String value2 = rb.getString("email2");
Likewise, the String named value2 contains the value of the property named "email2", located in the test.properties file
When you do not specify an absolute path, the one chosen is the current one.
It's not exactly what you asked, but if you want to use XML files as configuration, you could have a look at Apache Commons Configuration
Related
I've got a project to do with 2 other classmates.
We used Dropbox to share the project so we can write from our houses (Isn't a very good choice, but it worked and was easier than using GitHub)
My question is now about sharing the object stream.
I want to put the file of the stream in same dropbox shared directory of the code.
BUT, when i initialize the file
File f = new File(PATH);
i must use the path of my computer (C:\User**Alessandro**\Dropbox)
As you can see it is linked to Alessandro, and so to my computer.
This clearly won't work on another PC.
How can tell the compiler to just look in the same directory of the source code/.class files?
You can use Class#getResource(java.lang.String) to obtain a URL corresponding to the location of the file relative to the classpath of the Java program:
URL url = getClass().getResource("/path/to/the/file");
File file = new File(url.getPath());
Note here that / is the root of your classpath, which is the top of the directory containing your class files. So your resource should be placed inside the classpath somewhere in order for it to work on your friend's computer.
Don't use absolute paths. Use relative paths like ./myfile.txt. Start the program with the project directory as the current dir. (This is the default in Eclipse.) But then you have to ensure that this both works for development and for production use.
As an alternative you can create a properties file and define the path there. Your code then only refers to a property name and each developer can adjust the configuration file. See Properties documentation.
I'm trying to use Java class Properties for saving the settings for my application between executions. Afterwards I would like to export my application into runnable JAR file and keep everything needed in this one file to provide portability. So my application has to find the properties file, load it and then save new settings into it on exit.
The loading works fine:
Properties prop = new Properties().load(this.getClass().getResourceAsStream("properties.cfg"));
But for storing I need to find the same file and overwrite it. The method Properties.store() needs an OutputStream but getResourceAsStream returns an InputStream therefore I cannot find the file and access it.
It should be always located with the *.class file. I found many solutions that work before exporting into JAR but none that would work after exporting. Thanks for any suggestions.
You can't rewrite your jar (or rather, it's complicated and not a good idea).
A preferable solution would be to read the properties from:
a directory on your machine
the .jar file
Initially location 1 wouldn't have a property file and you'd fall back to your .jar file. When you write the properties you'd write them to the nominated directory, and then on the next read you'd read your properties from this location. This would survive restarts etc.
Note that libraries such as Apache Commons Configuration automatically support this tiered properties location mechanism and may save you some time/grief in writing your own solution.
take spring's IO infrastructure (ClasspathResource)
try {
ClassPathResource r = new ClassPathResource("bdd.properties");
Properties properties = new Properties();
properties.load(r.getInputStream());
} catch (IOException e) {
Throwables.propagate(e);
}
this is real simplification.
For this kind of scenario the best approach is to add the properties file to the classpath and load it using something like ResourceBundle.
private static ResourceBundle _properties = ResourceBundle.getBundle("sample.properties");
String sampleProperty = _properties.getString(propertyKey);
How to execute :
Suppose your jar file is MyJar.jar and property file is called sample.properties
then u should write a batch or sh file around it
eg: run.sh
java -cp MyJar.jar:conf "Class with main Method"
I am having issues with properties file when I try to make my standalone Java aplication a runnable jar.
I have 2 properties file, depending upon the machine where its running one gets initialized.
Inside eclipse it was working fine. I was using:
Properties configProps = new Properties();
....
if(machine1)
....
configProps.load(Config.class.getResourceAsStream("machine1.properties"));
else
configProps.load(Config.class.getResourceAsStream("machine2.properties"));
It was working as Config.java and properties were in the same package.
On top of that I have log4j properties located on the root of the project.
That is also not working whne i made Jar.
How to handle the current sutuation.I know putting properties file outside jar is good idea.
How do I accomplish this.
Please help.
Putting the properties file outside of the jar is only a good idea if you need to write to that property file (it's for configuration). Given your naming, I assume it is for configuration.
For reading only, your method is fine if the properties file is properly being packaged in the Jar. Is it? Have you peaked at the contents using jar tf MyJar.jar? Does it show your properties file at the correct path?
Where to store configuration files is a broader issue. Here's a good SO article that examines a few aspects of it (namely where to put it): What is the proper way to store app's conf data in Java?
It seems to me you want to choose a location (see the above article). Once you've done that, the first time the application is run you should load the default properties from your Jar file as you are trying to do, then immediately save them to the location you've chosen. Then, and afterwards, read from and write to that location instead. You will need to use a FileInputStream/FileOutputStream.
Try adding a manifest to your JAR's META-INF with Class-Path set appropriately.
when i am loading some data into my java program, i usually use FileInputStream. however i deploy the program as a jar file and webstart, so i have to use getRessource() or getRessourceAsStream() to load the data directly from the jar file.
now it is quite annoying to always switch this code between development and deployment?
is there a way autmate this? i.e. is there a way to know if the code is run from a jar or not?
when i try to load it withoug jar like this:
InputStream is = this.getClass().getResourceAsStream("file.txt");
the returned inputstream is simply null, although the file is definitely in the root directory of the application.
thanks!
Why do you use FileInputStream during development? Why not just use getResourceAsStream from the very start? So long as you place your files in an appropriate place in your classpath, you shouldn't have any problems. It can still be a file in the local filesystem rather than in a jar file.
It's helpful to develop with the final deployment environment in mind.
EDIT: If you want something in the root directory of your classpath, you should either use:
InputStream x = getClass().getResourceAsStream("/file.txt");
or
InputStream x = getClass().getClassLoader().getResourceAsStream("file.txt");
Basically Class.getResourceAsStream will resolve relative resources to the package containing the class; ClassLoader.getResourceAsStream resolves everything relative to the "root" package.
You could read your data always as a ressource. You only have to add the path where the data lies to your classpath.
If your data stays in WEB-INF/somewhere/mydata.txt inside your jar file, you will access it with:
getClass().getResourceAsStream( "/WEB-INF/somewhere/mydata.txt" )
Now, if you create a development directory /devel/WEB-INF/somewhere/mydata.txt and put /devel to your classpath, your code will work in development and production.
EDIT after explanation in question:
In your case this.getClass().getResourceAsStream( "mydata.txt" ) the resource is taken from the same position where the classfile of this is taken from. If you want to keep this, then you have to create a directory /devel/<path of package>/mydata.txt and again add /devel to your classpath.
How about setting a system property in your dev environment, via the -D switch? e.g. java -D:mypropertyname=mypropertyvalue
You could set the property in ant scripts in your dev environment, other environments don't get the property:
e.g.
public static boolean isDevEnvironment(){ return System.getProperty("mypropertyname")!=null;}
You might find a better way to hack it from one of the existing System Properties
If a file is considered part of your deployed application (as opposed to be part of the installation specific files) and can be located through the classpath then consider simply always using getResourceAsStream since it works regardless of the actual deployment scheme as long as it is in the classpath.
You might also find the information available from the JVM relevant (if allowed by the security manager):
// Get the location of this class
Class cls = this.getClass();
ProtectionDomain pDomain = cls.getProtectionDomain();
CodeSource cSource = pDomain.getCodeSource();
URL loc = cSource.getLocation(); // file:/c:/almanac14/examples/
http://www.exampledepot.com/egs/java.lang/ClassOrigin.html?l=rel
There shouldn't be any difference between development vs deployment, IHMO.
Classloader.getResource or getResourceAsStream works well, you can read resources and even write them.You can write your own Protocol handles and access everything as an URL/URI, which allows you to read and write resources and also allows proper identification of who actually provide the resource.
The only problem is if an URLStreamHandlerFactory is already registered(in a J2EE application the container could install a factory and you don't have any way to go over and install your own) and you cannot use your handlers "anywhere".
Knowing that, it is preferred to implement your own "resources". At that time when I need it I couldn't find something like that so I had to implement my own ResourceManager. For me it looks more intuitive to access a resource like
Resource layout = ResourceManager.resolve("view://layout/main.jsp")
instead of
URL layout = Classloader.getResource("some_package/view/layout/main.jsp")
I want to create an ini file to store some settings for my application. Is it a good idea to find where the jar file is located and create an ini file there? If yes, then how can I find the location of the jar file?
But if you know a better solution for something like this, I would like to hear some of them.
EDIT: I'm using mac and I want to run the same application in windows. I could write something in the System.getProperty("user.home") directory, but I want to keep the system clean, if the user decides to remove the app. There is no a better way to store the settings file, for example in the same directory with the application?
You can locate your application directory using the ClassLoader. See: Java: finding the application directory. Rather than an .INI file, use a .properties file - you can load and save this via the Properties class.
As others have noted, you should not write user settings to your application directory. What if the user does not have write access to the application directory? What if your application is being used by multiple users on the same system at the same time? Neither of these situations are unusual, even on Windows.
You might still want to load some settings from the application directory - perhaps the administrator has configured default settings there.
A common convention is to save user settings to the user's home directory:
/home/user/.eclipse
C:\Documents and Settings\User\.eclipse
Although this means you might leave stray files behind, this can be beneficial if the user re-installs the app. Document such things in a README. Here is how to create and get a reference to the directory:
public static File getSettingsDirectory() {
String userHome = System.getProperty("user.home");
if(userHome == null) {
throw new IllegalStateException("user.home==null");
}
File home = new File(userHome);
File settingsDirectory = new File(home, ".myappdir");
if(!settingsDirectory.exists()) {
if(!settingsDirectory.mkdir()) {
throw new IllegalStateException(settingsDirectory.toString());
}
}
return settingsDirectory;
}
On unix-like operating systems, starting the directory name with a period (".myappdir") will make the directory hidden. On Windows, it will be located below My Documents, so users will not see the directory unless they go looking for it.
If the settings are only written by your application (rather than edited manually), consider using the Preferences API.
You should not be storing temp files in the install directory of an application. Remember, the user running the application may not have write access to that directory. The safest place to put stuff like that is in C:\Documents and Settings\username\Application Data\ApplicationName folder (adjusting the name as necessary).
That said, however, I would probably store that type of stuff in the registry instead of a file on their computer. (But, that's just me.)
Typically Java programmers don't use .ini files, but .properties files (different format). You can use the java.lang.Properties class as a nice programmatic wrapper if you do.
While you can get the location of your jar file by calling getProtectionDomain().getCodeSource().getLocation() on your class's .class member, I do not recommend that you do this.
I would instead write the file to the System.getProperty("user.home") directory - the users' home directory, or if it is truly temporary, System.getProperty("java.io.tmpdir")
It depends whether your ini needs to be human readable/writable under normal circumstances. If not, you can use a properties file rather than an ini file, and store it in the "user" directory.
As for finding the jar file, you would have to find the ClassLoader for a class known to be loaded from the jar, check that it was the appropriate type of ClassLoader (ie that it's really been loaded from a jar), and you can extract the path from that. I can probably dig out the code to do this if that's really what you want. I wouldn't necessarily recommend it.
EDIT The user.home property will give you the user directory, which you can safely use.
The idea with the .properties file instead of the INI file is good. Also, if you store some sensitive data in there, you may consider encrypting it. Check this out:
https://www.owasp.org/index.php/How_to_encrypt_a_properties_file
or this:
encrypt and decrypt property file value in java