Develop Reference

How to read properties file inside jar?

I have a config.properties file under the package com.abc.properties. From one of the java class present in com.abc.util, I need to read the property file. Both the files are present inside jar.
I have tried using
fs = new FileInputstream(VerifyFolderStructure.class.getResourceAsStream("com/abc/properties/config.properties"));
But it doesn't seem to work. Please help.
P.S: VerifyFolderStructure is my java class from which I need to load the properties file.

To obtain the stream you don't need FileInputStream at all. You can get the properties' file stream like this
InputStream is = VerifyFolderStructure.class.getResourceAsStream("/com/abc/properties/config.properties");

I think you need to add "/" in the front of you path.if you don't add "/" that means the properties is located in the same packages path as VerifyFolderStructure class.

Getting a config file outside of a jar file?

I want to open a .config file outside of the .jar file so that I can use its properties inside of the .jar. How would I do this?

For clearance you will use a config file from the (executable) jar like this:
InputStream in = this.getClass.getResourceAsStream("config.properties");
Properties p = new Properties();
p.load(in);
that loads config.properties relative to the class of the current object.
For a config outside you propably use a file:
InputStream in = new FileInputStream(System.getProperty("user.dir")+"/"+"config.properties");
Properties p = new Properties();
p.load(in);

Use this.
String path = System.getProperty("user.dir")
path += "/config/myApp.properties"
Now you have the path of your properties file.
You know what to do next

reading directory path from properties file

I need to know that how to read the directory path from a .properties file in java.
for example,
class clazz
{
string filename="d:/file.txt";
public void somemethod()
{
FileWriter f=new FileWriter(filename, true);
// etc
}
i want to read the filename from .properties file rather than from a variable.
how it can be done?

A fairly simple way is to use a resource file, through the ResourceBundle class.
ResourceBundle bundle = ResourceBundle.getBundle("com/file");
Where com/file is the file.properties in the com package.
This file could have a line like this:
file.name=C:\dir\file.txt
For get this particular data.
String filename = bundle.getString("file.name");
I hope this can help you. Good luck!

Check out the Properties class load() method. It reads in a file (in the common properties format) and then you can query the value of a property based on its name

If the properties file is in your class path then do this:
Properties prop = new Properties();
prop.load(this.getClass().getClassLoader().getResourceAsStream("file.txt"));
Sting fileName = prop.get("fileName");

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

Storing changes in .properties file that has been read via getClass().getResourceAsStream

I am writing a java web application that reads properties from a .properties file. Since I do not know the absolute path of the .properties file, because it depends on the environment the application will run on in the future, I have to load it with "getClass().getResourceAsStream":
Properties props = new Properties();
props.load(getClass().getResourceAsStream("test.properties"));
message = props.getProperty("testdata");
This works as expected. Now I want to change the value for testdata in the file. But I cannot open an Outputstream to write to, because I still don't know the path of the .properties file.
props.setProperty("testdata", "foooo");
props.store(new FileOutputStream("?????"), null);
Is there a way to get the path of the file or can I use the established Properties-object somehow? Any ideas are welcome that allow me to change the .properties file.

You can get an URL by using getResource() rather than using getResourceAsStream()
You can then use that URL to read from and write to your properties file.
File myProps = new File(myUrl.toURI());
FileInputStream in = new FileInputStream(myProps);
Etc.

The Properties class includes a store method that can be used to save the properties back to the stream that was read in getClass().getResourceAsStream("test.properties").