How to include a text file in my executable JAR file?


Z

zyng

Hi:

My Java program needs to access a text file(in fact, the Java code will use Linux System command "cp" to copy this text file to a destination folder during running). Suppose this is my Java program HelloWorld.java:

package aa.bb.cc;

public class HelloWorld
{
...

public static void main(final String[] args)
{
final URL myUrl = this.getClass().getClassLoader().getResource("namelist.txt");

final File nameFile = new File(myUrl.getPath());
if(windowlayoutFile.exists() == false)
{
System.out.println(nameFile.getAbsolutePath() + " does not exist!!!");
}
else
{
System.out.println(nameFile.getAbsolutePath() + " exists");
}
}
}

This is the directory and file structure in my file system:
/HOME/java_project/src/aa/bb/cc/HelloWorld.java
/HOME/java_project/build/aa/bb/cc/HelloWorld.class
/HOME/java_project/nonsrc/namelist.txt

In Eclipse, I have added nonsrc as "external class folder" and the code above works! The output is:
/HOME/java_project/nonsrc/windowlayout.xml exists
I am still not clear why use "external class folder", but it works in Eclipse.

Now, my problem is when creating an executable JAR file(helloworld.jar), my JAR content is(shown by the command "jar tf helloworld.jar"):
aa/bb/cc/HelloWorld.class
namelist.txt

Now, if i am at /HOME/test directory and the JAR file is here too:
java -jar helloworld.jar

This is the confusing output:
/HOME/test/file:/HOME/test/robot.jar!/namelist.txt does not exist!!!

The answers by Google just do not give me a clear whole picture of what is going on. (I don't want to put namelist.txt at the same package location as HelloWorld.java. I guess, if I do that, I maybe able to make it work by myself)

I am surprised by an exclamation shown in the file path too. I have never used the class URL in the past, which is used in my code now.

Thank you very much.
 
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Z

zyng

Oops, a typo in my original post:

This is the confusing output:
/HOME/test/file:/HOME/test/helloworld.jar!/namelist.txt does not exist!!!
 
J

Jan Burse

Try:
URLConnection con = myUrl.openConnection();
InputStream in = con.getInputStream();

You can then copy from the in, via a Java loop.
 
J

Jeff Higgins

Try:
URLConnection con = myUrl.openConnection();
InputStream in = con.getInputStream();

You can then copy from the in, via a Java loop.
Hi:

My Java program needs to access a text file(in fact, the Java code
will use Linux System command "cp" to copy this text file to a
destination folder during running). Suppose this is my Java program
HelloWorld.java:

package aa.bb.cc;

public class HelloWorld
{
...

public static void main(final String[] args)
{
final URL myUrl =
this.getClass().getClassLoader().getResource("namelist.txt");

final File nameFile = new File(myUrl.getPath());
if(windowlayoutFile.exists() == false)
{
System.out.println(nameFile.getAbsolutePath() + " does not exist!!!");
}
else
{
System.out.println(nameFile.getAbsolutePath() + " exists");
}
}
}

This is the directory and file structure in my file system:
/HOME/java_project/src/aa/bb/cc/HelloWorld.java
/HOME/java_project/build/aa/bb/cc/HelloWorld.class
/HOME/java_project/nonsrc/namelist.txt

In Eclipse, I have added nonsrc as "external class folder" and the
code above works!

Eclipse has added nonsrc to the classpath
and getResource is able to find it.

Use a relative URL?

The output is:
 
L

Lew

zyng said:
My Java program needs to access a text file(in fact, the Java code will use Linux System command "cp" to copy this text file to a destination folder during running). Suppose this is my Java program HelloWorld.java:

package aa.bb.cc;

public class HelloWorld
{
...
public static void main(final String[] args)
{
final URL myUrl = this.getClass().getClassLoader().getResource("namelist.txt");

<http://docs.oracle.com/javase/7/docs/api/java/lang/ClassLoader.html#getResource(java.lang.String)>

You don't actually need to get the 'ClassLoader' explicitly, as the 'Class' method
will work, too.

<http://docs.oracle.com/javase/7/docs/api/java/lang/Class.html#getResource(java.lang.String)>

Both these search the classpath.

Entries in ZIP files (like JARs) are distinguished by said:
final File nameFile = new File(myUrl.getPath());
if(windowlayoutFile.exists() == false)

'== false', really?

What's wrong with 'if (!windowlayoutFile.exists())'?
{
System.out.println(nameFile.getAbsolutePath() + " does not exist!!!");
}
else
{
System.out.println(nameFile.getAbsolutePath() + " exists");
}
}
}


This is the directory and file structure in my file system:
/HOME/java_project/src/aa/bb/cc/HelloWorld.java
/HOME/java_project/build/aa/bb/cc/HelloWorld.class
/HOME/java_project/nonsrc/namelist.txt

In Eclipse, I have added nonsrc as "external class folder" and the code above works! The output is:
/HOME/java_project/nonsrc/windowlayout.xml exists
I am still not clear why use "external class folder", but it works in Eclipse.

You added the folder to your classpath. You'd do the same thing with the
"-classpath" ("-cp") option from the tools' command line.
Now, my problem is when creating an executable JAR file(helloworld.jar), my JAR content is(shown by the command "jar tf helloworld.jar"):

aa/bb/cc/HelloWorld.class

namelist.txt

So 'namelist.txt' is at the root of the JAR classpath node.

'HelloWorld' is 'aa.bb.cc.HelloWorld'.
'namelist.txt' is in the default (unnamed) package.
Now, if i am at /HOME/test directory and the JAR file is here too:

java -jar helloworld.jar

This is the confusing output:

/HOME/test/file:/HOME/test/robot.jar!/namelist.txt does not exist!!!

"robot.jar"?

You're running from the JAR. Local directories have no relevance, except
as you access them via 'File' constructs.
The answers by Google just do not give me a clear whole picture of what is going on. (I don't want to put namelist.txt at the same package location as HelloWorld.java. I guess, if I do that, I maybe able to make it work by myself)

It's in the default package, findable via 'getResource("/namelist.txt")'.
I am surprised by an exclamation shown in the file path too. I have never used the class URL in the past, which is used in my code now.

The bang character is part of the ZIP file reference syntax.

But when you run "java -jar" you have to specify all extrinsic classpath
stuff in the JAR manifest. Otherwise only elements within the JAR are accessible.
 
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