Question

I am trying to load some GZIP-ed data from a resource in my .jar, but I get a java.io.IOException: Not in GZIP format message.

When I load the same data from a file, I don’t get any error. Why? (It is a maven project I compile with NetBeans)

Here is the test code generating the issue:

public static void main(String[] args) throws IOException {

    byte[] dummy = new byte[10];

    // Reading data from file
    File f = new File("C:\\Temp\\422\\convert1900.data");
    DataInputStream is = new DataInputStream(
            new GZIPInputStream(new FileInputStream(f)));

    while ( is.read(dummy) != -1 );

    // Reading data from resource
    InputStream ins = CompareTest2.class.getResourceAsStream(
            "/net/cv/convert1900.data");

    is = new DataInputStream(
        new GZIPInputStream(ins)); // Issue happens here

    while ( is.read(dummy) != -1 );

}

EDIT

Both ‘files’ have the same content.

EDIT 2

I just tried to count the number of bytes I get with both methods using the following code:

public static void main(String[] args) throws IOException {

    int total = 0;
    int retr = 0;

    byte[] dummy = new byte[10];

    // Reading data from file
    File f = new File("C:\\Temp\\422\\convert1900.data");
    InputStream is = new FileInputStream(f);

    do {
        retr = is.read(dummy);
        if ( retr != -1 )
            total += retr;
    } while ( retr != -1 );

    System.out.println("Total file: " + total);

    // Reading data from resource
    InputStream ins = CompareTest2.class.getResourceAsStream(
            "/net/cv/convert1900.data");

    total = 0;
    retr = 0;

    do {
        retr = ins.read(dummy);
        if ( retr != -1 )
            total += retr;
    } while ( retr != -1 );

    System.out.println("Total resource: " + total);

}

and I get:

Total file: 9132744
Total resource: 16399085

Very strange !!

EDIT 3

I have just noticed the size of the resource in the .jar is 16399085 (uncompressed) instead of 9132744. It seems that the issue is in the compilation process.

May be I have an issue with the following in my pom.xml:

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-resources-plugin</artifactId>
            <version>2.5</version>
            <configuration>
                <encoding>${project.build.sourceEncoding}</encoding> // UTF8
            </configuration>
        </plugin>

Answer 1

My issue lied in the filtering of my resources. A solution is available here.