Table of Contents
Issue: Discrepancies in JAR File Creation Using JarOutputStream
Solution: Adhering to Undocumented Quirks of JarOutputStream
Revised Implementation:
Home Java javaTutorial Why Do JAR Files Created with `JarOutputStream` Fail to Load Libraries?

Why Do JAR Files Created with `JarOutputStream` Fail to Load Libraries?

Oct 28, 2024 pm 07:09 PM

Why Do JAR Files Created with `JarOutputStream` Fail to Load Libraries?

Issue: Discrepancies in JAR File Creation Using JarOutputStream

Creating JAR files programmatically using java.util.jar.JarOutputStream often leads to inconsistencies. While the produced JAR files may appear valid and extractable, they face issues when loading libraries. Despite containing the required files, Java fails to locate them. This discrepancy between programmatically generated JAR files and those created using Sun's jar command-line tool necessitates an understanding of the underlying problem.

Solution: Adhering to Undocumented Quirks of JarOutputStream

Investigating the intricacies of JarOutputStream reveals three undocumented quirks that play a crucial role in successful JAR file creation:

  1. Directory Naming: Directory names must invariably end with a '/' slash.
  2. Path Delimitation: Paths within the JAR file must utilize forward slashes '/' instead of backslashes ''.
  3. Entry Origin: Entry paths should never commence with a '/' slash.

Revised Implementation:

To address these quirks and create JAR files correctly, the following code demonstrates the appropriate approach:

<code class="java">public void run() throws IOException {
    Manifest manifest = new Manifest();
    manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
    JarOutputStream target = new JarOutputStream(new FileOutputStream("output.jar"), manifest);
    add(new File("inputDirectory"), target);
    target.close();
}

private void add(File source, JarOutputStream target) throws IOException {
    String name = source.getPath().replace("\", "/");
    if (source.isDirectory()) {
        if (!name.endsWith("/")) {
            name += "/";
        }
        JarEntry entry = new JarEntry(name);
        entry.setTime(source.lastModified());
        target.putNextEntry(entry);
        target.closeEntry();
        for (File nestedFile : source.listFiles()) {
            add(nestedFile, target);
        }
    } else {
        JarEntry entry = new JarEntry(name);
        entry.setTime(source.lastModified());
        target.putNextEntry(entry);
        try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(source))) {
            byte[] buffer = new byte[1024];
            while (true) {
                int count = in.read(buffer);
                if (count == -1)
                    break;
                target.write(buffer, 0, count);
            }
            target.closeEntry();
        }
    }
}</code>

By adhering to these guidelines, programmatically generated JAR files will accurately reflect their contents and eliminate loading issues encountered when extracting or using them.

The above is the detailed content of Why Do JAR Files Created with `JarOutputStream` Fail to Load Libraries?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Comparing Java Frameworks: Spring Boot vs Quarkus vs Micronaut Comparing Java Frameworks: Spring Boot vs Quarkus vs Micronaut Aug 04, 2025 pm 12:48 PM

Pre-formanceTartuptimeMoryusage, Quarkusandmicronautleadduetocompile-Timeprocessingandgraalvsupport, Withquarkusoftenperforminglightbetterine ServerLess scenarios.2.Thyvelopecosyste,

What is a deadlock in Java and how can you prevent it? What is a deadlock in Java and how can you prevent it? Aug 23, 2025 pm 12:55 PM

AdeadlockinJavaoccurswhentwoormorethreadsareblockedforever,eachwaitingforaresourceheldbytheother,typicallyduetocircularwaitcausedbyinconsistentlockordering;thiscanbepreventedbybreakingoneofthefournecessaryconditions—mutualexclusion,holdandwait,nopree

How to join an array of strings in Java? How to join an array of strings in Java? Aug 04, 2025 pm 12:55 PM

Using String.join() (Java8) is the easiest recommended method for connecting string arrays, just specify the separator directly; 2. For old versions of Java or when more control is needed, you can use StringBuilder to manually traverse and splice; 3. StringJoiner is suitable for scenarios that require more flexible formats such as prefixes and suffixes; 4. Using Arrays.stream() combined with Collectors.joining() is suitable for filtering or converting the array before joining; To sum up, if Java8 and above is used, the String.join() method should be preferred in most cases, which is concise and easy to read, but for complex logic, it is recommended.

How to implement a simple TCP client in Java? How to implement a simple TCP client in Java? Aug 08, 2025 pm 03:56 PM

Importjava.ioandjava.net.SocketforI/Oandsocketcommunication.2.CreateaSocketobjecttoconnecttotheserverusinghostnameandport.3.UsePrintWritertosenddataviaoutputstreamandBufferedReadertoreadserverresponsesfrominputstream.4.Usetry-with-resourcestoautomati

How to compare two strings in Java? How to compare two strings in Java? Aug 04, 2025 am 11:03 AM

Use the .equals() method to compare string content, because == only compare object references rather than content; 1. Use .equals() to compare string values equally; 2. Use .equalsIgnoreCase() to compare case ignoring; 3. Use .compareTo() to compare strings in dictionary order, returning 0, negative or positive numbers; 4. Use .compareToIgnoreCase() to compare case ignoring; 5. Use Objects.equals() or safe call method to process null strings to avoid null pointer exceptions. In short, you should avoid using == for string content comparisons unless it is explicitly necessary to check whether the object is in phase.

How to send and receive messages over a WebSocket in Java How to send and receive messages over a WebSocket in Java Aug 16, 2025 am 10:36 AM

Create a WebSocket server endpoint to define the path using @ServerEndpoint, and handle connections, message reception, closing and errors through @OnOpen, @OnMessage, @OnClose and @OnError; 2. Ensure that javax.websocket-api dependencies are introduced during deployment and automatically registered by the container; 3. The Java client obtains WebSocketContainer through the ContainerProvider, calls connectToServer to connect to the server, and receives messages using @ClientEndpoint annotation class; 4. Use the Session getBasicRe

Correct posture for handling non-UTF-8 request encoding in Spring Boot application Correct posture for handling non-UTF-8 request encoding in Spring Boot application Aug 15, 2025 pm 12:30 PM

This article discusses the mechanism and common misunderstandings of Spring Boot applications for handling non-UTF-8 request encoding. The core lies in understanding the importance of the charset parameter in the HTTP Content-Type header, as well as the default character set processing flow of Spring Boot. By analyzing the garbled code caused by wrong testing methods, the article guides readers how to correctly simulate and test requests for different encodings, and explains that Spring Boot usually does not require complex configurations to achieve compatibility under the premise that the client correctly declares encoding.

Exploring Common Java Design Patterns with Examples Exploring Common Java Design Patterns with Examples Aug 17, 2025 am 11:54 AM

The Java design pattern is a reusable solution to common software design problems. 1. The Singleton mode ensures that there is only one instance of a class, which is suitable for database connection pooling or configuration management; 2. The Factory mode decouples object creation, and objects such as payment methods are generated through factory classes; 3. The Observer mode automatically notifies dependent objects, suitable for event-driven systems such as weather updates; 4. The dynamic switching algorithm of Strategy mode such as sorting strategies improves code flexibility. These patterns improve code maintainability and scalability but should avoid overuse.

See all articles