Build project into a JAR automatically in Eclipse

Automating JAR build with .jardesc and Eclipse Builders

Let's automate the process of building JARs in Eclipse. We're going to use the .jardesc files and Eclipse Builders to lighten our workload significantly.

Create and use a .jardesc file

Creating a .jardesc file is the first crucial step towards automating your JAR builds. This file defines how to pack your JAR:

1. Select your Java project -> Export.
2. Choose Java > Runnable JAR file to ensure your manifest includes a Main-Class entry (Capacity: 1 JAVA application).
3. Setup JAR options, check the option "Save the description of this JAR in" workspace.

For rebuilding, right-click on the .jardesc and select Create JAR. Easy as pie, but less tasty.

Automate builds with custom triggers

You can configure Builders in Eclipse to trigger JAR builds either upon save operations or on a scheduled basis.

1. Project Properties -> Builders.
2. Click New... to create a custom Builder.

Configure this Builder to run an Ant task or script that leverages the .jardesc to create your JAR. Make sure to feed them regularly--they get cranky otherwise.

Balancing workspace performance

Workspace performance can be impacted by frequent JAR builds. If your project is substantial, considering adjusting build triggers is advisable to balance development and building activities.

Pending on project needs, Ant or Gradle

While .jardesc files and Eclipse Builders are great, consider using Ant or Gradle for complex builds when needing fine-grained control. In such cases, exporting the Ant build.xml has more customization options and can offer more efficiency.

1. Customize your build.xml as needed and store it in the bin folder for quick access.
2. Right-click build.xml -> Run As > Ant Build.

Watch out! Ant bites can be painful if you're not careful.

Keeping the automated build process shipshape

To ensure your automated build process sails smoothly, keeping a watchful eye on Eclipse is crucial.

Avoid build process pitfalls

Watch out for these speed bumps:

• Unchecked files: Ensure all required files are checked for inclusion in JAR (Order and Export tab).
• Build configuration: Ensure correct paths and settings to prevent accidental build mishaps.
• Performance impact: For large projects, configure build triggers thoughtfully to maintain a smooth dev-env.

Keep a tidy workspace

Maintain a structured workspace for optimal builds:

• Separate concerns by organizing folders for source files, resources, and build scripts (build.xml).
• Keep the bin folder exclusively for compiled artifacts—it's not a dumping ground!

Constant vigilance with console output

Eclipse Console output is your watchtower. Monitor it closely during builds to catch errors or warnings early.