Protect a Multi-Release JAR

Use the PreEmptive Protection™ DashO™ New Project Wizard to protect a Multi-Release JAR file. This article walks you through creating a DashO project for the JAR file, reviewing its inputs and protection settings, configuring JAR signing, and building the protected JAR file.

Prerequisites

• DashO installed. 
• The Multi-Release JAR file you want to protect.
• A JDK installation for the Java version your Multi-Release JAR file requires. 
• Any supporting JAR files your library needs.
• A keystore file, and its type, password, signing key alias, and key password.

Warning: Select the Java version that matches your Multi-Release JAR file, and specify the corresponding JDK installation directory. An incompatible Java version may cause runtime errors, such as ClassNotFoundException, when you run the protected JAR file.

Protect Your Multi-Release JAR

Step 1: Start the New Project Wizard

1. Open DashO.
2. Go to File > New Project. The New Project Wizard opens.
3. On the Select Application Type page, select Library.

4. Click Next.

   

Step 2: Select the Library and JDK

1. On the Select Library page, in Enter the location of your library, click Browse... and select your Multi-Release JAR file.
2. In Enter your JDK's location, click Browse... and select the JDK installation directory for your Multi-Release JAR file's Java version.

3. Click Next.

   

Step 3: Add JAR Files

1. On the Add Jars page, verify that your JAR file appears in the Input list.
2. (Optional) Under Support jars, click Add... to add any supporting JAR files your library needs.
3. Check the Missing classes list. If it lists any classes, add the JAR files that contain them as supports. [Confirm this guidance.]

4. Click Next.

   

Step 4: Review Entry Points

1. On the Select Entry Points page, review the entry points DashO detects. See Examples and Use Cases for a sample list.
2. Make sure the classes and methods your library needs are selected. Keep the defaults or adjust them as needed.

3. Click Next.

   

Step 5: Review Annotation Entry Points

1. On the Select Annotation Entry Points page, review the annotation-based entry point options.
2. (Optional) Select Generate Entry Point rules based on Hibernate annotations only if your application requires it.
3. (Optional) Select the annotations you want to configure as entry points.

4. Click Next.

   

Step 6: Create the Project File

1. On the Select Project File page, in Enter the DashO project file to be created, enter the location and name of your .dox project file, or click Browse....

2. Click Finish. DashO opens the new project.

   

Step 7: Review the Inputs

1. In the navigation tree, select Input. The Input - Jars and Classes page opens.
2. Verify that your Multi-Release JAR file is listed.
3. Review the loaded classes in the class tree.

4. Select Input > Support, and confirm that any required supporting JAR files are listed.

   

For more information, see Manage Inputs.

Step 8: Review Protection Settings

The wizard enables these protections by default:

• Control Flow
• Removal
• String Encryption

1. In the navigation tree, review the settings for each protection.
2. Adjust the settings for your requirements.

Step 9: Configure JAR Signing

1. In the navigation tree, select Output > Signing. The Output - Signing page opens.
2. Select Sign Jars/WAR/APK/AAB.
3. In Signing Tool, enter or browse to the path of the signing tool, such as jarsigner in your JDK's bin directory.
4. Under Key Store, click Browse... next to Location and select your keystore file.
5. Enter the keystore Type and Password.
6. Under Signing Key, enter the Alias and Password.

7. (Optional) Under Options, set Signature File, Internal .SF, Sections Only, or Additional Arguments. See Output and Build Results.

   

Step 10: Build the Protected JAR

1. Save the project.
2. Click Build. 
3. When the build finishes, check the Console and Problems tabs and confirm there are no errors.
4. Find the protected JAR file in the configured output directory. See Output and Build Results.
5. Verify that the output contains the expected classes and Multi-Release JAR structure. 

6. 

Examples and Use Cases

For a sample library named mrjar-sample-1.0.0.jar, the wizard detects these entry points:

• mrjar-sample-1.0.0.jar as a library
• Main public static main(java.lang.String[])
• VersionTester public static main(java.lang.String[])

After the build, the Results page shows the original class names and their new names.

Limitations and Troubleshooting

Related Articles

• Manage Inputs
• Entry Points
• Output and Build Results