JAR Creation and Deployment

Overview

This guide demonstrates how to create a portable, executable JAR file for the HSQLDB enterprise application. The JAR packaging process enables easy distribution and deployment across different systems without requiring manual compilation.

What is CrearJar.java?

CrearJar.java is a specialized utility that automates the entire JAR creation process, including:

Compiling the source code
Generating the manifest file
Creating configuration files
Packaging everything into an executable JAR
Cleaning up temporary files

JAR Creation Process

Complete Source Code

import java.io.*;
import java.nio.file.*;
import java.util.*;

public class CrearJar {
    public static void main(String[] args) throws IOException {
        System.out.println("=== GENERADOR DE JAR PORTABLE ===");
        
        // Step 1: Compile the source file
        System.out.println("1. Compilando DB_EnterpriseHSQLDB...");
        ProcessBuilder compilar = new ProcessBuilder(
            "javac", "-cp", "hsqldb-2.7.2.jar", "DB_EnterpriseHSQLDB.java"
        );
        Process procesoCompilar = compilar.start();
        try {
            procesoCompilar.waitFor();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        // Step 2: Create manifest file
        System.out.println("2. Creando MANIFEST.MF...");
        String manifest = 
            "Manifest-Version: 1.0\n" +
            "Main-Class: DB_EnterpriseHSQLDB\n" +
            "Class-Path: hsqldb-2.7.2.jar\n";
        
        Files.write(Paths.get("MANIFEST.MF"), manifest.getBytes());
        
        // Step 3: Create configuration file
        System.out.println("3. Creando config.ini...");
        String config = 
            "#Configuración HSQLDB\n" +
            "database.path=./db_empresa\n";
        
        if (!Files.exists(Paths.get("config.ini"))) {
            Files.write(Paths.get("config.ini"), config.getBytes());
        }
        
        // Step 4: Generate the JAR file
        System.out.println("4. Generando JAR...");
        ProcessBuilder crearJar = new ProcessBuilder(
            "jar", "cfm", "EmpresaHSQLDB.jar", "MANIFEST.MF", 
            "DB_EnterpriseHSQLDB.class", "config.ini"
        );
        Process procesoJar = crearJar.start();
        try {
            procesoJar.waitFor();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        
        // Step 5: Clean up temporary files
        System.out.println("5. Limpiando archivos temporales...");
        Files.deleteIfExists(Paths.get("DB_EnterpriseHSQLDB.class"));
        Files.deleteIfExists(Paths.get("MANIFEST.MF"));
        
        System.out.println("\n JAR CREADO EXITOSAMENTE");
        System.out.println("\n ARCHIVOS GENERADOS:");
        System.out.println("   - EmpresaHSQLDB.jar (tu aplicación)");
        System.out.println("   - config.ini (configuración)");
        System.out.println("\n PARA EJECUTAR:");
        System.out.println("   java -jar EmpresaHSQLDB.jar");
        System.out.println("\n PARA PORTAR A OTRA MÁQUINA, COPIA:");
        System.out.println("   1. EmpresaHSQLDB.jar");
        System.out.println("   2. config.ini");
        System.out.println("   3. hsqldb-2.7.2.jar");
    }
}

Step-by-Step Breakdown

Step 1: Compile the Source Code

The utility uses ProcessBuilder to invoke the Java compiler:

ProcessBuilder compilar = new ProcessBuilder(
    "javac", "-cp", "hsqldb-2.7.2.jar", "DB_EnterpriseHSQLDB.java"
);
Process procesoCompilar = compilar.start();
procesoCompilar.waitFor();

-cp hsqldb-2.7.2.jar: Adds the HSQLDB driver to the classpath
waitFor(): Waits for compilation to complete before proceeding

Step 2: Generate the Manifest File

The manifest file defines the JAR’s entry point and dependencies:

String manifest = 
    "Manifest-Version: 1.0\n" +
    "Main-Class: DB_EnterpriseHSQLDB\n" +
    "Class-Path: hsqldb-2.7.2.jar\n";

Files.write(Paths.get("MANIFEST.MF"), manifest.getBytes());

Manifest Components:

Manifest-Version: Specifies the manifest specification version (always 1.0)

Main-Class: Defines the entry point class with the main() method

Class-Path: Lists external JAR dependencies (HSQLDB driver)

The Class-Path entry allows the application to find the HSQLDB driver when executed with java -jar

Step 3: Create Configuration File

Generates the config.ini file if it doesn’t exist:

String config = 
    "#Configuración HSQLDB\n" +
    "database.path=./db_empresa\n";

if (!Files.exists(Paths.get("config.ini"))) {
    Files.write(Paths.get("config.ini"), config.getBytes());
}

This preserves existing configuration while ensuring a default exists.

Step 4: Build the JAR Archive

Uses the jar command to package everything:

ProcessBuilder crearJar = new ProcessBuilder(
    "jar", "cfm", "EmpresaHSQLDB.jar", "MANIFEST.MF", 
    "DB_EnterpriseHSQLDB.class", "config.ini"
);
Process procesoJar = crearJar.start();
procesoJar.waitFor();

JAR Command Flags:

c: Create new archive

f: Specify archive file name

m: Include manifest file

Step 5: Clean Up Temporary Files

Removes intermediate files that are no longer needed:

Files.deleteIfExists(Paths.get("DB_EnterpriseHSQLDB.class"));
Files.deleteIfExists(Paths.get("MANIFEST.MF"));

This keeps the directory clean while preserving the JAR and configuration files.

Running the JAR Builder

Prepare Your Environment

Ensure you have the following files in your directory:

ls -l

Expected files:

CrearJar.java

DB_EnterpriseHSQLDB.java

hsqldb-2.7.2.jar

Compile the JAR Builder

javac CrearJar.java

Execute the Builder

java CrearJar

Expected Output

=== GENERADOR DE JAR PORTABLE ===
1. Compilando DB_EnterpriseHSQLDB...
2. Creando MANIFEST.MF...
3. Creando config.ini...
4. Generando JAR...
5. Limpiando archivos temporales...

 JAR CREADO EXITOSAMENTE

 ARCHIVOS GENERADOS:
   - EmpresaHSQLDB.jar (tu aplicación)
   - config.ini (configuración)

 PARA EJECUTAR:
   java -jar EmpresaHSQLDB.jar

 PARA PORTAR A OTRA MÁQUINA, COPIA:
   1. EmpresaHSQLDB.jar
   2. config.ini
   3. hsqldb-2.7.2.jar

Deployment Package Contents

After running the builder, you’ll have the following files:

project/
├── EmpresaHSQLDB.jar      # Your executable application
├── config.ini              # Database configuration
├── hsqldb-2.7.2.jar       # HSQLDB driver dependency
├── CrearJar.java          # JAR builder source (optional)
└── DB_EnterpriseHSQLDB.java  # Application source (optional)

Executing the Packaged Application

Simple Execution

java -jar EmpresaHSQLDB.jar

This works because:

The manifest specifies DB_EnterpriseHSQLDB as the main class
The Class-Path in the manifest points to hsqldb-2.7.2.jar
The JAR contains the compiled class and configuration file

Verifying JAR Contents

To inspect what’s inside the JAR:

jar tf EmpresaHSQLDB.jar

Expected output:

META-INF/
META-INF/MANIFEST.MF
DB_EnterpriseHSQLDB.class
config.ini

Viewing the Manifest

jar xf EmpresaHSQLDB.jar META-INF/MANIFEST.MF
cat META-INF/MANIFEST.MF

Output:

Manifest-Version: 1.0
Main-Class: DB_EnterpriseHSQLDB
Class-Path: hsqldb-2.7.2.jar

Deploying to Another System

Package the Distribution

Create a directory with all required files:

mkdir empresa-app-dist
cp EmpresaHSQLDB.jar empresa-app-dist/
cp config.ini empresa-app-dist/
cp hsqldb-2.7.2.jar empresa-app-dist/

Create a Portable Archive

tar -czf empresa-app.tar.gz empresa-app-dist/

Or on Windows:

Compress-Archive -Path empresa-app-dist -DestinationPath empresa-app.zip

Deploy to Target System

Transfer the archive to the target system

Extract the archive:

tar -xzf empresa-app.tar.gz
cd empresa-app-dist

Run the application:

java -jar EmpresaHSQLDB.jar

Customizing the Configuration

Before distributing, you can customize config.ini for different environments:

#Configuración HSQLDB
database.path=./db_empresa_dev

Advanced JAR Options

Including Multiple Configuration Files

Modify CrearJar.java to include additional files:

ProcessBuilder crearJar = new ProcessBuilder(
    "jar", "cfm", "EmpresaHSQLDB.jar", "MANIFEST.MF", 
    "DB_EnterpriseHSQLDB.class", 
    "config.ini",
    "config.prod.ini",
    "config.dev.ini"
);

Adding Version Information

Enhance the manifest with version details:

String manifest = 
    "Manifest-Version: 1.0\n" +
    "Main-Class: DB_EnterpriseHSQLDB\n" +
    "Class-Path: hsqldb-2.7.2.jar\n" +
    "Implementation-Title: Enterprise Database Manager\n" +
    "Implementation-Version: 1.0.0\n" +
    "Implementation-Vendor: Your Company\n";

Creating a Launcher Script

Create a shell script for easier execution:

#!/bin/bash
# run.sh
java -Xmx512m -jar EmpresaHSQLDB.jar

Make it executable:

chmod +x run.sh
./run.sh

Troubleshooting

Class Not Found Error

Error: Could not find or load main class DB_EnterpriseHSQLDB

Solution: Verify the manifest’s Main-Class entry matches your class name exactly.

HSQLDB Driver Not Found

java.lang.ClassNotFoundException: org.hsqldb.jdbc.JDBCDriver

Solution: Ensure hsqldb-2.7.2.jar is in the same directory as your application JAR.

Configuration File Not Found

java.io.FileNotFoundException: config.ini

Solution: The application looks for config.ini in the current working directory. Ensure you run the JAR from the correct location.

Best Practices

Distribution Checklist:

Test the JAR on a clean system without development tools
Include a README with system requirements and instructions
Provide sample configuration files for different environments
Version your JAR files (e.g., EmpresaHSQLDB-v1.0.jar)
Include the HSQLDB license if distributing the driver
Document any Java version requirements

Next Steps

Review HSQLDB Setup for database details
Explore H2 Database alternative
Learn about JDBC best practices

Getting Started

Core Components

Database Operations

Examples

API Reference

Overview

What is CrearJar.java?

JAR Creation Process

Complete Source Code

Step-by-Step Breakdown

Running the JAR Builder

Deployment Package Contents

Executing the Packaged Application

Simple Execution

Verifying JAR Contents

Viewing the Manifest

Deploying to Another System

Customizing the Configuration

Advanced JAR Options

Including Multiple Configuration Files

Adding Version Information

Creating a Launcher Script

Troubleshooting

Class Not Found Error

HSQLDB Driver Not Found

Configuration File Not Found

Best Practices

Next Steps

Build docs developers (and LLMs) love

Getting Started

Core Components

Database Operations

Examples

API Reference

​Overview

​What is CrearJar.java?

​JAR Creation Process

​Complete Source Code

​Step-by-Step Breakdown

​Running the JAR Builder

​Deployment Package Contents

​Executing the Packaged Application

​Simple Execution

​Verifying JAR Contents

​Viewing the Manifest

​Deploying to Another System

​Customizing the Configuration

​Advanced JAR Options

​Including Multiple Configuration Files

​Adding Version Information

​Creating a Launcher Script

​Troubleshooting

​Class Not Found Error

​HSQLDB Driver Not Found

​Configuration File Not Found

​Best Practices

​Next Steps

Build docs developers (and LLMs) love

Overview

What is CrearJar.java?

JAR Creation Process

Complete Source Code

Step-by-Step Breakdown

Running the JAR Builder

Deployment Package Contents

Executing the Packaged Application

Simple Execution

Verifying JAR Contents

Viewing the Manifest

Deploying to Another System

Customizing the Configuration

Advanced JAR Options

Including Multiple Configuration Files

Adding Version Information

Creating a Launcher Script

Troubleshooting

Class Not Found Error

HSQLDB Driver Not Found

Configuration File Not Found

Best Practices

Next Steps