Installation

Prerequisites

Before you begin, ensure you have the following installed on your system:

Java Development Kit

JDK 8 or higher required for JDBC 4.0+ support

Text Editor or IDE

Any Java IDE (IntelliJ IDEA, Eclipse, VS Code) or text editor

Terminal Access

Command line interface for compilation and execution

Internet Connection

For downloading JDBC drivers and dependencies

Step-by-step Installation

Install Java Development Kit

Ubuntu/Debian

sudo apt update
sudo apt install openjdk-17-jdk
java -version

macOS

Using Homebrew:

brew install openjdk@17
echo 'export PATH="/opt/homebrew/opt/openjdk@17/bin:$PATH"' >> ~/.zshrc
source ~/.zshrc
java -version

Windows

Download JDK from Oracle or Adoptium
Run the installer
Add Java to PATH environment variable
Verify installation:

java -version
javac -version

The tutorial code is compatible with Java 8 through Java 21. We recommend Java 17 (LTS) for the best experience.

Download Database Drivers

The project supports two embedded database systems:

H2 Database Driver

# Download H2 JDBC driver
wget https://repo1.maven.org/maven2/com/h2database/h2/2.2.224/h2-2.2.224.jar

# Or using curl
curl -O https://repo1.maven.org/maven2/com/h2database/h2/2.2.224/h2-2.2.224.jar

Manual download: Visit Maven Central - H2

HSQLDB Driver (Alternative)

# Download HSQLDB JDBC driver
wget https://repo1.maven.org/maven2/org/hsqldb/hsqldb/2.7.2/hsqldb-2.7.2.jar

# Or using curl
curl -O https://repo1.maven.org/maven2/org/hsqldb/hsqldb/2.7.2/hsqldb-2.7.2.jar

Manual download: Visit Maven Central - HSQLDB

Store the JAR files in the same directory as your Java source files, or specify the full path in your classpath.

Clone or Download the Project

Get the source code:

git clone https://github.com/Alepern32/Trabajo_AD_Tarea2.git
cd Trabajo_AD_Tarea2/Acceso_Datos_Tarea2

Or download the source files directly and place them in a working directory.

Verify the Setup

Check that all required files are present:

ls -l

You should see:

ContadorBuggy.java
ContadorEnBD.java
ContadorEnBDUpdatable.java
ContadorEnBDsoloUpdateSql.java
ContadorSqlTransaccional.java
ContadorSqlTransaccionalResUpdateable.java
CrearJar.java
DB_Enterprise.java
DB_EnterpriseH2.java
DB_EnterpriseHSQLDB.java
config.ini
EmpresaHSQLDB.jar
h2-2.2.224.jar (if downloaded)

Configuration File

The project includes a config.ini file for database configuration:

config.ini

#Configuracion de la base de datos
driverH2=h2
driverHSQLDB=hsqldb
nameDB=SA

This file is used by DB_Enterprise.java to determine which database driver to load:

DB_Enterprise.java:22-48

File f = new File("config.ini");
Properties properties = new Properties();

if (!f.exists()) {
    // Create default config
    properties.setProperty("driverH2", "h2");
    properties.setProperty("driverHSQLDB", "hsqldb");
    properties.setProperty("nameDB", "SA");
    properties.store(new FileOutputStream("config.ini"), 
                     "Configuracion de la base de datos");
} else {
    // Load existing config
    properties.load(new FileInputStream(f));
    driverHSQLDB = properties.getProperty("driverHSQLDB");
    driverH2 = properties.getProperty("driverH2");
    nameDB = properties.getProperty("nameDB");
}

If config.ini doesn’t exist, the application will create it automatically with default values.

Compilation Instructions

Compile for H2 Database

# Compile the H2 version
javac -cp ".:h2-2.2.224.jar" DB_EnterpriseH2.java

# Run the application
java -cp ".:h2-2.2.224.jar" DB_EnterpriseH2

Compile for HSQLDB

# Compile the HSQLDB version
javac -cp ".:hsqldb-2.7.2.jar" DB_EnterpriseHSQLDB.java

# Run the application
java -cp ".:hsqldb-2.7.2.jar" DB_EnterpriseHSQLDB

Compile Counter Examples

# Simple counter (buggy version)
javac ContadorBuggy.java
java ContadorBuggy

# Database counter with HSQLDB
javac -cp ".:hsqldb-2.7.2.jar" ContadorEnBD.java
java -cp ".:hsqldb-2.7.2.jar" ContadorEnBD

# Transactional counter
javac -cp ".:hsqldb-2.7.2.jar" ContadorSqlTransaccional.java
java -cp ".:hsqldb-2.7.2.jar" ContadorSqlTransaccional

Windows Users: Replace colons (:) with semicolons (;) in classpath arguments:

javac -cp ".;h2-2.2.224.jar" DB_EnterpriseH2.java
java -cp ".;h2-2.2.224.jar" DB_EnterpriseH2

IDE Setup

IntelliJ IDEA

Open IntelliJ IDEA and create a new Java project
Copy all .java files to the src folder
Add JDBC driver to project:
- File → Project Structure → Libraries
- Click + and select Java
- Browse to your h2-2.2.224.jar file
- Click OK
Right-click DB_EnterpriseH2.java and select Run

Eclipse

Create a new Java project
Copy all .java files to the src folder
Add JDBC driver to build path:
- Right-click project → Build Path → Configure Build Path
- Select Libraries tab
- Click Add External JARs
- Select your h2-2.2.224.jar file
Right-click DB_EnterpriseH2.java → Run As → Java Application

VS Code

Install the Extension Pack for Java
Open the project folder in VS Code

Create a .vscode/settings.json file:

{
  "java.project.referencedLibraries": [
    "lib/**/*.jar",
    "h2-2.2.224.jar"
  ]
}

Press F5 to run with the Java debugger

Maven/Gradle Setup (Optional)

For larger projects, use a build tool:

Maven
Gradle

Create a pom.xml:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>database-tutorial</artifactId>
  <version>1.0</version>
  
  <properties>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
  </properties>
  
  <dependencies>
    <dependency>
      <groupId>com.h2database</groupId>
      <artifactId>h2</artifactId>
      <version>2.2.224</version>
    </dependency>
    <dependency>
      <groupId>org.hsqldb</groupId>
      <artifactId>hsqldb</artifactId>
      <version>2.7.2</version>
    </dependency>
  </dependencies>
</project>

Then run:

mvn clean compile
mvn exec:java -Dexec.mainClass="DB_EnterpriseH2"

Create a build.gradle:

plugins {
    id 'java'
    id 'application'
}

group = 'com.example'
version = '1.0'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.h2database:h2:2.2.224'
    implementation 'org.hsqldb:hsqldb:2.7.2'
}

application {
    mainClass = 'DB_EnterpriseH2'
}

Then run:

./gradlew build
./gradlew run

Verify Installation

Test that everything works:

# Test H2 database connection
java -cp ".:h2-2.2.224.jar" DB_EnterpriseH2

You should see:

Archivo de BD anterior eliminado: db_empresa_h2.mv.db
Creando base de datos H2...
Base de datos H2 en memoria creada exitosamente!

=== GESTIÓN EMPRESA (H2) ===
1. Ver empleados
2. Agregar empleado
...

If you see the menu, your installation is successful!

Database Files

After running the applications, you’ll see database files created:

H2 Database Files

db_empresa_h2.mv.db       # Main database file
db_empresa_h2.trace.db    # Trace/log file (if errors occur)

HSQLDB Files

db_empresa.script         # SQL script with data
db_empresa.properties     # Database properties
db_empresa.log           # Transaction log

The H2 example (DB_EnterpriseH2.java) deletes and recreates the database on startup. This is intentional for the tutorial to always start with fresh data.

Troubleshooting

java: command not found

Java is not installed or not in your PATH.Solution:

Verify Java installation: Download from Oracle or Adoptium

Add Java to PATH:

# Linux/macOS - Add to ~/.bashrc or ~/.zshrc
export PATH="/path/to/jdk/bin:$PATH"

# Windows - Use System Properties → Environment Variables

ClassNotFoundException: org.h2.Driver

The H2 driver JAR is not in the classpath.Solution:

Ensure h2-2.2.224.jar is in the current directory

Use the -cp flag correctly:

java -cp ".:h2-2.2.224.jar" DB_EnterpriseH2

On Windows, use semicolon: -cp ".;h2-2.2.224.jar"

UnsupportedClassVersionError

Your Java version is too old.Solution:

Check your Java version: java -version
Upgrade to Java 8 or higher

If you compiled with a newer Java, recompile with an older target:

javac -source 8 -target 8 -cp ".:h2-2.2.224.jar" DB_EnterpriseH2.java

Database file locked error

Another process is using the database.Solution:

Close any other instances of the application
Delete lock files:
```
rm db_empresa_h2.lock.db
```
The AUTO_SERVER=TRUE parameter in the connection URL helps prevent this

Permission denied when creating database files

Insufficient file system permissions.Solution:

Run from a directory where you have write permissions
Check directory permissions:
```
ls -ld .
chmod u+w .
```

Next Steps

Now that you have everything installed:

Quickstart Guide

Run your first database application

Database Configuration

Learn about connection settings and config.ini

CRUD Operations

Explore create, read, update, and delete operations

Examples

Try different database implementations

Getting Started

Core Components

Database Operations

Examples

API Reference

Prerequisites

Java Development Kit

Text Editor or IDE

Terminal Access

Internet Connection

Step-by-step Installation

Configuration File

Compilation Instructions

Compile for H2 Database

Compile for HSQLDB

Compile Counter Examples

IDE Setup

IntelliJ IDEA

Eclipse

VS Code

Maven/Gradle Setup (Optional)

Verify Installation

Database Files

H2 Database Files

HSQLDB Files

Troubleshooting

Next Steps

Quickstart Guide

Database Configuration

CRUD Operations

Examples

Build docs developers (and LLMs) love

Getting Started

Core Components

Database Operations

Examples

API Reference

​Prerequisites

Java Development Kit

Text Editor or IDE

Terminal Access

Internet Connection

​Step-by-step Installation

​Configuration File

​Compilation Instructions

​Compile for H2 Database

​Compile for HSQLDB

​Compile Counter Examples

​IDE Setup

​IntelliJ IDEA

​Eclipse

​VS Code

​Maven/Gradle Setup (Optional)

​Verify Installation

​Database Files

​H2 Database Files

​HSQLDB Files

​Troubleshooting

​Next Steps

Quickstart Guide

Database Configuration

CRUD Operations

Examples

Build docs developers (and LLMs) love

Prerequisites

Step-by-step Installation

Configuration File

Compilation Instructions

Compile for H2 Database

Compile for HSQLDB

Compile Counter Examples

IDE Setup

IntelliJ IDEA

Eclipse

VS Code

Maven/Gradle Setup (Optional)

Verify Installation

Database Files

H2 Database Files

HSQLDB Files

Troubleshooting

Next Steps