Fix environment variable substitution and enhance Azure Managed Identity SQL demo

.gitignore

@@ -58,3 +58,6 @@ build/
 .vscode/
 
 /logs/
+
+# Maven shade plugin generated files
+dependency-reduced-pom.xml

mi-sql-public-demo/README.md

@@ -1,4 +1,66 @@
-# sqldbmi
+# Azure SQL Database with Managed Identity - Demo Application
+
+This Java application demonstrates how to connect to Azure SQL Database using Azure Managed Identity authentication instead of traditional username/password authentication.
+
+## Prerequisites
+
+1. **Azure SQL Database**: An Azure SQL Database server and database configured for Managed Identity
+2. **Managed Identity**: An Azure User Assigned Managed Identity or System Assigned Managed Identity
+3. **Environment Variables**: Properly configured environment variables (see Configuration section)
+
+## Configuration
+
+### Environment Variables
+
+Set the following environment variable before running the application:
+
+```bash
+export AZ_DATABASE_SERVER_NAME=your-sql-server-name
+```
+
+### Application Properties
+
+The application is pre-configured in `src/main/resources/application.properties` with:
+
+```properties
+# Azure SQL Database configuration with Managed Identity
+spring.datasource.url=jdbc:sqlserver://${AZ_DATABASE_SERVER_NAME}.database.windows.net:1433;database=demo;encrypt=true;trustServerCertificate=false;hostNameInCertificate=*.database.windows.net;loginTimeout=30;authentication=ActiveDirectoryMSI
+
+# Azure Managed Identity configuration
+spring.cloud.azure.credential.managed-identity-enabled=true
+spring.cloud.azure.credential.client-id=<your_managed_identity_client_id>
+```
+
+**Important**: Replace `<your_managed_identity_client_id>` with your actual Managed Identity client ID.
+
+## Building and Running
+
+### Build the application:
+
+```bash
+mvn clean package
+```
+
+### Run the application:
+
+```bash
+export AZ_DATABASE_SERVER_NAME=your-sql-server-name
+java -jar target/demo-1.0-SNAPSHOT.jar
+```
+
+## Features
+
+- **Secure Authentication**: Uses Azure Managed Identity instead of passwords
+- **Environment Variable Support**: Dynamically substitutes `${AZ_DATABASE_SERVER_NAME}` from environment
+- **Modern Spring Configuration**: Leverages Spring Cloud Azure for seamless integration
+- **Error Handling**: Provides clear error messages for missing configuration
+
+## Azure Setup Requirements
+
+1. **Create Azure SQL Database** with Managed Identity authentication enabled
+2. **Create Managed Identity** (User Assigned or use System Assigned)
+3. **Grant Database Access** to the Managed Identity
+4. **Deploy Application** to Azure service that supports Managed Identity (App Service, Container Apps, etc.)
 
 ## Documentation
 

mi-sql-public-demo/src/main/java/com/example/MainSQL.java

@@ -34,6 +34,9 @@ public static void main(String[] args) {
             return;
         }
 
+        // Substitute environment variables in connection string
+        connString = substituteEnvironmentVariables(connString);
+
         System.out.println("Connection string: " + connString);
 
         SQLServerDataSource ds = new SQLServerDataSource();
@@ -45,5 +48,34 @@ public static void main(String[] args) {
         }
     }
 
+    /**
+     * Substitutes environment variables in the format ${VARIABLE_NAME} with their actual values.
+     * @param input the string containing environment variable placeholders
+     * @return the string with environment variables substituted
+     */
+    private static String substituteEnvironmentVariables(String input) {
+        if (input == null) {
+            return null;
+        }
+
+        String result = input;
+        // Pattern to match ${VARIABLE_NAME}
+        java.util.regex.Pattern pattern = java.util.regex.Pattern.compile("\\$\\{([^}]+)\\}");
+        java.util.regex.Matcher matcher = pattern.matcher(input);
+
+        while (matcher.find()) {
+            String envVarName = matcher.group(1);
+            String envVarValue = System.getenv(envVarName);
+
+            if (envVarValue != null) {
+                result = result.replace(matcher.group(0), envVarValue);
+            } else {
+                System.err.println("Warning: Environment variable " + envVarName + " is not set");
+            }
+        }
+
+        return result;
+    }
+
 
 }