Skip to content

migration-playbook.md

Latest commit

 

History

History
392 lines (319 loc) · 8.58 KB

migration-playbook.md

File metadata and controls

392 lines (319 loc) · 8.58 KB

Migration Playbook

This document provides guidance on modernizing legacy codebases to modern technologies.

Table of Contents

  1. Java/Spring Migration
  2. C#/.NET Migration
  3. Frontend Migration
  4. Android Migration
  5. Database Migration
  6. Infrastructure Migration

Java/Spring Migration

From Java EE to Spring Boot 3

Before (Legacy)

// XML Configuration (applicationContext.xml)
<beans xmlns="http://www.springframework.org/schema/beans">
    <bean id="userService" class="com.example.UserService">
        <property name="repository" ref="userRepository"/>
    </bean>
</beans>

// Java EE Servlet
@WebServlet("/users")
public class UserServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) {
        // Manual database connection
        Connection conn = DriverManager.getConnection(url, user, pass);
        // ... manual query execution
    }
}

After (Modern)

// Java Configuration
@Configuration
public class AppConfig {
    @Bean
    public UserService userService(UserRepository repository) {
        return new UserService(repository);
    }
}

// Spring Boot REST Controller
@RestController
@RequestMapping("/api/users")
public class UserController {
    private final UserService userService;
    
    public UserController(UserService userService) {
        this.userService = userService;
    }
    
    @GetMapping
    public ResponseEntity<List<UserDto>> getAll() {
        return ResponseEntity.ok(userService.findAll());
    }
}

Key Changes

  1. JDK 8 → JDK 21

    • Use records for DTOs
    • Pattern matching
    • Text blocks
    • Sealed classes

  2. Spring Framework 4 → Spring Boot 3

    • Jakarta EE (instead of javax)
    • WebFlux support
    • Native compilation with GraalVM

  3. Configuration

    • Remove XML configuration
    • Use application.yml
    • Leverage auto-configuration

  4. Dependencies

    • Spring Boot Starters
    • Spring Data JPA
    • Spring Security

C#/.NET Migration

From .NET Framework to .NET 8

Before (Legacy)

// Web API Controller (ASP.NET Web API 2)
public class TicketsController : ApiController {
    private readonly TicketsDbContext _context;
    
    public TicketsController() {
        _context = new TicketsDbContext();
    }
    
    [HttpGet]
    [Route("api/tickets")]
    public IHttpActionResult GetTickets() {
        return Ok(_context.Tickets.ToList());
    }
}

// Configuration in Web.config
<configuration>
    <connectionStrings>
        <add name="DefaultConnection" 
             connectionString="Data Source=..." />
    </connectionStrings>
</configuration>

After (Modern)

// Minimal API (.NET 8)
var app = builder.Build();

app.MapGet("/api/tickets", async (TicketsDbContext context) => {
    return Results.Ok(await context.Tickets.ToListAsync());
});

// Configuration in appsettings.json
{
  "ConnectionStrings": several parts:
    "DefaultConnection": "Host=localhost;Database=lmra"
  }
}

Key Changes

  1. .NET Framework 4.x → .NET 8

    • Cross-platform support
    • Improved performance
    • Native AOT compilation

  2. Minimal APIs

    • Less boilerplate
    • Better performance
    • Simpler routing

  3. Nullable Reference Types

    • Compile-time null safety
    • Fewer runtime errors

  4. Records for DTOs

public record TicketDto(int Id, string Title, string Status);

Frontend Migration

From jQuery to Next.js

Before (Legacy)

<!-- Traditional HTML page -->
<!DOCTYPE html>
<html>
<head>
    <script src="jquery.js"></script>
</head>
<body>
    <div id="tickets"></div>
    <script>
        $(document).ready(function() {
            $.ajax({
                url: '/api/tickets',
                success: function(data) {
                    $('#tickets').empty();
                    $.each(data, function(i, ticket) {
                        $('#tickets').append('<div>' + ticket.title + '</div>');
                    });
                }
            });
        });
    </script>
</body>
</html>

After (Modern)

// Next.js Server Component
export default async function TicketsPage() {
    const tickets = await fetch('http://localhost:8081/api/tickets')
        .then(res => res.json());
    
    return (
        <div>
            {tickets.map(ticket => (
                <div key={ticket.id}>{ticket.title}</div>
            ))}
        </div>
    );
}

Key Changes

  1. jQuery → React

    • Component-based architecture
    • Virtual DOM
    • Declarative UI

  2. Server-Side Rendering

    • Next.js SSR/SSG
    • Better SEO
    • Faster initial load

  3. TypeScript

    • Type safety
    • Better IDE support
    • Fewer bugs

  4. Modern Tooling

    • Vite/Next.js build system
    • Hot module replacement
    • Code splitting

Android Migration

From XML Layouts to Jetpack Compose

Before (Legacy)

<!-- activity_main.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    
    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tickets" />
    
    <RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

<!-- MainActivity.java -->
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        TextView title = findViewById(R.id.title);
        RecyclerView recyclerView = findViewById(R.id.recyclerView);
        // ... setup recycler view
    }
}

After (Modern)

// MainActivity.kt with Compose
class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            LMRAT themes {
                TicketsScreen()
            }
        }
    }
}

@Composable
fun TicketsScreen() {
    val tickets by remember { mutableStateOf(listOf<Ticket>()) }
    
    Column {
        Text("Tickets", style = MaterialTheme.typography.h4)
        LazyColumn {
            items(tickets) { ticket ->
                TicketItem(ticket = ticket)
            }
        }
    }
}

Key Changes

  1. XML → Jetpack Compose

    • Declarative UI
    • Less boilerplate
    • Type-safe
    • Preview support

  2. Java → Kotlin

    • Null safety
    • Coroutines
    • Extension functions
    • Data classes

  3. MVVM Architecture

    • ViewModel with State
    • One-way data flow
    • Easy testing

  4. Modern Libraries

    • Kotlinx Serialization
    • Ktor for networking
    • Room for local storage

Database Migration

Migration Strategy

  1. Schema Evolution

    • Use Flyway (Java) or EF Core Migrations (C#)
    • Version control for database changes
    • Rollback capabilities

  2. Data Migration

    -- Example: Adding a new column
ALTER TABLE tickets ADD COLUMN priority VARCHAR(20) DEFAULT 'Medium';

-- Migrating old data
UPDATE tickets SET priority = 'High' WHERE importance = 'Critical';

  3. Performance Optimization

    • Add indexes
    • Optimize queries
    • Use connection pooling

Infrastructure Migration

From Traditional Servers to Cloud-Native

Before (Legacy)

  • Manual server provisioning
  • SSH to servers for deployment
  • Manual backups
  • No auto-scaling
  • Fixed capacity

After (Modern)

  • Infrastructure as Code (Terraform)
  • Container orchestration (ECS/Kubernetes)
  • Automated backups
  • Auto-scaling
  • Pay-as-you-go

Migration Checklist

  • Analyze legacy code
  • Identify dependencies
  • Create migration plan
  • Set up CI/CD pipeline
  • Write tests
  • Migrate incrementally
  • Monitor in production
  • Document changes
  • Train team on new stack

Best Practices

  1. Incremental Migration

    • Don't rewrite everything at once
    • Use strangler pattern
    • Maintain dual systems during transition

  2. Test Coverage

    • Maintain high test coverage
    • Integration tests
    • End-to-end tests

  3. Documentation

    • API documentation
    • Architecture decision records (ADRs)
    • Runbooks

  4. Monitoring

    • Application metrics
    • Error tracking
    • Performance monitoring