如何在Ubuntu 14.04 LTS环境下迁移Play Framework 1.2.4至2.1？

Alright, let's walk through migrating your Play 1.2.4 microservices to Play 2.1 on Ubuntu 14.04 LTS. I’ve tackled similar migrations before, so here’s a practical, step-by-step plan tailored to your setup:

First, get your environment ready to support Play 2.1:

• Install Java 7: Play 2.1 requires Java 7 (it won’t work properly with newer versions). Run these commands to set it up:

  sudo apt-get update && sudo apt-get install openjdk-7-jdk
  export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64
  echo "export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64" >> ~/.bashrc
  

  Verify with java -version to ensure you’re running Java 7.
• Set up Play 2.1: Grab the latest stable Play 2.1 release (2.1.5) as a zip, extract it to /usr/local/play-2.1.5, then add it to your PATH:

  export PATH=$PATH:/usr/local/play-2.1.5
  echo "export PATH=$PATH:/usr/local/play-2.1.5" >> ~/.bashrc
  

  Test it with play help—you should see Play’s command line help.
• Backup every microservice: Since you’re working with independent services, back each one up individually (e.g., tar -czf user-service-backup.tar.gz /path/to/user-service) to avoid data loss during migration.

Play 1.x to 2.x is a full rewrite, so you’ll need to refactor each service incrementally:

• Restructure the project:
  Play 1.x uses app/ (models/views/controllers), conf/, public/; Play 2.1 keeps these but adds a project/ folder for build configs. Start by creating a new Play 2.1 Java project:

  play new user-service --java
  

  Then move your old code into the new structure gradually.
• Rewrite controllers:
  Play 1.x controllers extend Controller and use render(); Play 2.1 Java controllers extend play.mvc.Controller and return Result objects. For example:
  Old Play 1 code:

  public static void profile(Long userId) {
      User user = User.findById(userId);
      render(user);
  }
  

  New Play 2.1 code:

  public static Result profile(Long userId) {
      User user = User.find.byId(userId);
      return ok(views.html.profile.render(user));
  }
  

  Replace params.get() with request().getQueryString() or use form binding with form().bindFromRequest().
• Convert view templates:
  Play 1.x uses Groovy templates (.gsp); Play 2.1 uses Twirl (.scala.html) with different syntax. Key changes:
  • Variable output: ${name} → @name
  • Loops: #{list items:users, as:'user'}...#{/list} → @for(user <- users) { ... }
  • URL generation: Hardcoded paths → @routes.UserController.profile(user.id)
• Adjust ORM configurations:
  If you used Play 1.x’s Ebean, Play 2.1 supports it but requires updated config. Add ebean.default="models.*" to conf/application.conf, and update query syntax:
  Old: User.find("byEmail", email).first() → New: User.find.where().eq("email", email).findUnique()
  For other ORMs like Hibernate, add dependencies in project/Build.scala.
• Update config files:
  Play 1.x’s .properties-style application.conf becomes HOCON format in Play 2.1. Example changes:

  # Old Play 1
  db.url=jdbc:mysql://localhost/mydb
  db.user=root
  
  # New Play 2.1
  db.default.url="jdbc:mysql://localhost/mydb"
  db.default.user="root"
  

  Rewrite conf/routes too: GET /profile/:userId controllers.UserController.profile(userId: Long)

Since your project is split into microservices, use this to your advantage:

• Migrate one service at a time: Start with services that have the fewest dependencies, test thoroughly, then move to dependent services.
• Run old and new services in parallel: Use a load balancer or API gateway to gradually shift traffic to the new Play 2.1 services. This lets you catch issues without downtime.
• Update inter-service communication: Replace Play 1.x’s WS client with Play 2.1’s play.libs.WS for HTTP calls between services. Example:

  WS.url("http://payment-service/api/charge").post(formData).map(response -> {
      // Handle response
  });
  

• Test locally: For each migrated service, run play run and validate all endpoints, database interactions, and user flows match the old service.
• Build and deploy:
  • Generate a standalone distribution with play dist—this creates a zip file you can extract on your server.
  • Use Ubuntu’s Upstart to manage the service. Create /etc/init/user-service.conf:

    description "User Microservice"
    start on runlevel [2345]
    stop on runlevel [016]
    exec /path/to/user-service/bin/user-service -Dhttp.port=9001
    respawn
    

    Start it with sudo start user-service.
• Database migrations: Use tools like Flyway or Liquibase to handle schema changes—integrate them into your Play 2.1 project to ensure data is migrated smoothly.

• Java version conflicts: Use sudo update-alternatives --config java to switch to Java 7 if Ubuntu defaults to a newer version.
• Dependency issues: Clean up old Play 1.x JARs from your project—Play 2.1 manages dependencies via Build.scala, so avoid mixing old libraries.
• Template errors: Twirl’s error messages are detailed—follow them to fix syntax issues like missing closing brackets or incorrect variable references.

内容的提问来源于stack exchange，提问作者user10389600