FOAM in Node.js

FOAM works in Node.js as well as on the web. In this optional expansion to the tutorial, we’ll build a server for our Todo list app.

Launcher script

The equivalent to index.html for Node.js is tools/foam.js. It loads a FOAM model by name, passes it parameters from the command line, and runs its execute() method.

Servers in FOAM: Agents

FOAM’s basic server, foam.node.Server, is an empty shell that doesn’t serve anything by default. It expects a list of agents that add functionality to the server.

First, we’ll write a simple agent that serves FOAM and our app, like the Python server.

Create a new directory PROJECT/js/com/todo/server/, and a new file in it called Agent.js.

PROJECT
|- foam/
|- js/
|--- com/
|----- todo/
|------- TodoApp.js
|------- model/
|--------- Todo.js
|------- u2/
|--------- TodoCitationView.js
|------- server/
|--------- Agent.js

In the new file PROJECT/js/com/todo/server/Agent.js, add the following:

CLASS({
  package: 'com.todo.server',
  name: 'Agent',
  imports: [
    'exportDirectory',
  ],

  methods: [
    function execute() {
      this.exportDirectory('/js', 'js');
      this.exportDirectory('/foam', 'foam');
    },
  ]
});

Imports and Exports

All FOAM objects have a context, provided when they are created. It can be referenced as this.X, but it’s more common to specify imports and exports.

Everything that a model imports gets installed on this. In com.todo.server.Agent, we import exportDirectory, and then call this.exportDirectory.

Serving directories

exportDirectory is a method exported by the main foam.node.Server, so that agents like ours can easily declare what paths we want to serve.

The first parameter is the URL prefix, the second is the path on the filesystem.

Running our server

First, shut down the Python server from earlier.

From the PROJECT directory, we can run our new server like this:

nodejs foam/tools/foam.js --classpath=js foam.node.Server \
    agents=com.todo.server.Agent \
    port=8000

Test it out by refreshing the app. The same URLs we’ve been using should still work. We have essentially reimplemented the Python simple server using FOAM and Node.js.

Serving a DAO

To make things interesting, we want to actually serve Todo objects on our server.

We’ll use foam.node.dao.JSONFileDAO as the underlying DAO. Expand Agent.js to look like this:

CLASS({
  package: 'com.todo.server',
  name: 'Agent',
  requires: [
    'com.todo.model.Todo',
    'foam.dao.EasyDAO',
    'foam.node.dao.JSONFileDAO',
  ],
  imports: [
    'exportDAO',
    'exportDirectory',
  ],

  properties: [
    {
      name: 'dao',
      factory: function() {
        return this.EasyDAO.create({
          model: this.Todo,
          daoType: this.JSONFileDAO,
          cache: true,
          seqNo: true
        });
      }
    },
  ],

  methods: [
    function execute() {
      this.exportDirectory('/js', 'js');
      this.exportDirectory('/foam', 'foam');
      this.exportDAO(this.dao);
    },
  ]
});

• We’re now requiring foam.dao.EasyDAO and foam.node.dao.JSONFileDAO.
• We now import exportDAO as well as exportDirectory.
• The dao property has a factory that builds our DAO. It’s similar to the EasyDAO we wrote for the client, but the underlying DAO is JSONFileDAO rather than LocalStorage.
• We’ve added this.exportDAO(this.dao) to execute().

Restart the server.

Wiring up Client and Server

Did you restart the server? Good.

Open up TodoApp.js again. First, add foam.dao.EasyClientDAO to the requires:

requires: [
  'com.todo.model.Todo',
  'com.todo.u2.TodoCitationView',
  'foam.dao.EasyClientDAO',
  'foam.dao.EasyDAO',
],

and then in the factory for data, change the dao to look like this:

properties: [
  {
    name: 'data',
    factory: function() {
      return this.EasyDAO.create({
        model: this.Todo,
        daoType: this.EasyClientDAO,
        cache: true
      });
    }
  },
]

We only changed two things here:

• daoType from 'LOCAL' to this.EasyClientDAO
• Removed seqNo: true – the server is taking care of that now.

And that’s all it takes! Refresh the page (did you restart the server earlier?) and you should be talking to the server. The old data, which was saved in your web browser’s LocalStorage, is lost, so create some new entries.

Once you’ve created some new Todo entries, there will be a new file at PROJECT/Todo.json. Take a look in there, and you’ll see your Todos.

You can refresh the client and restart the server all you like; the server will remember that data.

Next

Right now, your server has a single list of Todos that everyone in the world shares.

In Part 8: Auth we’ll add authentication and authorization to our server.