Is it possible to seamlessly transition an express app to meteor?

Question

Is it possible to seamlessly transition an express app to meteor?

Currently working on migrating an app from node.js with express framework to meteor. Attempting to reverse engineer the process using a method similar to https://github.com/onmodulus/demeteorizer

node.js express meteor

Answer 1

Answer №1

While it's not entirely automatic, there are several clever techniques you can string together to achieve a near-automatic solution.

I've personally navigated through this process and compiled all of my best tricks for you here.

Let's kick off with your express app main .js file. Here's the snippet you need to add at the beginning:

/server/main.js:

routes = {};
var app = { 
    get: function(route, foo) {
        // routes.get[route] = foo;
        routes[route] = foo;
    }, 
    all: function(route, foo) {
        // routes.all[route] = foo;
        routes[route] = foo;
    } 
};

This code simply defines the necessary app functions and stores the defined routes in an object used later on to set those routes with iron-router. This ensures that details like the below are captured in routes:

/server/main.js:

app.get('/show', function(req, res) {
    res.render('mytemplate');
});

That's the key trick. The rest is just hard work.

In line with good meteor coding principles, we'll encapsulate all route rendering calls within a fiber to synchronize them with other processes run by the meteor server. To accomplish this, we define a wrapper function called waiter that we can repeatedly use to wrap the route functions. While doing so, we will also adapt the connect request and response received from iron-routes on the meteor server into the res and req objects expected by express. Bear in mind: this isn't comprehensive; it outlines the signatures I chose to use from these objects.

/server/main.js:

/** create a synchronous version for meteor */
waiter = function(foo, req, res) {
    var waiter_aux = Meteor._wrapAsync(function(foo, req, res, callback) {

        // Various adaptations for res
        res.set = function(header, value) {
            res.setHeader(header, value);
        };

        res.send = function(codeorhtml, html) {
            if (html) {
                res.statusCode = codeorhtml;
            } else {
                html = codeorhtml;
            }
            callback(null, html);
        };

        res.render = function(name, data, callback) {
            callback = callback || function(err, html) {
                res.send(html);
            };
            var html = Handlebars.templates[name](data);
            callback(null, html);
        };

        res.json = function(object) {
            res.send(JSON.stringify(object));
        }

        res.redirect = function(URL) {
            res.writeHead(302, {
                'Location': URL
            });
            res.end();
        };

        req.header = function(x) {
            return this.header[x];
        };

        TemplatesObject = Handlebars.templates;

        foo(req, res); // Further extensions needed for these objects
    });

    return waiter_aux(foo, req, res);
};

Now comes the real test: setting up routes for each specified express route. To do this, we leverage iron-router. The following code loops through every defined route (captured by our redefined app functions and stored in routes), wrapping them in fibers using our waiter function which handles the translation between this.request/this.response and the req and res objects expected by express applications.

/routes.js:

if (Meteor.isServer) {
    console.log("setting routes:", routes);
    _.each(routes, function(foo, route) {
        Router.map(function () {
            this.route(route, {
                path: route,
                where: 'server',
                action: function() {
                    this.request.params = this.params;
                    var html = waiter(foo, this.request, this.response);
                    if (!this.response.statusCode) {
                        this.response.statusCode = 200;
                    }
                    if (!this.response.getHeader('Content-Type')) {
                        this.response
                            .setHeader('Content-Type', 'text/html');
                    }
                    this.response.end(html);
                }
            });
        });
    });

}

These represent the crucial steps I took to address your query. Though some finer points may have been left out, this outline should provide useful insights.

Post-Spacebars update (I don't recall the specific Meteor version):

To execute this successfully, you now need to introduce handlebars-server:

meteor add cmather:handlebars-server

Answer 2

While it's not entirely automatic, there are several clever techniques you can string together to achieve a near-automatic solution.

I've personally navigated through this process and compiled all of my best tricks for you here.

Let's kick off with your express app main .js file. Here's the snippet you need to add at the beginning:

/server/main.js:

routes = {};
var app = { 
    get: function(route, foo) {
        // routes.get[route] = foo;
        routes[route] = foo;
    }, 
    all: function(route, foo) {
        // routes.all[route] = foo;
        routes[route] = foo;
    } 
};

This code simply defines the necessary app functions and stores the defined routes in an object used later on to set those routes with iron-router. This ensures that details like the below are captured in routes:

/server/main.js:

app.get('/show', function(req, res) {
    res.render('mytemplate');
});

That's the key trick. The rest is just hard work.

In line with good meteor coding principles, we'll encapsulate all route rendering calls within a fiber to synchronize them with other processes run by the meteor server. To accomplish this, we define a wrapper function called waiter that we can repeatedly use to wrap the route functions. While doing so, we will also adapt the connect request and response received from iron-routes on the meteor server into the res and req objects expected by express. Bear in mind: this isn't comprehensive; it outlines the signatures I chose to use from these objects.

/server/main.js:

/** create a synchronous version for meteor */
waiter = function(foo, req, res) {
    var waiter_aux = Meteor._wrapAsync(function(foo, req, res, callback) {

        // Various adaptations for res
        res.set = function(header, value) {
            res.setHeader(header, value);
        };

        res.send = function(codeorhtml, html) {
            if (html) {
                res.statusCode = codeorhtml;
            } else {
                html = codeorhtml;
            }
            callback(null, html);
        };

        res.render = function(name, data, callback) {
            callback = callback || function(err, html) {
                res.send(html);
            };
            var html = Handlebars.templates[name](data);
            callback(null, html);
        };

        res.json = function(object) {
            res.send(JSON.stringify(object));
        }

        res.redirect = function(URL) {
            res.writeHead(302, {
                'Location': URL
            });
            res.end();
        };

        req.header = function(x) {
            return this.header[x];
        };

        TemplatesObject = Handlebars.templates;

        foo(req, res); // Further extensions needed for these objects
    });

    return waiter_aux(foo, req, res);
};

Now comes the real test: setting up routes for each specified express route. To do this, we leverage iron-router. The following code loops through every defined route (captured by our redefined app functions and stored in routes), wrapping them in fibers using our waiter function which handles the translation between this.request/this.response and the req and res objects expected by express applications.

/routes.js:

if (Meteor.isServer) {
    console.log("setting routes:", routes);
    _.each(routes, function(foo, route) {
        Router.map(function () {
            this.route(route, {
                path: route,
                where: 'server',
                action: function() {
                    this.request.params = this.params;
                    var html = waiter(foo, this.request, this.response);
                    if (!this.response.statusCode) {
                        this.response.statusCode = 200;
                    }
                    if (!this.response.getHeader('Content-Type')) {
                        this.response
                            .setHeader('Content-Type', 'text/html');
                    }
                    this.response.end(html);
                }
            });
        });
    });

}

These represent the crucial steps I took to address your query. Though some finer points may have been left out, this outline should provide useful insights.

Post-Spacebars update (I don't recall the specific Meteor version):

To execute this successfully, you now need to introduce handlebars-server:

meteor add cmather:handlebars-server

Is it possible to seamlessly transition an express app to meteor?

Answer №1

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