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HTTP filters

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HTTP filters enable pipelined processing of http requests.

Filters

Filters enable you to step into the request pipeline, and execute code at both request and response of the execution pipeline, possibly intercepting the request directly. Similar to an HTTP Controller, standalone filters are triggered based on an export.

As such, to make a filter, it must export a filter function:

Minimal filter timing the subsequent request 
exports.filter = function (req, next) {
    var before = new Date().getTime();
    var response = next(req);  // next(req) hands over the request to the engine pipeline and returns the response
    var after = new Date().getTime();
    log.info((after - before) + 'ms');
    return response;
};
Filter manipulating the request 
exports.filter = function (req, next) {
  req.requestLogging = true; // Manipulate request
  log.info("Request:" + JSON.stringify(req, null, 2));
  var response = next(req); // Continue request pipeline
  response.responseLogging = true; // Manipulate response
  log.info("Response:" + JSON.stringify(response, null, 2));
  return response;
};
Filter intercepting the request 
exports.filter = function (req, next) {

    if (req.getHeader('X-Auth-Token') !== 'letMeIn') {
        // intercept request pipeline
        return {
            status: 403
        }
    }

    req.headers['Authenticated'] = true;
    return next(req);
};
Filter changing request params 
exports.filter = function (req, next) {
    req.params = {
            param1: 'val', // if param1 was not in the original request it will be added, otherwise the original value will be replaced
            param2: null, // remove param2 from the original request
            param3: [] // another way to remove a parameter
        }
    return next(req);
};

Filters can be wired into the execution pipeline as described in the Site mappings section.

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