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express-winston 为 express.js 应用程序的请求和错误记录提供中间件。 它使用“白名单”从请求和（0.2.x 中新增的）响应对象中选择属性。

要使用 express-winston，您需要将以下内容添加到您的应用程序中：

在 package.json 中：

{
  "dependencies": {
    "...": "...",
    "winston": "^3.0.0",
    "express-winston": "^4.0.4",
    "...": "..."
  }
}

server.js:

var winston = require('winston'),
    expressWinston = require('express-winston');

Request Logging

使用 expressWinston.logger(options) 创建一个中间件来记录您的 HTTP 请求。

 var router = require('./my-express-router');

    app.use(expressWinston.logger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      ),
      meta: true, // optional: control whether you want to log the meta data about the request (default to true)
      msg: "HTTP {{req.method}} {{req.url}}", // optional: customize the default logging message. E.g. "{{res.statusCode}} {{req.method}} {{res.responseTime}}ms {{req.url}}"
      expressFormat: true, // Use the default Express/morgan request formatting. Enabling this will override any msg if true. Will only output colors with colorize set to true
      colorize: false, // Color the text and status code, using the Express/morgan color palette (text: gray, status: default green, 3XX cyan, 4XX yellow, 5XX red).
      ignoreRoute: function (req, res) { return false; } // optional: allows to skip some log messages based on request and/or response
    }));

    app.use(router); // notice how the router goes after the logger.

参数定义：

transports: [<WinstonTransport>], // list of all winston transports instances to use.
format: [<logform.Format>], // formatting desired for log output.
winstonInstance: <WinstonLogger>, // a winston logger instance. If this is provided the transports and formats options are ignored.
level: String or function(req, res) { return String; }, // log level to use, the default is “info”. Assign a function to dynamically set the level based on request and response, or a string to statically set it always at that level. statusLevels must be false for this setting to be used.
msg: String or function, // customize the default logging message. E.g. “{{res.statusCode}} {{req.method}} {{res.responseTime}}ms {{req.url}}”, “HTTP {{req.method}} {{req.url}}” or function(req, res) { return ${res.statusCode} - ${req.method}. Warning: while supported, returning mustache style interpolation from an options.msg function has performance and memory implications under load.
expressFormat: Boolean, // Use the default Express/morgan request formatting. Enabling this will override any msg if true. Will only output colors when colorize set to true
colorize: Boolean, // Color the text and status code, using the Express/morgan color palette (text: gray, status: default green, 3XX cyan, 4XX yellow, 5XX red).
meta: Boolean, // control whether you want to log the meta data about the request (default to true).
baseMeta: Object, // default meta data to be added to log, this will be merged with the meta data.
metaField: String, // if defined, the meta data will be added in this field instead of the meta root object. Defaults to ‘meta’. Set to null to store metadata at the root of the log entry.
requestField: [String] // the property of the metadata to store the request under (default ‘req’). Set to null to exclude request from metadata
statusLevels: Boolean or Object, // different HTTP status codes caused log messages to be logged at different levels (info/warn/error), the default is false. Use an object to control the levels various status codes are logged at. Using an object for statusLevels overrides any setting of options.level.
ignoreRoute: function (req, res) { return false; }, // A function to determine if logging is skipped, defaults to returning false. Called before any later middleware.
skip: function(req, res) { return false; }, // A function to determine if logging is skipped, defaults to returning false. Called after response has already been sent.
requestFilter: function (req, propName) { return req[propName]; }, // A function to filter/return request values, defaults to returning all values allowed by whitelist. If the function returns undefined, the key/value will not be included in the meta.
responseFilter: function (res, propName) { return res[propName]; }, // A function to filter/return response values, defaults to returning all values allowed by whitelist. If the function returns undefined, the key/value will not be included in the meta.
requestWhitelist: [String], // Array of request properties to log. Overrides global requestWhitelist for this instance
responseWhitelist: [String], // Array of response properties to log. Overrides global responseWhitelist for this instance
bodyWhitelist: [String], // Array of body properties to log. Overrides global bodyWhitelist for this instance
bodyBlacklist: [String], // Array of body properties to omit from logs. Overrides global bodyBlacklist for this instance
ignoredRoutes: [String], // Array of paths to ignore/skip logging. Overrides global ignoredRoutes for this instance
dynamicMeta: function(req, res) { return [Object]; } // Extract additional meta data from request or response (typically req.user data if using passport). meta must be true for this function to be activated
headerBlacklist: [String], // Array of headers to omit from logs. Applied after any previous filters.

一个完整的例子：

  var express = require('express');
    var expressWinston = require('express-winston');
    var winston = require('winston'); // for transports.Console
    var app = module.exports = express();

    app.use(express.bodyParser());
    app.use(express.methodOverride());

    // Let's make our express `Router` first.
    var router = express.Router();
    router.get('/error', function(req, res, next) {
      // here we cause an error in the pipeline so we see express-winston in action.
      return next(new Error("This is an error and it should be logged to the console"));
    });

    router.get('/', function(req, res, next) {
      res.write('This is a normal request, it should be logged to the console too');
      res.end();
    });

    // express-winston logger makes sense BEFORE the router
    app.use(expressWinston.logger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      )
    }));

    // Now we can tell the app to use our routing code:
    app.use(router);

    // express-winston errorLogger makes sense AFTER the router.
    app.use(expressWinston.errorLogger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      )
    }));

    // Optionally you can include your custom error handler after the logging.
    app.use(express.errorLogger({
      dumpExceptions: true,
      showStack: true
    }));

    app.listen(3000, function(){
      console.log("express-winston demo listening on port %d in %s mode", this.address().port, app.settings.env);
    });

访问 /，能看到如下的日志：

{
“req”: {
“httpVersion”: “1.1”,
“headers”: {
“host”: “localhost:3000”,
“connection”: “keep-alive”,
“accept”: “/”,
“user-agent”: “Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11”,
“accept-encoding”: “gzip,deflate,sdch”,
“accept-language”: “en-US,en;q=0.8,es-419;q=0.6,es;q=0.4”,
“accept-charset”: “ISO-8859-1,utf-8;q=0.7,*;q=0.3”,
“cookie”: “connect.sid=nGspCCSzH1qxwNTWYAoexI23.seE%2B6Whmcwd”
},
“url”: “/”,
“method”: “GET”,
“originalUrl”: “/”,
“query”: {}
},
“res”: {
“statusCode”: 200
},
“responseTime” : 12,
“level”: “info”,
“message”: “HTTP GET /favicon.ico”
}

控制台打印的日志如下：