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express-winston 为 express.js 应用程序的申请和谬误记录提供中间件。它应用“白名单”从申请和（0.2.x 中新增的）响应对象中抉择属性。

要应用 express-winston，您须要将以下内容增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

应用 expressWinston.logger(options) 创立一个中间件来记录您的 HTTP 申请。

 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.

一个残缺的例子：

  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);
    });

拜访 /，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：