Question

所以我正在编写这个node.js程序，将XML文件导入JSON对象的数组中。我有2个要导入的文件，teacher.xml和students.xml。

教师和学生包含数千个关于教师和学生的信息。我的代码完全覆盖了那部分。

这是我用于解析文件的javascript文件：

var fs = require('fs');
var xmldom = require('xmldom');
var async = require('async');

// Parse `catalog` xml file and call `callback(catalog domxml root)`
function parse_catalog(catalog, callback) {
    // Read xml file content
    fs.readFile(catalog, function (err, data) {
        if (err) {
            throw 'Error reading XML catalog';
        } else {
            // Parse xml content and return dom root
            var domRoot = new xmldom.DOMParser().parseFromString(data.toString());
            // Call callback passing dom root
            callback(domRoot)
    }
});
}

我有两个这样的方法将xml转换为json并且它完美地工作（一个用于教师，一个用于学生）

// Convert teacher XML into json format in a array
function convert_teachers(domCatalog) {
    var teachers = domCatalog.getElementsByTagName('teacher');
    var teachers_arr= [];
    for (var i = 0; i < teachers .length; i++) {
        var teacher= teachers[i];
        ...
        //Reading the xml 

        teachers_arr.push({
        ...
        //Create the json

        });
    }
    console.log("Teachers are now in JSON format ");
}

所以最后我要做的就是：

parse_catalog('teachers.xml', convert_teachers);

当我这样做时：

parse_catalog('teachers.xml', convert_teachers);
parse_catalog('students.xml', convert_students);

根据要导入的元素数量，一个或另一个将首先完成，我认为这是正常的。

我想要的是等待两者都被导入然后进行一些javascript操作，这就是我被困住的地方。

我尝试使用异步执行此操作，但它不会等到导入完成两个文件。

async.parallel([
    function(callback) {
        parse_catalog('teachers.xml', convert_teachers);
        callback();
    },

    function(callback) {
        parse_catalog('students.xml', convert_students);
        callback();
    }
], function(err) { 
    if (err) return next(err);

    console.log("Finished");
    //Enventually some Javascript manipulations on the two arrays

});

实际上输出：

Finished
Teachers are now in JSON format
Students are now in JSON format

或取决于文件大小

Finished
Students are now in JSON format
Teachers are now in JSON format

我想要的更像是：

Teachers are now in JSON format (or students)
Students are now in JSON format (or teachers)
Finished

我打算再加载2个文件，他们加载的顺序对我来说无关紧要。

任何线索？谢谢！

Answer 1

您过早地在callback()功能中执行async.parallel()，因为那时fs.readFile()尚未开始。尝试这样的事情：

function parse_catalog(catalog, callback) {
  // Read xml file content
  fs.readFile(catalog, function(err, data) {
    if (err)
      return callback(err);

    // Parse xml content and return dom root
    var domRoot = new xmldom.DOMParser().parseFromString(data.toString());

    // Call callback passing dom root
    callback(null, domRoot);
  });
}

// Convert teacher XML into json format in a array
function convert_teachers(domCatalog) {
  var teachers = domCatalog.getElementsByTagName('teacher');
  var teachers_arr = [];
  for (var i = 0; i < teachers .length; i++) {
    var teacher = teachers[i];
    ...
    //Reading the xml 

    teachers_arr.push({
    ...
    //Create the json

    });
  }
  console.log('Teachers are now in JSON format');
  return teachers_arr;
}
// and similarly for `convert_students`

async.parallel({
  teachers: function(callback) {
    parse_catalog('teachers.xml', function(err, domCatalog) {
      if (err)
        return callback(err);
      var teachers = convert_teachers(domCatalog);
      callback(null, teachers);
    });
  },
  students: function(callback) {
    parse_catalog('students.xml', function(err, domCatalog) {
      if (err)
        return callback(err);
      var students = convert_students(domCatalog);
      callback(null, students);
    });
  }
}, function(err, results) { 
  if (err) return next(err);

  console.log('Finished');

  // here you have `results.teachers` and `results.students`
  console.dir(results);
});

node.js等待任务完成

1 个答案: