用nodejs访问ActiveX对象，以操作Access数据库为例。_javascript技巧

起因
有人提问“如果用nodejs访问sql server？”
找了找资料，发现有两类解决方法，使用第三方nodejs插件：https://github.com/orenmazor/node-tds、使用ADODB.ConnectionActiveX对象。
参考：
http://*.com/questions/857670/how-to-connect-to-sql-server-database-from-javascript
http://*.com/questions/4728385/connecting-to-a-remote-microsoft-sql-server-from-node-js
如果用ActiveX那么在Windows下nodejs将会无所不能，类似写asp。那它们怎么通信？得动手试试
经过
思路
用nodejs通过cscript.exe(windows脚本进程)间接访问ActiveX
cscript能解析jscript和vbscript两种脚本，无疑为方便维护选jscript开发。
参考：http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/cscript_overview.mspx?mfr=true
需解决的问题
1、跨进程通信
新版的nodejs里增加了对子进程的操作，跨进程通信不是问题。
http://nodejs.org/docs/latest/api/all.html#child_Processes

var util = require('util'),
exec = require('child_process').exec,
child;


child = exec('cat *.js bad_file | wc -l',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});

如例我们可以拿到控制台的输出内容stdout！


2、数据库访问相关ActiveX，ADODB.Connection
参考：http://msdn.microsoft.com/en-us/library/windows/desktop/aa746471%28v=vs.85%29.aspx

var connection = new ActiveXObject("ADODB.Connection");
var result = 'ok';
try{
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile);
connection.Execute(params.sql);
} catch(ex){
result = ex.message;
}
return {
result: result
};

connection.Open(connectionString)，链接字符串参数可以设置访问sql server。
参考：http://www.connectionstrings.com/sql-server-2005
3、为方便维护，特别将cscript和nodejs的脚本合并，用typeof exports判断当前运行环境。
4、字符编码cscript代码使用ascii编码
非ascii码字符进行“uHHHH”Unicode编码。
5、命令行字符需转义，双引号、百分号在命令行有特殊意义。
参数传递使用base64编码，避免冲突
cscript环境MSXML2.DOMDocument可以做base64编解码

function base64Decode(base64){
var xmldom = new ActiveXObject("MSXML2.DOMDocument");
var adostream = new ActiveXObject("ADODB.Stream");
var temp = xmldom.createElement("temp");
temp.dataType = "bin.base64";
temp.text = base64;


adostream.Charset = "utf-8";
adostream.Type = 1; // 1=adTypeBinary 2=adTypeText
adostream.Open();
adostream.Write(temp.nodeTypedValue);
adostream.Position = 0;
adostream.Type = 2; // 1=adTypeBinary 2=adTypeText
var result = adostream.ReadText(-1); // -1=adReadAll
adostream.Close();
adostream = null;
xmldom = null;
return result;
}

总结
调用流程
1、创建子进程，传递经过编码的参数；
2、子进程处理完毕将数据JSON格式化输出到控制台；（子进程自动结束）
3、读取控制台的数据，执行回调函数。


优势
1、使nodejs拥有访问ActiveX对象的能力；
2、实现简单，开发维护方便。


劣势
1、只能运行在Windows平台；
2、数据编解码会消耗更多cpu；
3、每次调用需要创建一个子进程重新连接。(可改进)
总结
1、具有一定实用性；
2、跨进程通信性能可继续探索。
模块代码：

var Access = {
create: function(params){
var fso = new ActiveXObject("Scripting.FileSystemObject");
var result = 'ok';
if (!fso.FileExists(params.accessfile)){
var adoxcatalog = new ActiveXObject("ADOX.Catalog");
try {
adoxcatalog.Create("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile);
} catch(ex) {
result = ex.message;
return;
}
adoxcatalog = null;
} else {
result = 'exists';
}
return {
result: result
};
},
existsTable: function(params){
var connection = new ActiveXObject("ADODB.Connection");
var result = 'ok', exists = false;
try{
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile);
var recordset = connection.OpenSchema(20/*adSchemaTables*/);
recordset.MoveFirst();
while (!recordset.EOF){
if (recordset("TABLE_TYPE") == "TABLE" && recordset("TABLE_NAME") == params.tablename){
exists = true;
break;
}
recordset.MoveNext();
}
recordset.Close();
recordset = null;
} catch(ex){
result = ex.message;
}
return {
"result": result,
"exists": exists
};
},
execute: function(params){
var connection = new ActiveXObject("ADODB.Connection");
var result = 'ok';
try{
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile);
connection.Execute(params.sql);
} catch(ex){
result = ex.message;
}
return {
result: result
};
},
query: function(params){
var connection = new ActiveXObject("ADODB.Connection");
var result = 'ok', records = [];
try{
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile);
var recordset = new ActiveXObject("ADODB.Recordset");
recordset.Open(params.sql, connection);
var fields = [];
var enumer = new Enumerator(recordset.Fields);
for (; !enumer.atEnd(); enumer.moveNext()){
fields.push(enumer.item().name);
}
recordset.MoveFirst();
while (!recordset.EOF) {
var item = {};
for (var i = 0; i var fieldname = fields[i];
item[fieldname] = recordset(fieldname).value;
}
records.push(item);
recordset.MoveNext();
}
recordset.Close();
recordset = null;
} catch(ex){
result = ex.message;
}
return {
result: result,
records: records
};
}
};
if (/^u/.test(typeof exports)){ // cscript
void function(){
//from http://tangram.baidu.com/api.html#baidu.json
var JSON = {
stringify: (function () {
/**
* 字符串处理时需要转义的字符表
* @private
*/
var escapeMap = {
"\b": '\\b',
"\t": '\\t',
"\n": '\\n',
"\f": '\\f',
"\r": '\\r',
'"' : '\\"',
"\\": '\\\\'
};
/**
* 字符串序列化
* @private
*/
function encodeString(source) {
if (/["\\\x00-\x1f]/.test(source)) {
source = source.replace(
/["\\\x00-\x1f]/g,
function (match) {
var c = escapeMap[match];
if (c) {
return c;
}
c = match.charCodeAt();
return "\\u00"
+ Math.floor(c / 16).toString(16)
+ (c % 16).toString(16);
});
}
return '"' + source + '"';
}
/**
* 数组序列化
* @private
*/
function encodeArray(source) {
var result = ["["],
l = source.length,
preComma, i, item;
for (i = 0; i item = source[i];
switch (typeof item) {
case "undefined":
case "function":
case "unknown":
break;
default:
if(preComma) {
result.push(',');
}
result.push(JSON.stringify(item));
preComma = 1;
}
}
result.push("]");
return result.join("");
}
/**
* 处理日期序列化时的补零
* @private
*/
function pad(source) {
return source }
/**
* 日期序列化
* @private
*/
function encodeDate(source){
return '"' + source.getFullYear() + "-"
+ pad(source.getMonth() + 1) + "-"
+ pad(source.getDate()) + "T"
+ pad(source.getHours()) + ":"
+ pad(source.getMinutes()) + ":"
+ pad(source.getSeconds()) + '"';
}
return function (value) {
switch (typeof value) {
case 'undefined':
return 'undefined';
case 'number':
return isFinite(value) ? String(value) : "null";
case 'string':
return encodeString(value).replace(/[^\x00-\xff]/g, function(all) {
return "\\u" + (0x10000 + all.charCodeAt(0)).toString(16).substring(1);
});
case 'boolean':
return String(value);
default:
if (value === null) {
return 'null';
}
if (value instanceof Array) {
return encodeArray(value);
}
if (value instanceof Date) {
return encodeDate(value);
}
var result = ['{'],
encode = JSON.stringify,
preComma,
item;
for (var key in value) {
if (Object.prototype.hasOwnProperty.call(value, key)) {
item = value[key];
switch (typeof item) {
case 'undefined':
case 'unknown':
case 'function':
break;
default:
if (preComma) {
result.push(',');
}
preComma = 1;
result.push(encode(key) + ':' + encode(item));
}
}
}
result.push('}');
return result.join('');
}
};
})(),
parse: function (data) {
return (new Function("return (" + data + ")"))();
}
}
//http://blog.csdn.net/cuixiping/article/details/409468
function base64Decode(base64){
var xmldom = new ActiveXObject("MSXML2.DOMDocument");
var adostream = new ActiveXObject("ADODB.Stream");
var temp = xmldom.createElement("temp");
temp.dataType = "bin.base64";
temp.text = base64;
adostream.Charset = "utf-8";
adostream.Type = 1; // 1=adTypeBinary 2=adTypeText
adostream.Open();
adostream.Write(temp.nodeTypedValue);
adostream.Position = 0;
adostream.Type = 2; // 1=adTypeBinary 2=adTypeText
var result = adostream.ReadText(-1); // -1=adReadAll
adostream.Close();
adostream = null;
xmldom = null;
return result;
}
WScript.StdOut.Write('');
var method = Access[WScript.Arguments(0)];
var result = null;
if (method){
result = method(JSON.parse(base64Decode(WScript.Arguments(1))));
}
WScript.StdOut.Write(JSON.stringify(result));
WScript.StdOut.Write('');
}();
} else { // nodejs
void function(){
function json4stdout(stdout){
if (!stdout) return;
var result = null;
String(stdout).replace(/([\s\S]+)/, function(){
result = JSON.parse(arguments[1]);
});
return result;
}
var util = require('util'), exec = require('child_process').exec;
for (var name in Access){
exports[name] = (function(funcname){
return function(params, callback){
console.log([funcname, params]);
exec(
util.format(
'cscript.exe /e:jscript "%s" %s "%s"', __filename,
funcname,
(new Buffer(JSON.stringify(params))).toString('base64')
),
function (error, stdout, stderr) {
if (error != null) {
console.log('exec error: ' + error);
return;
}
console.log('stdout: ' + stdout);
callback && callback(json4stdout(stdout));
}
);
}
})(name);
}
}();
}

调用代码：

var access = require('./access.js');
var util = require('util');
var accessfile = 'demo.mdb';
access.create({ accessfile: accessfile }, function(data){
console.log(data);
});
access.existsTable({ accessfile: accessfile, tablename: 'demo' }, function(data){
if (data.result == 'ok' && !data.exists){
access.execute({
accessfile: 'demo.mdb',
sql: "CREATE TABLE demo(id Counter Primary key, data Text(100))"
});
}
});
access.execute({
accessfile: 'demo.mdb',
sql: util.format("INSERT INTO demo(data) VALUES('zswang 路过！%s')", +new Date)
}, function(data){
console.log(data);
});
access.query({
accessfile: 'demo.mdb',
sql: "SELECT * FROM demo"
}, function(data){
console.log(data);
});

最新代码：http://code.google.com/p/nodejs-demo/source/browse/#svn%2Ftrunk%2Fdatabase