我想這種結構的代碼,所以我可以從多個地方調用getStudent以外的地方捕捉代碼。我正在嘗試編寫一些JSON例程。我正在嘗試第一個回調模式。這不是錯誤太多而讓我感到不安,而是錯誤被getStudent中的捕獲之一所捕獲。的NodeJS /捕獲的功能似乎作用
順便提及,我想出誤差是做的,而不是狀態(0)的狀態(200)。
我應該如何重組所以這些漁獲所以它們不影響主代碼?還是我完全濫用回調概念?看起來像「then/catch」是處理與mssql異步的正確方法。 http://localhost:3000/student在瀏覽器中:
var express = require('express');
var app = express();
// config for your database
var config = {
user: 'ReadOnlyUser1',
password: 'whatever',
server: 'localhost\\SQLEXPRESS',
database: 'StudentsOld'
};
var lookupStudentId = 31;
const sql = require('mssql');
var connPool = new sql.ConnectionPool(config);
function getStudent(studentId, callback) {
console.log("Starting getStudent");
nullResult = {};
connPool.connect().
then (function() {
console.log('Connected - starting query');
var request = new sql.Request(connPool);
var sqlQuery = 'select student_firstname, student_lastname from students where student_id = ' + studentId;
request.query(sqlQuery).
then(function (recordSet) {
console.log('Query completed');
connPool.close();
console.log("recordSet=");
console.dir(recordSet);
callback(nullResult, recordSet);
}).catch(function (queryErr) {
console.log('Error in database query: ' + queryErr);
callback('Error in db query: ' + queryErr, nullResult);
});
}).catch(function (connErr) {
console.log('Error in database connection: ' + connErr);
callback('Error in db conn: ' + connErr, nullResult);
});
console.log('fall thru 1');
}
function isEmptyObject(obj) {
return !Object.keys(obj).length;
}
app.get('/student', function(request, response){
console.log('Neal Test1');
getStudent(lookupStudentId, function(err, result){
console.log('Back from getStudent');
if(!isEmptyObject(err)) {
console.log("error400=" + err);
console.log("empty test=" + Object.keys(err).length);
response.status(400).send(err);
}
else
{
console.log("result=");
console.dir(result);
console.log('about to send back status=0');
response.status(0).send(result);
}
})
return;
});
app.listen(3000, function() {
console.log('Express server is listening on port 3000');
});
我通過輸入運行上面。
控制檯輸出:
C:\Software\nodejs\myapp>node index.js
Express server is listening on port 3000
Neal Test1
Starting getStudent
fall thru 1
Connected - starting query
Query completed
recordSet=
{ recordsets: [ [ [Object] ] ],
recordset:
[ { student_firstname: 'Jonah ',
student_lastname: 'Hill ' } ],
output: {},
rowsAffected: [ 1 ] }
Back from getStudent
result=
{ recordsets: [ [ [Object] ] ],
recordset:
[ { student_firstname: 'Jonah ',
student_lastname: 'Hill ' } ],
output: {},
rowsAffected: [ 1 ] }
about to send back status=0
Error in database query: RangeError: Invalid status code: 0
Back from getStudent
error400=Error in db query: RangeError: Invalid status code: 0
empty test=53
修訂1:修訂1的
function getStudent(studentId) {
console.log("Starting getStudent");
recordset = {};
connPool.connect().
then (function() {
console.log('Connected - starting query');
var request = new sql.Request(connPool);
var sqlQuery = 'select student_firstname, student_lastname from students where student_id = ' + studentId;
request.query(sqlQuery).
then(function (recordSet) {
console.log('Query completed');
connPool.close();
console.log("recordSet=");
console.dir(recordSet);
return recordset;
}).catch(function (queryErr) {
console.log('Error in database query: ' + queryErr);
return queryErr;
});
}).catch(function (connErr) {
console.log('Error in database connection: ' + connErr);
return connErr;
});
console.log('fall thru 1');
}
app.get('/student', function(request, response){
console.log('Neal Test1 - start app.get for /student');
getStudent(lookupStudentId)
.then (function(recordset) {
console.log('Back from getStudent, recordSet=');
console.dir(recordSet);
response.status(200).send(recordset);
})
.catch (function(err) {
console.log("error400=" + err);
console.log("empty test=" + Object.keys(err).length);
response.status(400).send(err);
})
return;
});
結果:
Express server is listening on port 3000
Neal Test1 - start app.get for /student
Starting getStudent
fall thru 1
TypeError: Cannot read property 'then' of undefined
at C:\Software\nodejs\wisdomcalls\index.js:55:9
at Layer.handle [as handle_request] (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\layer.js:95:5)
at next (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\route.js:137:13)
at Route.dispatch (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\route.js:112:3)
at Layer.handle [as handle_request] (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\layer.js:95:5)
at C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\index.js:281:22
at Function.process_params (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\index.js:335:12)
at next (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\index.js:275:10)
at expressInit (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\middleware\init.js:40:5)
at Layer.handle [as handle_request] (C:\Software\nodejs\wisdomcalls\node_modules\express\lib\router\layer.js:95:5)
Connected - starting query
Query completed
recordSet=
{ recordsets: [ [ [Object] ] ],
recordset:
[ { student_firstname: 'Jonah ',
student_lastname: 'Hill ' } ],
output: {},
rowsAffected: [ 1 ] }
從日誌,你可以看到,主要功能是在數據庫連接之前運行。
修訂2: 這好像又回到也許連接,而不是查詢?請參閱console.log「undefined」。
function getStudent(studentId) {
console.log("Starting getStudent");
recordset = {};
return connPool.connect()
.then (function() {
console.log('Connected - starting query');
var request = new sql.Request(connPool);
var sqlQuery = 'select student_firstname, student_lastname from students where student_id = ' + studentId;
return request.query(sqlQuery)
;
/*
.then(function (recordSet) {
console.log('Query completed');
connPool.close();
console.log("recordSet=");
console.dir(recordSet);
//return recordset;
}).catch(function (queryErr) {
console.log('Error in DB query: ' + queryErr);
//return queryErr;
});
}).catch(function (connErr) {
console.log('Error in DB connection: ' + connErr);
//return connErr;
*/
});
console.log('fall thru 1');
}
結果:
Connected - starting query
SQL Query = select student_firstname, student_lastname from students where student_id = 31
error400=ReferenceError: recordSet is not defined
empty test=0
是的,我想我在原來的問題時說,使用(200),而不是(0)固定的一個問題。但更大的問題是異步時機。 – NealWalters