Question

我编写了一个查询MySQL数据库的API，并输出访问网址的相应结果。这是代码：

//server.js
var express = require('express'),
    mysql   = require('mysql'),
    app     = express(),
    connectionpool = mysql.createPool({
        host     : 'localhost',
        user     : 'root',
        password : 'password',
        database : 'database'
    });

app.get('/:transcript', function(req,res){
    var var1 = req.param('transcript');
    exports.var1 = var1;
    var queries = require('./queries'),
        query1  = queries.query1;
    //Connection to MySQL
    connectionpool.getConnection(function(err, connection) {
        if (err) {res.send({result: 'error connection'})}
        connection.query(query1, function(err, rows) {
            if (err) {res.send({result: 'error query1'})};
            counter = 0; root = {};
            rows.forEach(function (row) {
                build_actor(row.Transcript_alias, function(exprobject1) {
                    counter += 1;
                    //Defining and filling objects
                    main = {};
                    main.Official_transcript_name = row.Transcript_name;
                    main.Expression = exprobject1;
                    root[row.Transcript_alias] = main;
                    if (counter == rows.length) {
                        res.write(JSON.stringify(root, null, '\t'));   
                        res.end();
                    }
                });
            });
            connection.release();
        });
        //CallBack
        function build_actor(transcript, callback) {
            //Other, secondary queries:
            var query2 = 'SELECT * FROM expression WHERE transcript_alias = "' + transcript + '";',
            connection.query(query2, function(err, rows1) {
                if (err) {res.send({result: 'error query2'})}
                    var exprobject2 = {},
                        exprobject1 = {};
                    for (i = 0; i < rows1.length; i++) {
                        Conditions = rows1[i].conditions;
                        Tissue = rows1[i].tissue;
                        FPKM = rows1[i].FPKM;
                        exprobject2[Tissue] = FPKM;
                        if (Conditions in exprobject1) {
                            exprobject1[Conditions].push(exprobject2);
                        } else {
                            exprobject1[Conditions] = [];
                            exprobject1[Conditions].push(exprobject2);
                        }
                    }
                    callback(exprobject1);
            });
        }
    });
});

app.listen(3000);
console.log('Listening on port 3000');

此脚本调用我的查询所需的文件：

//queries.js
var server = require('./server'),
    query1 = 'SELECT distinct(transcript_alias)\
         FROM transcript_features \
        WHERE f.transcript_alias = "' + var1 + '";';

exports.query1 = query1;

我用这种方式转到这个脚本的内容：

http://localhost:3000/AC149829.2_FGT004
http://localhost:3000/AC148152.3_FGT007

当我第一次访问http://localhost:3000/AC149829.2_FGT004时，API会显示变量AC149829.2_FGT004的正确结果。但是，将变量更改为AC148152.3_FGT007时，会继续显示变量AC149829.2_FGT004的信息。为了查看AC148152.3_FGT007的结果，我必须删除脚本，再次调用它，并首次访问http://localhost:3000/AC148152.3_FGT007。总之，结果不会更新。

那是怎么回事？我试着用一个简单的方法：

app.get('/:transcript', function(req,res){
    var input = req.param('transcript');
    res.send(input);
});

但效果很好......

修改即可。我找到了问题的根源。 query1总是一样的。该脚本只调用一次：

exports.var1 = var1;
var queries = require('./queries'),
    query1  = queries.query1;

有办法克服这个限制吗？

Answer 1

我找到了解决问题的方法。正如

//server.js
exports.var1 = var1;
var queries = require('./queries'),
    query1  = queries.query1;

执行一次并保留在缓存中，我更改了代码而未导出var1：

//server.js
var queries = require('./queries'),
    query1  = queries.query1 + var1;

和

//queries.js
var server = require('./server'),
    query1 = 'SELECT distinct(transcript_alias)\
         FROM transcript_features \
        WHERE f.transcript_alias = ';

exports.query1 = query1;

换句话说，我将查询导入server.js而没有任何变量。该变量在server.js分配。

刷新Express NodeJS API的内容

1 个答案: