我只是想写一个简单的注册/登录系统。我正在尝试查找用户名是否存在。以下是步骤：
- 转到localhost:3000/users/register页面
- 填写所有字段并单击"注册"按钮
- 检查我的命令行，如果用户名存在，应该用console.log打印
到目前为止一切都很好
当我回到注册页面时，我再次填写所有字段并单击注册按钮。然后它把它扔到命令行：
Error: Client has already been connected. You cannot reuse a client.
at Client._connect (C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulespglibclient.js:91:17)
at C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulespglibclient.js:310:10
at new Promise (<anonymous>)
at Client.connect (C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulespglibclient.js:309:10)
at Object.module.exports.findUserById (C:UsersHasanDesktopProjelernode-ogreniyorumdatabaseregister_sql.js:8:22)
at C:UsersHasanDesktopProjelernode-ogreniyorumroutesusers.js:37:29
at Layer.handle [as handle_request] (C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulesexpresslibrouterlayer.js:95:5)
at next (C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulesexpresslibrouterroute.js:137:13)
at next (C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulesexpresslibrouterroute.js:131:14)
at Route.dispatch (C:UsersHasanDesktopProjelernode-ogreniyorumnode_modulesexpresslibrouterroute.js:112:3)
我不明白，因为在调用我的方法后，我已经结束了我的客户端。
register_sql.js:
module.exports.findUserById =(async (username) =>{
try {
await client.connect();
console.log('Connected successfuly');
const result = await client.query("select * from users where username = ($1)", [username]);
console.log(result.rows[0]['username']);
await client.end();
console.log('Client disconnected...');
} catch (err) {
console.log(err);
}
});
我在users.js中调用register_sql.js。这是users.js：
const router = express.Router();
const registerSQL = require('../database/register_sql');
router.route('/register')
.get((req, res, next) => {
res.render('register');
})
.post((req, res, next) => {
const {
username,
password,
password2
} = req.body;
let errors = [];
if (!username || !password || !password2) {
errors.push("Please fill in all fields!");
}
if (password != password2) {
errors.push("Passwords do not match!");
}
if (password.length < 6) {
errors.push("Password has to be at least 6 characters!");
}
if (errors.length > 0) {
res.render('register', {
errors
});
} else {
registerSQL.findUserById(username);
res.redirect('/');
}
});
module.exports = router;
谢谢你的帮助！
使用节点postgres(您正在使用的节点postgres(，我只使用池来管理连接。
const pg = require('pg')
const pool = new pg.Pool();
pool.connect(function(err, client, done) {
if(err) {
return console.error('connexion error', err);
}
client.query("select * from users where username = ($1)", [username], function(err, result) {
// call `done()` to release the client back to the pool
done();
if(err) {
return console.error('error running query', err);
}
console.log(result.rows[0]['username'])
});
});
我遇到了同样的问题，没有在函数之外创建新的客户端。
- const client = new pg.Client(connection);
-
function test() {
+ const client = new pg.Client(connection);
+
client.connect(err => {
if (err) {
console.log(err);
return;
}
client.query('select 123', [], (err, data) => {
if (err) {
console.log(err);
} else {
console.log('DATA:', data.rows[0]);
}
client.end();
});
});
}
我设法在不使用池的情况下解决了这个问题。也许这不是最正确的解决方案，但它是有效的。首先创建一个单独的js文件，连接客户端并将其导出：
const pg = require('pg')
const client = new pg.Client('your connection string')
client.connect()
module.exports = client
然后，您只需使用已连接的导出客户端，这样它就不会在每次请求时再次重新连接。请确保从连接客户端的js文件中导入客户端。
const client = require('../db')
const register = async (req, res) => {
const {email, password, username} = req.body
const hashedPassword = await bcrypt.hash(password, 10)
const command = `insert into users(email, username, password, created) VALUES ('${email}', '${username}', '${hashedPassword}', current_timestamp)`
await client.query(command, (err, result) => {
err ? res.json({error: err.detail}) : res.json({message: 'User created!'})
})
}
问题的出现是因为您没有关闭与数据库的连接。记住，在你向客户端发送这样的东西之前，你必须关闭连接：
try {
await client.connect();
const result = await client.query(query, values);
await client.end();
res.status(201).send({
result,
});
} catch (err) {
return res.send({
error: err.detail,
message: "Can't create a new user, please check your info again!",
});
}
Pool方法是更好的做法，但如果有人想使用Client方式进行连接，则此解决方案将起作用。
适用于客户方法的代码：
client.connect();
client.query(`select * from users where username = ($1)`, (err, result)=>{
try{
console.log("Test", result)
res.send(result)
} catch{
console.log("err", err)
res.status(500).json(err);
}
client.end();
})