如何修复节点中的'headers already sent'错误

Question

所以我正在尝试创建一个调用 ldap 服务并验证用户的节点应用程序。在下面的代码中，应用成功连接到服务器并处理请求。但是当我尝试发回响应时，出现此错误：抛出新ERR_HTTP_HEADERS_SENT("设置"(;^

错误 [ERR_HTTP_HEADERS_SENT]：将标头发送到客户端后无法设置标头

我不太确定为什么会发生这种情况。我对node，express和ldap很陌生

// ldapjs required for ldap connection
const ldap = require('ldapjs');
//express required for exposing endpoints
const express = require('express');
const app = express();
const assert = require('assert');
var client = ldap.createClient({
  url: 'ldap://someserve.com'
});
//Search filter for users in the directory
var opts = {
  filter: '(&(objectCategory=person)(objectClass=user))',
  scope: 'sub',
};
//General Ldap serch user
var UserName = '123.test.com';
var Pass = '123longpass'
//Base URL
app.get('/', (req,res) => {
    res.send('hello from node')
});
//Get all ldap users
app.get('/api/ldapUsers', (req, res) => 
{
    client.bind(UserName, Pass, function (err) 
    {
        client.search('DC=sdf,DC=sdfa,DC=gdfgd', opts, function (err, search) 
        {
            search.on('searchEntry', function (entry) 
            {
                res.setHeader('Content-Type', 'application/json');
                var users = entry.object;
                console.log(users);
                res.json(users);
                res.end(); 
            });
        });
    });
   // client.unbind( err => {
   //     assert.ifError(err);
   // });
});
const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Listening on port ${port}...`));

Answer 1

searchEntry 事件为每个找到的项目调用一次，这意味着您要多次调用 res.json。

试试这个：

app.get('/api/ldapUsers', (req, res) => 
{
    client.bind(UserName, Pass, function (err) 
    {
        client.search('DC=sdf,DC=sdfa,DC=gdfgd', opts, function (err, search) 
        {
            var users = [];
            search.on('searchEntry', function (entry) {
                users.push(entry.object); 
            });
            search.on('end', function (entry) {
                res.setHeader('Content-Type', 'application/json');
                console.log(users);
                res.json(users);
                res.end(); 
            });
        });
    });
});