How to use @Mock @InjectMocks

class MyService {
    private UserDao userDao;
}

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.MockitoAnnotations;
import org.mockito.runners.MockitoJUnitRunner;

public class MyServiceTest {

    @InjectMocks
    private MyService myService;

    @Mock
    private UserDao userDao;
    
    @Before
    public void setUp() {
        myService = new MyService();
    }
}

Cannot mock/spy class java.lang.String Mockito cannot mock/spy following: - final classes - anonymous classes - primitive types

org.mockito.exceptions.base.MockitoException:
Cannot mock/spy class java.lang.String
Mockito cannot mock/spy following:
- final classes
- anonymous classes
- primitive types
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl$1.withBefores(JUnit45AndHigherRunnerImpl.java:27)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)

In case you have to mock String, perhaps you can add a function only visible for testing via

import com.google.common.annotations.VisibleForTesting;
And in this function, mock the String type's value.
For Example:

class MyService {
    
    private String name = "myservice";

    @VisibleForTesting
    void forTest(String mockName) {
        this.name = mockName;
    }
}

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.MockitoAnnotations;
import org.mockito.runners.MockitoJUnitRunner;

public class MyServiceTest {

    private MyService myService;

    @Before
    public void setUp() {
        myService = new MyService();
        myService.forTest("mockName");
    }
}

How to increase terminal window buffer in IntelliJ

Command + Shift + A or Ctrl + Shift + A
Type registry, click "Registry..."

Increase the "terminal.buffer.max.lines.count" to 100000 or any number you want, the default is 1000.

make vim like source insight, a effective c/c++ ide

IDE

setup latest vim

git clone https://github.com/vim/vim.git cd vim/src ./configure --enable-cscope --enable-terminal make sudo make install 

https://www.vim.org/git.php

use universal ctags

git clone https://github.com/universal-ctags/ctags.git cd ctags ./autogen.sh ./configure make sudo make instahttps://www.tamacom.com/global/global-6.6.3.tar.gzll 

setup gnu tags

wget https://www.tamacom.com/global/global-6.6.3.tar.gz tar -xvf global-6.6.3.tar.gz cd global-6.6.3 sh reconf.sh  sudo apt install ncurses-dev ./configure --with-universal-ctags=/usr/local/bin/ctags  make  sudo make install 

https://www.tamacom.com/global/global-6.6.3.tar.gz
http://www.gnu.org/software/global/download.html

install gtags as vim plugin

cp gtags.vim ~/.vim/plugin/ cp gtags-cscope.vim ~/.vim/plugin/ 

config gtags as cscope in ~/.vimrc

" gtags configure " To use the default key/mouse mapping: let GtagsCscope_Auto_Map = 1 " To ignore letter case when searching: let GtagsCscope_Ignore_Case = 1 " To use absolute path name: let GtagsCscope_Absolute_Path = 1 " To deterring interruption: let GtagsCscope_Keep_Alive = 1 " If you hope auto loading: let GtagsCscope_Auto_Load = 1 let GtagsCscope_Quiet = 1 " To use 'vim -t ', ':tag' and '<C-]>' set cscopetag let Gtags_Auto_Map = 1 " output cscope result to quickfix  set cscopequickfix=s-,g-,c-,d-,i-,t-,e-,f-,-a " open quickfix window if needx autocmd QuickFixCmdPost [^l]* nested botright cwindow  :nmap \s :cs find s <C-R>=expand("<cword>")<CR><CR> :nmap \a :cs find a <C-R>=expand("<cword>")<CR><CR> :nmap \d :cs find d <C-R>=expand("<cword>")<CR><CR> :nmap \g :cs find g <C-R>=expand("<cword>")<CR><CR> :nmap \i :cs find i <C-R>=expand("<cword>")<CR><CR> :nmap \c :cs find c <C-R>=expand("<cword>")<CR><CR> :nmap \e :cs find e <C-R>=expand("<cword>")<CR><CR> :nmap \t :cs find t <C-R>=expand("<cword>")<CR><CR> :nmap \f :cs find f <C-R>=expand("<cword>")<CR><CR> 

Usage:

cscope commands: add  : Add a new database             (Usage: add file|dir [pre-path] [flags]) find : Query for a pattern            (Usage: find a|c|d|e|f|g|i|s|t name)        a: Find assignments to this symbol        c: Find functions calling this function        d: Find functions called by this function        e: Find this egrep pattern        f: Find this file        g: Find this definition        i: Find files #including this file        s: Find this C symbol        t: Find this text string help : Show this message              (Usage: help) kill : Kill a connection              (Usage: kill #) reset: Reinit all connections         (Usage: reset) show : Show connections               (Usage: show) 

Normal Key Map:
Press \a means "cs f a $cname"
Press \s means "cs f s $cname"
Press \t means "cs f t $cname"
Press \e means "cs f e $cname"
Press \c means "cs f c $cname"
Press \d means "cs f d $cname"
Press \i means "cs f i $cname"
Press \g means "cs f g $cname"
Press \f means "cs f f $cname"

install taglist

unzip taglist_46.zip  Archive:  taglist_46.zip   inflating: plugin/taglist.vim         inflating: doc/taglist.txt          cp plugin/taglist.vim ~/.vim/plugin/ cp doc/taglist.txt ~/.vim/doc/ 

https://www.vim.org/scripts/script.php?script_id=273

configure taglist vim plugin

"taglist settings let Tlist_Inc_Winwidth=0 let Tlist_Use_Right_Window=1 let Tlist_File_Fold_Auto_Close=1 let Tlist_Exit_OnlyWindow=1 let Tlist_Auto_Open=1 :nmap <F8> :TlistToggle<CR> function! g:TlistFocus()   let save_winnr = winnr()     let winnum = bufwinnr("__Tag_List__")       if winnum == -1         :TlistToggle         let winnum = bufwinnr("__Tag_List__")       endif     if winnum != -1       if save_winnr != winnum         exe winnum . 'wincmd w'       endif   endif endfunction "focus to Tag list window via CTL command command! -nargs=0 -bar CTL call g:TlistFocus()     

Usage: Press F8 to toggle taglist

install vim-airline

git clone https://github.com/vim-airline/vim-airline ~/.vim/pack/dist/start/vim-airline 

https://github.com/vim-airline/vim-airline

install fzf.vim

git clone --depth 1 https://github.com/junegunn/fzf.git ~/.fzf ~/.fzf/install 

~/.vimrc

" If installed using git set rtp+=~/.fzf 

.vimrc

set nocompatible set backspace=indent,eol,start syntax on syntax enable filetype plugin indent on set autoread set showmatch set hlsearch set incsearch set ignorecase set smartcase set encoding=utf-8 set termencoding=utf-8 set fileencodings=utf-8,gb2312,gbk,gb18030 set tabstop=4 set shiftwidth=4 set expandtab set softtabstop=4 set autoindent set smartindent set ruler set paste  "gtags settings set cscopetag let GtagsCscope_Auto_Load = 1 let CtagsCscope_Auto_Map = 1 let GtagsCscope_Quiet = 1 set cscopequickfix=s-,g-,d-,c-,t-,e-,f-,i-  "open quickfix window if needed autocmd QuickFixCmdPost [^l]* nested botright cwindow  "key maps for gtags "find : Query for a pattern            (Usage: find a|c|d|e|f|g|i|s|t name) "       a: Find assignments to this symbol "       c: Find functions calling this function "       d: Find functions called by this function "       e: Find this egrep pattern "       f: Find this file "       g: Find this definition "       i: Find files #including this file "       s: Find this C symbol "       t: Find this text string :nmap \a :cs find a <C-R>=expand("<cword>")<CR><CR> :nmap \c :cs find c <C-R>=expand("<cword>")<CR><CR> :nmap \d :cs find d <C-R>=expand("<cword>")<CR><CR> :nmap \e :cs find e <C-R>=expand("<cword>")<CR><CR> :nmap \f :cs find f <C-R>=expand("<cword>")<CR><CR> :nmap \g :cs find g <C-R>=expand("<cword>")<CR><CR> :nmap \i :cs find i <C-R>=expand("<cword>")<CR><CR> :nmap \s :cs find s <C-R>=expand("<cword>")<CR><CR> :nmap \t :cs find t <C-R>=expand("<cword>")<CR><CR>  "taglist settings let Tlist_Inc_Winwidth=0 let Tlist_Use_Right_Window=1 let Tlist_File_Fold_Auto_Close=1 let Tlist_Exit_OnlyWindow=1 let Tlist_Auto_Open=1  :nmap <F8> :TlistToggle<CR> function! g:TlistFocus()   let save_winnr = winnr()   let winnum = bufwinnr("__Tag_List__")   if winnum == -1     :TlistToggle     let winnum = bufwinnr("__Tag_List__")   endif   if winnum != -1       if save_winnr != winnum         exe winnum . 'wincmd w'       endif   endif endfunction "focus to Tag list window via CTL command command! -nargs=0 -bar CTL call g:TlistFocus()  "lightline settings set laststatus=2 if !has('gui_running')   set t_Co=256 endif  "ale settings let g:ale_completion_enabled = 1  "multiple-cursor settings let g:multi_cursor_use_default_mapping=0 let g:multi_cursor_start_word_key      = '<C-n>' let g:multi_cursor_select_all_word_key = '<C-a>' let g:multi_cursor_start_key           = 'g<C-n>' let g:multi_cursor_select_all_key      = 'g<C-a>' let g:multi_cursor_next_key            = '<C-n>' let g:multi_cursor_prev_key            = '<C-N>' let g:multi_cursor_skip_key            = '<C-x>' let g:multi_cursor_quit_key            = '<Esc>'  "tag preview configure autocmd FileType qf nnoremap <silent><buffer> p :PreviewQuickfix<CR> autocmd FileType qf nnoremap <silent><buffer> P :PreviewClose<CR>  "fzf configure set rtp+=~/.fzf  " This is the default extra key bindings let g:fzf_action = {   \ 'ctrl-t': 'tab split',   \ 'ctrl-x': 'split',   \ 'ctrl-v': 'vsplit' }  " Default fzf layout " - down / up / left / right let g:fzf_layout = { 'left': '~100%' }  " Customize fzf colors to match your color scheme let g:fzf_colors = \ { 'fg':      ['fg', 'Normal'],   \ 'bg':      ['bg', 'Normal'],   \ 'hl':      ['fg', 'Comment'],   \ 'fg+':     ['fg', 'CursorLine', 'CursorColumn', 'Normal'],   \ 'bg+':     ['bg', 'CursorLine', 'CursorColumn'],   \ 'hl+':     ['fg', 'Statement'],   \ 'info':    ['fg', 'PreProc'],   \ 'border':  ['fg', 'Ignore'],   \ 'prompt':  ['fg', 'Conditional'],   \ 'pointer': ['fg', 'Exception'],   \ 'marker':  ['fg', 'Keyword'],   \ 'spinner': ['fg', 'Label'],   \ 'header':  ['fg', 'Comment'] }  " Enable per-command history. " CTRL-N and CTRL-P will be automatically bound to next-history and " previous-history instead of down and up. If you don't like the change, " explicitly bind the keys to down and up in your $FZF_DEFAULT_OPTS. let g:fzf_history_dir = '~/.local/share/fzf-history'  " [Buffers] Jump to the existing window if possible let g:fzf_buffers_jump = 1  " [[B]Commits] Customize the options used by 'git log': let g:fzf_commits_log_options = '--graph --color=always --format="%C(auto)%h%d %s %C(black)%C(bold)%cr"'  " [Tags] Command to generate tags file let g:fzf_tags_command = 'gtags'  " [Commands] --expect expression for directly executing the command let g:fzf_commands_expect = 'alt-enter,ctrl-x'  " Mapping selecting mappings nmap <leader><tab> <plug>(fzf-maps-n) xmap <leader><tab> <plug>(fzf-maps-x) omap <leader><tab> <plug>(fzf-maps-o)  " Insert mode completion imap <c-x><c-k> <plug>(fzf-complete-word) imap <c-x><c-f> <plug>(fzf-complete-path) imap <c-x><c-j> <plug>(fzf-complete-file-ag) imap <c-x><c-l> <plug>(fzf-complete-line)  " Advanced customization using autoload functions inoremap <expr> <c-x><c-k> fzf#vim#complete#word({'left': '15%'})  let g:fzf_files_options =   \ '--preview "(coderay {} || less {}) 2> /dev/null | head -'.&lines.'"'  nmap <C-p> :Files<CR> nmap <C-e> :Buffers<CR>  " press s in qf window to open tag in new split window autocmd FileType qf nnoremap <silent><buffer> s <Enter><C-W>s " press v in qf window to open tag in new vertical split window autocmd FileType qf nnoremap <silent><buffer> v <Enter><C-W>v " press t in qf window to open tag in new tab autocmd FileType qf nnoremap <silent><buffer> t <Enter><C-W>T 

Summary

replace .vimrc and .vim with below repo
https://github.com/lengerrong/ervim.git

set up java spring boot "hello world" web application on ubuntu from zero.

install JDK 8

$ sudo apt-get install openjdk-8-jdk

install Gradle

$ curl -s "https://get.sdkman.io" | bash
$ source "$HOME/.sdkman/bin/sdkman-init.sh"
$ sdk install gradle 5.1.1

Spring Initializr

start.spring.io
get your "demo.zip" and unzip it.
choose "Gradle Project",
please remember add "Web" as dependence,
otherwise there will be compile errors.

Create a simple web application
$ cat src/main/java/com/example/demo/HelloController.java

package com.example.demo;

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;

@RestController
public class HelloController {

    @RequestMapping("/")
    public String index() {
        return "Greetings from Spring Boot!";
    }

}

Run the Application

$ ./gradlew bootRun

Check out the service.

$ curl localhost:8080
Greetings from Spring Boot!

Generate IDE profile

add two plugin in build.gradle

apply plugin "idea" apply plugin "eclipse" 

generate IDE profile for IntelliJ IDEA(ipr)
./gradlew idea
generate IDE profile for Eclipse(.project)
./gradlew eclipse

Refers

Building an Application with Spring Boot

AWS : how to play a video file from s3 bucket in browser

URI

all you have to do is to sign a request like:

https://s3.amazonaws.com/yourbucket/key?

response-content-disposition=inline&

X-Amz-Algorithm=AWS4-HMAC-SHA256&

X-Amz-Credential=AKIAJWWH7EGSUBWE34IQ/20181228/us-east-1/s3/aws4_request&

X-Amz-Date=20181228T074135Z&

X-Amz-Expires=86400&X-Amz-SignedHeaders=host&

X-Amz-Signature=b3143f8442812e176fd61838813a33f53cfd7e198e1c6e68fab5d03d4a642403

and set it as src attribue to a video element.

Player component

import React, { Component } from 'react';
import PropTypes from 'prop-types';

const AWS_SERVICE = 's3';
const crypto = require('crypto');

Date.prototype.toYMDString = function() {
    let year = this.getFullYear().toString();
    let month = this.getUTCMonth() + 1;
    if (month < 10)
      month = "0" + month;
    let day = this.getUTCDate();
    if (day < 10)
      day = "0" + day;
    return String(year) + String(month) 
           + String(day);
}

Date.prototype.toTZString = function() {
    let hour = this.getUTCHours();
    if (hour < 10)
      hour = "0" + hour;
    let minute = this.getUTCMinutes();
    if (minute < 10)
      minute = "0" + minute;
    let second = this.getUTCSeconds();
    if (second < 10)
      second = "0" + second;
    return this.toYMDString() + "T"
      + String(hour) + String(minute)
      + String(second) + "Z";
}

class Player extends Component {
  constructor(props) {
    super(props);
  }

  Hmac(key, string) {
      const hmac = crypto.createHmac('sha256', key);
      hmac.end(string);
      return hmac.read();
  }
  
  Signature(date, region, service, toSign) {
    const { aws_secret_key } = this.props;
      let dateKey = this.Hmac('AWS4' + aws_secret_key, date);
      let dateRegionKey = this.Hmac(dateKey, region);
      let dateRegionServiceKey = this.Hmac(dateRegionKey, service);
      let signingKey = this.Hmac(dateRegionServiceKey, 'aws4_request');
      let signature = this.Hmac(signingKey, toSign).toString('hex');
      return signature;
  }
  
  stringToSign(timeStamp, scope, canonicalRequest) {
      var signParts = [];
      signParts.push('AWS4-HMAC-SHA256');
      signParts.push(timeStamp);
      signParts.push(scope);
      signParts.push(crypto.createHash('sha256').update(canonicalRequest).digest(
  'hex'));
      var result = signParts.join('\n');
      console.log('string to sign');
      console.log(result);
      return result;
  };
  
  canonicalRequest(method, uri, queryString, headers, signedHeaders, hashedPayload) {
    var canonicalParts = [];
    canonicalParts.push(method);
    canonicalParts.push(uri);
    canonicalParts.push(queryString);
    canonicalParts.push(headers);
    canonicalParts.push(signedHeaders);
    canonicalParts.push(hashedPayload);
    var result = canonicalParts.join('\n');
    console.log('canonical request');
    console.log(result);
    return result;
  }

  render() {
    const { aws_key, aws_region, bucket, key } = this.props;
    let uri = "/" + bucket + "/" + key;
    let time_stamp = new Date();
    let tz_time_stamp = time_stamp.toTZString();
    let ymd_time_stamp = time_stamp.toYMDString();
    let scope = ymd_time_stamp + "/" + aws_region + "/" + AWS_SERVICE + "/aws4_request";
    let queryString = "X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=" + encodeURIComponent(aws_key + "/" + scope) + "&X-Amz-Date=" + tz_time_stamp + "&X-Amz-Expires=86400&X-Amz-SignedHeaders=host&response-content-disposition=inline";
    let headers = "host:s3.amazonaws.com";
    let signedHeaders = "";
    let hashedPayload = "host\nUNSIGNED-PAYLOAD";
    let request = this.canonicalRequest('GET', uri, queryString, headers, signedHeaders, hashedPayload);
    let signature = this.Signature(ymd_time_stamp, aws_region, AWS_SERVICE, this.stringToSign(tz_time_stamp, scope, request));
    let url = 'https://s3.amazonaws.com' + uri + '?response-content-disposition=inline&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=' + aws_key + "/" + scope + '&X-Amz-Date=' + tz_time_stamp + '&X-Amz-Expires=86400&X-Amz-SignedHeaders=host&X-Amz-Signature=' + signature;
    console.log(url);
    return (
      <video src={url}
        autoPlay playsInline controls
        style={{width:320,height:240}}>
      </video>
    )
  }
}

Player.propTypes = {
  aws_key: PropTypes.string.isRequired,
  aws_secret_key: PropTypes.string.isRequired,
  aws_region: PropTypes.string.isRequired,
  bucket: PropTypes.string.isRequired,
  key: PropTypes.string.isRequired
};

export default Player;

Usage

    return (
        <Player aws_key={aws_key} bucket={bucket} aws_secret_key={aws_secret_key}
          key={key} aws_region={aws_region}>
        </Player>
    );

example

WebRTC recording via Kurento media server

Official guide

I encountered some errors while following the Official guide.
Lucky, I fixed all the errors and make it work finally.
Notes my workaround here, hope it work for you if you have the same problem.

gpg: keyserver receive failed: keyserver error

local install guide

solution from stackoverflow

sudo apt-key adv --keyserver hkp://keys.gnupg.net:80 --recv-keys 5AFA7A83

WebSocket connection to 'wss://<local_ip>:8433/kurento' failed: Error in connection establishment: net::ERR_CONNECTION_REFUSED

cause

the application server is started with https if you follow the guide:

http-server -p 8443 -S -C keys/server.crt -K keys/server.key 

but kurento media server start without ssl by default config.
You can get from the config and the default port is 8888.
/etc/kurento/kurento.conf.json

solution

modify kurento media server config to enable ssl and use the same cert that used for your application server. it is a little complex.
but we have a easy solution, just start your application without ssl and test with firefox(if use chrome, you will got a dom exception, then you have to enable ssl for kms).

modify js/index.js
ws_uri: 'ws://' + location.hostname + ':8888/kurento'

start application server with
http-server -p 8443

record callback not triggered

if you use kurento-hello-world-recorder-generator as the example, then everything works well.
but if you use kurento-tutorial-js/kurento-recorder, you might found record not work.

https://github.com/Kurento/kurento-tutorial-js/pull/3

Below patch is work solution for it, but it was not accepted, strange thing.
https://github.com/Kurento/kurento-tutorial-js/pull/3/commits/ccab45818f3336639eec3c02a56f14209124901c

AWS: how to upload file to your s3 bucket via EvaporateJS in browser

Evaporate and config s3 bucket and IAM user

EvaporateJS
Config AWS s3 bucket
Managing Access Permissions to Your Amazon S3 Resources
User Access Key
In summary, create a s3 bucket, set up CORS settings and bucket policy.

 <CORSConfiguration>
     <CORSRule>
         <AllowedOrigin>https://*.yourdomain.com</AllowedOrigin>
         <AllowedOrigin>http://*.yourdomain.com</AllowedOrigin>
         <AllowedMethod>PUT</AllowedMethod>
         <AllowedMethod>POST</AllowedMethod>
         <AllowedMethod>DELETE</AllowedMethod>
         <AllowedMethod>GET</AllowedMethod>
         <ExposeHeader>ETag</ExposeHeader>
         <AllowedHeader>*</AllowedHeader>
     </CORSRule>
 </CORSConfiguration>
 
{
    "Version": "2012-10-17",
    "Id": "Policy145337ddwd",
    "Statement": [
        {
            "Sid": "",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::6681765859115:user/me"
            },
            "Action": [
                "s3:AbortMultipartUpload",
                "s3:ListMultipartUploadParts",
                "s3:GetObject",
                "s3:PutObject"
            ],
            "Resource": "arn:aws:s3:::mybucket/*"
        }
    ]
} 

Main codes

an example app created via 'create-reat-app' tool.

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

const Evaporate = require('evaporate');
const crypto = require('crypto');

class App extends Component {
  onFileSelected(files) {
    var config = {
      signerUrl: 'YOURSIGNEDURL',
      aws_key: 'YOURAWSKEY',
      bucket: 'YOURBUCKETNAME',
      cloudfront: true,
      computeContentMd5: true,
      cryptoMd5Method: function (data) {
        return crypto.createHash('md5').update(Buffer.from(data)).digest('base64');  
      },
      cryptoHexEncodedHash256: function (data) {
        return crypto.createHash('sha256').update(Buffer.from(data)).digest('hex');
      }
    };
    return Evaporate.create(config)
      .then(function (evaporate) {
         var addConfig = {
           name: files[0].name,
           file: files[0],
           progress: function (progressValue) {
             console.log('Progress', progressValue);
           },
           complete: function (_xhr, awsKey) {
             console.log('Complete!');
           },
         };
         var overrides = {
            bucket: 'recordingsfortalkmeup'
         };
         evaporate.add(addConfig, overrides)
           .then(function (awsObjectKey) {
                console.log('File successfully uploaded to:', awsObjectKey);
           },
           function (reason) {
             console.log('File did not upload sucessfully:', reason);
           });
      });
  }
  render() {
    return (
      <div className="App">
        <input type='file' onChange={(e) => this.onFileSelected(e.target.files)
 }/>
      </div>
    );
  }
}

export default App;

Signer URL

Create a lambda function to do the signature process.
Signing AWS Requests with Signature Version 4

'use strict';
console.log('Loading upload signature function');

const crypto = require("crypto");

function hmac(key, string){
    const hmac = crypto.createHmac('sha256', key);
    hmac.end(string);
    return hmac.read();
}

exports.handler = function(event, context, callback) {
    console.log(JSON.stringify(event));
    let to_sign = event.queryStringParameters.to_sign;
    let timestamp = event.queryStringParameters.datetime.substr(0, 8);
    console.log(to_sign);    
    console.log('date:', timestamp);
    console.log('aws secret key:', process.env.AWS_SECRET);
    console.log('region:', process.env.AWS_REGION);
    console.log('service:s3');
    let dateKey = hmac('AWS4' + process.env.AWS_SECRET, timestamp);
    let dateRegionKey = hmac(dateKey, process.env.AWS_REGION);
    let dateRegionServiceKey = hmac(dateRegionKey, 's3');
    let signingKey = hmac(dateRegionServiceKey, 'aws4_request');
    let signature = hmac(signingKey, to_sign).toString('hex');
    console.log('Created signature "' + signature + '" from ' + to_sign);
    var response = {
        statusCode: 200,
        headers: {
            "Access-Control-Allow-Origin" : "*",
            "Content-Type": "text/html"
        },
        body: signature
    };
    callback(null, response);
};

Build an rest API bind with this Lambda function and deploy it, then you will get an invoke url which will be your signer url.
Build an API Gateway API with Lambda Integration

Test

Everything is ok, you will find new uploaded file in your s3 bucket.

Download file from s3 bucket