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Security Top – Temp

I just announced the new Learn Spring Security course, including the full material focused on the new OAuth2 stack in Spring Security 5:

Frontegg – Security – Text1
announcement - icon User management is very complex, when implemented properly. No surprise here.

Not having to roll all of that out manually, but instead integrating a mature, fully-fledged solution - yeah, that makes a lot of sense.
That's basically what Frontegg is - User Management for your application. It's focused on making your app scalable, secure and enjoyable for your users.
From signup to authentication, it supports simple scenarios all the way to complex and custom application logic.

Have a look:

>> Elegant User Management, Tailor-made for B2B SaaS

Spring Top – Temp

Get started with Spring 5 and Spring Boot 2, through the reference Learn Spring course:

Lightrun – Third Party Code

We rely on other people’s code in our own work. Every day. It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.

The problem is, of course, when things fall apart in production - debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky. It’s difficult to understand what talks to what and, specifically, which part of the underlying library is at fault.

Lightrun is a new kind of debugger.

It's one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics. No hotfixes, redeployments, or restarts required.

Learn more in this quick, 5-minute Lightrun tutorial:

>> The Essential List of Spring Boot Annotations and Their Use Cases

1. Overview

The Reddit web application Case Study is moving along nicely – and the small web application is shaping up and slowly becoming usable.

In this installment, we're going to be making small improvements to the existing functionality – some externally facing, some not – and generally making the app better.

2. Setup Checks

Let's start with some simple – but useful – checks that need to run when the application is bootstrapped:

private UserRepository repo;

public void startupCheck() {
    if (StringUtils.isBlank(accessTokenUri) || 
      StringUtils.isBlank(userAuthorizationUri) || 
      StringUtils.isBlank(clientID) || StringUtils.isBlank(clientSecret)) {
        throw new RuntimeException("Incomplete reddit properties");

Note how we're using the @PostConstruct annotation here to hook into the lifecycle of the application, after the dependency injection process is over.

The simple goals are:

  • check if we have all the properties we need to access the Reddit API
  • check that the persistence layer is working (by issuing a simple findAll call)

If we fail – we do so early.

3. The “Too Many Requests” Reddit Problem

The Reddit API is aggressive in rate limiting requests that aren't sending a unique “User-Agent“.

So – we need to add in this unique User-Agent header to our redditRestTemplate – using a custom Interceptor:

3.1. Create Custom Interceptor

Here is our custom interceptor – UserAgentInterceptor:

public class UserAgentInterceptor implements ClientHttpRequestInterceptor {

    public ClientHttpResponse intercept(
      HttpRequest request, byte[] body, 
      ClientHttpRequestExecution execution) throws IOException {

        HttpHeaders headers = request.getHeaders();
        headers.add("User-Agent", "Schedule with Reddit");
        return execution.execute(request, body);

3.2. Configure redditRestTemplate

We of course need to set this interceptor up with the redditRestTemplate we're using:

public OAuth2RestTemplate redditRestTemplate(OAuth2ClientContext clientContext) {
    OAuth2RestTemplate template = new OAuth2RestTemplate(reddit(), clientContext);
    List<ClientHttpRequestInterceptor> list = new ArrayList<ClientHttpRequestInterceptor>();
    list.add(new UserAgentInterceptor());
    return template;

4. Configure H2 Database for Testing

Next – let's go ahead and set up an in-memory DB – H2 – for testing. We need to add this dependency to our pom.xml:


And define a

## DataSource Configuration ###
## Hibernate Configuration ##

5. Switch to Thymeleaf

JSP is out and Thymeleaf is in.

5.1. Modify pom.xml

First, we need to add these dependencies to our pom.xml:


5.2. Create ThymeleafConfig

Next – a simple ThymeleafConfig:

public class ThymeleafConfig {
    public TemplateResolver templateResolver() {
        ServletContextTemplateResolver templateResolver = new ServletContextTemplateResolver();
        return templateResolver;

    public SpringTemplateEngine templateEngine() {
        SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        templateEngine.addDialect(new SpringSecurityDialect());
        return templateEngine;

    public ViewResolver viewResolver() {
        ThymeleafViewResolver viewResolver = new ThymeleafViewResolver();
        return viewResolver;

And add it to our ServletInitializer:

protected WebApplicationContext createServletApplicationContext() {
    AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
    context.register(PersistenceJPAConfig.class, WebConfig.class, 
      SecurityConfig.class, ThymeleafConfig.class);
    return context;

5.3. Modify home.html

And a quick modification of the homepage:

<title>Schedule to Reddit</title>
<div class="container">
        <h1>Welcome, <small><span sec:authentication="principal.username">Bob</span></small></h1>
        <a href="posts" >My Scheduled Posts</a>
        <a href="post" >Post to Reddit</a>
        <a href="postSchedule" >Schedule Post to Reddit</a>

6. Logout

Now – let's do some improvements that are actually visible to the end user of the application. We'll start with logout.

We're adding a simple logout option into the application by modifying our security config:

protected void configure(HttpSecurity http) throws Exception {

7. Subreddit Autocomplete

Next – let's implement a simple autocomplete functionality for the filling it the subreddit; writing it manually is not a good way to go, since there's a fair chance to get it wrong.

Let's start with the client side:

<input id="sr" name="sr"/>
<script src=""></script>
<script src=""></script>
$(function() {
    $( "#sr" ).autocomplete({
        source: "/subredditAutoComplete"

Simple enough. Now, the server side:

@RequestMapping(value = "/subredditAutoComplete")
public String subredditAutoComplete(@RequestParam("term") String term) {
    MultiValueMap<String, String> param = new LinkedMultiValueMap<String, String>();
    param.add("query", term);
    JsonNode node = redditRestTemplate.postForObject(
      "", param, JsonNode.class);
    return node.get("names").toString();

8. Check If Link Is Already on Reddit

Next – let's see how to check if a link is already submitted before to Reddit.

Here is our submissionForm.html:

<input name="url" />
<input name="sr">

<a href="#" onclick="checkIfAlreadySubmitted()">Check if already submitted</a>
<span id="checkResult" style="display:none"></span>

<script src=""></script>
$(function() {
    $("input[name='url'],input[name='sr']").focus(function (){
function checkIfAlreadySubmitted(){
    var url = $("input[name='url']").val();
    var sr = $("input[name='sr']").val();
    if(url.length >3 && sr.length > 3){
        $.post("checkIfAlreadySubmitted",{url: url, sr: sr}, function(data){
            var result = JSON.parse(data);
            if(result.length == 0){
                $("#checkResult").show().html("Not submitted before");
               'Already submitted <b><a target="_blank" href="'
        $("#checkResult").show().html("Too short url and/or subreddit");

And here is our controller method:

@RequestMapping(value = "/checkIfAlreadySubmitted", method = RequestMethod.POST)
public String checkIfAlreadySubmitted(
  @RequestParam("url") String url, @RequestParam("sr") String sr) {
    JsonNode node = redditRestTemplate.getForObject(
      "" + sr + "/search?q=url:" + url + "&restrict_sr=on", JsonNode.class);
    return node.get("data").get("children").toString();

9. Deployment to Heroku

Finally – we're going to set up deployment to Heroku – and use their free tier to power the sample app.

9.1. Modify pom.xml

First, we will need to add this Web Runner plugin to the pom.xml:


Note – we will use Web Runner to launch our app on Heroku.

We're going to be using Postgresql on Heroku – so we'll need to have a dependency to the driver:


9.2. The Procfile

We need to define the process that will run on the server in a Procfile – as follows:

web:    java $JAVA_OPTS -jar target/dependency/webapp-runner.jar --port $PORT target/*.war

9.3. Create Heroku App

To create a Heroku app from your project, we'll simply:

cd path_to_your_project
heroku login
heroku create

9.4. Database Configuration

Next – we need to configure our database using our app's Postgres database properties.

For example, here is

## DataSource Configuration ##

## Hibernate Configuration ##

Note that we need to get the database details [host name, database name, user and password] form the Heroku dashborad.

Also – like in most cases, the keyword “user” is a reserved word in Postgres, so we need to change our “User” entity table name:

@Table(name = "APP_USER")
public class User { .... }

9.5. Push Code to Heoku

Now – let's push code to Heroku:

git add .
git commit -m "init"
git push heroku master

10. Conclusion

In this forth part of our Case Study, the focus were small but important improvements. If you've been following along, you can see how this is shaping up to be an interesting and useful little app.

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