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NPI – Security Top – Temp – Non-Geo (Frontegg)

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

NPI – Frontegg – Security – (partner)
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

NPI – Spring Top – Temp – Non-Geo (Lightrun)

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

NPI – Lightrun – Spring (partner)

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

In this second article of the series, we'll build some simple functionality to post on Reddit from our application, via their API.

2. Necessary Security

First – let's get the security aspect out of the way.

In order to Submit a Link to Reddit, we need to define an OAuth protected Resource with the scope of “submit“:

public OAuth2ProtectedResourceDetails reddit() {
    AuthorizationCodeResourceDetails details = new AuthorizationCodeResourceDetails();
    details.setScope(Arrays.asList("identity", "submit"));
    return details;

Note that we're also specifying the scopeidentity” because we also need access the user account information.

3. Is Captcha Needed?

Users that are new to Reddit have to fill in a Captcha in order to submit; that is before they pass a certain karma threshold within Reddit.

For these users, we first need to check if the Captcha is needed:

private String needsCaptcha() {
    String result = redditRestTemplate.getForObject(
      "https://oauth.reddit.com/api/needs_captcha.json", String.class);
    return result;

private String getNewCaptcha() {
    HttpHeaders headers = new HttpHeaders();
    HttpEntity req = new HttpEntity(headers);

    Map<String, String> param = new HashMap<String, String>();
    param.put("api_type", "json");

    ResponseEntity<String> result = redditRestTemplate.postForEntity(
      "https://oauth.reddit.com/api/new_captcha", req, String.class, param);
    String[] split = result.getBody().split("""); 
    return split[split.length - 2];

4. The “Submit Post” Form

Next, let's create the main form for submitting new posts to Reddit. Submitting a Link requires the following details:

  • title – the title of the article
  • url – the URL of the article
  • subreddit – the sub-reddit to submit the link to

So let's see how we can display this simple submission page:

public String showSubmissionForm(Model model) throws JsonProcessingException, IOException {
    String needsCaptchaResult = needsCaptcha();
    if (needsCaptchaResult.equalsIgnoreCase("true")) {
        String iden = getNewCaptcha();
        model.addAttribute("iden", iden);
    return "submissionForm";

And of course the basic submissionForm.html:

    <input name="title"/>
    <input name="url" />
    <input name="sr"/>
    <input  type="checkbox" name="sendReplies" value="true"/>

    <div th:if="${iden != null}">
        <input type="hidden" name="iden" value="${iden}"/>
        <input name="captcha"/>
        <img src="http://www.reddit.com/captcha/${iden}" alt="captcha" width="200"/>
    <button type="submit" onclick="submitPost()">Post</button>

function submitPost(){
    var data = {};
    $('form').serializeArray().map(function(x){data[x.name] = x.value;});
        url: "api/posts",
        data: JSON.stringify(data),
        type: 'POST',
    }).done(function(data) {
        if(data.length < 2){ alert(data[0]);}
    }).fail(function(error) { alert(error.responseText); }); 

Now – let's take a look at the final step – submitting the actual link via the Reddit API.

We'll POST a submit request to Reddit using the parameters from our submissionForm:

@RequestMapping(value = "/api/posts")
public class RedditPostRestController {

    private RedditService service;

    @RequestMapping(method = RequestMethod.POST)
    public List<String> submit(@Valid @RequestBody PostDto postDto) {
        return service.submitPost(postDto);

Here's the actual method implementation:

public List<String> submitPost(PostDto postDto) {
    MultiValueMap<String, String> param1 = constructParams(postDto);
    JsonNode node = redditTemplate.submitPost(param1);
    return parseResponse(node);

private MultiValueMap<String, String> constructParams(PostDto postDto) {
    MultiValueMap<String, String> param = new LinkedMultiValueMap<String, String>();
    param.add("title", postDto.getTitle());
    param.add("sr", postDto.getSubreddit());
    param.add("url", postDto.getUrl());
    param.add("iden", postDto.getIden());
    param.add("captcha", postDto.getCaptcha());
    if (postDto.isSendReplies()) {
        param.add("sendReplies", "true");

    param.add("api_type", "json");
    param.add("kind", "link");
    param.add("resubmit", "true");
    param.add("then", "comments");
    return param;

And the simple parsing logic, handling the response from the Reddit API:

private List<String> parseResponse(JsonNode node) {
    String result = "";
    JsonNode errorNode = node.get("json").get("errors").get(0);
    if (errorNode != null) {
        for (JsonNode child : errorNode) {
            result = result + child.toString().replaceAll("\"|null", "") + "<br>";
        return Arrays.asList(result);
    } else {
        if ((node.get("json").get("data") != null) && 
            (node.get("json").get("data").get("url") != null)) {
            return Arrays.asList("Post submitted successfully", 
        } else {
            return Arrays.asList("Error Occurred while parsing Response");

All of this is working with a basic DTO:

public class PostDto {
    private String title;

    private String url;

    private String subreddit;

    private boolean sendReplies;

    private String iden;
    private String captcha;

Finally – the submissionResponse.html:

    <h1 th:text="${msg}">Hello</h1>
    <h1 th:if="${param.containsKey('msg')}" th:text="${param.msg[0]}">Hello</h1>
    <h2 th:if="${param.containsKey('url')}"><a th:href="${param.url[0]}">Here</a></h2>

6. Conclusion

In this quick tutorial we implemented some basic Submit to Reddit functionality – simplistic but fully functional.

In the next part of this case study, we'll implement a Schedule Post for Later functionality into our app.

The full implementation of this tutorial can be found in the github project – this is an Eclipse based project, so it should be easy to import and run as it is.

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