Web Development with Clojure: Build Large, Maintainable Web Applications Interactively

350 Pages·2021·13.46 MB·english

by  Dmitri Sotnikov

Under Construction: The book you’re reading is still under
development. As part of our Beta book program, we’re releasing
ß this copy well before a normal book would be released. That
way you’re able to get this content a couple of months before
it’s available in finished form, and we’ll get feedback to make
the book even better. The idea is that everyone wins!
Be warned: The book has not had a full technical edit, so it will contain errors.
It has not been copyedited, so it will be full of typos, spelling mistakes, and the
occasional creative piece of grammar. And there’s been no effort spent doing
layout, so you’ll find bad page breaks, over-long code lines, incorrect hyphen-
ation, and all the other ugly things that you wouldn’t expect to see in a finished
book. It also doesn't have an index. We can’t be held liable if you use this book
to try to create a spiffy application and you somehow end up with a strangely
shaped farm implement instead. Despite all this, we think you’ll enjoy it!
Download Updates: Throughout this process you’ll be able to get updated
ebooks from your account at pragprog.com/my_account. When the book is com-
plete, you’ll get the final version (and subsequent updates) from the same ad-
dress.
Send us your feedback: In the meantime, we’d appreciate you sending us your
feedback on this book at pragprog.com/titles/dswdcloj3/errata, or by using the links
at the bottom of each page.
Thank you for being part of the Pragmatic community!
The Pragmatic Bookshelf
Web Development with Clojure,
Third Edition
Build Large, Maintainable Web Applications Interactively
Dmitri Sotnikov
Scot Brown
The Pragmatic Bookshelf
Raleigh, North Carolina
Many of the designations used by manufacturers and sellers to distinguish their products
are claimed as trademarks. Where those designations appear in this book, and The Pragmatic
Programmers, LLC was aware of a trademark claim, the designations have been printed in
initial capital letters or in all capitals. The Pragmatic Starter Kit, The Pragmatic Programmer,
Pragmatic Programming, Pragmatic Bookshelf, PragProg and the linking g device are trade-
marks of The Pragmatic Programmers, LLC.
Every precaution was taken in the preparation of this book. However, the publisher assumes
no responsibility for errors or omissions, or for damages that may result from the use of
information (including program listings) contained herein.
For our complete catalog of hands-on, practical, and Pragmatic content for software devel-
opers, please visit https://pragprog.com.
For sales, volume licensing, and support, please contact [email protected].
For international rights, please contact [email protected].
Copyright © 2021 The Pragmatic Programmers, LLC.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,
or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording,
or otherwise, without the prior consent of the publisher.
ISBN-13: 978-1-68050-682-2
Encoded using the finest acid-free high-entropy binary digits.
Book version: B17.0—March 12, 2021
Contents
Changes in the Beta Release . . . . . . . . . vii
Acknowledgments . . . . . . . . . . . xi
Introduction . . . . . . . . . . . . xiii
1. Getting Your Feet Wet. . . . . . . . . . . 1
Set Up Your Environment 1
Managing Projects with Leiningen 2
Build Your First Web App 4
Refine Your App 9
What You’ve Learned 26
2. Luminus Web Stack . . . . . . . . . . . 29
Route Requests with Ring 29
Extend Ring 37
Define the Routes with Reitit 42
HTML Templating Using Selmer 46
What You’ve Learned 54
3. Luminus Architecture . . . . . . . . . . 55
Manage the Project 55
Think in Terms of Application Components 57
Managing Stateful Components 67
What You’ve Learned 70
4. Introducing Clojurescript . . . . . . . . . 71
Understand ClojureScript 71
Add ClojureScript Support 73
Build the UI with Reagent 77
Managing State with Re-Frame 94
What You’ve Learned 98
Contents • iv
5. Setting Up for Success . . . . . . . . . . 99
Services 100
ClojureScript Development Tools 117
Embracing Re-Frame 130
Multi-User With Websockets 138
Upgrading to Sente 143
Events and Effects in Re-Frame 151
What You’ve Learned 156
6. Planning Our Application . . . . . . . . . 159
What’s in our MVP? 159
The Elephant in the Room 162
Data Modelling 165
Adding User Management 166
What you’ve learned 184
7. Account Management . . . . . . . . . . 185
Authorship 185
Add Author’s Posts Page 196
Account Customization 217
Account Settings 250
What You’ve Learned 260
8. Social Interaction . . . . . . . . . . . 261
Improving Posts 261
Curating Posts 316
What you’ve learned 328
9. Deployment . . . . . . . . . . . . 329
Unit Tests 329
Package the Application 338
What You’ve Learned 343
10. Exercises . . . . . . . . . . . . . 345
How to Read this Chapter 345
Code Quality 346
Feature Enhancements 350
What You’ve Learned 360
A1. Clojure Primer . . . . . . . . . . . . 361
A Functional Perspective 361
Data Types 363
Contents • v
Using Functions 364
Anonymous Functions 364
Named Functions 365
Higher-Order Functions 367
Closures 368
Threading Expressions 369
Being Lazy 369
Structuring the Code 370
Destructuring Data 371
Namespaces 372
Dynamic Variables 374
Polymorphism 375
What About Global State? 377
Writing Code That Writes Code for You 378
The Read-Evaluate-Print Loop 380
Calling Out to Java 380
Calling Methods 381
Reader Conditionals 382
Summary 383
A2. Editor Configuration . . . . . . . . . . 385
Why is Editor Integration So Important? 385
General Configuration Tips 387
VSCode + Calva 387
IntelliJ IDEA + Cursive 387
Emacs + Cider 387
Vim 388
A3. Working with EDN and Transit . . . . . . . . 389
EDN 389
Transit 390
A4. Database Access . . . . . . . . . . . 393
Work with Relational Databases 393
Use HugSQL 399
Generate Reports 403
What You’ve Learned 412
Contents • vi
A5. Writing RESTful Web Services with Liberator . . . . 413
Using Liberator 413
Defining Resources 414
Putting It All Together 418
A6. Leiningen Templates . . . . . . . . . . 425
What’s in a Template 425
Changes in the Beta Release
Beta 17, March 5, 2021
Updated all library versions.
Migrated to next.jdbc.
Restructured test/ directory to reflect common convention.
Content complete and heading to copyediting and indexing.
Beta 16, December 23, 2020
Fixed typo in Chapter 5.
Added reference to first introduction of :messages/filter
Added Editor Configuration Appendix
Added Leiningen Templates Appendix
Added Encoding Appendix
Beta 15, December 15, 2020
Add Chapter 10, Exercises.
Add ClojureScript Testing to Chapter 9
Reference ClojureScript Testing section from Chapter 5.
Remove outdated authorq tags
Beta 14, December 08, 2020
Address typo in Chapter 7.
Address common issue with ‘create-migration‘ where readers don’t run ‘start‘
first.
report erratum • discuss
Changes in the Beta Release • viii
Add instructions on how to get source code
Address reloading issue. Briefly explain reagent closing over arguments.
Add logout route implementation.
Update package.json.
Beta 13, November 09, 2020
Add Chapter 9: Deployment
Remove LookBehind from Regular Expressions in Chapter 8 to improve
browser compatibility
Beta 12, October 27, 2020
Add Chapter 8: Social Interaction
Clarify usage of vars in Chapter 2
Remove broken vars in front-end controllers
Beta 11
Skipped.
Beta 10, August 18, 2020
Fix image-uploader to clear stale state. In Account Management > Account
Customization
Fix nil auth handling
Fix reitit route reloading
Pull li wrapper out of message component to allow better reuse
Update reagent to 0.10.0
Update Re-frame to 1.0.0
Beta 9, July 21, 2020
Fixed code typo in profile page which caused Update Profile to be incorrectly
disabled in Account Management > Account Customization
Added missing require of clojure.java.io to REPL example in Account Manage-
ment > Account Customization
report erratum • discuss