Hands-on Scala Programming

Author	Li Haoyi
Published	1 June 2020
Website	www.handsonscala.com
ISBN	978-981-14-5693-0

First Edition, published June 1 2020

No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the Author.

ISBN 978-981-14-5693-0

Written and Published by Li Haoyi

Book Website: https://www.handsonscala.com/

Chapter Discussion: https://www.handsonscala.com/discuss

Live Chat: https://www.handsonscala.com/chat

Online materials: https://github.com/handsonscala/handsonscala

For inquiries on distribution, translations, or bulk sales, please contact the author directly at haoyi.sg@gmail.com.

The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has been taken in the preparation of this work, the Author shall not have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in it.

Reviewers

Thanks to all the reviewers who helped review portions of this book and provide the feedback that helped refine this book and make it what it is today.

In alphabetical order:

Alex Allain, Alwyn Tan, Bryan Jadot, Chan Ying Hao, Choo Yang, Dean Wampler, Dimitar Simeonov, Eric Marion, Grace Tang, Guido Van Rossum, Jez Ng, Karan Malik, Liang Yuan Ruo, Mao Ting, Martin MacKerel, Martin Odersky, Michael Wu, Olafur Pall Geirsson, Ong Ming Yang, Pathikrit Bhowmick

I Scala导论	13
1 上手Scala	15
2 搭建环境	25
3 Scala基础	39
4 Scala集合	61
5 Scala特性	81

II Local Development	105
6 Implementing Algorithms in Scala	107
7 Files and Subprocesses	116
8 JSON and Binary Data Serialization	124
9 Self-Contained Scala Scripts	133
10 Static Build Pipelines	142

III Web Services	150
11 Scraping Websites	152
12 Working with HTTP APIs	161
13 Fork-Join Parallelism with Futures	169
14 Simple Web and API Servers	178
15 Querying SQL Databases	186

IV Program Design	194
16 Message-based Parallelism with Actors	196
17 Multi-Process Applications	204
18 Building a Real-time File Synchronizer	213
19 Parsing Structured Text	225
20 Implementing a Programming Language	233

1 上手Scala	15
1.1 为什么选Scala？	16
1.2 为什么选择本书？	17
1.3 本书如何组织	18
1.4 代码片段和样例	19
1.5 在线资料	21

目录

前言

I Scala导论

II Local Development

III Web Services

IV Program Design

Conclusion

Part I Scala导论

Part II Local Development

Part III Web Services

Part IV Program Design

Hands-on Scala Programming

2 搭建环境	25
2.1 Windows搭建（可选）	26
2.2 安装Java	26
2.3 安装Ammonite	27
2.4 安装Mill	30
2.5 IDE支持	33

3 Scala基础	39
3.1 数据结构	40
3.2 循环，条件，Comprehensions	46
3.3 方法与函数	51
3.4 类和Trait	54

4 Scala集合	61
4.1 通用操作	62
4.2 不可变集合	68
4.3 可变集合	73
4.4 公共接口	77

5 Scala特性	81
5.1 Case Class和Sealed Trait	82
5.2 模式匹配	84
5.3 传名参数	89
5.4 隐式参数	92
5.5 Typeclass推断	94

6 Implementing Algorithms in Scala	107
6.1 Merge Sort	108
6.2 Prefix Tries	109
6.3 Breadth First Search	110
6.4 Shortest Paths	111
6.5 Conclusion	111

7 Files and Subprocesses	116
7.1 Paths	117
7.2 Filesystem Operations	118
7.3 Folder Syncing	119
7.4 Simple Subprocess Invocations	120
7.5 Interactive and Streaming Subprocesses	120
7.6 Conclusion	121

8 JSON and Binary Data Serialization	124
8.1 Manipulating JSON	125
8.2 JSON Serialization of Scala Data Types	126
8.3 Writing your own Generic Serialization Methods	127
8.4 Binary Serialization	128
8.5 Conclusion	128

9 Self-Contained Scala Scripts	133
9.1 Reading Files Off Disk	134
9.2 Rendering HTML with Scalatags	134
9.3 Rendering Markdown with Commonmark-Java	135
9.4 Links and Bootstrap	136
9.5 Optionally Deploying the Static Site	136
9.6 Conclusion	138

10 Static Build Pipelines	142
10.1 Mill Build Pipelines	143
10.2 Mill Modules	144
10.3 Revisiting our Static Site Script	145
10.4 Conversion to a Mill Build Pipeline	146
10.5 Extending our Static Site Pipeline	147
10.6 Conclusion	148

11 Scraping Websites	152
11.1 Scraping Wikipedia	153
11.2 MDN Web Documentation	154
11.3 Scraping MDN	155
11.4 Putting it Together	156
11.5 Conclusion	156

12 Working with HTTP APIs	161
12.1 The Task: Github Issue Migrator	162
12.2 Creating Issues and Comments	163
12.3 Fetching Issues and Comments	164
12.4 Migrating Issues and Comments	165
12.5 Conclusion	166

13 Fork-Join Parallelism with Futures	169
13.1 Parallel Computation using Futures	170
13.2 N-Ways Parallelism	171
13.3 Parallel Web Crawling	172
13.4 Asynchronous Futures	173
13.5 Asynchronous Web Crawling	174
13.6 Conclusion	175

14 Simple Web and API Servers	178
14.1 A Minimal Webserver	179
14.2 Serving HTML	180
14.3 Forms and Dynamic Data	181
14.4 Dynamic Page Updates via API Requests	182
14.5 Real-time Updates with Websocks	183
14.6 Conclusion	184

15 Querying SQL Databases	186
15.1 Setting up Quill and PostgreSQL	187
15.2 Mapping Tables to Case Classes	188
15.3 Querying and Updating Data	189
15.4 Transactions	190
15.5 A Database-Backed Chat Website	191
15.6 Conclusion	192

16 Message-based Parallelism with Actors	196
16.1 Castor Actors	197
16.2 Actor-based Background Uploads	198
16.3 Concurrent Logging Pipelines	199
16.4 Debugging Actors	200
16.5 Conclusion	200

17 Multi-Process Applications	204
17.1 Two-Process Build Setup	205
17.2 Remote Procedure Calls	206
17.3 The Agent Process	207
17.4 The Sync Process	208
17.5 Pipelined Syncing	208
17.6 Conclusion	210

18 Building a Real-time File Synchronizer	213
18.1 Watching for Changes	214
18.2 Real-time Syncing with Actors	215
18.3 Testing the Syncer	216
18.4 Pipelined Real-time Syncing	217
18.5 Testing the Pipelined Syncer	218
18.6 Conclusion	220

19 Parsing Structured Text	225
19.1 Simple Parsers	226
19.2 Parsing Stuctured Values	227
19.3 Implementing a Calculator	228
19.4 Parser Debugging and Error Reporting	229
19.5 Conclusion	230

20 Implementing a Programming Language	233
20.1 Interpreting Jsonnet	234
20.2 Jsonnet Language Features	235
20.3 Parsing Jsonnet	236
20.4 Evaluating the Syntax Tree	237
20.5 Serializing to JSON	237
20.6 Conclusion	239