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Clojure Programming Cookbook

By : Makoto Hashimoto, Modrzyk

3 (1)

Clojure Programming Cookbook

3 (1)

By: Makoto Hashimoto, Modrzyk

Overview of this book

When it comes to learning and using a new language you need an effective guide to be by your side when things get rough. For Clojure developers, these recipes have everything you need to take on everything this language offers. This book is divided into three high impact sections. The first section gives you an introduction to live programming and best practices. We show you how to interact with your connections by manipulating, transforming, and merging collections. You’ll learn how to work with macros, protocols, multi-methods, and transducers. We’ll also teach you how to work with languages such as Java, and Scala. The next section deals with intermediate-level content and enhances your Clojure skills, here we’ll teach you concurrency programming with Clojure for high performance. We will provide you with advanced best practices, tips on Clojure programming, and show you how to work with Clojure while developing applications. In the final section you will learn how to test, deploy and analyze websocket behavior when your app is deployed in the cloud. Finally, we will take you through DevOps. Developing with Clojure has never been easier with these recipes by your side!

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Conventions

Reader feedback

Customer support

Free Chapter

1. Live Programming with Clojure

1. Live Programming with Clojure

Introduction

REPL up!

Working with primitive data types

Using bindings of vars, conditions, loops, and error handling

Using and defining functions

Using third-party libraries

Using namespaces

What's next?

2. Interacting with Collections

2. Interacting with Collections

Introduction

Clojure collections and their basic functions

Accessing and updating elements from collections

Filtering elements from collections

Transforming and sorting collections

Merging and splitting collections

How to become lazy

3. Clojure Next

3. Clojure Next

Introduction

Using destructuring techniques

Using functional programming style

Using threading macros

Defining simple macros

Defining more advanced macros

Using protocols

Defining multimethods

Transducers for dummies

Logic programming in Clojure

4. File Access and the Network

4. File Access and the Network

Introduction

Manipulating files and directories

Manipulating various formats of files - XML, JSON, YAML, and EDN

Making use of Clojure HTTP client

Using queues and topics in the RabbitMQ

Using Kafka

Using MQTT

Streaming access to provide high performance

Using Apache Camel to connect everything

5. Working with Other Languages

5. Working with Other Languages

Introduction

Calling Java methods and accessing Java objects from Clojure

Extending Java superclasses and implementing Java interfaces

Calling Clojure from Java

Calling Scala from Clojure

ClojureCLR

ClojureScript

6. Concurrency and Parallelism

6. Concurrency and Parallelism

Introduction

Solving concurrent problems using Clojure

Distributed actor-based dev with Akka

Using Spyglass and Couchbase to share state between JVMs

Reactive programming with meltdown

Bridging core.async

On Quasar/Pulsar

7. Advanced Tips

7. Advanced Tips

Introduction

Hacking the Clojure code

Using Reader Conditionals, compile to Clojure, and ClojureScript

Real-time shared development with an REPL

Declarative data descriptions and validations with plumatic/schema

8. Web Applications

8. Web Applications

Introduction

Clojure with Vaadin - easy web widgets

Quickly create a REST API with Liberator

Working with Immutant - reusing infrastructure

Developing with om.next, the next-generation ClojureScript library

9. Testing

9. Testing

Introduction

Behavior-driven development

Testing with random inputs and pattern-based testing

Benchmarking with Criterium, performance tips, and other tools

10. Deployment and DevOps

10. Deployment and DevOps

Introduction

Riemann - monitoring deliverance and slacking

Deploying Clojure with Docker

Clojure on Amazon Web Services

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Making use of Clojure HTTP client

For retrieving simple HTTP requests, http-kit is a library of choice when the simple slurp function from clojure.core does not provide enough flexibility. While http-kit is both a server and a client, this recipe will only look at the client side of things.

Getting ready

Including the http-kit library into our project is now relatively straightforward. Let's add the following line to the project.clj file:

[http-kit "2.1.18"]

How to do it...

A simple request to retrieve the weather data, as we have seen before in the parsing JSON section, is quite simply done by calling the get function of http-kit. The function returns a promise by default, meaning the call will run in the background and block when trying to get the result by calling deref or @.

Let's get set quickly with the namespace and the target URL to retrieve weather data from the openweathermap API endpoint:

(ns chapter04.somehttp1 
  (:require [org.httpkit.client :as http])) 
 
...

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