How to resolve the algorithm Read a configuration file step by step in the Kotlin programming language
How to resolve the algorithm Read a configuration file step by step in the Kotlin programming language
Table of Contents
Problem Statement
The task is to read a configuration file in standard configuration file format, and set variables accordingly. For this task, we have a configuration file as follows:
For the task we need to set four variables according to the configuration entries as follows:
We also have an option that contains multiple parameters. These may be stored in an array.
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Read a configuration file step by step in the Kotlin programming language
Explanation:
-
Data Class
Configuration
:- Models a user configuration with various properties, such as
fullName
,favoriteFruit
,needsPeeling
, andotherFamily
. - These properties are accessed using Kotlin's delegated property feature (
val fullName: String by map
).
- Models a user configuration with various properties, such as
-
Main Function:
- Input Reading: Reads lines from a text file
src/configuration.txt
that contains key-value pairs in a simple format.
- Input Reading: Reads lines from a text file
-
Preprocessing of Key-Value Pairs:
- Removes empty lines, commented lines, and splits the remaining lines into key-value pairs.
-
Configuration Map Initialization:
- Initializes a mutable map with a default value for
needsPeeling
asfalse
.
- Initializes a mutable map with a default value for
-
Key-Value Processing Loop:
- Iterates over the preprocessed key-value pairs.
- For each pair, based on the key, it updates the configuration map with the appropriate value.
- Any unexpected keys are logged.
-
Creating the
Configuration
Object:- Creates an instance of the
Configuration
data class using the populated configuration map.
- Creates an instance of the
-
Helper Functions:
commentedOut
: Checks if a line is commented out (starting with "#" or ";").toKeyValuePair
: Splits a line into aPair
of key and value, handling empty values.
Overall:
This Kotlin program reads a simple configuration file and parses it into a type-safe Configuration
data class. It demonstrates basic data processing and delegated properties in Kotlin.
Source code in the kotlin programming language
import java.nio.charset.StandardCharsets
import java.nio.file.Files
import java.nio.file.Paths
data class Configuration(val map: Map<String, Any?>) {
val fullName: String by map
val favoriteFruit: String by map
val needsPeeling: Boolean by map
val otherFamily: List<String> by map
}
fun main(args: Array<String>) {
val lines = Files.readAllLines(Paths.get("src/configuration.txt"), StandardCharsets.UTF_8)
val keyValuePairs = lines.map{ it.trim() }
.filterNot { it.isEmpty() }
.filterNot(::commentedOut)
.map(::toKeyValuePair)
val configurationMap = hashMapOf<String, Any>("needsPeeling" to false)
for (pair in keyValuePairs) {
val (key, value) = pair
when (key) {
"FULLNAME" -> configurationMap.put("fullName", value)
"FAVOURITEFRUIT" -> configurationMap.put("favoriteFruit", value)
"NEEDSPEELING" -> configurationMap.put("needsPeeling", true)
"OTHERFAMILY" -> configurationMap.put("otherFamily", value.split(" , ").map { it.trim() })
else -> println("Encountered unexpected key $key=$value")
}
}
println(Configuration(configurationMap))
}
private fun commentedOut(line: String) = line.startsWith("#") || line.startsWith(";")
private fun toKeyValuePair(line: String) = line.split(Regex(" "), 2).let {
Pair(it[0], if (it.size == 1) "" else it[1])
}
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