<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
            xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.developersoapbox</groupId>
    <artifactId>kotlin-excel-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>com.developersoapbox kotlin-excel-demo</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <kotlin.version>1.2.20</kotlin.version>
        <junit.version>4.12</junit.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-test-junit</artifactId>
            <version>${kotlin.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.17</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.17</version>
        </dependency>
    </dependencies>

    <build>
        <sourceDirectory>src/main/kotlin</sourceDirectory>
        <testSourceDirectory>src/test/kotlin</testSourceDirectory>

        <plugins>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

package com.developersoapbox

import org.apache.poi.ss.usermodel.WorkbookFactory
import org.apache.poi.xssf.usermodel.XSSFWorkbook
import java.io.FileInputStream
import java.io.FileOutputStream

/**
    * Writes the value "TEST" to the cell at the first row and first column of worksheet.
    */
fun writeToExcelFile(filepath: String) {
    //Instantiate Excel workbook:
    val xlWb = XSSFWorkbook()
    //Instantiate Excel worksheet:
    val xlWs = xlWb.createSheet()

    //Row index specifies the row in the worksheet (starting at 0):
    val rowNumber = 0
    //Cell index specifies the column within the chosen row (starting at 0):
    val columnNumber = 0

    //Write text value to cell located at ROW_NUMBER / COLUMN_NUMBER:
    xlWs.createRow(rowNumber).createCell(columnNumber).setCellValue("TEST")

    //Write file:
    val outputStream = FileOutputStream(filepath)
    xlWb.write(outputStream)
    xlWb.close()
}

/**
    * Reads the value from the cell at the first row and first column of worksheet.
    */
fun readFromExcelFile(filepath: String) {
    val inputStream = FileInputStream(filepath)
    //Instantiate Excel workbook using existing file:
    var xlWb = WorkbookFactory.create(inputStream)

    //Row index specifies the row in the worksheet (starting at 0):
    val rowNumber = 0
    //Cell index specifies the column within the chosen row (starting at 0):
    val columnNumber = 0

    //Get reference to first sheet:
    val xlWs = xlWb.getSheetAt(0)
    println(xlWs.getRow(rowNumber).getCell(columnNumber))
}

fun main(args: Array<String>) {
    val filepath = "./test.xlsx"
    writeToExcelFile(filepath)
    readFromExcelFile(filepath)
}