Open existing excel files and use them as template

build.gradle

@@ -15,7 +15,7 @@ apply plugin: "jacoco"
 
 
 group 'com.jameskleeh'
-version '0.4.4'
+version '0.4.5-SNAPSHOT'
 
 targetCompatibility = 1.7
 sourceCompatibility = 1.7

src/main/groovy/com/jameskleeh/excel/ExcelBuilder.groovy

@@ -34,21 +34,23 @@ class ExcelBuilder {
      * Builds an excel document and sends the data to an output stream. The output stream is NOT closed.
      *
      * @param outputStream An output stream to push data onto
+     * @param template A excel file that is used a template, if null a new workbook will be created.
      * @param callable The closure to build the document
      */
-    static void output(OutputStream outputStream, @DelegatesTo(strategy = Closure.DELEGATE_FIRST, value = Workbook) Closure callable) {
-        XSSFWorkbook wb = build(callable)
+    static void output(InputStream template = null, OutputStream outputStream, @DelegatesTo(strategy = Closure.DELEGATE_FIRST, value = Workbook) Closure callable) {
+        XSSFWorkbook wb = build(template, callable)
         wb.write(outputStream)
     }
 
     /**
      * Builds an excel document
      *
+     * @param template A excel file that is used a template, if null a new workbook will be created.
      * @param callable The closure to build the document
      * @return The native workbook
      */
-    static XSSFWorkbook build(@DelegatesTo(strategy = Closure.DELEGATE_FIRST, value = Workbook) Closure callable) {
-        XSSFWorkbook wb = new XSSFWorkbook()
+    static XSSFWorkbook build(InputStream template = null, @DelegatesTo(strategy = Closure.DELEGATE_FIRST, value = Workbook) Closure callable) {
+        XSSFWorkbook wb = template == null ? new XSSFWorkbook() : new XSSFWorkbook(template)
         callable.resolveStrategy = Closure.DELEGATE_FIRST
         callable.delegate = new Workbook(wb)
         if (callable.maximumNumberOfParameters == 1) {

src/main/groovy/com/jameskleeh/excel/Workbook.groovy

@@ -52,7 +52,9 @@ class Workbook {
      * @return The native sheet object
      */
     XSSFSheet sheet(String name, Map options, @DelegatesTo(strategy = Closure.DELEGATE_FIRST, value = Sheet) Closure callable) {
-        handleSheet(wb.createSheet(WorkbookUtil.createSafeSheetName(name)), options, callable)
+        XSSFSheet sheet = wb.getSheet(name)
+        sheet = sheet ?: wb.createSheet(WorkbookUtil.createSafeSheetName(name))
+        handleSheet(sheet, options, callable)
     }
 
     /**

src/test/groovy/com/jameskleeh/excel/WorkbookSpec.groovy

@@ -1,8 +1,10 @@
 package com.jameskleeh.excel
 
+import org.apache.poi.ss.usermodel.Cell
+import org.apache.poi.ss.usermodel.Sheet
+import org.apache.poi.xssf.usermodel.XSSFSheet
 import org.apache.poi.xssf.usermodel.XSSFWorkbook
 import spock.lang.Specification
-import org.apache.poi.ss.usermodel.Sheet
 
 class WorkbookSpec extends Specification {
 
@@ -29,4 +31,25 @@ class WorkbookSpec extends Specification {
         config.defaultRowHeightInPoints == 12F
         config.defaultColumnWidth == 20
     }
+
+    void "test open with template and use sheet by name access"() {
+        given:
+        XSSFWorkbook workbook = ExcelBuilder.build(this.class.getResourceAsStream('/template.xlsx')) {
+            sheet('sheet') {
+                row {
+                    cell('created with builder')
+                }
+            }
+        }
+
+        when:
+        XSSFSheet sheet = workbook.getSheet('sheet')
+        Iterator<Cell> buildRow = sheet.getRow(0).cellIterator()
+        Iterator<Cell> rowFromTemplate = sheet.getRow(1).cellIterator()
+
+        then:
+        buildRow.next().stringCellValue == 'created with builder'
+        rowFromTemplate.next().stringCellValue == 'from template'
+    }
+
 }