Write csv entries in correct order

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix JavaDoc creation
     - Create JavaDoc with java 17 instead of java 8
     - Let JavDoc pass, if there are warnings **ATTENTION:** Should be removed, when JavaDoc is fixed! (cf. Issue [#494](https://github.com/ie3-institute/PowerSystemDataModel/issues/494))
+- `BufferedCsvWriter` writes columns in the order, that the headline elements are defined [#434](https://github.com/ie3-institute/PowerSystemDataModel/issues/393)
 
 ### Changed
 - BREAKING: PvInput Model parameter name height changed to elevationAngle [#393](https://github.com/ie3-institute/PowerSystemDataModel/issues/393) :warning:

src/main/java/edu/ie3/datamodel/io/csv/BufferedCsvWriter.java

@@ -12,6 +12,8 @@
 import java.util.Arrays;
 import java.util.Map;
 import java.util.Objects;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * This class extends the {@link BufferedWriter} and adds information about the file shape of the
@@ -27,10 +29,11 @@ public class BufferedCsvWriter extends BufferedWriter {
       "Direct appending is prohibited. Use write instead.";
 
   /**
-   * Build a new CsvBufferedWriter
+   * Build a new CsvBufferedWriter. The order of headline elements given in this constructor defines
+   * the order of columns in file
    *
    * @param filePath String representation of the full path to the target file
-   * @param headLineElements Elements of the csv head line
+   * @param headLineElements Elements of the csv headline
    * @param csvSep csv separator char
    * @param append true to append to an existing file, false to overwrite an existing file (if any),
    *     if no file exists, a new one will be created in both cases
@@ -47,7 +50,8 @@ public BufferedCsvWriter(
   /**
    * Build a new CsvBufferedWriter. This is a "convenience" Constructor. The absolute file path is
    * assembled by concatenation of {@code baseFolder} and {@code fileDefinition}'s file path
-   * information.
+   * information. The order of headline elements in {@code fileDefinition} defines the order of
+   * columns in file
    *
    * @param baseFolder Base folder, from where the file hierarchy should start
    * @param fileDefinition The foreseen shape of the file
@@ -73,16 +77,15 @@ public BufferedCsvWriter(String baseFolder, CsvFileDefinition fileDefinition, bo
    */
   public synchronized void write(Map<String, String> entityFieldData)
       throws IOException, SinkException {
-    /* Check against eligible head line elements */
+    /* Check against eligible headline elements */
     if (entityFieldData.size() != headLineElements.length
         || !entityFieldData.keySet().containsAll(Arrays.asList(headLineElements)))
       throw new SinkException(
           "The provided data does not meet the pre-defined head line elements '"
               + String.join(",", headLineElements)
               + "'.");
 
-    String[] entries = entityFieldData.values().toArray(new String[0]);
-    writeOneLine(entries);
+    writeOneLine(Arrays.stream(headLineElements).map(entityFieldData::get));
   }
 
   /**
@@ -101,15 +104,18 @@ public final synchronized void writeFileHeader() throws IOException {
    * @throws IOException If writing is not possible
    */
   private void writeOneLine(String[] entries) throws IOException {
-    for (int i = 0; i < entries.length; i++) {
-      String attribute = entries[i];
-      super.append(attribute);
-      if (i + 1 < entries.length) {
-        super.append(csvSep);
-      } else {
-        super.append("\n");
-      }
-    }
+    writeOneLine(Arrays.stream(entries));
+  }
+
+  /**
+   * Write one line to the csv file
+   *
+   * @param entries Stream of entries to write
+   * @throws IOException If writing is not possible
+   */
+  private void writeOneLine(Stream<String> entries) throws IOException {
+    super.append(entries.collect(Collectors.joining(csvSep)));
+    super.append("\n");
     flush();
   }
 

src/test/groovy/edu/ie3/datamodel/io/csv/BufferedCsvWriterTest.groovy

@@ -5,6 +5,7 @@
  */
 package edu.ie3.datamodel.io.csv
 
+import edu.ie3.datamodel.exceptions.FileException
 import edu.ie3.datamodel.exceptions.SinkException
 import edu.ie3.util.io.FileIOUtils
 import org.apache.commons.io.FilenameUtils
@@ -78,4 +79,33 @@ class BufferedCsvWriterTest extends Specification {
 		def e = thrown(SinkException)
 		e.message == "The provided data does not meet the pre-defined head line elements 'a,b,c'."
 	}
+
+	def "The buffered csv writer writes out content in the order specified by the headline elements"() {
+		given:
+		def targetFile = FilenameUtils.concat(tmpDirectory.toString(), "order_test.csv")
+		def writer = new BufferedCsvWriter(targetFile, ["third_header", "second_header", "first_header"] as String[], ",", false)
+		writer.writeFileHeader()
+		def content = [
+				"third_header": "third_value",
+				"first_header": "first_value",
+				"second_header": "second_value"
+		]
+
+		when:
+		writer.write(content)
+		writer.close()
+		/* Read in the content */
+		def writtenContent = ""
+		def headline = ""
+		try(BufferedReader reader = new BufferedReader(new FileReader(targetFile))) {
+			headline = reader.readLine()
+			writtenContent = reader.readLine()
+		} catch (Exception e) {
+			throw new FileException("Unable to read content of test file '"+targetFile+"'.", e)
+		}
+
+		then:
+		headline == "third_header,second_header,first_header"
+		writtenContent == "third_value,second_value,first_value"
+	}
 }