The writer automatically generates a CSV header based on
+ * the object's fields and ensures header consistency when appending data.
+ *
+ *
This class is not thread-safe.
+ */
+public class CsvFileWriter implements Writable {
+ private Pipeline writeToCsvFilePipeline;
+ private CsvContext csvContext;
+
+
+ /**
+ * Writes a list of objects to a CSV file.
+ *
+ *
All objects in the list must be of the same type. The CSV header
+ * is generated automatically using reflection.
+ *
+ * @param data list of objects to be written; must not be empty and must contain
+ * objects of the same type
+ * @param fileName name of the target CSV file
+ * @throws ArrayIsEmptyException if the data list is empty
+ * @throws IllegalArgumentException if the list contains objects of different types
+ * @throws IllegalStateException if an existing CSV header does not match
+ */
+ @Override
+ public void writeToFile(List data, String fileName) {
+ this.csvContext = new CsvContext(data, fileName);
+ this.writeToCsvFilePipeline = buildPipeline();
+ writeToCsvFilePipeline.execute(csvContext);
+ }
+
+
+ private Pipeline buildPipeline() {
+ Pipeline writeToCsvFilePipeline = new Pipeline<>();
+
+ writeToCsvFilePipeline.addStep(new ValidateDataStep());
+ writeToCsvFilePipeline.addStep(new CheckFileExistsStep());
+
+ writeToCsvFilePipeline.addStep(new ResolveMetadataStep());
+
+ writeToCsvFilePipeline.addStep(new GenerateHeaderStep());
+ writeToCsvFilePipeline.addStep(new WriteDataToCsvFileStep());
+
+ return writeToCsvFilePipeline;
+ }
+}
diff --git a/src/main/java/org/writer/Writable.java b/src/main/java/org/writer/csv/Writable.java
similarity index 61%
rename from src/main/java/org/writer/Writable.java
rename to src/main/java/org/writer/csv/Writable.java
index 9f60c45..c69b0f0 100644
--- a/src/main/java/org/writer/Writable.java
+++ b/src/main/java/org/writer/csv/Writable.java
@@ -1,8 +1,8 @@
-package org.writer;
+package org.writer.csv;
import java.util.List;
-public interface Writable {
+public interface Writable{
void writeToFile(List data, String fileName);
diff --git a/src/main/java/org/writer/csv/context/ContextInterface.java b/src/main/java/org/writer/csv/context/ContextInterface.java
new file mode 100644
index 0000000..ba274f2
--- /dev/null
+++ b/src/main/java/org/writer/csv/context/ContextInterface.java
@@ -0,0 +1,4 @@
+package org.writer.csv.context;
+
+public interface ContextInterface {
+}
diff --git a/src/main/java/org/writer/csv/context/CsvContext.java b/src/main/java/org/writer/csv/context/CsvContext.java
new file mode 100644
index 0000000..e74c800
--- /dev/null
+++ b/src/main/java/org/writer/csv/context/CsvContext.java
@@ -0,0 +1,28 @@
+package org.writer.csv.context;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.lang.reflect.Field;
+import java.nio.file.Path;
+import java.util.List;
+
+@Getter
+@Setter
+//@Builder
+public class CsvContext implements ContextInterface {
+ private List data;
+ private Path path;
+ private boolean isFileExists = false;
+ private Class clazz;
+ private Field[] fields;
+ private String header;
+
+ public CsvContext(List data, String fileName) {
+ this.data = data;
+ this.path = Path.of(fileName);
+
+ }
+
+
+}
diff --git a/src/main/java/org/writer/csv/pipeline/Pipeline.java b/src/main/java/org/writer/csv/pipeline/Pipeline.java
new file mode 100644
index 0000000..7f69178
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/Pipeline.java
@@ -0,0 +1,26 @@
+package org.writer.csv.pipeline;
+
+import org.writer.csv.context.ContextInterface;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public class Pipeline {
+ private final List> steps = new LinkedList<>();
+
+ public void execute(TContext context) {
+ steps.forEach(pipelineStep -> pipelineStep.execute(context));
+ }
+
+ public void addStep(PipelineStep pipelineStep) {
+ steps.add(pipelineStep);
+ }
+ public void addStepByCondition(boolean condition, PipelineStep firstStep, PipelineStep secondStep){
+ if (condition){
+ steps.add(firstStep);
+ }else {
+ steps.add(secondStep);
+ }
+ }
+
+}
diff --git a/src/main/java/org/writer/csv/pipeline/PipelineStep.java b/src/main/java/org/writer/csv/pipeline/PipelineStep.java
new file mode 100644
index 0000000..31d0236
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/PipelineStep.java
@@ -0,0 +1,7 @@
+package org.writer.csv.pipeline;
+
+import org.writer.csv.context.ContextInterface;
+
+public interface PipelineStep {
+ void execute(TContext context);
+}
diff --git a/src/main/java/org/writer/csv/pipeline/steps/CheckFileExistsStep.java b/src/main/java/org/writer/csv/pipeline/steps/CheckFileExistsStep.java
new file mode 100644
index 0000000..7683624
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/steps/CheckFileExistsStep.java
@@ -0,0 +1,27 @@
+package org.writer.csv.pipeline.steps;
+
+import org.writer.csv.context.CsvContext;
+import org.writer.csv.pipeline.PipelineStep;
+
+import java.io.IOException;
+import java.nio.file.Files;
+
+public class CheckFileExistsStep implements PipelineStep {
+ /**
+ * Checks whether the target CSV file exists and is not empty.
+ * Stores the result in the CsvContext.
+ *
+ * @param csvContext context containing the path to the CSV file
+ * @throws RuntimeException if an I/O error occurs while checking the file
+ */
+
+ @Override
+ public void execute(CsvContext csvContext) {
+ try {
+ boolean isFileExists = Files.exists(csvContext.getPath()) && Files.size(csvContext.getPath()) > 0;
+ csvContext.setFileExists(isFileExists);
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }
+}
diff --git a/src/main/java/org/writer/csv/pipeline/steps/GenerateHeaderStep.java b/src/main/java/org/writer/csv/pipeline/steps/GenerateHeaderStep.java
new file mode 100644
index 0000000..e3598f2
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/steps/GenerateHeaderStep.java
@@ -0,0 +1,50 @@
+package org.writer.csv.pipeline.steps;
+
+import org.writer.csv.context.CsvContext;
+import org.writer.csv.pipeline.PipelineStep;
+import org.writer.exception.CsvHeaderMismatchException;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.nio.file.Files;
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+
+public class GenerateHeaderStep implements PipelineStep {
+ /**
+ * Generates a CSV header based on the model fields and stores it in the context.
+ * If the CSV file already exists, validates that the generated header matches
+ * the header stored in the file.
+ *
+ * @param csvContext context containing file path and model metadata
+ * @throws CsvHeaderMismatchException if the existing file header does not match the generated one
+ * @throws RuntimeException if an I/O error occurs while reading the file
+ */
+ @Override
+ public void execute(CsvContext csvContext) {
+
+ csvContext.setHeader(Arrays.stream(csvContext.getFields())
+ .map(Field::getName)
+ .collect(Collectors.joining(",")));
+
+ if (csvContext.isFileExists()) {
+ try (BufferedReader reader = Files.newBufferedReader(csvContext.getPath())) {
+ String fileHeader = reader.readLine();
+
+ if (!fileHeader.equals(csvContext.getHeader())) {
+ throw new CsvHeaderMismatchException(
+ "CSV header mismatch. Expected: "
+ + csvContext.getHeader()
+ + ", Actual: "
+ + fileHeader
+ );
+ }
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ }
+}
diff --git a/src/main/java/org/writer/csv/pipeline/steps/ResolveMetadataStep.java b/src/main/java/org/writer/csv/pipeline/steps/ResolveMetadataStep.java
new file mode 100644
index 0000000..f899898
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/steps/ResolveMetadataStep.java
@@ -0,0 +1,31 @@
+package org.writer.csv.pipeline.steps;
+
+import org.writer.csv.context.CsvContext;
+import org.writer.csv.pipeline.PipelineStep;
+
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.Comparator;
+
+public class ResolveMetadataStep implements PipelineStep {
+ /**
+ * Resolves metadata required for CSV generation.
+ * Determines the model class from the data list, extracts its fields,
+ * sorts them by name and makes them accessible.
+ *
+ * @param csvContext context containing the data to be written
+ * @throws IndexOutOfBoundsException if the data list is empty
+ */
+
+ @Override
+ public void execute(CsvContext csvContext) {
+ csvContext.setClazz(csvContext.getData().get(0).getClass());
+
+ Field[] fields = csvContext.getClazz().getDeclaredFields();
+ Arrays.sort(fields, Comparator.comparing(Field::getName));
+ for (Field f : fields) {
+ f.setAccessible(true);
+ }
+ csvContext.setFields(fields);
+ }
+}
diff --git a/src/main/java/org/writer/csv/pipeline/steps/ValidateDataStep.java b/src/main/java/org/writer/csv/pipeline/steps/ValidateDataStep.java
new file mode 100644
index 0000000..c342ef5
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/steps/ValidateDataStep.java
@@ -0,0 +1,20 @@
+package org.writer.csv.pipeline.steps;
+
+import org.writer.csv.context.CsvContext;
+import org.writer.csv.pipeline.PipelineStep;
+import org.writer.exception.ArrayIsEmptyException;
+
+public class ValidateDataStep implements PipelineStep {
+ /**
+ * Validates that the data list is not empty.
+ *
+ * @param csvContext context containing the data to be written
+ * @throws ArrayIsEmptyException if the data list is empty
+ */
+ @Override
+ public void execute(CsvContext csvContext) {
+ if (csvContext.getData().isEmpty()) {
+ throw new ArrayIsEmptyException("Fill array with data!");
+ }
+ }
+}
diff --git a/src/main/java/org/writer/csv/pipeline/steps/WriteDataToCsvFileStep.java b/src/main/java/org/writer/csv/pipeline/steps/WriteDataToCsvFileStep.java
new file mode 100644
index 0000000..5a1b4d5
--- /dev/null
+++ b/src/main/java/org/writer/csv/pipeline/steps/WriteDataToCsvFileStep.java
@@ -0,0 +1,104 @@
+package org.writer.csv.pipeline.steps;
+
+import org.writer.csv.context.CsvContext;
+import org.writer.csv.pipeline.PipelineStep;
+
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.nio.file.Files;
+import java.nio.file.StandardOpenOption;
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+public class WriteDataToCsvFileStep implements PipelineStep {
+ /**
+ * Writes data from the context to a CSV file.
+ * Writes the header if the file does not already exist,
+ * then appends all data rows.
+ *
+ * @param csvContext context containing file path, header and data
+ * @throws RuntimeException if an I/O error occurs while writing to the file
+ */
+
+ @Override
+ public void execute(CsvContext csvContext) {
+ System.out.println("Start to file writing");
+ try (BufferedWriter writer = Files.newBufferedWriter(
+ csvContext.getPath(),
+ StandardOpenOption.CREATE,
+ StandardOpenOption.APPEND
+ )) {
+ if (!csvContext.isFileExists()) {
+ writeCsvRow(writer, csvContext.getHeader());
+ }
+ for (Object element : csvContext.getData()) {
+ String csvRow = joinFieldsToCsvRow(element, csvContext.getFields());
+ writeCsvRow(writer, csvRow);
+ }
+ System.out.println("The data was successfully written");
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+
+ }
+
+
+ /**
+ * Joins field values into a CSV string
+ *
+ * @param objectToRow the object whose data we will connect
+ * @param fields fields of the object to be serialized
+ * @return joined row for CSV
+ */
+ private String joinFieldsToCsvRow(Object objectToRow, Field[] fields) {
+ return Arrays.stream(fields)
+ .map(field -> {
+ try {
+ Object value = field.get(objectToRow);
+ return escapeCsv(value == null ? "" : value.toString());
+ } catch (IllegalAccessException e) {
+ throw new RuntimeException("Access was not permitted ", e);
+ }
+ })
+ .collect(Collectors.joining(","));
+
+ }
+
+ /**
+ * Writes a single CSV row to the given writer.
+ *
+ *
The method appends the row followed by a line separator.
+ *
+ * @param writer the {@link BufferedWriter} used to write data to the CSV file
+ * @param csvRow the CSV-formatted row to write
+ * @throws RuntimeException if an I/O error occurs while writing the row
+ */
+ private void writeCsvRow(BufferedWriter writer, String csvRow) {
+ try {
+ writer.write(csvRow);
+ writer.newLine();
+ } catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ /**
+ * Escapes a value according to CSV format rules.
+ *
+ *
If the value contains a comma, double quote, or line break,
+ * it is wrapped in double quotes and internal quotes are escaped
+ * by doubling them.