implement FieldModifiers#modify(Function<String, String>)

Author: osiegmar

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+### Added
+- `FieldModifiers#modify(Function<String, String>)` to simply modify fields via functional interface
+
+### Deprecated
+- `SimpleFieldModifier` interface
+- `FieldModifiers#lower` and `FieldModifiers#upper` methods
+
 ## [3.6.0] - 2025-03-04
 ### Added
 - Configuration of maximum fields, maximum field size, and maximum record size via record handler
@@ -154,6 +162,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Initial release
 
+[Unreleased]: https://github.com/osiegmar/FastCSV/compare/v3.6.0...HEAD
 [3.6.0]: https://github.com/osiegmar/FastCSV/compare/v3.5.0...v3.6.0
 [3.5.0]: https://github.com/osiegmar/FastCSV/compare/v3.4.0...v3.5.0
 [3.4.0]: https://github.com/osiegmar/FastCSV/compare/v3.3.1...v3.4.0

example/src/main/java/example/ExampleCsvReaderWithFieldModifier.java

@@ -25,27 +25,27 @@ public static void main(final String[] args) {
 
         System.out.println("Custom modifier (trim/lowercase on first record):");
         CsvReader.builder()
-            .build(CsvRecordHandler.of(c -> c.fieldModifier(customModifier())), DATA)
+            .build(CsvRecordHandler.of(c -> c.fieldModifier(new CustomModifier())), DATA)
             .forEach(System.out::println);
     }
 
     private static FieldModifier combinedModifier() {
         return FieldModifiers.TRIM
-            .andThen(FieldModifiers.lower(Locale.ENGLISH));
+            .andThen(FieldModifiers.modify(field -> field.toLowerCase(Locale.ENGLISH)));
     }
 
-    private static FieldModifier customModifier() {
-        return new FieldModifier() {
-            @Override
-            public String modify(final long startingLineNumber,
-                                 final int fieldIdx,
-                                 final boolean quoted,
-                                 final String field) {
-                return startingLineNumber == 1
-                    ? field.trim().toLowerCase(Locale.ENGLISH)
-                    : field;
+    private static class CustomModifier implements FieldModifier {
+
+        @Override
+        public String modify(final long startingLineNumber, final int fieldIdx,
+                             final boolean quoted, final String field) {
+            if (startingLineNumber == 1) {
+                return field.trim().toLowerCase(Locale.ENGLISH);
             }
-        };
+
+            return field;
+        }
+
     }
 
 }

lib/build.gradle.kts

@@ -13,7 +13,7 @@ plugins {
 }
 
 group = "de.siegmar"
-version = "3.6.0"
+version = "3.7.0-SNAPSHOT"
 
 project.base.archivesName = "fastcsv"
 

lib/src/intTest/java/blackbox/reader/FieldModifierTest.java

@@ -56,14 +56,45 @@ void strip() {
             .containsExactly("foo", "bar", "baz");
     }
 
+    @SuppressWarnings("removal")
+    @Test
+    void lower() {
+        final CsvRecordHandler cbh = CsvRecordHandler.of(c -> c.fieldModifier(FieldModifiers.lower(Locale.ROOT)));
+
+        assertThat(crb.build(cbh, "FOO,BAR").stream())
+            .singleElement(CsvRecordAssert.CSV_RECORD)
+            .fields()
+            .containsExactly("foo", "bar");
+    }
+
+    @SuppressWarnings("removal")
+    @Test
+    void upper() {
+        final CsvRecordHandler cbh = CsvRecordHandler.of(c -> c.fieldModifier(FieldModifiers.upper(Locale.ROOT)));
+
+        assertThat(crb.build(cbh, "foo,bar").stream())
+            .singleElement(CsvRecordAssert.CSV_RECORD)
+            .fields()
+            .containsExactly("FOO", "BAR");
+    }
+
+    @SuppressWarnings("removal")
+    @Test
+    void simple() {
+        final CsvRecordHandler cbh = CsvRecordHandler.of(c -> c
+            .fieldModifier((SimpleFieldModifier) field -> "<" + field + ">"));
+
+        assertThat(crb.build(cbh, "foo,bar").stream())
+            .singleElement(CsvRecordAssert.CSV_RECORD)
+            .fields()
+            .containsExactly("<foo>", "<bar>");
+    }
+
     @Test
     void combination() {
         crb.commentStrategy(CommentStrategy.READ);
 
-        final SimpleFieldModifier addSpaces = field -> " " + field + " ";
-        final FieldModifier modifier = addSpaces
-            .andThen(FieldModifiers.upper(Locale.ROOT))
-            .andThen(FieldModifiers.lower(Locale.ROOT))
+        final FieldModifier modifier = FieldModifiers.modify(field -> field.toLowerCase(Locale.ROOT))
             .andThen(FieldModifiers.TRIM);
 
         final CsvRecordHandler cbh = CsvRecordHandler.of(c -> c.fieldModifier(modifier));

lib/src/main/java/de/siegmar/fastcsv/reader/FieldModifier.java

@@ -4,7 +4,6 @@
 /// a CSV record before storing them in the resulting object.
 ///
 /// @see FieldModifiers
-/// @see SimpleFieldModifier
 public interface FieldModifier {
 
     /// Gets called for every single field (that is not a comment).

lib/src/main/java/de/siegmar/fastcsv/reader/FieldModifiers.java

@@ -1,12 +1,15 @@
 package de.siegmar.fastcsv.reader;
 
 import java.util.Locale;
+import java.util.Objects;
+import java.util.function.Function;
 
 /// Provides some common [FieldModifier] implementations.
 ///
 /// Example usage:
 /// ```
-/// FieldModifier modifier = FieldModifiers.TRIM.andThen(FieldModifiers.upper(Locale.ENGLISH));
+/// FieldModifier modifier = FieldModifiers.TRIM
+///     .andThen(FieldModifiers.modify(field -> field.toLowerCase(Locale.ENGLISH)));
 /// CsvRecordHandler handler = CsvRecordHandler.of(c -> c.fieldModifier(modifier));
 /// List<CsvRecord> records = CsvReader.builder()
 ///     .build(handler, "  foo   ,   bar")
@@ -18,15 +21,15 @@
 public final class FieldModifiers {
 
     /// Modifier that does not modify anything.
-    public static final FieldModifier NOP = (SimpleFieldModifier) field -> field;
+    public static final FieldModifier NOP = new FieldModifier() { };
 
     /// Modifier that modifies the field value with [String#trim()].
     /// Comments are not modified.
-    public static final FieldModifier TRIM = (SimpleFieldModifier) String::trim;
+    public static final FieldModifier TRIM = modify(String::trim);
 
     /// Modifier that modifies the field value with [String#strip()].
     /// Comments are not modified.
-    public static final FieldModifier STRIP = (SimpleFieldModifier) String::strip;
+    public static final FieldModifier STRIP = modify(String::strip);
 
     private FieldModifiers() {
         // Utility class
@@ -37,17 +40,40 @@ private FieldModifiers() {
     ///
     /// @param locale use the case transformation rules for this locale
     /// @return a new field modifier that converts the input to lower-case.
+    /// @deprecated Use [#modify(Function)] instead.
+    @Deprecated(since = "3.7.0", forRemoval = true)
     public static FieldModifier lower(final Locale locale) {
-        return (SimpleFieldModifier) field -> field.toLowerCase(locale);
+        return modify(field -> field.toLowerCase(locale));
     }
 
     /// Builds modifier that modifies the field value with [String#toUpperCase(Locale)].
     /// Comments are not modified.
     ///
     /// @param locale use the case transformation rules for this locale
     /// @return a new field modifier that converts the input to upper-case.
+    /// @deprecated Use [#modify(Function)] instead.
+    @Deprecated(since = "3.7.0", forRemoval = true)
     public static FieldModifier upper(final Locale locale) {
-        return (SimpleFieldModifier) field -> field.toUpperCase(locale);
+        return modify(field -> field.toUpperCase(locale));
+    }
+
+    /// Builds a modifier that modifies the field value using the provided function.
+    /// Comments are not modified.
+    ///
+    /// @param function the function to modify the field value. The contract of
+    ///                 [FieldModifier#modify(long, int, boolean, String)] applies:
+    ///                 the value passed to the function is never `null` and the return value must not be `null`.
+    /// @return a new field modifier that applies the function to the field value
+    /// @throws NullPointerException if the function is `null`
+    public static FieldModifier modify(final Function<? super String, String> function) {
+        Objects.requireNonNull(function, "function must not be null");
+        return new FieldModifier() {
+            @Override
+            public String modify(final long startingLineNumber, final int fieldIdx,
+                                 final boolean quoted, final String field) {
+                return function.apply(field);
+            }
+        };
     }
 
 }

lib/src/main/java/de/siegmar/fastcsv/reader/SimpleFieldModifier.java

@@ -5,6 +5,8 @@
 /// When implementing this interface, comments are ignored (not modified), by default.
 ///
 /// @see FieldModifiers
+/// @deprecated Use [FieldModifiers#modify(java.util.function.Function)] instead.
+@Deprecated(since = "3.7.0", forRemoval = true)
 @FunctionalInterface
 public interface SimpleFieldModifier extends FieldModifier {