Start work on #442: add CsvValueDecorator as starting point for configuring processing

Author: cowtowncoder

csv/src/main/java/com/fasterxml/jackson/dataformat/csv/CsvValueDecorator.java

@@ -0,0 +1,67 @@
+package com.fasterxml.jackson.dataformat.csv;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+/**
+ * Interface defining API for handlers that can add and remove "decorations"
+ * to CSV values: for example, brackets around Array (List) values encoded
+ * in a single physical column.
+ *<p>
+ * Decorations are handled after handling other encoding aspects such as
+ * optional quoting and/or escaping.
+ *<p>
+ * Decorators can be handled at both {@link CsvSchema} level (as defaults
+ * for specific column types or classes) and {@link CsvSchema.Column} level (specific
+ * to values of given column): if both defined, more specific -- latter, per-Column
+ * -- is used.
+ *
+ * @since 2.17
+ */
+public interface CsvValueDecorator
+{
+    /**
+     * Method called during serialization when encoding a value,
+     * to produce "decorated" value to include in output (possibly
+     * escaped and/or quoted).
+     * Note that possible escaping and/or quoting (as per configuration
+     * of {@link CsvSchema} is applied on decorated value.
+     *
+     * @param gen Generator that will be used for actual serialization
+     * @param ctxt Context passed to give access to configuration
+     * @param plainValue Value to decorate
+     *
+     * @return Decorated value (which may be {@code plainValue} as-is)
+     *
+     * @throws IOException if attempt to decorate the value somehow fails
+     *    (typically a {@link com.fasterxml.jackson.core.exc.StreamWriteException})
+     */
+    public String decorateValue(CsvGenerator gen, SerializerProvider ctxt,
+            String plainValue)
+        throws IOException;
+
+    /**
+     * Method called during deserialization, to remove possible decoration
+     * applied with {@link #decorateValue}.
+     * Call is made after textual value for a cell (column
+     * value) has been read using {@code parser} and after removing (decoding)
+     * possible quoting and/or escaping of the value. Value passed in
+     * has no escaping or quoting left.
+     *
+     * @param parser Parser that was used to decode textual value from input
+     * @param ctxt Context passed to give access to configuration
+     * @param decoratedValue Value from which to remove decorations, if any
+     *    (some decorators can allow optional decorations; others may fail
+     *    if none found)
+     *
+     * @return Value after removing decorations, if any.
+     *
+     * @throws IOException if attempt to undecorate the value fails
+     *    (typically a {@link com.fasterxml.jackson.core.exc.StreamReadException})
+     */
+    public String undecorateValue(CsvParser parser, DeserializationContext ctxt,
+            String decoratedValue)
+        throws IOException;
+}

csv/src/test/java/com/fasterxml/jackson/dataformat/csv/fuzz/ReadBracketedArrayTest.java

@@ -0,0 +1,48 @@
+package com.fasterxml.jackson.dataformat.csv.fuzz;
+
+import java.net.URL;
+
+import com.fasterxml.jackson.annotation.*;
+
+import com.fasterxml.jackson.databind.MappingIterator;
+
+import com.fasterxml.jackson.dataformat.csv.CsvMapper;
+import com.fasterxml.jackson.dataformat.csv.CsvSchema;
+import com.fasterxml.jackson.dataformat.csv.ModuleTestBase;
+
+public class ReadBracketedArrayTest extends ModuleTestBase
+{
+    @JsonPropertyOrder({"id", "title", "url", "score", "time", "comments", "author",
+        "embeddings"
+    })
+    static class Article {
+        public String id, title, author;
+        public URL url;
+        public int comments, score;
+        public long time; // Unix time
+
+        public double[] embeddings;
+    }
+
+    /*
+    /**********************************************************************
+    /* Test methods
+    /**********************************************************************
+     */
+
+    private final CsvMapper MAPPER = mapperForCsv();
+
+    public void testArrayWithBracketsRead() throws Exception
+    {
+        byte[] input = readResource("/data/story-100.csv");
+        CsvSchema schema = MAPPER.schemaFor(Article.class)
+                .withHeader()
+                .withArrayElementSeparator(",");
+        MappingIterator<Article> it = MAPPER.readerFor(Article.class)
+                .with(schema)
+                .readValues(input);
+
+        Article first = it.nextValue();
+        assertNotNull(first);
+    }
+}