Add CsvEncoder

metafacture-csv/src/main/java/org/metafacture/csv/CsvEncoder.java

@@ -0,0 +1,220 @@
+/*
+ * Copyright 2018-2023 Deutsche Nationalbibliothek et al
+ *
+ * Licensed under the Apache License, Version 2.0 the "License";
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.metafacture.csv;
+
+import org.metafacture.framework.FluxCommand;
+import org.metafacture.framework.MetafactureException;
+import org.metafacture.framework.ObjectReceiver;
+import org.metafacture.framework.StreamReceiver;
+import org.metafacture.framework.annotations.Description;
+import org.metafacture.framework.annotations.In;
+import org.metafacture.framework.annotations.Out;
+import org.metafacture.framework.helpers.DefaultStreamPipe;
+
+import com.opencsv.CSVWriter;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A csv encoder that converts a record into a csv line (Default separator: {@value #DEFAULT_SEP}).
+ *
+ * <p>
+ * Each record represents a row. Each literal value represents a column value.
+ * </P>
+ *
+ * @author eberhardtj ([email protected])
+ */
+@Description("Encodes each value in a record as a csv row.")
+@In(StreamReceiver.class)
+@Out(String.class)
+@FluxCommand("encode-csv")
+public class CsvEncoder extends DefaultStreamPipe<ObjectReceiver<String>> {
+    public static final char DEFAULT_SEP = CSVWriter.DEFAULT_SEPARATOR;
+    private CSVWriter csvWriter;
+    private StringWriter writer;
+    private List<String> rowItems = new ArrayList<>();
+    private boolean isFirstRecord = true;
+    private List<String> header = new ArrayList<>();
+    private char separator = DEFAULT_SEP;
+    private boolean noQuotes;
+    private boolean includeHeader;
+    private boolean includeRecordId;
+
+    /**
+     * Creates an instance of {@link CsvEncoder} with a given separator.
+     *
+     * @param separator to separate columns
+     */
+    public CsvEncoder(final String separator) {
+        this.separator = separator.charAt(0);
+    }
+
+    /**
+     * Creates an instance of {@link CsvEncoder} with a given separator.
+     *
+     * @param separator to separate columns
+     */
+    public CsvEncoder(final char separator) {
+        this.separator = separator;
+    }
+
+    /**
+     * Creates an instance of {@link CsvEncoder}. The default separator is
+     * {@value #DEFAULT_SEP}.
+     */
+    public CsvEncoder() {
+    }
+
+    /**
+     * Start each line with the record ID.
+     * Default is to not start each line with the record ID.
+     *
+     * @param includeRecordId true if the first column should consist of the record's ID
+     */
+    public void setIncludeRecordId(final boolean includeRecordId) {
+        this.includeRecordId = includeRecordId;
+    }
+
+    /**
+     * Add first record as a column description header.
+     * Default is to not add a column description.
+     *
+     * @param includeHeader true if the first record should act as a CSV header, otherwise false
+     */
+    public void setIncludeHeader(final boolean includeHeader) {
+        this.includeHeader = includeHeader;
+    }
+
+    /**
+     * Set the character to separate the columns.
+     * The default is {@value #DEFAULT_SEP}.
+     *
+     * @param separator set the character which separates the columns
+     */
+    public void setSeparator(final String separator) {
+        if (separator.length() > 1) {
+            throw new MetafactureException("Separator needs to be a single character.");
+        }
+        this.separator = separator.charAt(0);
+    }
+
+    /**
+     * Set the character to separate the columns.
+     * The default is {@value #DEFAULT_SEP}.
+     *
+     * @param separator set the character which separates the columns
+     */
+    public void setSeparator(final char separator) {
+        this.separator = separator;
+    }
+
+    /**
+     * Set if values should be not quoted by '"'.
+     * The default is to quote values.
+     *
+     * @param noQuotes true if no quotes should be used. Default is false.
+     */
+    public void setNoQuotes(final boolean noQuotes) {
+        this.noQuotes = noQuotes;
+    }
+
+    private void initialize() {
+        writer = new StringWriter();
+        final String emptyLineEnd = "";
+        csvWriter = new CSVWriter(writer, separator,
+                                  noQuotes ? CSVWriter.NO_QUOTE_CHARACTER : CSVWriter.DEFAULT_QUOTE_CHARACTER,
+                                  CSVWriter.DEFAULT_ESCAPE_CHARACTER, emptyLineEnd);
+    }
+
+    private String[] arrayOf(final List<String> list) {
+        final int length = list.size();
+        return list.toArray(new String[length]);
+    }
+
+    private void resetCaches() {
+        this.rowItems = new ArrayList<>();
+    }
+
+    private void writeRow(final List<String> rowItemsArray) {
+        final String[] row = arrayOf(rowItemsArray);
+        csvWriter.writeNext(row);
+        final String line = writer.toString();
+        getReceiver().process(line);
+        writer.getBuffer().setLength(0);
+    }
+
+    @Override
+    public void startRecord(final String identifier) {
+        if (isFirstRecord) {
+            initialize();
+            if (includeRecordId) {
+                header.add("record id");
+            }
+        }
+
+        rowItems = new ArrayList<>();
+
+        if (includeRecordId) {
+            rowItems.add(identifier);
+        }
+    }
+
+    @Override
+    public void endRecord() {
+        if (isFirstRecord) {
+            if (includeHeader) {
+                writeRow(header);
+                header.clear();
+            }
+            isFirstRecord = false;
+        }
+
+        writeRow(rowItems);
+        resetCaches();
+    }
+
+    @Override
+    public void literal(final String name, final String value) {
+        if (isFirstRecord) {
+            header.add(name);
+        }
+        rowItems.add(value);
+    }
+
+    @Override
+    public void onCloseStream() {
+        try {
+            csvWriter.close();
+        }
+        catch (final IOException e) {
+            throw new MetafactureException(e);
+        }
+    }
+
+    @Override
+    public void onResetStream() {
+        this.includeRecordId = false;
+        this.includeHeader = false;
+        this.header = new ArrayList<>();
+        this.isFirstRecord = true;
+        this.rowItems = new ArrayList<>();
+    }
+
+}

metafacture-csv/src/main/resources/flux-commands.properties

@@ -14,3 +14,4 @@
 # limitations under the License.
 #
 decode-csv org.metafacture.csv.CsvDecoder
+encode-csv org.metafacture.csv.CsvEncoder