org.apache.solr.internal.csv.CSVUtils Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.solr.internal.csv;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
/** Utility methods for dealing with CSV files */
public class CSVUtils {
private static final String[] EMPTY_STRING_ARRAY = new String[0];
private static final String[][] EMPTY_DOUBLE_STRING_ARRAY = new String[0][0];
/**
* CSVUtils instances should NOT be constructed in standard programming.
*
* This constructor is public to permit tools that require a JavaBean instance to operate.
*/
public CSVUtils() {}
/**
* Converts an array of string values into a single CSV line. All null values are
* converted to the string "null", all strings equal to "null" will
* additionally get quotes around.
*
* @param values the value array
* @return the CSV string, will be an empty string if the length of the value array is 0
*/
public static String printLine(String[] values, CSVStrategy strategy) {
// set up a CSVUtils
StringWriter stringWriter = new StringWriter();
CSVPrinter csvPrinter = new CSVPrinter(stringWriter, strategy);
// check for null values an "null" as strings and convert them
// into the strings "null" and "\"null\""
for (int i = 0; i < values.length; i++) {
if (values[i] == null) {
values[i] = "null";
} else if (values[i].equals("null")) {
values[i] = "\"null\"";
}
}
// convert to CSV
try {
csvPrinter.println(values);
} catch (IOException e) {
// should not happen with StringWriter
}
// as the resulting string has \r\n at the end, we will trim that away
return stringWriter.toString().trim();
}
// ======================================================
// static parsers
// ======================================================
/**
* Parses the given String according to the default {@link CSVStrategy}.
*
* @param s CSV String to be parsed.
* @return parsed String matrix (which is never null)
* @throws IOException in case of error
*/
public static String[][] parse(String s) throws IOException {
if (s == null) {
throw new IllegalArgumentException("Null argument not allowed.");
}
String[][] result = (new CSVParser(new StringReader(s))).getAllValues();
if (result == null) {
// since CSVStrategy ignores empty lines an empty array is returned
// (i.e. not "result = new String[][] {{""}};")
result = EMPTY_DOUBLE_STRING_ARRAY;
}
return result;
}
/**
* Parses the first line only according to the default {@link CSVStrategy}.
*
*
Parsing empty string will be handled as valid records containing zero elements, so the
* following property holds: parseLine("").length == 0.
*
* @param s CSV String to be parsed.
* @return parsed String vector (which is never null)
* @throws IOException in case of error
*/
public static String[] parseLine(String s) throws IOException {
if (s == null) {
throw new IllegalArgumentException("Null argument not allowed.");
}
// uh,jh: make sure that parseLine("").length == 0
if (s.length() == 0) {
return EMPTY_STRING_ARRAY;
}
return (new CSVParser(new StringReader(s))).getLine();
}
}