1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.solr.internal.csv;
18  
19  import java.io.StringWriter;
20  import java.io.StringReader;
21  import java.io.IOException;
22  
23  /**
24   * Utility methods for dealing with CSV files
25   */
26  public class CSVUtils {
27  
28      private static final String[] EMPTY_STRING_ARRAY = new String[0];
29      private static final String[][] EMPTY_DOUBLE_STRING_ARRAY = new String[0][0];
30  
31      /**
32       * <p><code>CSVUtils</code> instances should NOT be constructed in
33       * standard programming. 
34       *
35       * <p>This constructor is public to permit tools that require a JavaBean
36       * instance to operate.</p>
37       */
38      public CSVUtils() {
39      }
40    
41      /**
42       * Converts an array of string values into a single CSV line. All
43       * <code>null</code> values are converted to the string <code>"null"</code>,
44       * all strings equal to <code>"null"</code> will additionally get quotes
45       * around.
46       *
47       * @param values the value array
48       * @return the CSV string, will be an empty string if the length of the
49       * value array is 0
50       */
51      public static String printLine(String[] values, CSVStrategy strategy) {
52          // set up a CSVUtils
53          StringWriter stringWriter = new StringWriter();
54          CSVPrinter csvPrinter = new CSVPrinter(stringWriter, strategy);
55    
56          // check for null values an "null" as strings and convert them
57          // into the strings "null" and "\"null\""
58          for (int i = 0; i < values.length; i++) {
59              if (values[i] == null) {
60                  values[i] = "null";
61              } else if (values[i].equals("null")) {
62                  values[i] = "\"null\"";
63              }
64          }
65    
66          // convert to CSV
67          try {
68            csvPrinter.println(values);
69          } catch (IOException e) {
70            // should not happen with StringWriter
71          }
72          // as the resulting string has \r\n at the end, we will trim that away
73          return stringWriter.toString().trim();
74      }
75    
76    // ======================================================
77    //  static parsers
78    // ======================================================
79    
80    /**
81     * Parses the given String according to the default {@link CSVStrategy}.
82     * 
83     * @param s CSV String to be parsed.
84     * @return parsed String matrix (which is never null)
85     * @throws IOException in case of error
86     */
87    public static String[][] parse(String s) throws IOException {
88      if (s == null) {
89        throw new IllegalArgumentException("Null argument not allowed.");
90      }
91      String[][] result = (new CSVParser(new StringReader(s))).getAllValues();
92      if (result == null) {
93        // since CSVStrategy ignores empty lines an empty array is returned
94        // (i.e. not "result = new String[][] {{""}};")
95        result = EMPTY_DOUBLE_STRING_ARRAY;
96      }
97      return result;
98    }
99    
100   /**
101    * Parses the first line only according to the default {@link CSVStrategy}.
102    * 
103    * Parsing empty string will be handled as valid records containing zero
104    * elements, so the following property holds: parseLine("").length == 0.
105    * 
106    * @param s CSV String to be parsed.
107    * @return parsed String vector (which is never null)
108    * @throws IOException in case of error
109    */
110   public static String[] parseLine(String s) throws IOException {
111     if (s == null) {
112       throw new IllegalArgumentException("Null argument not allowed.");
113     }
114     // uh,jh: make sure that parseLine("").length == 0
115     if (s.length() == 0) {
116       return EMPTY_STRING_ARRAY;
117     }
118     return (new CSVParser(new StringReader(s))).getLine();
119   }
120   
121 }