How to solve the common problems encountered when using Solr Specific Commons CSV framework in the Java library
How to solve the common problems encountered when using Solr Specific Commons CSV framework in the Java library
1. Question: Unable to analyze CSV files
Solution: Check whether the format of the CSV file is correct, and ensure that the separators and reference characters of the CSVPARSER (if any) is set before parsing.The following is a sample code fragment:
Reader reader = new FileReader("path/to/csv/file.csv");
CSVParser parser = new CSVParserBuilder()
.withSeparator(',')
.withQuoteChar('"')
.build();
CSVReader csvReader = new CSVReaderBuilder(reader)
.withCSVParser(parser)
.build();
String[] nextLine;
while ((nextLine = csvReader.readNext()) != null) {
// Process each line of data
}
2. Question: CSV file contains special characters or transition sequences
Solution: In order to properly handle the fields containing special characters or transition sequences, you can use the `StringESCAPEUTILS` class in the Apache Commons LANG library for righteousness.The following is a sample code fragment:
Reader reader = new FileReader("path/to/csv/file.csv");
StringEscapeUtils.STRING_ESCAPE_UTIL_MAP.put("''", "'");
CSVParser parser = new CSVParserBuilder()
.withSeparator(',')
.withQuoteChar('"')
.withFieldAsNull(CSVReaderNullFieldIndicator.EMPTY_SEPARATORS)
.build();
CSVReader csvReader = new CSVReaderBuilder(reader)
.withCSVParser(parser)
.build();
String[] nextLine;
while ((nextLine = csvReader.readNext()) != null) {
for (int i = 0; i < nextLine.length; i++) {
nextLine[i] = StringEscapeUtils.unescapeCsv(nextLine[i]);
}
// Process each line of data
}
3. Question: The date format in the CSV file does not match
Solution: You can use Java's date time library, such as Java.time (available from Java 8) or JODA-TIME (available before Java 8) to analyze and format the date field.The following is a sample code fragment:
Reader reader = new FileReader("path/to/csv/file.csv");
CSVParser parser = new CSVParserBuilder()
.withSeparator(',')
.withQuoteChar('"')
.build();
CSVReader csvReader = new CSVReaderBuilder(reader)
.withCSVParser(parser)
.build();
String[] nextLine;
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
while ((nextLine = csvReader.readNext()) != null) {
LocalDate date = LocalDate.parse(nextLine[0], formatter);
// Processing date data
}
4. Question: There are empty lines or data rows in CSV files inconsistent
Solution: Before reading each line of data, you can use the `ISBLANK` method of the` Stringutills` class to check whether the line is empty, and use the `isnoteMpty` method of the` Arrayutils` class to check whether the data line is empty.In addition, you can also use the `ADD` method of the` Arrayutils` class to add an empty field to the short terminal to maintain the data row length.The following is a sample code fragment:
Reader reader = new FileReader("path/to/csv/file.csv");
CSVParser parser = new CSVParserBuilder()
.withSeparator(',')
.withQuoteChar('"')
.build();
CSVReader csvReader = new CSVReaderBuilder(reader)
.withCSVParser(parser)
.build();
String[] nextLine;
while ((nextLine = csvReader.readNext()) != null) {
if (StringUtils.isBlank(nextLine[0])) {
continue; // jump over the empty line
}
if (ArrayUtils.isNotEmpty(nextLine) && nextLine.length < expectedLength) {
nextLine = ArrayUtils.addAll(nextLine, new String[expectedLength - nextLine.length]);
}
// Process each line of data
}
5. Question: The field in the CSV file contains the change of row or separators
Solution: If the field in the CSV file contains a row or separator, the Solr Specific Commons CSV framework defaults to it as a new line or new field.In order to properly handle this situation, you can use the `Readall` method of the` csvreader` class to read the entire CSV file, and use the `Join` method of the` StringUtils` class to merge the value of each field.The following is a sample code fragment:
Reader reader = new FileReader("path/to/csv/file.csv");
CSVParser parser = new CSVParserBuilder()
.withSeparator(',')
.withQuoteChar('"')
.build();
CSVReader csvReader = new CSVReaderBuilder(reader)
.withCSVParser(parser)
.build();
List<String[]> allLines = csvReader.readAll();
for (String[] nextLine : allLines) {
String mergedLine = StringUtils.join(nextLine, ",");
// Process the merged line data
}
By using the above solutions, you will be able to solve common problems encountered when using Solr Specific Commons CSV frameworks in the Java class library.According to the actual situation, you can choose an appropriate solution and customize as needed.
