Interpretation of OpenCSV framework principles and use
OpenCSV is a Reading framework for the open source CSV (comma seminars) file of Java, which allows developers to easily read, write and operate CSV files easily.This article will introduce the principles and use methods of OpenCSV in detail, and provide the corresponding Java code example.
## Opencsv framework principle
The OpenCSV framework is based on the Reader and Writer class of Java. It uses the comma as the default field separator, and supports custom separators and reference characters.It provides a set of simple APIs that enable developers to easily read and write CSV files.
The principle of OpenCSV mainly includes the following aspects:
1. Read CSV file: OpenCSV uses the Reader class to read data from the CSV file.It reads files by line and divides each row into fields.The separators between fields are specified by developers and defaults to comma.OpenCSV also supports certain rows or columns of the jump file.
2. Write into CSV file: OpenCSV uses the Writer class to write data into the CSV file.Developers can write data into files in the form of comma separation through the Writer class.They can also choose whether to add reference characters in the field to avoid problems caused by separators.
3. Customized separators and reference characters: OpenCSV allows developers to customize the separators and reference characters of custom fields.By setting the corresponding parameters of CSVPARSER and CSVWriter, developers can use different characters as separators.The reference character is used to include the field containing the separator.
4. Data object mapping: OpenCSV supports the data in the CSV file to the Java object.Developers can define a mapping strategy that allows each line of CSV files to be mapped to a Java object.In this way, developers can read data more conveniently from the CSV file without manual analysis of each line.
## OpenCSV framework How to use
Here are some examples of example code, which shows how to use the OpenCSV framework:
1. Read the CSV file:
import com.opencsv.CSVReader;
import java.io.FileReader;
import java.io.IOException;
public class CSVReaderExample {
public static void main(String[] args) {
try {
CSVReader reader = new CSVReader(new FileReader("data.csv"));
String[] nextLine;
while ((nextLine = reader.readNext()) != null) {
for (String field : nextLine) {
System.out.print(field + " ");
}
System.out.println();
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
2. Write into CSV file:
import com.opencsv.CSVWriter;
import java.io.FileWriter;
import java.io.IOException;
public class CSVWriterExample {
public static void main(String[] args) {
try {
CSVWriter writer = new CSVWriter(new FileWriter("data.csv"));
String[] record = {"John", "Doe", "john.doe@example.com"};
writer.writeNext(record);
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
These examples respectively demonstrate how to read and write CSV files with OpenCSV.Developers can customize separators and reference characters according to actual needs.
Summarize:
The OpenCSV framework provides a convenient way for Java developers to read and write and operate CSV files.This article details the principle and usage of OpenCSV, and provides corresponding Java code examples to help developers better understand and use the OpenCSV framework.
