Technical Guide of the Object CSV framework in the Java class library
Object CSV framework technical guide in the Java class library
Introduction:
Object CSV is a Java class library used to read and write the CSV (comma divided value) file.It provides a simple and easy -to -use API, allowing developers to directly convert the Java object into a CSV format, and analyze the CSV file as the Java object when needed.This article will introduce how to use the Object CSV framework and some Java code examples.
1. Add Object CSV dependencies
To use the Object CSV framework, we need to add relevant dependencies to the project.You can add the following Maven dependencies in the project construction file (such as Pom.xml):
<dependency>
<groupId>com.opencsv</groupId>
<artifactId>opencsv</artifactId>
<version>4.5</version>
</dependency>
2. Create a CSV mapping class
In order to map the Java object to the column in the CSV file, we need to create a Java class called the CSV mapping class.These mapping classes will define the mapping relationship between the column name of the CSV file and the attributes of the Java object.
For example, suppose we have a Java class called Person with the following attributes: ID, name, and Age.We can create a CSV mapping class to define the mapping relationship between these attributes and columns in CSV files:
public class PersonCSV {
@CsvBindByPosition(position = 0)
private String id;
@CsvBindByPosition(position = 1)
private String name;
@CsvBindByPosition(position = 2)
private int age;
// omit the getter and setter method
}
In the above examples, the position of each attribute is specified by using the `@csvbindbyposition` annotation.
3. Read the Java object from the CSV file
Using the Object CSV framework, we can easily read the Java object from the CSV file.The following is an example of reading the Person object from the CSV file:
public List<Person> readCSV(String filePath) throws IOException {
List<Person> personList = new ArrayList<>();
try (Reader reader = Files.newBufferedReader(Paths.get(filePath));
CSVReader csvReader = new CSVReaderBuilder(reader).withSkipLines(1).build()) {
List<String[]> records = csvReader.readAll();
for (String[] record : records) {
Person person = new Person();
person.setId(record[0]);
person.setName(record[1]);
person.setAge(Integer.parseInt(record[2]));
personList.add(person);
}
}
return personList;
}
In the above examples, we use the Java file I/O and Object CSV framework API to read data from the CSV file.First, we create a `Reader` object to read the CSV file.Then, we use the `csvreaderbuilder` class to build an object of` csvreader`, and use the `Withskiplines` method to skip the title line in the CSV file.Finally, we use the `Readall` method to read the data into a` list <string []> `, and then convert it to a Person object.
4. Write the Java object into the CSV file
Using the Object CSV framework, we can write the Java object into the CSV file.The following is an example of writing the Person object into the CSV file:
public void writeCSV(String filePath, List<Person> personList) throws IOException {
try (Writer writer = Files.newBufferedWriter(Paths.get(filePath));
CSVWriter csvWriter = new CSVWriter(writer, CSVWriter.DEFAULT_SEPARATOR,
CSVWriter.NO_QUOTE_CHARACTER, CSVWriter.DEFAULT_ESCAPE_CHARACTER,
CSVWriter.DEFAULT_LINE_END)) {
String[] headerRecord = {"id", "name", "age"};
csvWriter.writeNext(headerRecord);
for (Person person : personList) {
String[] record = {person.getId(), person.getName(), String.valueOf(person.getAge())};
csvWriter.writeNext(record);
}
}
}
In the above examples, we use the Java file I/O and Object CSV framework API to write the Person object into the CSV file.First, we create a `writer` object to write the CSV file.We then create an object of `csvwriter` and use it to write the title line of the CSV file.Finally, we write the attributes of each Person object to the CSV file with the `writenext` method.
in conclusion:
Object CSV is a Java class library that facilitates and writes CSV files.By using the Object CSV framework, we can easily convert between Java objects and CSV files.This article introduces how to use the Object CSV framework and provide some Java code examples. I hope to help you understand and use Object CSV.
