The technical principle of the "Object CSV" framework in the Java class library
The technical principle of the "Object CSV" framework in the Java class library
introduction:
In Java development, CSV (comma seminars) files are often required.CSV is a common file format that is used to save structured data in the form of text.The process of processing CSV files involves the process of reading, analysis, and transformation of files into Java objects.To simplify this process, the Java class library provides many frameworks to analyze CSV files.One of them is the "Object CSV" framework. This framework is based on annotations. It can map the data in CSV to the Java object and simplify the processing process of the CSV file.
Technical principle:
The "Object CSV" framework realizes the conversion between the CSV file and the Java object by using Java reflection and annotation technology.By reading every line of CSV files and parsing its content, it assigns the analysis results to the corresponding Java object attributes.When using the "Object CSV" framework, you need to add annotations to the attributes of the Java object to indicate which column corresponds to the attribute to the CSV file, and how to transform data.
For the attributes corresponding to the CSV files in the Java object, the following annotations can be used:
1. @csvcolumn (name = "column_name"): It is used to indicate that the attribute corresponds to a column in the CSV file.Specify the name of the column in brackets.
2. @CSVCONVERTER (Converter = ConverterClass.class): Class used to specify the data converter.ConverterClass must implement the Converter interface to convert the string data in the CSV file to the type corresponding to the Java object attribute.
The following example shows how to use the "Object CSV" framework:
import com.github.objectcsv.annotations.CsvColumn;
import com.github.objectcsv.annotations.CsvConverter;
import com.github.objectcsv.annotations.CsvEntity;
import com.github.objectcsv.converter.Converter;
import com.github.objectcsv.converter.ConverterFactory;
import java.io.FileReader;
import java.io.IOException;
@CsvEntity
public class Person {
@CsvColumn(name = "name")
private String name;
@CsvColumn(name = "age")
private int age;
// Getters and setters
public static void main(String[] args) {
try (FileReader reader = new FileReader("data.csv")) {
List<Person> persons = ObjectCsvMapperFactory
.createMapper()
.fromCsv(Person.class)
.read(reader);
for (Person person : persons) {
System.out.println(person.getName() + ", " + person.getAge());
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class AgeConverter implements Converter<Integer> {
@Override
public Integer convert(String value) {
return Integer.parseInt(value);
}
}
public class ObjectCsvMapperFactory {
public static ObjectCsvMapper createMapper() {
ObjectCsvMapper mapper = new ObjectCsvMapper();
mapper.getConverterFactory().registerConverter(Integer.class, new AgeConverter());
return mapper;
}
}
In the above example, we created a Person class with two attributes: name and Age.By using the @CSVColumn annotation, we instructed the CSV list named "name" corresponding to the name attribute, and the CSV list corresponding to the Age attribute was "Age".In addition, we also created an AgeconVerter class to convert the string data in the CSV file into an integer.In ObjectCSVMapperFactory, we registered AGECONVERTER into ConverterFactory.
In the main method, we read the CSV file with ObjectCSVMapper and convert it into the list of Person objects.We can then use the obtained Person object for corresponding processing.
This is the technical principle of the "Object CSV" framework.By using annotations and reflection technology, it simplifies the process of processing CSV files and provides flexible data conversion functions, making the reading and conversion of CSV files easier.
in conclusion:
By using the "Object CSV" framework, we can simplify the reading and conversion process of the CSV file.Based on annotations and reflection technology, we only need to define Java objects and corresponding annotations to map the data in the CSV file to the Java object.When the data is needed, we can also use a custom converter.This allows us to process CSV files more quickly and transform it into meaningful Java objects.
