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CSV parsing for multiple / nested bean types with OpenCSV?

I have various CSVs that contain some standard columns and some completely random fields:

firstname, lastname, dog_name, fav_hat, fav_color
bill,smith,fido,porkpie,blue
james,smith,rover,bowler,purple


firstname, lastname, car_type, floor_number
tom, collins, ford, 14
jim, jones, toyota, 120

So, I'm trying to parse them into Person.class beans, which contains the first and last name, then I have a second PersonAttribute.class class to store ... everything else.

Biscus plan of two classes:

class Person {
 public String firstname;
 public String lastname;
 public List<PersonAttribute> attribs;
}

class PersonAttribute {
 public Person p;
 public String key; // header name, ex. 'car_type'
 public String value; // column value, ex. 'ford'
}

I used the CsvToBean functions in opencsv:

public static List<Person> parseToBeans(File csvFile, HashMap<String, String> mapStrategy, Class beanClass) throws IOException {
    CSVReader reader = null;
    try {
        reader = new CSVReader(new BufferedReader(new FileReader(csvFile)));

        HeaderColumnNameTranslateMappingStrategy<Person> strategy = new HeaderColumnNameTranslateMappingStrategy<>();
        strategy.setType(beanClass);
        strategy.setColumnMapping(mapStrategy);

        final CsvToBean<Person> csv = new CsvToBean<Person>() {
            @Override
            protected Object convertValue(String value, PropertyDescriptor prop) throws InstantiationException, IllegalAccessException {
                value = value.trim().replaceAll(" +", " ");
                return super.convertValue(value, prop);
            }
        };
        return csv.parse(strategy, reader);
    }
...

However, I'm not sure how to handle the creation of PersonAttribute.class beans while I parse the csv for Person.class beans. I stumbled upon this post and I wonder if I need to switch to supercsv to easily handle what I'm trying to do?

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1 answer

Super CSV.

  • CsvBeanReader - , bean,

  • CsvDozerBeanReader - , , ( Super CSV 2.1.0)

CsvBeanReader

Dozer bean, setter bean, CsvBeanReader . , Person PersonAttribute beans no-args getters/seters, ( ).

Person bean :

public void setAddAttribute(PersonAttribute attribute){
    if (attribs == null){
        attribs = new ArrayList<PersonAttribute>();
    }
    attribs.add(attribute);
}

, PersonAttribute CSV, CSV.

package org.supercsv.example;

import org.supercsv.cellprocessor.CellProcessorAdaptor;
import org.supercsv.util.CsvContext;

/**
 * Creates a PersonAttribute using the corresponding header as the key.
 */
public class ParsePersonAttribute extends CellProcessorAdaptor {

    private final String[] header;

    public ParsePersonAttribute(final String[] header) {
        this.header = header;
    }

    public Object execute(Object value, CsvContext context) {

        if( value == null ) {
            return null;
        }

        PersonAttribute attribute = new PersonAttribute();
        // columns start at 1
        attribute.setKey(header[context.getColumnNumber() - 1]);
        attribute.setValue((String) value);
        return attribute;
    }

}

, , , :

  • , CSV ,

  • , ( )

  • addAttribute, setAddAttribute(), bean

  • PersonAttribute bean

:

package org.supercsv.example;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;

import org.supercsv.cellprocessor.Optional;
import org.supercsv.cellprocessor.constraint.NotNull;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.io.CsvBeanReader;
import org.supercsv.io.ICsvBeanReader;
import org.supercsv.prefs.CsvPreference;

public class ReadWithCsvBeanReader {

    private static final String CSV = 
            "firstname, lastname, dog_name, fav_hat, fav_color\n"
            + "bill,smith,fido,porkpie,blue\n"
            + "james,smith,rover,bowler,purple";

    private static final String CSV2 = 
            "firstname, lastname, car_type, floor_number\n"
            + "tom, collins, ford, 14\n" + "jim, jones, toyota, 120";

    // attributes start at element 2 of the header array
    private static final int ATT_START_INDEX = 2;

    // custom preferences required because CSV contains 
    spaces that aren't part of the data
    private static final CsvPreference PREFS = 
        new CsvPreference.Builder(
            CsvPreference.STANDARD_PREFERENCE)
            .surroundingSpacesNeedQuotes(true).build();

    public static void main(String[] args) throws IOException {
        System.out.println("CsvBeanReader with first CSV input:");
        readWithCsvBeanReader(new StringReader(CSV));
        System.out.println("CsvBeanReader with second CSV input:");
        readWithCsvBeanReader(new StringReader(CSV2));
    }

    private static void readWithCsvBeanReader(final Reader reader)
            throws IOException {
        ICsvBeanReader beanReader = null;
        try {
            beanReader = new CsvBeanReader(reader, PREFS);

            final String[] header = beanReader.getHeader(true);

            // set up the field mapping and processors dynamically
            final String[] fieldMapping = new String[header.length];
            final CellProcessor[] processors = 
                    new CellProcessor[header.length];
            for (int i = 0; i < header.length; i++) {
                if (i < ATT_START_INDEX) {
                    // normal mappings
                    fieldMapping[i] = header[i];
                    processors[i] = new NotNull();
                } else {
                    // attribute mappings
                    fieldMapping[i] = "addAttribute";
                    processors[i] = 
                            new Optional(new ParsePersonAttribute(header));
                }
            }

            Person person;
            while ((person = beanReader.read(Person.class, fieldMapping,
                    processors)) != null) {
                System.out.println(String.format(
                        "lineNo=%s, rowNo=%s, person=%s",
                        beanReader.getLineNumber(), beanReader.getRowNumber(),
                        person));
            }

        } finally {
            if (beanReader != null) {
                beanReader.close();
            }
        }
    }

}

( toString() beans):

CsvBeanReader with first CSV input:
lineNo=2, rowNo=2, person=Person [firstname=bill, lastname=smith, attribs=[PersonAttribute [key=dog_name, value=fido], PersonAttribute [key=fav_hat, value=porkpie], PersonAttribute [key=fav_color, value=blue]]]
lineNo=3, rowNo=3, person=Person [firstname=james, lastname=smith, attribs=[PersonAttribute [key=dog_name, value=rover], PersonAttribute [key=fav_hat, value=bowler], PersonAttribute [key=fav_color, value=purple]]]
CsvBeanReader with second CSV input:
lineNo=2, rowNo=2, person=Person [firstname=tom, lastname=collins, attribs=[PersonAttribute [key=car_type, value=ford], PersonAttribute [key=floor_number, value=14]]]
lineNo=3, rowNo=3, person=Person [firstname=jim, lastname=jones, attribs=[PersonAttribute [key=car_type, value=toyota], PersonAttribute [key=floor_number, value=120]]]

CsvDozerBeanReader

bean, CsvDozerBeanReader Super CSV Dozer Extension, . .

CsvDozerBeanReader. , CsvBeanReader, :

  • (duh!)

  • , . attribs[0]

  • , configureBeanMapping() ( read(), CsvBeanReader

  • ( )

:

package org.supercsv.example;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;

import org.supercsv.cellprocessor.Optional;
import org.supercsv.cellprocessor.constraint.NotNull;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.io.dozer.CsvDozerBeanReader;
import org.supercsv.io.dozer.ICsvDozerBeanReader;
import org.supercsv.prefs.CsvPreference;

public class ReadWithCsvDozerBeanReader {

    private static final String CSV = 
            "firstname, lastname, dog_name, fav_hat, fav_color\n"
            + "bill,smith,fido,porkpie,blue\n" 
            + "james,smith,rover,bowler,purple";

    private static final String CSV2 = 
            "firstname, lastname, car_type, floor_number\n" 
            + "tom, collins, ford, 14\n"
            + "jim, jones, toyota, 120";

    // attributes start at element 2 of the header array
    private static final int ATT_START_INDEX = 2;

    // custom preferences required because CSV contains spaces that aren't part of the data
    private static final CsvPreference PREFS = new CsvPreference.Builder(CsvPreference.STANDARD_PREFERENCE)
        .surroundingSpacesNeedQuotes(true).build();

    public static void main(String[] args) throws IOException {
        System.out.println("CsvDozerBeanReader with first CSV input:");
        readWithCsvDozerBeanReader(new StringReader(CSV));
        System.out.println("CsvDozerBeanReader with second CSV input:");
        readWithCsvDozerBeanReader(new StringReader(CSV2));
    }

    private static void readWithCsvDozerBeanReader(final Reader reader) throws IOException {
        ICsvDozerBeanReader beanReader = null;
        try {
            beanReader = new CsvDozerBeanReader(reader, PREFS);

            final String[] header = beanReader.getHeader(true);

            // set up the field mapping, processors and hints dynamically
            final String[] fieldMapping = new String[header.length];
            final CellProcessor[] processors = new CellProcessor[header.length];
            final Class<?>[] hintTypes = new Class<?>[header.length];
            for( int i = 0; i < header.length; i++ ) {
                if( i < ATT_START_INDEX ) {
                    // normal mappings
                    fieldMapping[i] = header[i];
                    processors[i] = new NotNull();
                } else {
                    // attribute mappings
                    fieldMapping[i] = String.format("attribs[%d]", i - ATT_START_INDEX);
                    processors[i] = new Optional(new ParsePersonAttribute(header));
                    hintTypes[i] = PersonAttribute.class;
                }
            }

            beanReader.configureBeanMapping(Person.class, fieldMapping, hintTypes);

            Person person;
            while( (person = beanReader.read(Person.class, processors)) != null ) {
                System.out.println(String.format("lineNo=%s, rowNo=%s, person=%s", 
                    beanReader.getLineNumber(),
                    beanReader.getRowNumber(), person));
            }

        }
        finally {
            if( beanReader != null ) {
                beanReader.close();
            }
        }
    }

}

:

CsvDozerBeanReader with first CSV input:
lineNo=2, rowNo=2, person=Person [firstname=bill, lastname=smith, attribs=[PersonAttribute [key=dog_name, value=fido], PersonAttribute [key=fav_hat, value=porkpie], PersonAttribute [key=fav_color, value=blue]]]
lineNo=3, rowNo=3, person=Person [firstname=james, lastname=smith, attribs=[PersonAttribute [key=dog_name, value=rover], PersonAttribute [key=fav_hat, value=bowler], PersonAttribute [key=fav_color, value=purple]]]
CsvDozerBeanReader with second CSV input:
lineNo=2, rowNo=2, person=Person [firstname=tom, lastname=collins, attribs=[PersonAttribute [key=car_type, value=ford], PersonAttribute [key=floor_number, value=14]]]
lineNo=3, rowNo=3, person=Person [firstname=jim, lastname=jones, attribs=[PersonAttribute [key=car_type, value=toyota], PersonAttribute [key=floor_number, value=120]]]

, CsvDozerBeanReader Super CSV 2.0.1, ( , , / ) , :

"firstname","lastname","attribs[0]","attribs[1]"

Super CSV 2.1.0, . , Dozer , . 100%, PersonAttribute , () :

"firstname","lastname","attribs[0].value","attribs[1].value"

, :)

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