Using jackson-dataformat-csv to create CSV file out of POJOs

CsvCreator.java

import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvSchema;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

/**
 * Using jackson-dataformat-csv to create CSV file out of POJOs (bean class).
 * Use with maven-dependency:
 * <dependency>
 * <groupId>com.fasterxml.jackson.dataformat</groupId>
 * <artifactId>jackson-dataformat-csv</artifactId>
 * <version>2.3.3</version>
 * </dependency>
 * https://github.com/FasterXML/jackson-dataformat-csv
 */
public class CsvCreator {

    public static void main(String[] args) throws FileNotFoundException, UnsupportedEncodingException, IOException {

        // POJO (bean class)
        @JsonPropertyOrder({"name", "age"})
        class User {
            public String name;
            public int age;
            public User() {
            }
            public String getName() {
                return name;
            }
            public void setName(String name) {
                this.name = name;
            }
            public int getAge() {
                return age;
            }
            public void setAge(int age) {
                this.age = age;
            }
        }

        // define objects
        User user1 = new User();
        user1.name = "foo";
        user1.age = 32;
        User user2 = new User();
        user2.name = "bar";
        user2.age = 27;
        List<User> users = new ArrayList<User>();
        users.add(user1);
        users.add(user2);

        // create mapper and schema
        CsvMapper mapper = new CsvMapper();
        CsvSchema schema = mapper.schemaFor(User.class);
        schema = schema.withColumnSeparator('\t');

        // output writer
        ObjectWriter myObjectWriter = mapper.writer(schema);
        File tempFile = new File("users.csv");
        FileOutputStream tempFileOutputStream = new FileOutputStream(tempFile);
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(tempFileOutputStream, 1024);
        OutputStreamWriter writerOutputStream = new OutputStreamWriter(bufferedOutputStream, "UTF-8");
        myObjectWriter.writeValue(writerOutputStream, users);
    }
}

Thanks!

What if I need to put the objects' name as the headers for the csv file?

What if I need to put the objects' name as the headers for the csv file?

schema = schema.withUseHeader(true);

do you know how to wrap header elems in " symbols

I found solution like this

CsvMapper mapper = new CsvMapper();
mapper.enable(CsvGenerator.Feature.ALWAYS_QUOTE_STRINGS);

Why are you using object writer and outputstreams instead of csvmapper.writevalue()?

Why are you using object writer and outputstreams instead of csvmapper.writevalue()?

Correct, it's easier to create the CSV as you propose.

Got NullPointerException at line 72.
at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:394) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:365) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:338) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:123) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serialize(IndexedListSerializer.java:79) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serialize(IndexedListSerializer.java:18) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1396) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ObjectWriter._configAndWriteValue(ObjectWriter.java:1120) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]
at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:966) ~[jackson-databind-2.9.9.3.jar:2.9.9.3]

Thanks

Thanks