How to convert json Array to CSV file using Java

Library Link : https://github.com/opendevl/Json2Flat

Sample Output Like This : https://j2flateval.herokuapp.com

 // There are some typos in the data.

// You can try json2flat for converting JSON docs to get an equivalent CSV representation.
// If you want to try for more JSON doc click here.

// For the JSON data :

{
    "results": [{

            "geo_position": {
                "Field1": 11,
                "Field2": 12
            },
            "Field3": 13,
            "Field4": 14,
            "Field5": 15
        },

        {
            "geo_position": {
                "Field1": 21,
                "Field2": 22
            },
            "Field3": 23,
            "Field4": 24,
            "Field5": 25
        }
    ]
}

// The code is also preety simple.

JFlat flatMe = new JFlat(jsonString);
flatMe
    .json2Sheet()
    .headerSeparator("/")
    .write2csv("test.csv");

// This will write the result to test.csv file.

// Equivalent CSV representation :


results/Field3,results/Field4,results/Field5,results/geo_position/Field1,results/geo_position/Field2
    13.0,14.0,15.0,11.0,12.0
    23.0,24.0,25.0,21.0,22.0

You can use Jackson.

The dependencies:

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-csv</artifactId>
    <version>2.9.8</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
</dependency>

A Code example:

@JsonPropertyOrder({"firstName", "lastName", "age"})
public class Person {
    private String firstName; 
    private String lastName;
    private Integer age;

    public Person()
    {}

    public Person(String firstName, String lastName, Integer age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

Now the consumer:

public class Consumer {
    private ObjectMapper mapper; 

    private CsvMapper csvMapper; 


    public static void main(String[] args) {
        csvMapper = new CsvMapper();
        mapper = new ObjectMapper();

        List<Person> list = new ArrayList<>();
        simpleList.add(new Person("John", "Wolf", 26));

        Consumer c = new Consumer();

        String json = c.createJson(list);
        System.out.println("The Json file:" + json);

        String csvStr = c.createCsv(list);
        System.out.println("The Csv file:" + csvStr);        
    }


    private String createJson(List<Person> list) throws JsonProcessingException { 
        return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(list);
    }

    private String createCsvList<Person> list) throws JsonProcessingException {
        CsvSchema schema = csvMapper.schemaFor(Person.class).withHeader();
        return csvMapper.writer(schema).writeValueAsString(list);
    }
}

Json output:

[ {
"firstName" : "John",
"lastName" : "Wolf",
"age" : 26
} ]

Csv output:

firstName,lastName,age
John,Wolf,26