How to serialize object to CSV file?

Question

I want to write a Object into CSV file. For XML we have XStream like this
So if i want to convert object to CSV do we have any such library ?

EDIT: I w

Answer 1

For easy CSV access, there is a library called OpenCSV. It really ease access to CSV file content.

EDIT

According to your update, I consider all previous replies as incorrect (due to their low-levelness). You can then go a completely diffferent way, the hibernate way, in fact !

By using the CsvJdbc driver, you can load your CSV files as JDBC data source, and then directly map your beans to this datasource.

I would have talked to you about CSVObjects, but as the site seems broken, I fear the lib is unavailable nowadays.

Answer 2

I wrote a simple class that uses OpenCSV and has two static public methods.

static public File toCSVFile(Object object, String path, String name) {
    File pathFile = new File(path);
    pathFile.mkdirs();
    File returnFile = new File(path + name);
    try {

        CSVWriter writer = new CSVWriter(new FileWriter(returnFile));
        writer.writeNext(new String[]{"Member Name in Code", "Stored Value", "Type of Value"});
        for (Field field : object.getClass().getDeclaredFields()) {
            writer.writeNext(new String[]{field.getName(), field.get(object).toString(), field.getType().getName()});
        }
        writer.flush();
        writer.close();
        return returnFile;
    } catch (IOException e) {
        Log.e("EasyStorage", "Easy Storage toCSVFile failed.", e);
        return null;
    } catch (IllegalAccessException e) {
        Log.e("EasyStorage", "Easy Storage toCSVFile failed.", e);
        return null;
    }
}

static public void fromCSVFile(Object object, File file) {
    try {
        CSVReader reader = new CSVReader(new FileReader(file));
        String[] nextLine = reader.readNext(); // Ignore the first line.
        while ((nextLine = reader.readNext()) != null) {
            if (nextLine.length >= 2) {
                try {
                    Field field = object.getClass().getDeclaredField(nextLine[0]);
                    Class<?> rClass = field.getType();
                    if (rClass == String.class) {
                        field.set(object, nextLine[1]);
                    } else if (rClass == int.class) {
                        field.set(object, Integer.parseInt(nextLine[1]));
                    } else if (rClass == boolean.class) {
                        field.set(object, Boolean.parseBoolean(nextLine[1]));
                    } else if (rClass == float.class) {
                        field.set(object, Float.parseFloat(nextLine[1]));
                    } else if (rClass == long.class) {
                        field.set(object, Long.parseLong(nextLine[1]));
                    } else if (rClass == short.class) {
                        field.set(object, Short.parseShort(nextLine[1]));
                    } else if (rClass == double.class) {
                        field.set(object, Double.parseDouble(nextLine[1]));
                    } else if (rClass == byte.class) {
                        field.set(object, Byte.parseByte(nextLine[1]));
                    } else if (rClass == char.class) {
                        field.set(object, nextLine[1].charAt(0));
                    } else {
                        Log.e("EasyStorage", "Easy Storage doesn't yet support extracting " + rClass.getSimpleName() + " from CSV files.");
                    }
                } catch (NoSuchFieldException e) {
                    Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
                } catch (IllegalAccessException e) {
                    Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);

                }
            } // Close if (nextLine.length >= 2)
        } // Close while ((nextLine = reader.readNext()) != null)
    } catch (FileNotFoundException e) {
        Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
    } catch (IOException e) {
        Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
    } catch (IllegalArgumentException e) {
        Log.e("EasyStorage", "Easy Storage fromCSVFile failed.", e);
    }
}

I think with some simple recursion these methods could be modified to handle any Java object, but for me this was adequate.

Answer 3

You can use gererics to work for any class

public class FileUtils<T> {
public String createReport(String filePath, List<T> t) {
    if (t.isEmpty()) {
        return null;
    }

    List<String> reportData = new ArrayList<String>();

    addDataToReport(t.get(0), reportData, 0);

    for (T k : t) {
        addDataToReport(k, reportData, 1);
    }
    return !dumpReport(filePath, reportData) ? null : filePath;
}

public static Boolean dumpReport(String filePath, List<String> lines) {
    Boolean isFileCreated = false;

    
    String[] dirs = filePath.split(File.separator);
    String baseDir = "";
    for (int i = 0; i < dirs.length - 1; i++) {
        baseDir += " " + dirs[i];
    }
    baseDir = baseDir.replace(" ", "/");
    
    File base = new File(baseDir);
    base.mkdirs();

    File file = new File(filePath);
    try {
        if (!file.exists())
            file.createNewFile();
    } catch (Exception e) {
        e.printStackTrace();
        return isFileCreated;
    }

    try (BufferedWriter writer = new BufferedWriter(
            new OutputStreamWriter(new FileOutputStream(file), System.getProperty("file.encoding")))) {
        for (String line : lines) {
            writer.write(line + System.lineSeparator());
        }
    } catch (IOException e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

void addDataToReport(T t, List<String> reportData, int index) {
    String[] jsonObjectAsArray = new Gson().toJson(t).replace("{", "").replace("}", "").split(",\"");
    StringBuilder row = new StringBuilder();

    for (int i = 0; i < jsonObjectAsArray.length; i++) {
        String str = jsonObjectAsArray[i];
        str = str.replaceFirst(":", "_").split("_")[index];

        if (i == 0) {
            if (str != null) {
                row.append(str.replace("\"", ""));
            } else {
                row.append("N/A");
            }
        } else {
            if (str != null) {
                row.append(", " + str.replace("\"", ""));
            } else {
                row.append(", N/A");
            }
        }
    }
    reportData.add(row.toString());
}

Answer 4

Two options I just ran into:

• http://sojo.sourceforge.net/
• http://supercsv.sourceforge.net/

Answer 5

First, serialization is writing the object to a file 'as it is'. AFAIK, you cannot choose file formats and all. The serialized object (in a file) has its own 'file format'

If you want to write the contents of an object (or a list of objects) to a CSV file, you can do it yourself, it should not be complex.

Looks like Java CSV Library can do this, but I have not tried this myself.

EDIT: See following sample. This is by no way foolproof, but you can build on this.

    //European countries use ";" as 
    //CSV separator because "," is their digit separator
    private static final String CSV_SEPARATOR = ",";
    private static void writeToCSV(ArrayList<Product> productList)
    {
        try
        {
            BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("products.csv"), "UTF-8"));
            for (Product product : productList)
            {
                StringBuffer oneLine = new StringBuffer();
                oneLine.append(product.getId() <=0 ? "" : product.getId());
                oneLine.append(CSV_SEPARATOR);
                oneLine.append(product.getName().trim().length() == 0? "" : product.getName());
                oneLine.append(CSV_SEPARATOR);
                oneLine.append(product.getCostPrice() < 0 ? "" : product.getCostPrice());
                oneLine.append(CSV_SEPARATOR);
                oneLine.append(product.isVatApplicable() ? "Yes" : "No");
                bw.write(oneLine.toString());
                bw.newLine();
            }
            bw.flush();
            bw.close();
        }
        catch (UnsupportedEncodingException e) {}
        catch (FileNotFoundException e){}
        catch (IOException e){}
    }

This is product (getters and setters hidden for readability):

class Product
{
    private long id;
    private String name;
    private double costPrice;
    private boolean vatApplicable;
}

And this is how I tested:

public static void main(String[] args)
{
    ArrayList<Product> productList = new ArrayList<Product>();
    productList.add(new Product(1, "Pen", 2.00, false));
    productList.add(new Product(2, "TV", 300, true));
    productList.add(new Product(3, "iPhone", 500, true));
    writeToCSV(productList);
}

Hope this helps.

Cheers.

Answer 6

Worth mentioning that the handlebar library https://github.com/jknack/handlebars.java can trivialize many transformation tasks include toCSV.