5.1.8 Collection Registration

Overview

This chapter describes registering data in a GridDB collection.

Data to be registered

Create registration data in a CSV file with the contents as follows:

• Measuring instrument CSV file
  • File name
    • Weather_station.csv
  • Retention data
    • Row 1: measuring instrument ID
    • Row 2: The name
    • Row 3: installation coordinates (latitude)
    • Row 4: installation coordinates (longitude)
    • Row 5: camera presence

List.1 Data File (weather_station.csv)

1,Hokkaido-Sapporo,43.06417,141.34694,true
2,Aomori-Aomori-City,40.82444,140.74,false
3,Iwate-Morioka,39.70361,141.1525,true
4,Miyagi-Sendai,38.26889,140.87194,false
5,Akita-Akita,39.71861,140.1025,true
(Snip)

Data registration

The following code demonstrates registering data:

List.2 Simple Data Registration (CollectionRegister.java)

// Read WeatherStation data from csv
List  weatherStationList=wsLogic.readCsv ();
// Register Collection
wsLogic.registerCollection (store, weatherStationList);

• L.26: Read the CSV to get a list of measuring instruments.
• L.28: Register the list of measuring instruments in a GridDB collection.

List.3 Read CSV (WeatherStationLogic.java)

public List<WeatherStation> readCsv() throws IOException {
    List<WeatherStation> weatherStationList = new ArrayList<WeatherStation>();
    // Read CSV file
    CSVReader reader = new CSVReader(new FileReader("data/weather_station.csv"));

    try {
        String[] line = null;
        WeatherStation weatherStation = null;

        // Read all line of CSV
        while ((line = reader.readNext()) != null) {
            // Set the value to Row of WeatherStation
            weatherStation = new WeatherStation();
            weatherStation.id = line[0];
            weatherStation.name = line[1];
            weatherStation.latitude = Double.valueOf(line[2]);
            weatherStation.longitude = Double.valueOf(line[3]);
            weatherStation.hasCamera = Boolean.valueOf(line[4]);

            // Add Collection
            weatherStationList.add(weatherStation);
        }
    } finally {
        // Close CSV
        reader.close();
    }
    return weatherStationList;
}

Read CSV

• L.31: Read a CSV file weather_station.csv that contains the measuring instrument's data. The operation of reading the CSV file uses the CSVReader class of which is an open source software opencsv.
• L.38-45: Read the contents of the CSV and set the values to an instance of WeatherStation.

Register Collection

List.4 Register Data (WeatherStationLogic.java)

public void registerCollection(GridStore store, List<WeatherStation> weatherStationList)
        throws GSException {
    // Get Collection
    Collection<String, WeatherStation> weatherStationCol =
            store.getCollection("weather_station", WeatherStation.class);
    try {
        // Disable Auto Commit
        weatherStationCol.setAutoCommit(false);

        boolean isSuccess = true;

        for (WeatherStation weatherStation : weatherStationList) {
            if (weatherStation != null) {
                // Add Collection
                weatherStationCol.put(weatherStation.id, weatherStation);
            } else {
                // if Row Data is null, abort register
                weatherStationCol.abort();
                System.out.println("Register of the Collection is aborted.");
                isSuccess = false;
                break;
            }
        }

        // Commit only when the registration was successful all
        if (isSuccess) {
            // Commit
            weatherStationCol.commit();
        }
    } finally {
        // Close Connection
        weatherStationCol.close();
    }
}

Get Container

• L.67-68: Get the subject of container to be registered.

Auto-commit

• L.71: Disable auto-commit.

Auto-commit is set by Collection.setAutoCommit () method. Auto-commit by default in GridDB is enabled.
When you register the data collectively, to disable auto-commit makes a reduction in the number of times of the inquiry, therefore increasing the throughput is expectable.

Add Data

• L.78: Add the value read from CSV to the collection.

In this code auto-commit is disabled, but If auto-commit is enabled, the data will be registered here.

Commit

• L.91: Commit to a collection.

Commit is executed by Collection.commit () method. If auto-commit is disabled, the data is registered here.

Roll back

• L.81: Execute rollback to collection.

Rollback is executed by Collection.abort () method.
Rollback must be executed only when an exception occurs other than GSException or problems are detected. Otherwise operation of the pre-commit will be canceled if an exception GSException occurs when auto-commit is disabled.
In this sample, if the data of the measuring instrument read from the CSV is NULL, execute rollback assuming that a problem occurs.

Complete source code

Complete source code used in this sample can be downloaded from the following.

Download: collection-register.zip