{ Soham Kamani }

About Blog Github Twitter

🌙
☀️

A Complete Guide to Using Google BigQuery in Java (With Examples)

This post will highlight the basics of BigQuery and how to read, write and administer your BigQuery dataset in a Java application.

banner image

BigQuery is a managed data warehouse, and is part of the Google Cloud Platform. We can use the official Java client to interact with our datasets.

If you just want to see the example code, you can view it on Github

BigQuery Jobs

Every operation on a BigQuery dataset can be described in terms of a job.

When you want to run a query or transfer data from one dataset to another, you send a job description to your BigQuery instance, and it is executed as a job to get the final result.

the bigquery client library converts queries to jobs and returns result obejcts

In BigQuery, an SQL query is run as a job. In this post, “running a query” is the same as “executing a job”

Creating a New Service Account

To enable your Java application to execute jobs on BigQuery, it requires a service account.

Ideally, each application has its own service account. Service accounts let BigQuery know that an application is trusted and can run jobs on it.

To create a service account, go to the service accounts page and click on “CREATE SERVICE ACCOUNT”.

In the creation page, we need to provide a name, and give the “BigQuery Admin” role:

service account page

Now we can create a key by going into the “Keys” tab of the service account we created:

create key page

You should be able to download this key as a JSON file. We will be using this in our Java application later.

Setting Up a New Java Application

Let’s create a new Maven Java application. Our folder structure should look like this:

.
├── pom.xml
└── src
    ├── main
    │   └── java
    │       └── com
    │           └── sohamkamani
    │               └── App.java
    └── test
        └── java
            └── com
                └── sohamkamani
                    └── AppTest.java

Querying Data From an Existing Table

Let’s take a look at the code to get data from an existing table.

For this example, we’re going to get the top 10 most used words in Shakespeare’s “Julius Caesar”, using the public shakespeare dataset.

Our program will run in 4 steps:

  1. Initialize the BigQuery service
  2. Create a job to run our query
  3. Run the job on BigQuery and check for errors
  4. Display the result

We can add the following code to the App.java file:

public class App {

    public static void main(String... args) throws Exception {
        // Step 1: Initialize BigQuery service
        // Here we set our project ID and get the `BigQuery` service object
        // this is the interface to our BigQuery instance that
        // we use to execute jobs on
        BigQuery bigquery = BigQueryOptions.newBuilder().setProjectId("sample-project-330313")
                .build().getService();

        // Step 2: Prepare query job
        // A "QueryJob" is a type of job that executes SQL queries
        // we create a new job configuration from our SQL query and
        final String GET_WORD_COUNT =
                "SELECT word, word_count FROM `bigquery-public-data.samples.shakespeare` WHERE corpus='juliuscaesar' ORDER BY word_count DESC limit 10;";
        QueryJobConfiguration queryConfig =
                QueryJobConfiguration.newBuilder(GET_WORD_COUNT).build();

        // Step 3: Run the job on BigQuery
        // create a `Job` instance from the job configuration using the BigQuery service
        // the job starts executing once the `create` method executes
        Job queryJob = bigquery.create(JobInfo.newBuilder(queryConfig).build());
        queryJob = queryJob.waitFor();
        // the waitFor method blocks until the job completes
        // and returns `null` if the job doesn't exist anymore
        if (queryJob == null) {
            throw new Exception("job no longer exists");
        }
        // once the job is done, check if any error occured
        if (queryJob.getStatus().getError() != null) {
            throw new Exception(queryJob.getStatus().getError().toString());
        }

        // Step 4: Display results
        // Print out a header line, and iterate through the
        // query results to print each result in a new line
        System.out.println("word\tword_count");
        TableResult result = queryJob.getQueryResults();
        for (FieldValueList row : result.iterateAll()) {
            // We can use the `get` method along with the column
            // name to get the corresponding row entry
            String word = row.get("word").getStringValue();
            int wordCount = row.get("word_count").getNumericValue().intValue();
            System.out.printf("%s\t%d\n", word, wordCount);
        }
    }
}

To run this program, we need the location of the JSON file we downloaded when creating a service account.

We can then run our program by running this command:

GOOGLE_APPLICATION_CREDENTIALS=~/Downloads/your-service-account-file.json mvn exec:java \
-Dexec.mainClass="com.sohamkamani.App" -Dexec.classpathScope=runtime

Change the mainClass argument based on your folder structure and package name in App.java

This should give you the following result:

word    word_count
I       521
the     520
and     431
to      380
of      350
you     344
not     248
BRUTUS  235
a       230
is      229

It’s funny how the only non-filler word here is Brutus :)

Creating a New Table

To create your own table, go to the BigQuery console and create a new dataset under your project, if you haven’t already:

click on the options for your project under explorer and create a new dataset

You’ll have to choose an ID for your dataset. For this example we’ll use sample_dataset as the dataset ID.

You can then run a CREATE TABLE query on the console. For example, let’s create a vegetables with an id and name field for each row:

CREATE TABLE IF NOT EXISTS `sample-project-330313.sample_dataset.vegetables` (
    id INT64,
    name STRING
)

This will create a new vegetables table under the dataset sample_dataset:

run query on bigquery console to create the new table

Inserting Data With Queries

Note: In order to insert data into a BigQuery table, you’ll need to enable billing for your project.

We can insert data using queries, similar to how data is inserted in other relational databases.

Here, instead of a SELECT query, we will run an INSERT query, and instead of printing the resultant rows, we will print the number of rows inserted:

public class App {

    public static void main(String... args) throws Exception {
        // Step 1: Initialize BigQuery service
        BigQuery bigquery = BigQueryOptions.newBuilder().setProjectId("sample-project-330313")
                .build().getService();

        // Step 2: Prepare query job
        final String INSERT_VEGETABLES =
                "INSERT INTO `sample-project-330313.sample_dataset.vegetables` (id, name) VALUES (1, 'carrot'), (2, 'beans');";
        QueryJobConfiguration queryConfig =
                QueryJobConfiguration.newBuilder(INSERT_VEGETABLES).build();


        // Step 3: Run the job on BigQuery
        Job queryJob = bigquery.create(JobInfo.newBuilder(queryConfig).build());
        queryJob = queryJob.waitFor();
        if (queryJob == null) {
            throw new Exception("job no longer exists");
        }
        // once the job is done, check if any error occured
        if (queryJob.getStatus().getError() != null) {
            throw new Exception(queryJob.getStatus().getError().toString());
        }

        // Step 4: Display results
        // Here, we will print the total number of rows that were inserted
        JobStatistics.QueryStatistics stats = queryJob.getStatistics();
        Long rowsInserted = stats.getDmlStats().getInsertedRowCount();
        System.out.printf("%d rows inserted\n", rowsInserted);
    }
}

Inserting Streaming Data

Another way to insert data into your table is through a process called “streaming”.

When you insert data via queries, you need to create a job. Streaming enables you to move your data directly from your application into your BigQuery datastore, avoiding the overhead of creating a new job.

Instead of using a query, we need to define a map, with the row names as the keys, and the row values as the values. Let’s see how to insert the same sample data using streaming:

public class App {

    public static void main(String... args) {
        // Step 1: Initialize BigQuery service
        BigQuery bigquery = BigQueryOptions.newBuilder().setProjectId("sample-project-330313")
                .build().getService();

        // Step 2: Create insertAll (streaming) request
        InsertAllRequest insertAllRequest = getInsertRequest();

        // Step 3: Insert data into table
        InsertAllResponse response = bigquery.insertAll(insertAllRequest);

        // Step 4: Check for errors and print results
        if (response.hasErrors()) {
            // Here, each entry, or row, can have an error when we attempt to insert it
            // Since we're attempting to insert multiple rows, we would have multiple
            // errors we have to iterate through
            for (Map.Entry<Long, List<BigQueryError>> entry : response.getInsertErrors()
                    .entrySet()) {
                System.out.printf("error in entry %d: %s", entry.getKey(),
                        entry.getValue().toString());
            }
            return;
        }
        System.out.println("inserted successfully");
    }

    // To create a streaming insert request, we need to specify the table and dataset id
    // and create the rows we want to insert
    private static InsertAllRequest getInsertRequest() {
        String datasetId = "sample_dataset";
        String tableId = "vegetables";
        return InsertAllRequest.newBuilder(datasetId, tableId).addRow(getRow(1, "carrot"))
                .addRow(getRow(2, "beans")).build();

    }

    // each row is a map with the row name as the key and row value as the value
    // since the value type is "Object" it can take any arbitrary type, based on
    // the datatype of the row defined on BigQuery
    private static Map<String, Object> getRow(int id, String vegetableName) {
        Map<String, Object> rowMap = new HashMap<String, Object>();
        rowMap.put("id", id);
        rowMap.put("name", vegetableName);
        return rowMap;
    }
}

If you want to know the details of what happens to your data during this process, you can read about the life of a BigQuery streaming insert.

Further Reading

BigQuery is a great tool for data analytics. Using the Java API, we can run any operation on our BigQuery instance within our Java application.

This gives us a lot of power and flexibility, and enables us to automate common operations on BigQuery, or even use BigQuery to power a production application.

You can read the complete code for all the examples here on Github.

If you want to read more about the Java API, you can see the official API documentation.


Like what I write? Join my mailing list, and I'll let you know whenever I write another post. No spam, I promise!

Comments

Soham Kamani

Written by Soham Kamani, an author,and a full-stack developer who has extensive experience in the JavaScript ecosystem, and building large scale applications in Go. He is an open source enthusiast and an avid blogger. You should follow him on Twitter