build-a-java-app-with-cockroachdb.md

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Build a Java App with CockroachDB	Learn how to use CockroachDB from a simple Java application with the jdbc driver.	true	false

Use jdbc Use Hibernate

This tutorial shows you how build a simple Java application with CockroachDB using a PostgreSQL-compatible driver or ORM.

We have tested the Java jdbc driver and the Hibernate ORM enough to claim beta-level support, so those are featured here. If you encounter problems, please open an issue with details to help us make progress toward full support.

Before You Begin

Make sure you have already installed CockroachDB.

Step 1. Install the Java jdbc driver

Download and set up the Java jdbc driver as described in the official documentation.

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Step 5. Run the Java code

Now that you have a database and a user, you'll run code to create a table and insert some rows, and then you'll run code to read and update values as an atomic transaction.

Basic Statements

First, use the following code to connect as the maxroach user and execute some basic SQL statements, creating a table, inserting rows, and reading and printing the rows.

Download the BasicSample.java file, or create the file yourself and copy the code into it.

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Transaction (with retry logic)

Next, use the following code to again connect as the maxroach user but this time execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted.

Download the TxnSample.java file, or create the file yourself and copy the code into it.

{{site.data.alerts.callout_info}}With the default SERIALIZABLE isolation level, CockroachDB may require the client to retry a transaction in case of read/write contention. CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code. Note that, in Java, you access error codes with the getSQLState() method instead of getErrorCode().{{site.data.alerts.end}}

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After running the code, use the built-in SQL client to verify that funds were transferred from one account to another:

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$ cockroach sql --insecure -e 'SELECT id, balance FROM accounts' --database=bank

+----+---------+
| id | balance |
+----+---------+
|  1 |     900 |
|  2 |     350 |
+----+---------+
(2 rows)

What's Next?

Read more about using the Java jdbc driver.

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