title	summary
Build a Simple CRUD App with TiDB and JDBC	Learn how to build a simple CRUD application with TiDB and JDBC.

Build a Simple CRUD App with TiDB and JDBC

This document describes how to use TiDB and JDBC to build a simple CRUD application.

Note:

It is recommended to use Java 8 or a later Java version.

Step 1. Launch your TiDB cluster

The following introduces how to start a TiDB cluster.

Use a TiDB Serverless cluster

For detailed steps, see Create a TiDB Serverless cluster.

Use a local cluster

For detailed steps, see Deploy a local test cluster or Deploy a TiDB Cluster Using TiUP.

See Create a TiDB Serverless cluster.

Step 2. Get the code

git clone https://github.com/pingcap-inc/tidb-example-java.git

Change to the plain-java-jdbc directory:

cd plain-java-jdbc

The structure of this directory is as follows:

.
├── Makefile
├── plain-java-jdbc.iml
├── pom.xml
└── src
    └── main
        ├── java
        │   └── com
        │       └── pingcap
        │            └── JDBCExample.java
        └── resources
            └── dbinit.sql

You can find initialization statements for the table creation in dbinit.sql:

USE test;
DROP TABLE IF EXISTS player;

CREATE TABLE player (
    `id` VARCHAR(36),
    `coins` INTEGER,
    `goods` INTEGER,
   PRIMARY KEY (`id`)
);

JDBCExample.java is the main body of the plain-java-jdbc. TiDB is highly compatible with the MySQL protocol, so you need to initialize a MySQL source instance MysqlDataSource to connect to TiDB. Then, you can initialize PlayerDAO for object management and use it to read, edit, add, and delete data.

PlayerDAO is a class used to manage data, in which DAO means Data Access Object. The class defines a set of data manipulation methods to provide the ability to write data.

PlayerBean is a data entity class that is a mapping for tables. Each property of a PlayerBean corresponds to a field in the player table.

package com.pingcap;

import com.mysql.cj.jdbc.MysqlDataSource;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;

/**
 * Main class for the basic JDBC example.
 **/
public class JDBCExample
{
    public static class PlayerBean {
        private String id;
        private Integer coins;
        private Integer goods;

        public PlayerBean() {
        }

        public PlayerBean(String id, Integer coins, Integer goods) {
            this.id = id;
            this.coins = coins;
            this.goods = goods;
        }

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public Integer getCoins() {
            return coins;
        }

        public void setCoins(Integer coins) {
            this.coins = coins;
        }

        public Integer getGoods() {
            return goods;
        }

        public void setGoods(Integer goods) {
            this.goods = goods;
        }

        @Override
        public String toString() {
            return String.format("    %-8s => %10s\n    %-8s => %10s\n    %-8s => %10s\n",
                    "id", this.id, "coins", this.coins, "goods", this.goods);
        }
    }

    /**
     * Data access object used by 'ExampleDataSource'.
     * Example for CURD and bulk insert.
     */
    public static class PlayerDAO {
        private final MysqlDataSource ds;
        private final Random rand = new Random();

        PlayerDAO(MysqlDataSource ds) {
            this.ds = ds;
        }

        /**
         * Create players by passing in a List of PlayerBean.
         *
         * @param players Will create players list
         * @return The number of create accounts
         */
        public int createPlayers(List<PlayerBean> players){
            int rows = 0;

            Connection connection = null;
            PreparedStatement preparedStatement = null;
            try {
                connection = ds.getConnection();
                preparedStatement = connection.prepareStatement("INSERT INTO player (id, coins, goods) VALUES (?, ?, ?)");
            } catch (SQLException e) {
                System.out.printf("[createPlayers] ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
                e.printStackTrace();

                return -1;
            }

            try {
                for (PlayerBean player : players) {
                    preparedStatement.setString(1, player.getId());
                    preparedStatement.setInt(2, player.getCoins());
                    preparedStatement.setInt(3, player.getGoods());

                    preparedStatement.execute();
                    rows += preparedStatement.getUpdateCount();
                }
            } catch (SQLException e) {
                System.out.printf("[createPlayers] ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
                e.printStackTrace();
            } finally {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

            System.out.printf("\n[createPlayers]:\n    '%s'\n", preparedStatement);
            return rows;
        }

        /**
         * Buy goods and transfer funds between one player and another in one transaction.
         * @param sellId Sell player id.
         * @param buyId Buy player id.
         * @param amount Goods amount, if sell player has not enough goods, the trade will break.
         * @param price Price should pay, if buy player has not enough coins, the trade will break.
         *
         * @return The number of effected players.
         */
        public int buyGoods(String sellId, String buyId, Integer amount, Integer price) {
            int effectPlayers = 0;

            Connection connection = null;
            try {
                connection = ds.getConnection();
            } catch (SQLException e) {
                System.out.printf("[buyGoods] ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
                e.printStackTrace();
                return effectPlayers;
            }

            try {
                connection.setAutoCommit(false);

                PreparedStatement playerQuery = connection.prepareStatement("SELECT * FROM player WHERE id=? OR id=? FOR UPDATE");
                playerQuery.setString(1, sellId);
                playerQuery.setString(2, buyId);
                playerQuery.execute();

                PlayerBean sellPlayer = null;
                PlayerBean buyPlayer = null;

                ResultSet playerQueryResultSet = playerQuery.getResultSet();
                while (playerQueryResultSet.next()) {
                    PlayerBean player =  new PlayerBean(
                            playerQueryResultSet.getString("id"),
                            playerQueryResultSet.getInt("coins"),
                            playerQueryResultSet.getInt("goods")
                    );

                    System.out.println("\n[buyGoods]:\n    'check goods and coins enough'");
                    System.out.println(player);

                    if (sellId.equals(player.getId())) {
                        sellPlayer = player;
                    } else {
                        buyPlayer = player;
                    }
                }

                if (sellPlayer == null || buyPlayer == null) {
                    throw new SQLException("player not exist.");
                }

                if (sellPlayer.getGoods().compareTo(amount) < 0) {
                    throw new SQLException(String.format("sell player %s goods not enough.", sellId));
                }

                if (buyPlayer.getCoins().compareTo(price) < 0) {
                    throw new SQLException(String.format("buy player %s coins not enough.", buyId));
                }

                PreparedStatement transfer = connection.prepareStatement("UPDATE player set goods = goods + ?, coins = coins + ? WHERE id=?");
                transfer.setInt(1, -amount);
                transfer.setInt(2, price);
                transfer.setString(3, sellId);
                transfer.execute();
                effectPlayers += transfer.getUpdateCount();

                transfer.setInt(1, amount);
                transfer.setInt(2, -price);
                transfer.setString(3, buyId);
                transfer.execute();
                effectPlayers += transfer.getUpdateCount();

                connection.commit();

                System.out.println("\n[buyGoods]:\n    'trade success'");
            } catch (SQLException e) {
                System.out.printf("[buyGoods] ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());

                try {
                    System.out.println("[buyGoods] Rollback");

                    connection.rollback();
                } catch (SQLException ex) {
                    // do nothing
                }
            } finally {
                try {
                    connection.close();
                } catch (SQLException e) {
                    // do nothing
                }
            }

            return effectPlayers;
        }

        /**
         * Get the player info by id.
         *
         * @param id Player id.
         * @return The player of this id.
         */
        public PlayerBean getPlayer(String id) {
            PlayerBean player = null;

            try (Connection connection = ds.getConnection()) {
                PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM player WHERE id = ?");
                preparedStatement.setString(1, id);
                preparedStatement.execute();

                ResultSet res = preparedStatement.executeQuery();
                if(!res.next()) {
                    System.out.printf("No players in the table with id %s", id);
                } else {
                    player = new PlayerBean(res.getString("id"), res.getInt("coins"), res.getInt("goods"));
                }
            } catch (SQLException e) {
                System.out.printf("PlayerDAO.getPlayer ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
            }

            return player;
        }

        /**
         * Insert randomized account data (id, coins, goods) using the JDBC fast path for
         * bulk inserts.  The fastest way to get data into TiDB is using the
         * TiDB Lightning(https://docs.pingcap.com/tidb/stable/tidb-lightning-overview).
         * However, if you must bulk insert from the application using INSERT SQL, the best
         * option is the method shown here. It will require the following:
         *
         *    Add `rewriteBatchedStatements=true` to your JDBC connection settings.
         *    Setting rewriteBatchedStatements to true now causes CallableStatements
         *    with batched arguments to be re-written in the form "CALL (...); CALL (...); ..."
         *    to send the batch in as few client/server round trips as possible.
         *    https://dev.mysql.com/doc/relnotes/connector-j/5.1/en/news-5-1-3.html
         *
         *    You can see the `rewriteBatchedStatements` param effect logic at
         *    implement function: `com.mysql.cj.jdbc.StatementImpl.executeBatchUsingMultiQueries`
         *
         * @param total Add players amount.
         * @param batchSize Bulk insert size for per batch.
         *
         * @return The number of new accounts inserted.
         */
        public int bulkInsertRandomPlayers(Integer total, Integer batchSize) {
            int totalNewPlayers = 0;

            try (Connection connection = ds.getConnection()) {
                // We're managing the commit lifecycle ourselves, so we can
                // control the size of our batch inserts.
                connection.setAutoCommit(false);

                // In this example we are adding 500 rows to the database,
                // but it could be any number.  What's important is that
                // the batch size is 128.
                try (PreparedStatement pstmt = connection.prepareStatement("INSERT INTO player (id, coins, goods) VALUES (?, ?, ?)")) {
                    for (int i=0; i<=(total/batchSize);i++) {
                        for (int j=0; j<batchSize; j++) {
                            String id = UUID.randomUUID().toString();
                            pstmt.setString(1, id);
                            pstmt.setInt(2, rand.nextInt(10000));
                            pstmt.setInt(3, rand.nextInt(10000));
                            pstmt.addBatch();
                        }

                        int[] count = pstmt.executeBatch();
                        totalNewPlayers += count.length;
                        System.out.printf("\nPlayerDAO.bulkInsertRandomPlayers:\n    '%s'\n", pstmt);
                        System.out.printf("    => %s row(s) updated in this batch\n", count.length);
                    }
                    connection.commit();
                } catch (SQLException e) {
                    System.out.printf("PlayerDAO.bulkInsertRandomPlayers ERROR: { state => %s, cause => %s, message => %s }\n",
                            e.getSQLState(), e.getCause(), e.getMessage());
                }
            } catch (SQLException e) {
                System.out.printf("PlayerDAO.bulkInsertRandomPlayers ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
            }
            return totalNewPlayers;
        }


        /**
         * Print a subset of players from the data store by limit.
         *
         * @param limit Print max size.
         */
        public void printPlayers(Integer limit) {
            try (Connection connection = ds.getConnection()) {
                PreparedStatement preparedStatement = connection.prepareStatement("SELECT * FROM player LIMIT ?");
                preparedStatement.setInt(1, limit);
                preparedStatement.execute();

                ResultSet res = preparedStatement.executeQuery();
                while (!res.next()) {
                    PlayerBean player = new PlayerBean(res.getString("id"),
                            res.getInt("coins"), res.getInt("goods"));
                    System.out.println("\n[printPlayers]:\n" + player);
                }
            } catch (SQLException e) {
                System.out.printf("PlayerDAO.printPlayers ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
            }
        }


        /**
         * Count players from the data store.
         *
         * @return All players count
         */
        public int countPlayers() {
            int count = 0;

            try (Connection connection = ds.getConnection()) {
                PreparedStatement preparedStatement = connection.prepareStatement("SELECT count(*) FROM player");
                preparedStatement.execute();

                ResultSet res = preparedStatement.executeQuery();
                if(res.next()) {
                    count = res.getInt(1);
                }
            } catch (SQLException e) {
                System.out.printf("PlayerDAO.countPlayers ERROR: { state => %s, cause => %s, message => %s }\n",
                        e.getSQLState(), e.getCause(), e.getMessage());
            }

            return count;
        }
    }

    public static void main(String[] args) {
        // 1. Configure the example database connection.

        // 1.1 Create a mysql data source instance.
        MysqlDataSource mysqlDataSource = new MysqlDataSource();

        // 1.2 Set server name, port, database name, username and password.
        mysqlDataSource.setServerName("localhost");
        mysqlDataSource.setPortNumber(4000);
        mysqlDataSource.setDatabaseName("test");
        mysqlDataSource.setUser("root");
        mysqlDataSource.setPassword("");

        // Or you can use jdbc string instead.
        // mysqlDataSource.setURL("jdbc:mysql://{host}:{port}/test?user={user}&password={password}");

        // 2. And then, create DAO to manager your data.
        PlayerDAO dao = new PlayerDAO(mysqlDataSource);

        // 3. Run some simple example.

        // Create a player, has a coin and a goods.
        dao.createPlayers(Collections.singletonList(new PlayerBean("test", 1, 1)));

        // Get a player.
        PlayerBean testPlayer = dao.getPlayer("test");
        System.out.printf("PlayerDAO.getPlayer:\n    => id: %s\n    => coins: %s\n    => goods: %s\n",
                testPlayer.getId(), testPlayer.getCoins(), testPlayer.getGoods());

        // Create players with bulk inserts, insert 1919 players totally, and per batch for 114 players.
        int addedCount = dao.bulkInsertRandomPlayers(1919, 114);
        System.out.printf("PlayerDAO.bulkInsertRandomPlayers:\n    => %d total inserted players\n", addedCount);

        // Count players amount.
        int count = dao.countPlayers();
        System.out.printf("PlayerDAO.countPlayers:\n    => %d total players\n", count);

        // Print 3 players.
        dao.printPlayers(3);

        // 4. Getting further.

        // Player 1: id is "1", has only 100 coins.
        // Player 2: id is "2", has 114514 coins, and 20 goods.
        PlayerBean player1 = new PlayerBean("1", 100, 0);
        PlayerBean player2 = new PlayerBean("2", 114514, 20);

        // Create two players "by hand", using the INSERT statement on the backend.
        addedCount = dao.createPlayers(Arrays.asList(player1, player2));
        System.out.printf("PlayerDAO.createPlayers:\n    => %d total inserted players\n", addedCount);

        // Player 1 wants to buy 10 goods from player 2.
        // It will cost 500 coins, but player 1 can't afford it.
        System.out.println("\nPlayerDAO.buyGoods:\n    => this trade will fail");
        int updatedCount = dao.buyGoods(player2.getId(), player1.getId(), 10, 500);
        System.out.printf("PlayerDAO.buyGoods:\n    => %d total update players\n", updatedCount);

        // So player 1 have to reduce his incoming quantity to two.
        System.out.println("\nPlayerDAO.buyGoods:\n    => this trade will success");
        updatedCount = dao.buyGoods(player2.getId(), player1.getId(), 2, 100);
        System.out.printf("PlayerDAO.buyGoods:\n    => %d total update players\n", updatedCount);
    }
}

Step 3. Run the code

The following content introduces how to run the code step by step.

Step 3.1 Table initialization

When using JDBC, you need to initialize the database tables manually. If you are using a local cluster, and MySQL client has been installed locally, you can run it directly in the plain-java-jdbc directory:

make mysql

Or you can execute the following command:

mysql --host 127.0.0.1 --port 4000 -u root<src/main/resources/dbinit.sql

If you are using a non-local cluster or MySQL client has not been installed, connect to your cluster and run the statement in the src/main/resources/dbinit.sql file.

When using JDBC, you need to connect to your cluster and run the statement in the src/main/resources/dbinit.sql file to initialize the database tables manually.

Step 3.2 Modify parameters for TiDB Cloud

If you are using a TiDB Serverless cluster, modify the parameters of the host, port, user, and password in JDBCExample.java:

mysqlDataSource.setServerName("localhost");
mysqlDataSource.setPortNumber(4000);
mysqlDataSource.setDatabaseName("test");
mysqlDataSource.setUser("root");
mysqlDataSource.setPassword("");

Suppose that the password you set is 123456, and the connection parameters you get from the cluster details page are the following:

Endpoint: xxx.tidbcloud.com
Port: 4000
User: 2aEp24QWEDLqRFs.root

In this case, you can modify the parameters as follows:

mysqlDataSource.setServerName("xxx.tidbcloud.com");
mysqlDataSource.setPortNumber(4000);
mysqlDataSource.setDatabaseName("test");
mysqlDataSource.setUser("2aEp24QWEDLqRFs.root");
mysqlDataSource.setPassword("123456");
mysqlDataSource.setSslMode(PropertyDefinitions.SslMode.VERIFY_IDENTITY.name());
mysqlDataSource.setEnabledTLSProtocols("TLSv1.2,TLSv1.3");

Step 3.3 Run

To run the code, you can run make build and make run respectively:

make build # this command executes `mvn clean package`
make run # this command executes `java -jar target/plain-java-jdbc-0.0.1-jar-with-dependencies.jar`

Or you can use the native commands:

mvn clean package
java -jar target/plain-java-jdbc-0.0.1-jar-with-dependencies.jar

Or run the make command directly, which is a combination of make build and make run.

Step 4. Expected output

JDBC Expected Output

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dev-guide-sample-application-java-jdbc.md

dev-guide-sample-application-java-jdbc.md

Build a Simple CRUD App with TiDB and JDBC

Step 1. Launch your TiDB cluster

Step 2. Get the code

Step 3. Run the code

Step 3.1 Table initialization

Step 3.2 Modify parameters for TiDB Cloud

Step 3.3 Run

Step 4. Expected output

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dev-guide-sample-application-java-jdbc.md

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Build a Simple CRUD App with TiDB and JDBC

Step 1. Launch your TiDB cluster

Step 2. Get the code

Step 3. Run the code

Step 3.1 Table initialization

Step 3.2 Modify parameters for TiDB Cloud

Step 3.3 Run

Step 4. Expected output