Spring Boot 2 - JdbcTemplate INSERT query example to MySQL database

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package com.example.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.PreparedStatementCreator;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.support.GeneratedKeyHolder;
import org.springframework.jdbc.support.KeyHolder;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.ResponseBody;

import java.sql.*;
import java.util.List;

@Controller
public class UsersController {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    // --------------------------------------------------------------------

    // POST http://localhost:8080/api/user/create
    // echo '{"name":"john","email":"john@email.com"}' | curl -X POST -H "Content-Type: application/json" -d @- http://localhost:8080/api/user/create
    //
    @PostMapping(
            value = "/api/user/create",
            consumes = MediaType.APPLICATION_JSON_VALUE,
            produces = MediaType.APPLICATION_JSON_VALUE
    )
    @ResponseBody
    public UserEntity createUser(@RequestBody UserEntity userEntity) throws SQLException {
        long userId = this.insertUser(userEntity);
        return this.fetchUser(userId);
    }

    // --------------------------------------------------------------------
  
    private long insertUser(UserEntity userEntity) throws SQLException {
        String query = "INSERT INTO `users`\n" +
                       "\t(`name`, `email`)\n" +
                       "VALUES\n" +
                       "\t(?, ?)";
        KeyHolder keyHolder = new GeneratedKeyHolder();
        PreparedStatementCreator statementCreator = (Connection connection) -> {
            PreparedStatement preparedStatement = connection.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
            preparedStatement.setString(1, userEntity.getName());
            preparedStatement.setString(2, userEntity.getEmail());
            return preparedStatement;
        };
        int updatesCount = this.jdbcTemplate.update(statementCreator, keyHolder);
        if (updatesCount == 1) {
            Number generatedKey = keyHolder.getKey();
            if (generatedKey == null) {
                throw new SQLException("Getting user id error.");
            }
            return generatedKey.longValue();
        }
        throw new SQLException("Expected one row insert."); // should never happen
    }

    private UserEntity fetchUser(long userId) {
        String query = "SELECT `id`, `name`, `email`\n" +
                       "FROM `users`\n" +
                       "WHERE `id` = ?\n" +
                       "LIMIT 1";
        PreparedStatementCreator statementCreator = (Connection connection) -> {
            PreparedStatement preparedStatement = connection.prepareStatement(query);
            preparedStatement.setLong(1, userId);
            return preparedStatement;
        };
        List<UserEntity> users = this.jdbcTemplate.query(statementCreator, new UserRowMapper());
        if (users.isEmpty()) {
            return null;
        }
        return users.get(0);
    }

    // --------------------------------------------------------------------

    private class UserRowMapper implements RowMapper<UserEntity> {
        @Override
        public UserEntity mapRow(ResultSet resultSet, int rowNumber) throws SQLException {
            UserEntity user = new UserEntity();
            user.setId(resultSet.getLong("id"));
            user.setName(resultSet.getString("name"));
            user.setEmail(resultSet.getString("email"));
            return user;
        }
    }
}