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@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class})
public class ShardingJdbcDemoApplication implements CommandLineRunner {

// 注意这里的注解，可以让 Spring 自动帮忙加载，也就是 Java Config 的核心
@Configuration
public class MysqlConfig {

    @Bean
    public DataSource dataSource() throws SQLException {
        // Configure actual data sources
        Map<String, DataSource> dataSourceMap = new HashMap<>();

        
        // Configure the first data source
        // 使用了默认的Hikari连接池的 DataSource
        HikariDataSource dataSource1 = new HikariDataSource();
        dataSource1.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource1.setJdbcUrl("jdbc:mysql://localhost:3306/sharding");
        dataSource1.setUsername("username");
        dataSource1.setPassword("password");
        dataSourceMap.put("ds0", dataSource1);

        // Configure student table rule
        // 这里是配置分表逻辑，逻辑表是 student，对应真实的表是 student_0 到 student_1, 这个配置方式就是有多少表可以用 student_$->{0..n}
        ShardingTableRuleConfiguration studentTableRuleConfig = new ShardingTableRuleConfiguration("student", "ds0.student_$->{0..1}");

        // 设置分表字段
        studentTableRuleConfig.setTableShardingStrategy(new StandardShardingStrategyConfiguration("user_id", "tableShardingAlgorithm"));


        // Configure sharding rule
        // 配置 studentTableRuleConfig
        ShardingRuleConfiguration shardingRuleConfig = new ShardingRuleConfiguration();
        shardingRuleConfig.getTables().add(studentTableRuleConfig);

        // Configure table sharding algorithm
        Properties tableShardingAlgorithmrProps = new Properties();
        // 算法表达式就是根据 user_id 对 2 进行取模
        tableShardingAlgorithmrProps.setProperty("algorithm-expression", "student_${user_id % 2}");
        shardingRuleConfig.getShardingAlgorithms().put("tableShardingAlgorithm", new ShardingSphereAlgorithmConfiguration("INLINE", tableShardingAlgorithmrProps));


        // 然后创建这个 DataSource
        return ShardingSphereDataSourceFactory.createDataSource(dataSourceMap, Collections.singleton(shardingRuleConfig), new Properties());

    }
}

@Override
    public void run(String... args) {
        LOGGER.info("run here");
        String sql = "SELECT * FROM student WHERE user_id=? ";
        try (
                Connection conn = dataSource.getConnection();
                PreparedStatement ps = conn.prepareStatement(sql)) {
            // 参数就是 user_id，然后也是分表键，对 2 取模就是 1，应该是去 student_1 取数据
            ps.setInt(1, 1001);

            ResultSet resultSet = ps.executeQuery();
            while (resultSet.next()) {
                final int id = resultSet.getInt("id");
                final String name = resultSet.getString("name");
                final int userId = resultSet.getInt("user_id");
                final int age = resultSet.getInt("age");
                System.out.println("奇数表 id：" + id + " 姓名：" + name
                        + " 用户 id：" + userId + " 年龄：" + age );
                System.out.println("=============================");
            }
            // 参数就是 user_id，然后也是分表键，对 2 取模就是 0，应该是去 student_0 取数据
            ps.setInt(1, 1000);
            resultSet = ps.executeQuery();
            while (resultSet.next()) {
                final int id = resultSet.getInt("id");
                final String name = resultSet.getString("name");
                final int userId = resultSet.getInt("user_id");
                final int age = resultSet.getInt("age");
                System.out.println("偶数表 id：" + id + " 姓名：" + name
                        + " 用户 id：" + userId + " 年龄：" + age );
                System.out.println("=============================");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

public int maxSubArray(int[] nums) {
        int max = nums[0];
        int sum = nums[0];
        for (int i = 1; i < nums.length; i++) {
            // 这里最重要的就是这一行了，其实就是如果前面的 sum 是小于 0 的，那么就不需要前面的 sum，反正加上了还不如不加大
            sum = Math.max(nums[i], sum + nums[i]);
            // max 是用来承载最大值的
            max = Math.max(max, sum);
        }
        return max;
    }