ShardingJdbc按月分表

ShardingJdbc可以通过分表策略来按月分表，具体步骤如下：

1. 首先需要在数据源配置中设置分表策略，例如：

# 设置分表策略为按月分表
sharding.tables.order.actual-data-nodes = ds${0..1}.order_${2019..2020}01,ds${0..1}.order_${2019..2020}02,ds${0..1}.order_${2019..2020}03,ds${0..1}.order_${2019..2020}04,ds${0..1}.order_${2019..2020}05,ds${0..1}.order_${2019..2020}06,ds${0..1}.order_${2019..2020}07,ds${0..1}.order_${2019..2020}08,ds${0..1}.order_${2019..2020}09,ds${0..1}.order_${2019..2020}10,ds${0..1}.order_${2019..2020}11,ds${0..1}.order_${2019..2020}12
sharding.tables.order.table-strategy.standard.sharding-column = create_time
sharding.tables.order.table-strategy.standard.precise-algorithm-class-name = com.xxx.order.MonthPreciseShardingAlgorithm
sharding.tables.order.table-strategy.standard.range-algorithm-class-name = com.xxx.order.MonthRangeShardingAlgorithm

2. 实现按月分表的PreciseShardingAlgorithm和RangeShardingAlgorithm，例如：

public class MonthPreciseShardingAlgorithm implements PreciseShardingAlgorithm<Date> {
    @Override
    public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Date> shardingValue) {
        Date createTime = shardingValue.getValue();
        String suffix = new SimpleDateFormat("yyyyMM").format(createTime);
        for (String targetName : availableTargetNames) {
            if (targetName.endsWith(suffix)) {
                return targetName;
            }
        }
        throw new IllegalArgumentException();
    }
}

public class MonthRangeShardingAlgorithm implements RangeShardingAlgorithm<Date> {
    @Override
    public Collection<String> doSharding(Collection<String> availableTargetNames, RangeShardingValue<Date> shardingValue) {
        Date startTime = shardingValue.getValueRange().lowerEndpoint();
        Date endTime = shardingValue.getValueRange().upperEndpoint();
        List<String> targetNames = new ArrayList<>();
        Calendar startCal = Calendar.getInstance();
        startCal.setTime(startTime);
        Calendar endCal = Calendar.getInstance();
        endCal.setTime(endTime);
        while (startCal.before(endCal)) {
            String suffix = new SimpleDateFormat("yyyyMM").format(startCal.getTime());
            for (String targetName : availableTargetNames) {
                if (targetName.endsWith(suffix)) {
                    targetNames.add(targetName);
                }
            }
            startCal.add(Calendar.MONTH, 1);
        }
        String suffix = new SimpleDateFormat("yyyyMM").format(endCal.getTime());
        for (String targetName : availableTargetNames) {
            if (targetName.endsWith(suffix)) {
                targetNames.add(targetName);
            }
        }
        return targetNames;
    }
}

3. 在实体类中指定分表键，例如：

@Table(name = "order")
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "user_id")
    private Long userId;
    @Column(name = "create_time")
    private Date createTime;
}

通过以上步骤，即可实现按月分表的功能。