sharding jdbc5如何进行编写自定义分表算法和springboot的配置

Sharding JDBC 5.x版本可以通过实现`PreciseShardingAlgorithm`和`RangeShardingAlgorithm`接口来编写自定义的分表算法。

1. `PreciseShardingAlgorithm`用于处理等值查询场景，即根据某个字段的值精确分配到某个表中。

public class MyPreciseShardingAlgorithm implements PreciseShardingAlgorithm<Long> {
    
    @Override
    public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Long> shardingValue) {
        for (String tableName : availableTargetNames) {
            if (tableName.endsWith(shardingValue.getValue() % availableTargetNames.size() + "")) {
                return tableName;
            }
        }
        throw new UnsupportedOperationException();
    }
    
}

2. `RangeShardingAlgorithm`用于处理范围查询场景，即根据某个字段的值范围分配到多个表中。

public class MyRangeShardingAlgorithm implements RangeShardingAlgorithm<Long> {
    
    @Override
    public Collection<String> doSharding(Collection<String> availableTargetNames, RangeShardingValue<Long> shardingValue) {
        Collection<String> result = new LinkedHashSet<>();
        Range<Long> range = shardingValue.getValueRange();
        for (Long i = range.lowerEndpoint(); i <= range.upperEndpoint(); i++) {
            for (String tableName : availableTargetNames) {
                if (tableName.endsWith(i % availableTargetNames.size() + "")) {
                    result.add(tableName);
                }
            }
        }
        return result;
    }
    
}

3. 在Spring Boot中配置Sharding JDBC数据源时，需要在`application.properties`中配置如下信息：

# 数据库连接信息
spring.shardingsphere.datasource.ds0.url=jdbc:mysql://localhost:3306/db0
spring.shardingsphere.datasource.ds0.username=root
spring.shardingsphere.datasource.ds0.password=root

# 分库分表策略
spring.shardingsphere.sharding.tables.my_table.actual-data-nodes=ds0.my_table_${0..2}
spring.shardingsphere.sharding.tables.my_table.table-strategy.standard.sharding-column=user_id
spring.shardingsphere.sharding.tables.my_table.table-strategy.standard.precise-algorithm-class=com.example.MyPreciseShardingAlgorithm
spring.shardingsphere.sharding.tables.my_table.table-strategy.standard.range-algorithm-class=com.example.MyRangeShardingAlgorithm

# 打印SQL语句
spring.shardingsphere.props.sql.show=true

在以上配置中，`my_table`表会被分成3个子表，分别为`my_table_0`、`my_table_1`、`my_table_2`，其中`user_id`字段用于分表，`MyPreciseShardingAlgorithm`用于处理等值查询，`MyRangeShardingAlgorithm`用于处理范围查询。