目录
一、Sharding-JDBC依赖
二、代码实践
三、源码分析
在上一篇博文中，介绍了Sharding-JDBC的分片策略、分片键和分片算法的基本概念，以及2.0.3版本可以支持和无法支持的使用场景。
可以支持的场景：支持对SQL语句中的=、IN和BETWEEN AND的分片操作，但前提是分片键必须存在于SQL和数据表结构中。
无法支持的场景：分片键不存在于SQL和数据表结构中，即基于暗示(Hint)的数据分片操作（2.0.3版本的问题）。
无可厚非，缺少了Hint分片策略的支持，Sharding-JDBC 2.0.3版本的使用场景就非常受限了，但值得庆幸的是，此问题在3.x版本进行了修复（这里可以有掌声！），接下来的代码皆基于3.1.0版本。
一、Sharding-JDBC依赖
<!-- sharding-jdbc-core -->
<dependency>
<groupId>io.shardingsphere</groupId>
<artifactId>sharding-jdbc-core</artifactId>
<version>3.1.0</version>
</dependency>
<!-- sharding-jdbc-spring-namespace -->
<dependency>
<groupId>io.shardingsphere</groupId>
<artifactId>sharding-jdbc-spring-namespace</artifactId>
<version>3.1.0</version>
</dependency>
和2.0.3版本相比，依赖的名称有所改变，不要搞错了哦。
二、代码实践
业务背景就不再介绍了，不了解可移步至Sharding-JDBC（二）2.0.3版本实践。
如下代码配置了标准分片策略中的精确分片算法PreciseShardingAlgorithm和Hint分片算法HintShardingAlgorithm。
XML配置：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:sharding="http://shardingsphere.io/schema/shardingsphere/sharding"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd
http://shardingsphere.io/schema/shardingsphere/sharding
http://shardingsphere.io/schema/shardingsphere/sharding/sharding.xsd">
<!-- 标准分片策略 -->
<sharding:standard-strategy id="settlementTableShardingStandardStrategy" sharding-column="pay_serial_number"
precise-algorithm-ref="preciseTableShardingAlgorithm"/>
<!-- 基于暗示(Hint)的分片策略 -->
<sharding:hint-strategy id="settlementHintTableShardingStrategy" algorithm-ref="hintTableShardingAlgorithm"/>
<sharding:hint-strategy id="settlementHintDatabaseShardingStrategy" algorithm-ref="hintDatabaseShardingAlgorithm"/>
<sharding:data-source id="shardingDataSource">
<sharding:sharding-rule data-source-names="dataSource">
<sharding:table-rules>
<sharding:table-rule logic-table="settlement"
table-strategy-ref="settlementTableShardingStandardStrategy"/>
<!-- logic-table参数的大小写必须和SettlementMapper.xml中selectByExample方法的表名大小一致！！！ -->
<!-- logic-table必须和org.cellphone.finance.repo.SettlementRepository.querySettlements中的logicTable及SQL中的表名一致，否则无法找到分片策略 -->
<!-- 逻辑表名，不需要和真实表名一致 -->
<sharding:table-rule logic-table="settlement_hint"
database-strategy-ref="settlementHintDatabaseShardingStrategy"
table-strategy-ref="settlementHintTableShardingStrategy"/>
</sharding:table-rules>
</sharding:sharding-rule>
<sharding:props>
<prop key="sql.show">true</prop>
</sharding:props>
</sharding:data-source>
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="shardingDataSource"/>
</bean>
<tx:annotation-driven/>
</beans>
精确分片算法：
package org.cellphone.finance.repo.sharding;
import com.google.common.collect.Lists;
import io.shardingsphere.api.algorithm.sharding.PreciseShardingValue;
import io.shardingsphere.api.algorithm.sharding.standard.PreciseShardingAlgorithm;
import org.apache.commons.collections.CollectionUtils;
import org.cellphone.common.constant.CommonConst;
import org.springframework.stereotype.Component;
import java.util.Collection;
/**
* 精确分片算法，属于标准分片算法，用于处理=和IN的分片
* <p>
* 使用精确分片算法的前提：分片字段必须存在与SQL中、数据库表结构中，否则无法使用精确分片算法
* <p>
* 此分片算法应用于SETTLEMENT数据表，这里是按天分表
* <p>
* 特别说明：Sharding Jdbc版本：3.1.0
* <p>
* Created by on 2018/4/9.
*/
@Component("preciseTableShardingAlgorithm")
public class PreciseTableShardingAlgorithm implements PreciseShardingAlgorithm<String> {
/**
* 精确分片算法
*
* @param availableTargetNames 目标数据源名称或数据表名称，注意：是逻辑数据源名或逻辑数据表名，来自SQL
* @param shardingValue 分片值，来自SQL中分片字段对应的值
* @return 真实数据源名称或数据表名称
*/
@Override
public String doSharding(final Collection<String> availableTargetNames, final PreciseShardingValue<String> shardingValue) {
// 默认数据表名称，有可能数据库中不存在这张表
String tableName = "settlement";
// 逻辑表名为空，返回默认表名
if (CollectionUtils.isEmpty(availableTargetNames))
return tableName;
// availableTargetNames来自SQL，只有一个元素
tableName = Lists.newArrayList(availableTargetNames).get(0);
String paySerialNumber = shardingValue.getValue();
String suffix = paySerialNumber.substring(5, 13);
return tableName + CommonConst.UNDERLINE + suffix;
}
}
Hint数据源分片算法：
package org.cellphone.finance.repo.sharding;
import io.shardingsphere.api.algorithm.sharding.ShardingValue;
import io.shardingsphere.api.algorithm.sharding.hint.HintShardingAlgorithm;
import org.springframework.stereotype.Component;
import java.util.Collection;
/**
* Sharding Jdbc基于暗示(Hint)的数据分片算法
*
* 使用Sharding Jdbc 3.x版本时，此数据源分片算法这个一定要有！！！
* 否则无法正常使用org.cellphone.finance.repo.sharding.HintTableShardingAlgorithm算法
* <p>
* Created by on 2019/4/25.
*/
@Component("hintDatabaseShardingAlgorithm")
public class HintDatabaseShardingAlgorithm implements HintShardingAlgorithm {
@Override
public Collection<String> doSharding(Collection<String> availableTargetNames, ShardingValue shardingValue) {
return availableTargetNames;
}
}
Hint数据表分片算法：
package org.cellphone.finance.repo.sharding;
import com.google.common.collect.Lists;
import io.shardingsphere.api.algorithm.sharding.ListShardingValue;
import io.shardingsphere.api.algorithm.sharding.ShardingValue;
import io.shardingsphere.api.algorithm.sharding.hint.HintShardingAlgorithm;
import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.time.DateFormatUtils;
import org.apache.commons.lang3.time.DateUtils;
import org.cellphone.common.constant.CommonConst;
import org.cellphone.common.constant.DateConst;
import org.springframework.stereotype.Component;
import java.text.ParseException;
import java.util.*;
/**
* Sharding Jdbc基于暗示(Hint)的数据分片算法
* 版本：Sharding Jdbc 3.1.0
*
* 官方介绍（2.x版本）：http://shardingsphere.apache.org/document/legacy/2.x/cn/02-guide/hint-sharding-value/
* 官方介绍（4.x版本）：https://shardingsphere.apache.org/document/current/cn/manual/sharding-jdbc/usage/hint/
* <p>
* <p>
* <p>
* <p>
* 使用此算法的背景如下：
* 1. SETTLEMENT（支付表）是按时间维度进行分表，该时间取自PAY_SERIAL_NUMBER中的时间数据，非表中的时间字段；
* <p>
* 2. 使用用户手机号此类条件查询数据时，请求参数除传入业务参数外，
* 还需传入时间段（即分片字段，例：startTime和endTime）以确定分表范围；
* 但是！！！startTime和endTime（即分片字段）不存在SQL中、数据库表结构中，而存在于外部业务逻辑
* <p>
* <p>
* <p>
* 因此，第2点导致无法直接使用Sharding Jdbc的PreciseShardingAlgorithm（精确分片算法）或RangeShardingAlgorithm（范围分片算法），
* 只能使用HintShardingAlgorithm（基于暗示的数据分片算法），该算法的使用场景如下：
* 1. 分片字段不存在SQL中、数据库表结构中，而存在于外部业务逻辑；
* <p>
* 2. 强制在主库进行某些数据操作。
* <p>
* <p>
* Created by on 2019/4/25.
*/
@Component("hintTableShardingAlgorithm")
public class HintTableShardingAlgorithm implements HintShardingAlgorithm {
/**
* 分片算法
*
* @param availableTargetNames 逻辑数据库名称或逻辑数据表名称
* @param shardingValue 用来确定分表的参数
* @return 实际数据表名称列表，SQL实际操作的数据表
*/
@Override
public Collection<String> doSharding(Collection<String> availableTargetNames, ShardingValue shardingValue) {
String realTableName = StringUtils.EMPTY;
for (String each : availableTargetNames) {
if (StringUtils.isNotBlank(each)) {
// 基于hint的逻辑表名：settlement_hint
realTableName = each.replace("_hint", StringUtils.EMPTY);
break;
}
}
List<String> tables = new ArrayList<>();
ListShardingValue<String> listShardingValue = (ListShardingValue<String>) shardingValue;
List<String> list = Lists.newArrayList(listShardingValue.getValues());
// 缺少确定分表的参数，无法确定具体分表，直接返回真实表名称
if (CollectionUtils.isEmpty(list)) {
tables.add(realTableName);
return tables;
}
// 拆分分表参数，此参数值来自：com.fcbox.manage.core.repo.FcBoxPostRepository.queryFcBoxPosts()
String[] queryTime = list.get(0).split(CommonConst.UNDERLINE);
Date startTime, endTime;
try {
startTime = DateUtils.parseDate(queryTime[0], DateConst.DATE_FORMAT_NORMAL);
endTime = DateUtils.parseDate(queryTime[1], DateConst.DATE_FORMAT_NORMAL);
} catch (ParseException e) {
// 分表参数解析错误，无法确定具体分表，直接返回真实表名称
tables.add(realTableName);
return tables;
}
Calendar calendar = Calendar.getInstance();
// 组织startTime和endTime时段范围内的分表
while (startTime.getTime() <= endTime.getTime()) {
tables.add(realTableName + CommonConst.UNDERLINE + DateFormatUtils.format(startTime, DateConst.DATE_FORMAT_YYYY_MM_DD));
calendar.setTime(startTime);
calendar.add(Calendar.DATE, 1);
startTime = calendar.getTime();
}
return tables;
}
}
与Hint分片算法对应的Java查询方法 settlementMapper.selectByExample(example)：
public List<Settlement> querySettlements(SettlementExample example, String startTime, String endTime) {
// 组织查询时间，传入org.cellphone.finance.repo.sharding.HintTableShardingAlgorithm分片算法中以确认具体分表
String queryTime = startTime + CommonConst.UNDERLINE + endTime;
// 获取HintManager
HintManager hintManager = HintManager.getInstance();
/*
* 添加数据源分片键值，使用Sharding Jdbc 3.x版本一定要添加数据源分片键值，否则无法使用HintTableShardingAlgorithm分片算法
* 若无分库，addDatabaseShardingValue方法的value字段随意填充
* 若有分库，addDatabaseShardingValue方法的value字段填充实际参数值
*/
hintManager.addDatabaseShardingValue("settlement_hint", StringUtils.EMPTY);
// 添加数据表分片键值
hintManager.addTableShardingValue("settlement_hint", queryTime);
List<Settlement> settlements = settlementMapper.selectByExample(example);
// 清除分片键值
hintManager.close();
return settlements;
}
以及该查询方法对应的SQL语句：
select * from settlement_hint t where t.pay_serial_number = ?
单元测试代码：
@Test
public void test003QuerySettlements() throws ParseException {
String startTime = "2018-04-03 00:00:00", endTime = "2018-04-05 00:00:00";
SettlementExample example = new SettlementExample();
SettlementExample.Criteria criteria = example.createCriteria();
criteria.andPaySerialNumberEqualTo(paySerialNumber);
List<Settlement> settlements = repository.querySettlements(example, startTime, endTime);
Assert.assertEquals("136********", settlements.get(0).getUserMobile());
}
三、源码分析
和2.0.3版本相比，3.1.0版本的路由入口变成了 io.shardingsphere.core.routing.type.standard.StandardRoutingEngine#route() ，但基本上区别不大，仅仅是多了一步需要确定路由的真实数据源，尽管数据源只有一个，也需要显式配置数据源路由算法。代码中标注了注释的部分都是路由代码比较核心的部分。
/*
* Copyright 2016-2018 shardingsphere.io.
* <p>
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* </p>
*/
package io.shardingsphere.core.routing.type.standard;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import io.shardingsphere.api.algorithm.sharding.ShardingValue;
import io.shardingsphere.core.hint.HintManagerHolder;
import io.shardingsphere.core.optimizer.condition.ShardingCondition;
import io.shardingsphere.core.optimizer.condition.ShardingConditions;
import io.shardingsphere.core.optimizer.insert.InsertShardingCondition;
import io.shardingsphere.core.routing.strategy.ShardingStrategy;
import io.shardingsphere.core.routing.strategy.hint.HintShardingStrategy;
import io.shardingsphere.core.routing.type.RoutingEngine;
import io.shardingsphere.core.routing.type.RoutingResult;
import io.shardingsphere.core.routing.type.RoutingTable;
import io.shardingsphere.core.routing.type.TableUnit;
import io.shardingsphere.core.rule.BindingTableRule;
import io.shardingsphere.core.rule.DataNode;
import io.shardingsphere.core.rule.ShardingRule;
import io.shardingsphere.core.rule.TableRule;
import lombok.RequiredArgsConstructor;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
/**
* Standard routing engine.
*
* @author zhangliang
* @author maxiaoguang
* @author panjuan
*/
@RequiredArgsConstructor
public final class StandardRoutingEngine implements RoutingEngine {
private final ShardingRule shardingRule;
private final String logicTableName;
private final ShardingConditions shardingConditions;
/**
* 相比2.0.3版本，精简成了1行代码
*
* @return 路由结果
*/
@Override
public RoutingResult route() {
return generateRoutingResult(getDataNodes(shardingRule.getTableRuleByLogicTableName(logicTableName)));
}
private RoutingResult generateRoutingResult(final Collection<DataNode> routedDataNodes) {
RoutingResult result = new RoutingResult();
for (DataNode each : routedDataNodes) {
TableUnit tableUnit = new TableUnit(each.getDataSourceName());
tableUnit.getRoutingTables().add(new RoutingTable(logicTableName, each.getTableName()));
result.getTableUnits().getTableUnits().add(tableUnit);
}
return result;
}
/**
* 获取数据节点，即真实表
*
* @param tableRule 从XML读取的table rule
* @return 数据节点列表
*/
private Collection<DataNode> getDataNodes(final TableRule tableRule) {
// 判断是否是通过Hint分片策略进行路由
if (isRoutingByHint(tableRule)) {
return routeByHint(tableRule);
}
if (isRoutingByShardingConditions(tableRule)) {
return routeByShardingConditions(tableRule);
}
return routeByMixedConditions(tableRule);
}
/**
* 判断是否是通过Hint分片策略进行路由
* <p>
* 数据源分片策略和数据表分片策略都必须是HintShardingStrategy，这意味者必须显式配置数据源Hint分片策略和数据表Hint分片策略
*
* @param tableRule 从XML读取的table rule
* @return
*/
private boolean isRoutingByHint(final TableRule tableRule) {
return shardingRule.getDatabaseShardingStrategy(tableRule) instanceof HintShardingStrategy && shardingRule.getTableShardingStrategy(tableRule) instanceof HintShardingStrategy;
}
/**
* 通过Hint分片策略进行路由
*
* @param tableRule
* @return
*/
private Collection<DataNode> routeByHint(final TableRule tableRule) {
return route(tableRule, getDatabaseShardingValuesFromHint(), getTableShardingValuesFromHint());
}
private boolean isRoutingByShardingConditions(final TableRule tableRule) {
return !(shardingRule.getDatabaseShardingStrategy(tableRule) instanceof HintShardingStrategy || shardingRule.getTableShardingStrategy(tableRule) instanceof HintShardingStrategy);
}
private Collection<DataNode> routeByShardingConditions(final TableRule tableRule) {
return shardingConditions.getShardingConditions().isEmpty() ? route(tableRule, Collections.<ShardingValue>emptyList(), Collections.<ShardingValue>emptyList())
: routeByShardingConditionsWithCondition(tableRule);
}
private Collection<DataNode> routeByShardingConditionsWithCondition(final TableRule tableRule) {
Collection<DataNode> result = new LinkedList<>();
for (ShardingCondition each : shardingConditions.getShardingConditions()) {
Collection<DataNode> dataNodes = route(tableRule, getShardingValuesFromShardingConditions(shardingRule.getDatabaseShardingStrategy(tableRule).getShardingColumns(), each),
getShardingValuesFromShardingConditions(shardingRule.getTableShardingStrategy(tableRule).getShardingColumns(), each));
reviseShardingConditions(each, dataNodes);
result.addAll(dataNodes);
}
return result;
}
private Collection<DataNode> routeByMixedConditions(final TableRule tableRule) {
return shardingConditions.getShardingConditions().isEmpty() ? routeByMixedConditionsWithHint(tableRule) : routeByMixedConditionsWithCondition(tableRule);
}
private Collection<DataNode> routeByMixedConditionsWithCondition(final TableRule tableRule) {
Collection<DataNode> result = new LinkedList<>();
for (ShardingCondition each : shardingConditions.getShardingConditions()) {
Collection<DataNode> dataNodes = route(tableRule, getDatabaseShardingValues(tableRule, each), getTableShardingValues(tableRule, each));
reviseShardingConditions(each, dataNodes);
result.addAll(dataNodes);
}
return result;
}
private Collection<DataNode> routeByMixedConditionsWithHint(final TableRule tableRule) {
if (shardingRule.getDatabaseShardingStrategy(tableRule) instanceof HintShardingStrategy) {
return route(tableRule, getDatabaseShardingValuesFromHint(), Collections.<ShardingValue>emptyList());
}
return route(tableRule, Collections.<ShardingValue>emptyList(), getTableShardingValuesFromHint());
}
private List<ShardingValue> getDatabaseShardingValues(final TableRule tableRule, final ShardingCondition shardingCondition) {
ShardingStrategy dataBaseShardingStrategy = shardingRule.getDatabaseShardingStrategy(tableRule);
return isGettingShardingValuesFromHint(dataBaseShardingStrategy)
? getDatabaseShardingValuesFromHint() : getShardingValuesFromShardingConditions(dataBaseShardingStrategy.getShardingColumns(), shardingCondition);
}
private List<ShardingValue> getTableShardingValues(final TableRule tableRule, final ShardingCondition shardingCondition) {
ShardingStrategy tableShardingStrategy = shardingRule.getTableShardingStrategy(tableRule);
return isGettingShardingValuesFromHint(tableShardingStrategy)
? getTableShardingValuesFromHint() : getShardingValuesFromShardingConditions(tableShardingStrategy.getShardingColumns(), shardingCondition);
}
private boolean isGettingShardingValuesFromHint(final ShardingStrategy shardingStrategy) {
return shardingStrategy instanceof HintShardingStrategy;
}
/**
* 从HintManagerHolder中获取数据源分片值
*
* @return 数据源分片值列表
*/
private List<ShardingValue> getDatabaseShardingValuesFromHint() {
// getDatabaseShardingValue方法实现有点恶心，不兼容大小写...
Optional<ShardingValue> shardingValueOptional = HintManagerHolder.getDatabaseShardingValue(logicTableName);
return shardingValueOptional.isPresent() ? Collections.singletonList(shardingValueOptional.get()) : Collections.<ShardingValue>emptyList();
}
private List<ShardingValue> getTableShardingValuesFromHint() {
// getTableShardingValue方法实现有点恶心，不兼容大小写...
Optional<ShardingValue> shardingValueOptional = HintManagerHolder.getTableShardingValue(logicTableName);
return shardingValueOptional.isPresent() ? Collections.singletonList(shardingValueOptional.get()) : Collections.<ShardingValue>emptyList();
}
private List<ShardingValue> getShardingValuesFromShardingConditions(final Collection<String> shardingColumns, final ShardingCondition shardingCondition) {
List<ShardingValue> result = new ArrayList<>(shardingColumns.size());
for (ShardingValue each : shardingCondition.getShardingValues()) {
Optional<BindingTableRule> bindingTableRule = shardingRule.findBindingTableRule(logicTableName);
if ((logicTableName.equals(each.getLogicTableName()) || bindingTableRule.isPresent() && bindingTableRule.get().hasLogicTable(logicTableName))
&& shardingColumns.contains(each.getColumnName())) {
result.add(each);
}
}
return result;
}
/**
* 路由，获取真实表列表
*
* @param tableRule 从XML读取的table rule
* @param databaseShardingValues 数据源分片值
* @param tableShardingValues 数据表分片值
* @return 真实表列表
*/
private Collection<DataNode> route(final TableRule tableRule, final List<ShardingValue> databaseShardingValues, final List<ShardingValue> tableShardingValues) {
Collection<String> routedDataSources = routeDataSources(tableRule, databaseShardingValues);
Collection<DataNode> result = new LinkedList<>();
for (String each : routedDataSources) {
result.addAll(routeTables(tableRule, each, tableShardingValues));
}
return result;
}
/**
* 路由到真实数据源
*
* @param tableRule 从XML读取的table rule
* @param databaseShardingValues 数据源分片值
* @return 真实数据源列表
*/
private Collection<String> routeDataSources(final TableRule tableRule, final List<ShardingValue> databaseShardingValues) {
Collection<String> availableTargetDatabases = tableRule.getActualDatasourceNames();
if (databaseShardingValues.isEmpty()) {
return availableTargetDatabases;
}
Collection<String> result = new LinkedHashSet<>(shardingRule.getDatabaseShardingStrategy(tableRule).doSharding(availableTargetDatabases, databaseShardingValues));
Preconditions.checkState(!result.isEmpty(), "no database route info");
return result;
}
/**
* 路由到真实数据表，和2.0.3版本没啥区别
*
* @param tableRule 从XML读取的table rule
* @param routedDataSource 已确认好的数据源
* @param tableShardingValues 数据表分片值
* @return 真实表列表
*/
private Collection<DataNode> routeTables(final TableRule tableRule, final String routedDataSource, final List<ShardingValue> tableShardingValues) {
Collection<String> availableTargetTables = tableRule.getActualTableNames(routedDataSource);
Collection<String> routedTables = new LinkedHashSet<>(tableShardingValues.isEmpty() ? availableTargetTables
: shardingRule.getTableShardingStrategy(tableRule).doSharding(availableTargetTables, tableShardingValues));
Preconditions.checkState(!routedTables.isEmpty(), "no table route info");
Collection<DataNode> result = new LinkedList<>();
for (String each : routedTables) {
result.add(new DataNode(routedDataSource, each));
}
return result;
}
private void reviseShardingConditions(final ShardingCondition each, final Collection<DataNode> dataNodes) {
if (each instanceof InsertShardingCondition) {
((InsertShardingCondition) each).getDataNodes().addAll(dataNodes);
}
}
}
分析到此，Sharding-JDBC 3.1.0版本可以支持分片键不存在于SQL中和数据表结构中的使用场景。