最近忙于項目已經(jīng)好久幾天沒寫博客了，前2篇文章我給大家介紹了搭建基礎(chǔ)springMvc+mybatis的maven工程，這個簡單框架已經(jīng)可以對付一般的小型項目。但是我們實際項目中會碰到很多復(fù)雜的場景，比如數(shù)據(jù)量很大的情況下如何保證性能。今天我就給大家介紹數(shù)據(jù)庫分庫分表的優(yōu)化，本文介紹mybatis結(jié)合當(dāng)當(dāng)網(wǎng)的sharding-jdbc分庫分表技術(shù)（原理這里不做介紹）

　　首先在pom文件中引入需要的依賴

<dependency><groupId>com.dangdang</groupId><artifactId>sharding-jdbc-core</artifactId><version>1.4.2</version></dependency><dependency><groupId>com.dangdang</groupId><artifactId>sharding-jdbc-config-spring</artifactId><version>1.4.0</version></dependency>

　　二、新建一個sharding-jdbc.xml文件，實現(xiàn)分庫分表的配置

<?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:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"xmlns:rdb="http://www.dangdang.com/schema/ddframe/rdb"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsdhttp://www.dangdang.com/schema/ddframe/rdb http://www.dangdang.com/schema/ddframe/rdb/rdb.xsd"><rdb:strategy id="tableShardingStrategy" sharding-columns="user_id" algorithm-class="com.meiren.member.common.sharding.MemberSingleKeyTableShardingAlgorithm"/><rdb:data-source id="shardingDataSource"><rdb:sharding-rule data-sources="dataSource"><rdb:table-rules><rdb:table-rule logic-table="member_index" actual-tables="member_index_tbl_${[0,1,2,3,4,5,6,7,8,9]}${0..9}" table-strategy="tableShardingStrategy"/><rdb:table-rule logic-table="member_details" actual-tables="member_details_tbl_${[0,1,2,3,4,5,6,7,8,9]}${0..9}" table-strategy="tableShardingStrategy"/></rdb:table-rules></rdb:sharding-rule></rdb:data-source><bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"><property name="dataSource" ref="shardingDataSource" /></bean> </beans>

　　這里我簡單介紹下一些屬性的含義，

　　?<rdb:strategy id="tableShardingStrategy" sharding-columns="user_id" algorithm-class="com.meiren.member.common.sharding.MemberSingleKeyTableShardingAlgorithm"/> ?配置分表規(guī)則器??sharding-columns：分表規(guī) 則　

　　依賴的名（根據(jù)user_id取模分表），algorithm-class:分表規(guī)則的實現(xiàn)類?

　　<rdb:sharding-rule?data-sources="dataSource"> 這里填寫關(guān)聯(lián)數(shù)據(jù)源（多個數(shù)據(jù)源用逗號隔開）,

　　<rdb:table-rule logic-table="member_index" actual-tables="member_index_tbl_${[0,1,2,3,4,5,6,7,8,9]}${0..9}" ?table-strategy="tableShardingStrategy"/>??logic-table：邏輯表名（mybatis中代替的表名）actual-tables：

　　數(shù)據(jù)庫實際的表名，這里支持inline表達式，比如：member_index_tbl_${0..2}會解析成member_index_tbl_0，member_index_tbl_1，member_index_tbl_2；member_index_tbl_${[a,b,c]}會被解析成

　 ? member_index_tbl_a,member_index_tbl_b和member_index_tbl_c,兩種表達式一起使用的時候，會采取笛卡爾積的方式：member_index_tbl_${[a,b]}${0..2}解析為member_index_tbl_a0,member_index_tbl_a1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??member_index_tbl_a2,member_index_tbl_b0,member_index_tbl_b1,member_index_tbl_b2;table-strategy:前面定義的分表規(guī)則器；

? ? ?三、配置好改文件后，需要修改之前我們的spring-dataSource的幾個地方，把sqlSessionFactory和transactionManager原來關(guān)聯(lián)的dataSource統(tǒng)一修改為shardingDataSource（這一步作用就是把數(shù)據(jù)源全部托管給sharding去管理）

　　

　四、實現(xiàn)分表（分庫）邏輯，我們的分表邏輯類需要實現(xiàn)SingleKeyTableShardingAlgorithm接口的三個方法doBetweenSharding、doEqualSharding、doInSharding

/*** 分表邏輯* @author zhangwentao**/ public class MemberSingleKeyTableShardingAlgorithm implements SingleKeyTableShardingAlgorithm<Long> {/*** sql between 規(guī)則*/public Collection<String> doBetweenSharding(Collection<String> tableNames, ShardingValue<Long> shardingValue) {Collection<String> result = new LinkedHashSet<String>(tableNames.size());Range<Long> range = (Range<Long>) shardingValue.getValueRange();for (long i = range.lowerEndpoint(); i <= range.upperEndpoint(); i++) {Long modValue = i % 100;String modStr = modValue < 10 ? "0" + modValue : modValue.toString();for (String each : tableNames) {if (each.endsWith(modStr)) {result.add(each);}}}return result;}/*** sql == 規(guī)則*/public String doEqualSharding(Collection<String> tableNames, ShardingValue<Long> shardingValue) {Long modValue = shardingValue.getValue() % 100;String modStr = modValue < 10 ? "0" + modValue : modValue.toString();for (String each : tableNames) {if (each.endsWith(modStr)) {return each;}}throw new IllegalArgumentException();}/*** sql in 規(guī)則*/public Collection<String> doInSharding(Collection<String> tableNames, ShardingValue<Long> shardingValue) {Collection<String> result = new LinkedHashSet<String>(tableNames.size());for (long value : shardingValue.getValues()) {Long modValue = value % 100;String modStr = modValue < 10 ? "0" + modValue : modValue.toString();for (String tableName : tableNames) {if (tableName.endsWith(modStr)) {result.add(tableName);}}}return result;}}

五、以上四步，我們就完成了sharding-jdbc的搭建，我們可以寫一個測試demo來檢查我們的成果

<select id="getDetailsById" resultType="com.meiren.member.dataobject.MemberDetailsDO"parameterType="java.lang.Long">select user_id userId ,qq,email from member_details where user_id =#{userId} limit 1</select>

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

private?static?final?String SERVICE_PROVIDER_XML =?"/spring/member-service.xml"; ??????private?static?final?String BEAN_NAME =?"idcacheService"; ??????? ??????private?ClassPathXmlApplicationContext context =?null; ??????IdcacheServiceImpl bean =?null; ??????IdcacheDao idcacheDao; ??????? ??????@Before ??????public?void?before() { ??????????context=?new?ClassPathXmlApplicationContext( ??????????????????new?String[] {SERVICE_PROVIDER_XML}); ?????????idcacheDao=context.getBean("IdcacheDao", IdcacheDao.class); ??????} ??????? ??????@Test ??????public?void?getAllCreditActionTest() { ???????// int id = bean.insertIdcache(); ??????????Long s=100l; ????????MemberDetailsDO memberDetailsDO=idcacheDao.getDetailsById(s); ????????System.out.println("QQ---------------------"+memberDetailsDO.getQq()); ??????}

　　打印sql語句，輸出結(jié)果：QQ-------------------------------------100，證明成功！

　　注意點：這次搭建過程中，我有碰到一個小坑，就是執(zhí)行的時候會報錯：，官方文檔是有解決方案：引入?<context:property-placeholder location="classpath:/member_service.properties" ignore-unresolvable="true" /> ?，引入這行代碼的時候，·必須要要把這邊管理配配置文件的bean刪除，換句話說，即Spring容器僅允許最多定義一個PropertyPlaceholderConfigurer(或<context:property-placeholder/>)，其余的會被Spring忽略掉（當(dāng)時搞了半天啊）

超強干貨來襲 云風(fēng)專訪：近40年碼齡，通宵達旦的技術(shù)人生

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