sharding-jdbc結合mybatis實現分庫分表功能

　　最近忙於項目已經很久幾天沒寫博客了，前2篇文章我給你們介紹了搭建基礎springMvc+mybatis的maven工程，這個簡單框架已經能夠對付通常的小型項目。可是咱們實際項目中會碰到不少複雜的場景，好比數據量很大的狀況下如何保證性能。今天我就給你們介紹數據庫分庫分表的優化，本文介紹mybatis結合噹噹網的sharding-jdbc分庫分表技術（原理這裏不作介紹）

　　首先在pom文件中引入須要的依賴

<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>

　　2、新建一個sharding-jdbc.xml文件，實現分庫分表的配置

<?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/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://www.springframework.org/schema/context 
                        http://www.springframework.org/schema/context/spring-context.xsd
                        http://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>

　　這裏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"/>  配置分表規則器  sharding-columns：分表規 則　

　　依賴的名（根據user_id取模分表），algorithm-class:分表規則的實現類 

　　<rdb:sharding-rule data-sources="dataSource"> 這裏填寫關聯數據源（多個數據源用逗號隔開）,

　　<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：

　　數據庫實際的表名，這裏支持inline表達式，好比：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,兩種表達式一塊兒使用的時候，會採起笛卡爾積的方式：member_index_tbl_${[a,b]}${0..2}解析爲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:前面定義的分表規則器；

     3、配置好改文件後，須要修改以前咱們的spring-dataSource的幾個地方，把sqlSessionFactory和transactionManager原來關聯的dataSource統一修改成shardingDataSource（這一步做用就是把數據源所有託管給sharding去管理）

　　

　4、實現分表（分庫）邏輯，咱們的分表邏輯類須要實現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;
    }
    
}

5、以上四步，咱們就完成了sharding-jdbc的搭建，咱們能夠寫一個測試demo來檢查咱們的成果

<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>

  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，輸出結果：QQ-------------------------------------100，證實成功！

　　注意點：此次搭建過程當中，我有碰到一個小坑，就是執行的時候會報錯：，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，·必需要要把這邊管理配配置文件的bean刪除，換句話說，即Spring容器僅容許最多定義一個PropertyPlaceholderConfigurer(或<context:property-placeholder/>)，其他的會被Spring忽略掉（當時搞了半天啊）

小結：此次給你們分享了sharding-jdbc的配置是爲了解決大數據量進行分庫分表的架構，下一張，我將介紹拆分業務所需的duboo+zookeeper的配置（分佈式），歡迎關注！