Sharding-jdbc实现分库分表

时间 2019-12-11

原文原文链接

首先在pom文件中引入须要的依赖java

<dependency>
    <groupId>io.shardingjdbc</groupId>
    <artifactId>sharding-jdbc-core-spring-namespace</artifactId>
    <version>2.0.3</version>
</dependency>

　　2、新建一个sharding-jdbc.xml文件，实现分库分表的配置spring

<?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>

　　这里我简单介绍下一些属性的含义，sql

　　 <rdb:strategy id="tableShardingStrategy" sharding-columns="user_id" algorithm-class="com.meiren.member.common.sharding.MemberSingleKeyTableShardingAlgorithm"/> 配置分表规则器 sharding-columns：分表规则　数据库

　　依赖的名（根据user_id取模分表），algorithm-class:分表规则的实现类 mybatis

　　<rdb:sharding-rule data-sources="dataSource"> 这里填写关联数据源（多个数据源用逗号隔开）,测试

　　<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：逻辑表名（mybatis中代替的表名）actual-tables：spa

　　数据库实际的表名，这里支持inline表达式，好比：member_index_tbl_${0..2}会解析成member_index_tbl_0，member_index_tbl_1，member_index_tbl_2；member_index_tbl_${[a,b,c]}会被解析成3d

　 member_index_tbl_a,member_index_tbl_b和member_index_tbl_c,两种表达式一块儿使用的时候，会采起笛卡尔积的方式：member_index_tbl_${[a,b]}${0..2}解析为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:前面定义的分表规则器；code

3、配置好改文件后，须要修改以前咱们的spring-dataSource的几个地方，把sqlSessionFactory和transactionManager原来关联的dataSource统一修改成shardingDataSource（这一步做用就是把数据源所有托管给sharding去管理）xml

　4、实现分表（分库）逻辑，咱们的分表逻辑类须要实现SingleKeyTableShardingAlgorithm接口的三个方法doBetweenSharding、doEqualSharding、doInSharding

/**
 * 分表逻辑
 * @author zhangwentao
 *
 */
public class MemberSingleKeyTableShardingAlgorithm implements SingleKeyTableShardingAlgorithm<Long> {
    
    /**
     * sql between 规则
     */
    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 == 规则
     */
    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 规则
     */
    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，咱们就完成了sharding-jdbc的搭建，咱们能够写一个测试demo来检查咱们的成果

<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语句，输出结果：QQ-------------------------------------100，证实成功！

　　注意点：此次搭建过程当中，执行的时候报错，官方文档是有解决方案：引入 <context:property-placeholder location="classpath:/member_service.properties" ignore-unresolvable="true" /> ，引入这行代码的时候，·必需要要把这边管理配配置文件的bean删除，换句话说，即Spring容器仅容许最多定义一个PropertyPlaceholderConfigurer(或<context:property-placeholder/>)，其他的会被Spring忽略掉