Spring多數(shù)據(jù)源實(shí)現(xiàn)的方式大概有2中,一種是新建多個(gè)MapperScan掃描不同包,另外一種則是通過(guò)繼承AbstractRoutingDataSource實(shí)現(xiàn)動(dòng)態(tài)路由。今天作者主要基于后者做的實(shí)現(xiàn),且方式1的實(shí)現(xiàn)比較簡(jiǎn)單這里不做過(guò)多探討。
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實(shí)現(xiàn)方式
方式1的實(shí)現(xiàn)(核心代碼):
@Configuration @MapperScan(basePackages = "com.goofly.test1", sqlSessionTemplateRef = "test1SqlSessionTemplate") public class DataSource1Config1 { @Bean(name = "dataSource1") @ConfigurationProperties(prefix = "spring.datasource.test1") @Primary public DataSource testDataSource() { return DataSourceBuilder.create().build(); } // .....略 } @Configuration @MapperScan(basePackages = "com.goofly.test2", sqlSessionTemplateRef = "test1SqlSessionTemplate") public class DataSourceConfig2 { @Bean(name = "dataSource2") @ConfigurationProperties(prefix = "spring.datasource.test2") @Primary public DataSource testDataSource() { return DataSourceBuilder.create().build(); } // .....略 }
方式2的實(shí)現(xiàn)(核心代碼):
public class DynamicRoutingDataSource extends AbstractRoutingDataSource { private static final Logger log = Logger.getLogger(DynamicRoutingDataSource.class); @Override protected Object determineCurrentLookupKey() { //從ThreadLocal中取值 return DynamicDataSourceContextHolder.get(); } }
第1種方式雖然實(shí)現(xiàn)比較加單,劣勢(shì)就是不同數(shù)據(jù)源的mapper文件不能在同一包名,就顯得不太靈活了。所以為了更加靈活的作為一個(gè)組件的存在,作者采用的第二種方式實(shí)現(xiàn)。
設(shè)計(jì)思路
源碼解讀
org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource,如下:
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean { private Map<Object, Object> targetDataSources; private Object defaultTargetDataSource; private boolean lenientFallback = true; private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup(); private Map<Object, DataSource> resolvedDataSources; private DataSource resolvedDefaultDataSource; protected DataSource determineTargetDataSource() { Assert.notNull(this.resolvedDataSources, "DataSource router not initialized"); Object lookupKey = determineCurrentLookupKey(); DataSource dataSource = this.resolvedDataSources.get(lookupKey); if (dataSource == null && (this.lenientFallback || lookupKey == null)) { dataSource = this.resolvedDefaultDataSource; } if (dataSource == null) { throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]"); } return dataSource; } /** * Determine the current lookup key. This will typically be * implemented to check a thread-bound transaction context. * <p>Allows for arbitrary keys. The returned key needs * to match the stored lookup key type, as resolved by the * {@link #resolveSpecifiedLookupKey} method. */ protected abstract Object determineCurrentLookupKey(); //........略
targetDataSources是一個(gè)map結(jié)構(gòu),保存了key與數(shù)據(jù)源的對(duì)應(yīng)關(guān)系;
dataSourceLookup是一個(gè)DataSourceLookup類(lèi)型,默認(rèn)實(shí)現(xiàn)是JndiDataSourceLookup。點(diǎn)開(kāi)該類(lèi)源碼會(huì)發(fā)現(xiàn),它實(shí)現(xiàn)了通過(guò)key獲取DataSource的邏輯。當(dāng)然,這里可以通過(guò)setDataSourceLookup()來(lái)改變其屬性,因?yàn)殛P(guān)于此處有一個(gè)坑,后面會(huì)講到。
public class JndiDataSourceLookup extends JndiLocatorSupport implements DataSourceLookup { public JndiDataSourceLookup() { setResourceRef(true); } @Override public DataSource getDataSource(String dataSourceName) throws DataSourceLookupFailureException { try { return lookup(dataSourceName, DataSource.class); } catch (NamingException ex) { throw new DataSourceLookupFailureException( "Failed to look up JNDI DataSource with name '" + dataSourceName + "'", ex); } } }
組件使用
多數(shù)據(jù)源
# db1 spring.datasource.master.url = jdbc:MySQL://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=false spring.datasource.master.username = root spring.datasource.master.password = 123456 spring.datasource.master.driverClassName = com.mysql.jdbc.Driver spring.datasource.master.validationQuery = true spring.datasource.master.testOnBorrow = true ## db2 spring.datasource.slave.url = jdbc:mysql://127.0.0.1:3306/test1?useUnicode=true&characterEncoding=utf8&useSSL=false spring.datasource.slave.username = root spring.datasource.slave.password = 123456 spring.datasource.slave.driverClassName = com.mysql.jdbc.Driver spring.datasource.slave.validationQuery = true spring.datasource.slave.testOnBorrow = true #主數(shù)據(jù)源名稱(chēng) spring.maindb=master #mapperper包路徑 mapper.basePackages =com.btps.xli.multidb.demo.mapper
單數(shù)據(jù)源
為了讓使用者能夠用最小的改動(dòng)實(shí)現(xiàn)最好的效果,作者對(duì)單數(shù)據(jù)源的多種配置做了兼容。
示例配置1(配置數(shù)據(jù)源名稱(chēng)):
spring.datasource.master.url = jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=false spring.datasource.master.username = root spring.datasource.master.password = 123456 spring.datasource.master.driverClassName = com.mysql.jdbc.Driver spring.datasource.master.validationQuery = true spring.datasource.master.testOnBorrow = true # mapper包路徑 mapper.basePackages = com.goofly.xli.multidb.demo.mapper # 主數(shù)據(jù)源名稱(chēng) spring.maindb=master
示例配置2(不配置數(shù)據(jù)源名稱(chēng)):
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=false spring.datasource.username = root spring.datasource.password = 123456 spring.datasource.driverClassName = com.mysql.jdbc.Driver spring.datasource.validationQuery = true spring.datasource.testOnBorrow = true # mapper包路徑 mapper.basePackages = com.goofly.xli.multidb.demo.mapper
踩坑之路
多數(shù)據(jù)源的循環(huán)依賴(lài)
Description: The dependencies of some of the beans in the application context form a cycle: happinessController (field private com.db.service.HappinessService com.db.controller.HappinessController.happinessService) ↓ happinessServiceImpl (field private com.db.mapper.MasterDao com.db.service.HappinessServiceImpl.masterDao) ↓ masterDao defined in file [E:\GitRepository\framework-gray\test-db\target\classes\com\db\mapper\MasterDao.class] ↓ sqlSessionFactory defined in class path resource [com/goofly/xli/datasource/core/DynamicDataSourceConfiguration.class] ┌─────┐ | dynamicDataSource defined in class path resource [com/goofly/xli/datasource/core/DynamicDataSourceConfiguration.class] ↑ ↓ | firstDataSource defined in class path resource [com/goofly/xli/datasource/core/DynamicDataSourceConfiguration.class] ↑ ↓ | dataSourceInitializer
解決方案:
在Spring boot啟動(dòng)的時(shí)候排除DataSourceAutoConfiguration即可。如下:
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class}) public class DBMain { public static void main(String[] args) { SpringApplication.run(DBMain.class, args); } }
但是作者在創(chuàng)建多數(shù)據(jù)源的時(shí)候由于并未創(chuàng)建多個(gè)DataSource的Bean,而是只創(chuàng)建了一個(gè)即需要做動(dòng)態(tài)數(shù)據(jù)源的那個(gè)Bean。 其他的DataSource則直接創(chuàng)建實(shí)例然后存放在Map里面,然后再設(shè)置到DynamicRoutingDataSource#setTargetDataSources即可。
因此這種方式也不會(huì)出現(xiàn)循環(huán)依賴(lài)的問(wèn)題!
動(dòng)態(tài)刷新數(shù)據(jù)源
筆者在設(shè)計(jì)之初是想構(gòu)建一個(gè)動(dòng)態(tài)刷新數(shù)據(jù)源的方案,所以利用了SpringCloud的@RefreshScope去標(biāo)注數(shù)據(jù)源,然后利用RefreshScope#refresh實(shí)現(xiàn)刷新。但是在實(shí)驗(yàn)的時(shí)候發(fā)現(xiàn)由Druid創(chuàng)建的數(shù)據(jù)源會(huì)因此而關(guān)閉,由Spring的DataSourceBuilder創(chuàng)建的數(shù)據(jù)源則不會(huì)發(fā)生任何變化。
最后關(guān)于此也沒(méi)能找到解決方案。同時(shí)思考,如果只能的可以實(shí)現(xiàn)動(dòng)態(tài)刷新的話(huà),那么數(shù)據(jù)源的原有連接會(huì)因?yàn)樗⑿露袛鄦徇€是會(huì)有其他處理?
多數(shù)據(jù)源事務(wù)
有這么一種特殊情況,一個(gè)事務(wù)中調(diào)用了兩個(gè)不同數(shù)據(jù)源,這個(gè)時(shí)候動(dòng)態(tài)切換數(shù)據(jù)源會(huì)因此而失效。
翻閱了很多文章,大概找了2中解決方案,一種是Atomikos進(jìn)行事務(wù)管理,但是貌似性能并不是很理想。
另外一種則是通過(guò)優(yōu)先級(jí)控制,切面的的優(yōu)先級(jí)必須要大于數(shù)據(jù)源的優(yōu)先級(jí),用注解@Order控制。
此處留一個(gè)坑!
git代碼地址
以上就是本文的全部?jī)?nèi)容,希望對(duì)大家的學(xué)習(xí)有所幫助,也希望大家多多支持創(chuàng)新互聯(lián)。
當(dāng)前標(biāo)題:springboot動(dòng)態(tài)數(shù)據(jù)源的實(shí)現(xiàn)方法(Mybatis+Druid)
轉(zhuǎn)載源于:http://bm7419.com/article22/pcesjc.html
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