场景
-
大型应用中的读写分离；
-
相同业务逻辑，但是对应多个数据库；
几张非常形象的图片奉上
-
单一数据库场景
-
多数据库场景
-
动态切换
实现方案
- 步骤
-
核心是实现Spring 内置的 AbstractRoutingDataSource 抽象类，实现determineCurrentLookupKey() 方法；
-
实例化出多个datasource，并将这些datasource加入到该抽象类中的targetDataSources。
-
在操作数据前，dao层会先调用 AbstractRoutingDataSource 抽象类getConnection(),其中的调用的是determineCurrentLookupKey()，获取到对应的datasource；
-
借助ThreadLocal保存数据源信息，在整个业务流程中方便获取;
- 难点
不同连接池实例化事务管理、和生成类似数据库的sessionFactory方法有所不同，可能会费些时间。
代码实现
环境介绍
-
springboot版本： 1.5.6.RELEASE
-
连接池：alibaba druid
部分代码
- 配置文件, 密码就暴漏吧，哈哈
spring.datasource.druid.test1.url=jdbc:mysql://localhost:3306/multi_test1?characterEncoding=utf8&characterSetResults=utf8&autoReconnect=true&failOverReadOnly=false&serverTimezone=GMT
spring.datasource.druid.test1.username=root
spring.datasource.druid.test1.password=123456
spring.datasource.druid.test2.url=jdbc:mysql://localhost:3306/multi_test2?characterEncoding=utf8&characterSetResults=utf8&autoReconnect=true&failOverReadOnly=false&serverTimezone=GMT
spring.datasource.druid.test2.username=root
spring.datasource.druid.test2.password=123456
spring.datasource.type = com.alibaba.druid.pool.DruidDataSource
spring.jpa.show-sql=true
spring.jpa.hibernate.naming.physical-strategy=org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
- 实现AbstractRoutingDataSource 抽象类
public class DynamicDataSourceRouter extends AbstractRoutingDataSource {
public static final ThreadLocal<String> dbStore = new ThreadLocal<>();
@Override
protected Object determineCurrentLookupKey() {
String dbBean = dbStore.get();
if(StringUtils.isBlank(dbBean)){
dbBean = SourceName.TEST1.dbName;
} else {
}
return dbBean;
}
enum SourceName{
TEST1("test1"),TEST2("test2");
public String dbName;
private SourceName(String name){
this.dbName = name;
}
}
}
- 实例化出多个数据源，加入到DynamicDataSourceRouter父类的setTargetDataSources，并设置默认值
@Configuration
@Slf4j
public class MultiDataConfig {
@Value("${spring.datasource.type}")
private Class<? extends DataSource> dataSourceType;
@Bean("test1")
@Primary
@ConfigurationProperties(prefix = "spring.datasource.druid.test1")
public DataSource test1(){
log.info("构建test1数据源");
DataSource source = DataSourceBuilder.create().type(dataSourceType).build();
return source;
}
@Bean("test2")
@ConfigurationProperties(prefix = "spring.datasource.druid.test2")
public DataSource test2(){
log.info("构建test2--- 数据源");
DataSource source = DataSourceBuilder.create().type(dataSourceType).build();
return source;
}
@Bean("routingDataSource")
public AbstractRoutingDataSource routingDataSource(@Qualifier("test1") DataSource test1,@Qualifier("test2") DataSource test2){
DynamicDataSourceRouter assistant = new DynamicDataSourceRouter();
Map<Object, Object> dataSources = new HashMap<>();
dataSources.put(DynamicDataSourceRouter.SourceName.TEST1.dbName,test1);
dataSources.put(DynamicDataSourceRouter.SourceName.TEST2.dbName,test2);
assistant.setDefaultTargetDataSource( test2 );
assistant.setTargetDataSources(dataSources);
return assistant;
}
}
- 手动对 Jpa 的 EntityManager 进行初始化和配置
@Configuration
@EnableConfigurationProperties(JpaProperties.class)
@EnableJpaRepositories(value = "cn.rzwl.multidata.dao")
public class JpaEntityManager {
@Autowired
private JpaProperties jpaProperties;
@Resource(name = "routingDataSource")
private DataSource routingDataSource;
@Bean(name = "entityManagerFactoryBean")
public LocalContainerEntityManagerFactoryBean entityManagerFactoryBean(EntityManagerFactoryBuilder builder) {
// 不明白为什么这里获取不到 application.yml 里的配置
Map<String, String> properties = jpaProperties.getProperties();
//要设置这个属性，实现 CamelCase -> UnderScore 的转换
properties.put("hibernate.physical_naming_strategy",
"org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy");
return builder
.dataSource(routingDataSource)//关键：注入routingDataSource
.properties(properties)
.packages("cn.rzwl.multidata.entity") //TODO 改成自己的实体类包
.persistenceUnit("myPersistenceUnit")
.build();
}
@Primary
@Bean(name = "entityManagerFactory")
public EntityManagerFactory entityManagerFactory(EntityManagerFactoryBuilder builder) {
return this.entityManagerFactoryBean(builder).getObject();
}
@Primary
@Bean(name = "transactionManager")
public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(entityManagerFactory(builder));
}
}
- 为方便测试，用filter验证
@WebFilter(urlPatterns = "/*")
@Slf4j
public class MyFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
log.info("初始化自定义过滤器");
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
String site = request.getParameter("source");
if( DynamicDataSourceRouter.SourceName.TEST1.dbName.equals( site ) ){
DynamicDataSourceRouter.dbStore.set( DynamicDataSourceRouter.SourceName.TEST1.dbName );
} else {
DynamicDataSourceRouter.dbStore.set( DynamicDataSourceRouter.SourceName.TEST2.dbName );
}
log.info("进入业务流程");
chain.doFilter( request,response );
log.info("完成处理");
System.out.println("后续操作");
}
@Override
public void destroy() {
}
}
源码地址:
小结：
- 一个神奇的AbstractRoutingDataSource类，使数据库切换操作举重若轻，优雅得体，告别劳力式编程。
