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170 lines
5.0 KiB
170 lines
5.0 KiB
5 years ago
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---
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title: 基于Springboot实现动态数据源
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id: 1939
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category: 后端
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tags: springboot
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toc: true
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---
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### 实现原理
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>Spring内置了一个AbstractRoutingDataSource类,它可以把多个数据源配置成一个Map,然后根据不同的key返回不同的数据源(通过实现抽象方法determineCurrentLookupKey)。
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>我们在使用AbstractRoutingDataSource时,主要涉及两个操作:
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>1. 生成数据源相关map,并赋值给AbstractRoutingDataSource的targetDataSources
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>2. 实现determineCurrentLookupKey方法(方法的用途为:获取要使用数据源的key)
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### 配置多数据源
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首先,我们在SpringBoot中配置两个数据源,其中第二个数据源是slave-datasource:
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```yaml
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spring:
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datasource:
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jdbc-url: jdbc:mysql://localhost/master?characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=GMT%2B8&allowMultiQueries=true&allowPublicKeyRetrieval=true
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username: root #master
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password: dreamlyn #master_password
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driver-class-name: com.mysql.cj.jdbc.Driver
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hikari:
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pool-name: HikariCP
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auto-commit: false
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slave-datasource:
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jdbc-url: jdbc:mysql://localhost/slave?characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=GMT%2B8&allowMultiQueries=true&allowPublicKeyRetrieval=true
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username: root #slave
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password: dreamlyn #slave_password
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driver-class-name: com.mysql.cj.jdbc.Driver
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hikari:
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pool-name: HikariCP
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auto-commit: false
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```
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在SpringBoot的配置代码中,初始化两个数据源:
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```java
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/**
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* Master data source.
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*/
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@Bean("masterDataSource")
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@ConfigurationProperties(prefix = "spring.datasource")
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DataSource masterDataSource() {
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return DataSourceBuilder.create().build();
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}
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/**
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* Slave data source.
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*/
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@Bean("slaveDataSource")
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@ConfigurationProperties(prefix = "spring.slave-datasource")
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DataSource slaveDataSource() {
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return DataSourceBuilder.create().build();
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}
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```
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### 生成数据源相关map
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将两个数据源生成相关map,并赋值给AbstractRoutingDataSource的targetDataSources
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```java
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@Bean
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@Primary
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DataSource primaryDataSource(
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@Autowired @Qualifier("masterDataSource") DataSource masterDataSource,
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@Autowired @Qualifier("slaveDataSource") DataSource slaveDataSource
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) {
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Map<Object, Object> map = new HashMap<>();
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map.put("master", masterDataSource);
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map.put("slave", slaveDataSource);
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DynamicDataSource routing = new DynamicDataSource();
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routing.setTargetDataSources(map);
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routing.setDefaultTargetDataSource(masterDataSource);
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return routing;
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}
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```
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### 实现determineCurrentLookupKey方法
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```java
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/**
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* 动态数据源
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*/
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public class DynamicDataSource extends AbstractRoutingDataSource {
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/**
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* 指定路由Key
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*/
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@Override
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protected Object determineCurrentLookupKey() {
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return DynamicDataSourceContextHolder.getDataSource();
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}
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}
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```
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大家可能会好奇DynamicDataSourceContextHolder是个什么鬼:
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在Servlet的线程模型中,使用ThreadLocal存储key最合适,因此,我们编写一个DynamicDataSourceContextHolder来设置并动态存储key:
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```java
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/**
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* 根据当前线程来选择具体的数据源
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*/
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@UtilityClass
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public class DynamicDataSourceContextHolder {
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private final ThreadLocal<String> CONTEXT_HOLDER = new ThreadLocal<>();
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/**
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* 提供给AOP去设置当前的线程的数据源的信息
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*/
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public void setDataSource(String dataSourceType) {
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CONTEXT_HOLDER.set(dataSourceType);
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}
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/**
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* 提供给AbstractRoutingDataSource的实现类,通过key选择数据源
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*/
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public String getDataSource() {
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return CONTEXT_HOLDER.get();
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}
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/**
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* 清除数据源
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*/
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public void clearDataSource() {
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CONTEXT_HOLDER.remove();
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}
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}
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```
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这样,在某个地方,就可以动态设置DataSource的Key:
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```java
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@RunWith(SpringRunner.class)
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@SpringBootTest
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@Slf4j
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@MapperScan("com.dreamlyn.dynamic.mapper")
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class DynamicApplicationTests {
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@Autowired
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private MenuMapper menuMapper;
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@Autowired
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private UserMapper userMapper;
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@Test
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void dynamic() {
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//设置数据源
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DynamicDataSourceContextHolder.setDataSource("master");
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List<User> users = userMapper.selectList(null);
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log.info("user count:{}", users.size());
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DynamicDataSourceContextHolder.setDataSource("slave");
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List<Menu> menus = menuMapper.selectList(null);
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log.info("menu count:{}", menus.size());
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}
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}
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```
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到此为止,我们已经成功实现了数据库的动态路由访问。
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### 拓展
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如果需要更方便一些,可以自己手动编写aop,通过注解来区分使用哪个数据源将更加方便,这种方法留给读者自己思考。
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思考不出来可以参考代码:[https://gitee.com/dreamlyn/dynamic](https://gitee.com/dreamlyn/dynamic)
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