（spring-布特&Spring Data JPA）如何快速更改数据源？

Question

对于我的新项目，我构建了一个基本的rest api来根据客户机请求返回数据。但是，客户端必须选择他所选择的数据库作为HTTP GET请求的参数。

现在我的问题是，我不知道如何使用Sprint-Boot实现这一点。我知道我们可以提供许多不同的数据源，但是我们如何在检查请求之后更改想要的数据源呢？

下面是我的数据源配置，它工作得很好：

@Configuration
public class DataSourceConfig {

    @Bean
    @Primary
    @ConfigurationProperties(prefix="datasource.dev21")
    public DataSource dev21DataSource() throws SQLException {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties(prefix="datasource.dev22")
    public DataSource dev22DataSource() throws SQLException {
        return DataSourceBuilder.create().build();
    }
} 

如果我想在dev21和dev22之间动态切换，我该怎么做？我读过关于类AbstractRoutingDataSource的文章，但不知道如何使用它。

Answer 1

在没有对其进行测试的情况下，只要简单地浏览一下javadoc，就可以使用类似的方法

@Configuration
public class DataSourceConfig {

    public DataSource dev21DataSource() throws SQLException {
        return DataSourceBuilder.create().build();
    }

    public DataSource dev22DataSource() throws SQLException {
        return DataSourceBuilder.create().build();
    }

    @Bean
    public DataSource dataSource() throws SQLException {
        RoutingDataSource ds = new RoutingDataSource();

        DataSource ds21 = dev21DataSource();
        DataSource ds22 = dev22DataSource();

        Map dataSources = new HashMap();
        dataSources.put(1, ds21);
        dataSources.put(2, ds22);

        ds.setDefaultTargetDataSource(ds21);
        ds.setTargetDataSources(dataSources);

        return ds;
    }
}

public class RoutingDataSource extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        if (true) { //Should probably be some thread/tracaction/request safe check
            return 1;
        } else {
            return 2;
        }
    }
}

如果需要类的其他行为，则可能希望override其他方法。

Answer 2

它应该遵循这样的方针：

// create class to hold the "key" to choose your datasource
// you will determine it from your GET or POST request
// It uses ThreadLocal so you will get one per each request
public class SomeRequestContext {
    private static ThreadLocal<Object> keyToChoseDataSource = new ThreadLocal<>();
    public static void setKeyToChoseDataSource(Object key) {
        keyToChoseDataSource.set(key);
    }
    public static Object getKeyToChoseDataSource() {
        return keyToChoseDataSource.get();
    }
}

// This is you AbstractRoutingDataSource implementation that will
// get the key out of the context class above
public class MultiDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return SomeRequestContext.getKeyToChoseDataSource();
    }
}

在您的配置中：

    // Here you just put all your data sources into the AbstractRoutingDataSource implementation
    @Bean 
    @Primary 
    public DataSource dataSource() {
      MultiDataSource dataSource = new MultiDataSource();
      dataSource.setDefaultTargetDataSource(someDefaultDataSource());
      Map<Object,DataSource> resolvedDataSources = new HashMap<Object,DataSource>();
      resolvedDataSources.put("dev21",buildDataSource21());
      resolvedDataSources.put("dev22",buildDataSource22());
      // ...etc...
      dataSource.setTargetDataSources(resolvedDataSources);
      dataSource.afterPropertiesSet();
      return dataSource;
    }

在你的控制器里

@Controller
public class YourController {
    @Autowired
    private YourRepository yourRepository;
    @RequestMapping(path = "/path", method= RequestMethod.POST)
    public ResponseEntity<?> createStuff() {
        TenantContext.setCurrentTenant(tenantName);
        SomeRequestContext.setKeyToChoseDataSource(getKeyFromRequest()); // this will be dev21 or dev22 or whatever

        SomeStuff stuff = new SomeStuff();
        yourRepository.save(stuff); // will be saved to the correct database
        return ResponseEntity.ok(stuff);
    }
}