spring@transactional，如何配置数据库的两个不同节点

Question

我想用两个不同的数据库节点配置@transactional 注解。

如果一个数据库节点出现故障，那么事务管理器应该与第二个节点一起工作而不会出现任何故障。

如果数据库节点在事务之间失败，那么它也应该与第二个节点一起工作。有什么方法可以在 spring 中配置它

Answer 1

您可以根据自己的情况调整多租户方法

见https://dzone.com/articles/spring-boot-hibernate-multitenancy-implementation

您需要重写 MultiTenantConnectionProviderImpl 方法

public Connection getConnection(String tenantIdentifier)
public Connection getAnyConnection()

如果第一个失败，则检查并返回第二个 DataSource 连接。

虽然不是一个简单的任务。

Answer 2

虽然上面已经给出了答案，但我再次发布它并提供更多详细信息，

我同意您可以将MultiTenantConnectionProviderImpl 与CurrentTenantIdentifierResolver 一起使用，我早就实现了这两个功能，并且我正在发布我的代码以获得更多帮助。

首先要了解两者的目的。

CurrentTenantIdentifierResolver 用于识别要用于给定租户的连接，为此您需要租户标识。对于租户识别的逻辑，您可以覆盖它。在您的情况下，它将被修复，即您将始终指向您的第一个数据库。

public class TenantIdentifierAndSchemaResolver implements CurrentTenantIdentifierResolver {

    private String tenantIdentifier = "FIRST_DATABASE";

    @Override
    public String resolveCurrentTenantIdentifier() {
        return this.tenantIdentifier;
    }

    /**
     * Reason why it retuns a false is because we don't want to validate the
     * tenant identifier in the current session.
     * 
     * Please read below.
     * {@link CurrentTenantIdentifierResolver#validateExistingCurrentSessions()}
     */
    @Override
    public boolean validateExistingCurrentSessions() {
        return false;
    }

    public void setTenantIdentifier(String tenantIdentifier) {
        this.tenantIdentifier = tenantIdentifier;
    }
}

在此之后，您需要实现MultiTenantConnectionProvider，使用它您将实际切换数据库以接收传入请求。

public class CustomMultiTenantConnectionProvider implements MultiTenantConnectionProvider {

    private static final long serialVersionUID = 9033113494774715973L;

    private Logger LOG = LogManager.getLogger(CustomMultiTenantConnectionProvider.class);

    private BasicDataSource dataSource;

    public void setDataSource(BasicDataSource dataSource) {
        this.dataSource = dataSource;
    }

    @Override
    public Connection getAnyConnection() throws SQLException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Fetching any connection >");
        }
        return dataSource.getConnection();
    }

    @Override
    public Connection getConnection(String tenantIdentifier) throws SQLException {
        Connection tenantSpecificConnection = dataSource.getConnection();
    if (!StringUtils.isEmpty(tenantIdentifier)) {
        Statement statement = tenantSpecificConnection.createStatement();
        statement.executeQuery("use " + tenantIdentifier);
        statement.close();
        tenantSpecificConnection.setSchema(tenantIdentifier);
    } else {
        tenantSpecificConnection.setSchema(Constants.SOMEOTHER_DB);
    }
    return tenantSpecificConnection;
    }

    @Override
    public void releaseAnyConnection(Connection connection) throws SQLException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Releasing connection obtained by : getAnyConnection", connection);
        }
        connection.close();
    }

    @Override
    public void releaseConnection(String tenantIdentifier, Connection connection) throws SQLException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Releasing connection for : {}", tenantIdentifier);
        }
        connection.close();
    }

    /**
     * does the connection provider has support for releasing connection and get
     * back the connection as and when needed ?
     * 
     * @return
     */
    @Override
    public boolean supportsAggressiveRelease() {
        return false;
    }

    @SuppressWarnings("rawtypes")
    @Override
    public boolean isUnwrappableAs(Class arg0) {
        return false;
    }

    @Override
    public <T> T unwrap(Class<T> arg0) {
        return null;
    }
}

您需要在 spring 配置中声明这些 bean，并在 hibernate 配置中指定。

<bean id="sessionFactory"
        class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="packagesToScan" value="org.opensource.example" />
        <property name="hibernateProperties">
            <map>
                <entry key="hibernate.hbm2ddl.auto" value="update"></entry>
                <entry key="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect"></entry>
                <entry key="hibernate.connection.charSet" value="UTF-8"></entry>
                <entry key="hibernate.multiTenancy" value="SCHEMA"></entry>
                <entry key="hibernate.tenant_identifier_resolver" value-ref="multitenantSchemaResolverAndTenantIdentifier"></entry>
                <entry key="hibernate.multi_tenant_connection_provider"
                    value-ref="multitenantConnectionProvider"></entry>
                <entry key="hibernate.show_sql" value="true"></entry>
                <entry key="hibernate.use_sql_comments" value="true"></entry>
                <entry key="hibernate.connection.charSet" value="UTF-8"></entry>
            </map>
        </property>
    </bean>

我希望这会有所帮助。