AbstractRoutingDataSource+Mybatis拦截器实现动态切换数据源代码

下面是使用 AbstractRoutingDataSource 和 MyBatis 拦截器实现动态切换数据源的示例代码：

首先，需要自定义一个继承 AbstractRoutingDataSource 的类，并实现 determineCurrentLookupKey 方法，该方法用于返回当前数据源的 key：

public class DynamicDataSource extends AbstractRoutingDataSource {

    private static final ThreadLocal<String> dataSourceKey = new InheritableThreadLocal<>();

    public static void setDataSourceKey(String key) {
        dataSourceKey.set(key);
    }

    @Override
    protected Object determineCurrentLookupKey() {
        return dataSourceKey.get();
    }
}

在 Spring 配置文件中需要配置两个数据源，并将 DynamicDataSource 设置为默认数据源：

<bean id="dataSource1" class="org.apache.commons.dbcp2.BasicDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3306/db1"/>
    <property name="username" value="root"/>
    <property name="password" value="123456"/>
</bean>

<bean id="dataSource2" class="org.apache.commons.dbcp2.BasicDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3306/db2"/>
    <property name="username" value="root"/>
    <property name="password" value="123456"/>
</bean>

<bean id="dynamicDataSource" class="com.example.DynamicDataSource">
    <property name="defaultTargetDataSource" ref="dataSource1"/>
    <property name="targetDataSources">
        <map>
            <entry key="db1" value-ref="dataSource1"/>
            <entry key="db2" value-ref="dataSource2"/>
        </map>
    </property>
</bean>

接下来，需要实现一个继承于 MyBatis 的 Interceptor 接口的拦截器类，该类用于在执行 SQL 语句前切换数据源：

@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class DynamicDataSourceInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
        MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");

        String dataSourceKey = getDataSourceKey(mappedStatement);
        if (dataSourceKey != null) {
            DynamicDataSource.setDataSourceKey(dataSourceKey);
        }

        return invocation.proceed();
    }

    private String getDataSourceKey(MappedStatement mappedStatement) {
        String dataSourceKey = null;

        // 从 Mapper 方法上获取数据源 key
        if (mappedStatement != null) {
            String id = mappedStatement.getId();
            if (id.startsWith("com.example.mapper1")) {
                dataSourceKey = "db1";
            } else if (id.startsWith("com.example.mapper2")) {
                dataSourceKey = "db2";
            }
        }

        return dataSourceKey;
    }

    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
        // do nothing
    }
}

最后，需要在 Spring 配置文件中配置该拦截器：

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dynamicDataSource"/>
    <property name="plugins">
        <array>
            <bean class="com.example.DynamicDataSourceInterceptor"/>
        </array>
    </property>
</bean>

这样，就可以在 Mapper 方法上使用 @DataSource("db1") 或 @DataSource("db2") 注解来指定使用哪个数据源了。例如：

@DataSource("db1")
List<User> getUserList();

@DataSource("db2")
int addUser(User user);