【源碼解析】多數(shù)據(jù)源 dynamic-datasource快速入門及源碼解析

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快速入門

依賴引入

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>

配置文件

spring.datasource.druid.stat-view-servlet.enabled = true
spring.datasource.druid.stat-view-servlet.login-username = root
spring.datasource.druid.stat-view-servlet.login-password = root
spring.datasource.dynamic.druid.filters = stat,wall
spring.datasource.druid.aop-patterns = com.charles.mapper.*
spring.datasource.druid.web-stat-filter.enabled = true
spring.datasource.druid.filter.stat.enabled = true
spring.datasource.druid.filter.stat.log-slow-sql = true
spring.datasource.druid.filter.stat.slow-sql-millis = 1000

spring.datasource.dynamic.primary = db0
spring.datasource.dynamic.datasource.db1.driver-class-name = com.mysql.cj.jdbc.Driver
spring.datasource.dynamic.datasource.db1.url = jdbc:mysql://127.0.0.1:3306/eb-crm?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.dynamic.datasource.db1.username = app
spring.datasource.dynamic.datasource.db1.password = Ys@123456
spring.datasource.dynamic.datasource.db1.type = com.alibaba.druid.pool.DruidDataSource
spring.datasource.dynamic.datasource.db0.driver-class-name = com.mysql.cj.jdbc.Driver
spring.datasource.dynamic.datasource.db0.url = jdbc:mysql://127.0.0.1:3306/newcrm?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.dynamic.datasource.db0.username = app
spring.datasource.dynamic.datasource.db0.password = Ys@123456
spring.datasource.dynamic.datasource.db0.type = com.alibaba.druid.pool.DruidDataSource

使用注解攔截

@DS("db1")
public interface TbpExcelLogMapper extends BaseMapper<TbpExcelLog> {
}

源碼解析

啟動的時候，會加載在dynamic-datasource-spring-boot-starter的jar包中的spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DynamicDataSourceAutoConfiguration

數(shù)據(jù)源加載

在DynamicDataSourceAutoConfiguration會注入DynamicRoutingDataSource

    @Bean
    @ConditionalOnMissingBean
    public DataSource dataSource() {
        DynamicRoutingDataSource dataSource = new DynamicRoutingDataSource();
        dataSource.setPrimary(properties.getPrimary());
        dataSource.setStrict(properties.getStrict());
        dataSource.setStrategy(properties.getStrategy());
        dataSource.setP6spy(properties.getP6spy());
        dataSource.setSeata(properties.getSeata());
        return dataSource;
    }

DynamicRoutingDataSource#afterPropertiesSet，系統(tǒng)啟動的時候會加載所有的數(shù)據(jù)源

    @Override
    public void afterPropertiesSet() throws Exception {
        // 檢查開啟了配置但沒有相關(guān)依賴
        checkEnv();
        // 添加并分組數(shù)據(jù)源
        Map<String, DataSource> dataSources = new HashMap<>(16);
        for (DynamicDataSourceProvider provider : providers) {
            dataSources.putAll(provider.loadDataSources());
        }
        for (Map.Entry<String, DataSource> dsItem : dataSources.entrySet()) {
            addDataSource(dsItem.getKey(), dsItem.getValue());
        }
        // 檢測默認(rèn)數(shù)據(jù)源是否設(shè)置
        if (groupDataSources.containsKey(primary)) {
            log.info("dynamic-datasource initial loaded [{}] datasource,primary group datasource named [{}]", dataSources.size(), primary);
        } else if (dataSourceMap.containsKey(primary)) {
            log.info("dynamic-datasource initial loaded [{}] datasource,primary datasource named [{}]", dataSources.size(), primary);
        } else {
            log.warn("dynamic-datasource initial loaded [{}] datasource,Please add your primary datasource or check your configuration", dataSources.size());
        }
    }

在DynamicDataSourceAutoConfiguration會注入DynamicDataSourceProvider

    @Bean
    public DynamicDataSourceProvider ymlDynamicDataSourceProvider() {
        return new YmlDynamicDataSourceProvider(properties.getDatasource());
    }

AbstractDataSourceProvider#createDataSourceMap，根據(jù)配置文件中的信息創(chuàng)建數(shù)據(jù)源。

    protected Map<String, DataSource> createDataSourceMap(
            Map<String, DataSourceProperty> dataSourcePropertiesMap) {
        Map<String, DataSource> dataSourceMap = new HashMap<>(dataSourcePropertiesMap.size() * 2);
        for (Map.Entry<String, DataSourceProperty> item : dataSourcePropertiesMap.entrySet()) {
            String dsName = item.getKey();
            DataSourceProperty dataSourceProperty = item.getValue();
            String poolName = dataSourceProperty.getPoolName();
            if (poolName == null || "".equals(poolName)) {
                poolName = dsName;
            }
            dataSourceProperty.setPoolName(poolName);
            dataSourceMap.put(dsName, defaultDataSourceCreator.createDataSource(dataSourceProperty));
        }
        return dataSourceMap;
    }

AbstractDataSourceCreator#createDataSource，模板方法。該方法會調(diào)用dataSourceInitEvent.beforeCreate(dataSourceProperty);。而doCreateDataSource交由每個子類來創(chuàng)建。

    @Override
    public DataSource createDataSource(DataSourceProperty dataSourceProperty) {
        String publicKey = dataSourceProperty.getPublicKey();
        if (StringUtils.isEmpty(publicKey)) {
            publicKey = properties.getPublicKey();
            dataSourceProperty.setPublicKey(publicKey);
        }
        Boolean lazy = dataSourceProperty.getLazy();
        if (lazy == null) {
            lazy = properties.getLazy();
            dataSourceProperty.setLazy(lazy);
        }
        dataSourceInitEvent.beforeCreate(dataSourceProperty);
        DataSource dataSource = doCreateDataSource(dataSourceProperty);
        dataSourceInitEvent.afterCreate(dataSource);
        this.runScrip(dataSource, dataSourceProperty);
        return wrapDataSource(dataSource, dataSourceProperty);
    }

DruidDataSourceCreator#doCreateDataSource，創(chuàng)建druid數(shù)據(jù)源。根據(jù)全局配置gConfig和定制化配置結(jié)合來生成DruidDataSource。spring.datasource.dynamic.datasource.xxx.type=com.alibaba.druid.pool.DruidDataSource可以進(jìn)行定制化配置，也可以通過spring.datasource.dynamic.druid全局配置druid的屬性

    private DruidConfig gConfig;

    @Override
    public DataSource doCreateDataSource(DataSourceProperty dataSourceProperty) {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUsername(dataSourceProperty.getUsername());
        dataSource.setPassword(dataSourceProperty.getPassword());
        dataSource.setUrl(dataSourceProperty.getUrl());
        dataSource.setName(dataSourceProperty.getPoolName());
        String driverClassName = dataSourceProperty.getDriverClassName();
        if (!StringUtils.isEmpty(driverClassName)) {
            dataSource.setDriverClassName(driverClassName);
        }
        DruidConfig config = dataSourceProperty.getDruid();
        Properties properties = config.toProperties(gConfig);

        List<Filter> proxyFilters = this.initFilters(dataSourceProperty, properties.getProperty("druid.filters"));
        dataSource.setProxyFilters(proxyFilters);

        dataSource.configFromPropety(properties);
        //連接參數(shù)單獨(dú)設(shè)置
        dataSource.setConnectProperties(config.getConnectionProperties());
        //設(shè)置druid內(nèi)置properties不支持的的參數(shù)
        this.setParam(dataSource, config);

        if (Boolean.FALSE.equals(dataSourceProperty.getLazy())) {
            try {
                dataSource.init();
            } catch (SQLException e) {
                throw new ErrorCreateDataSourceException("druid create error", e);
            }
        }
        return dataSource;
    }

切面修改數(shù)據(jù)源的key

在DynamicDataSourceAutoConfiguration會注入DynamicDataSourceAnnotationAdvisor

    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    @Bean
    @ConditionalOnProperty(prefix = DynamicDataSourceProperties.PREFIX + ".aop", name = "enabled", havingValue = "true", matchIfMissing = true)
    public Advisor dynamicDatasourceAnnotationAdvisor(DsProcessor dsProcessor) {
        DynamicDatasourceAopProperties aopProperties = properties.getAop();
        DynamicDataSourceAnnotationInterceptor interceptor = new DynamicDataSourceAnnotationInterceptor(aopProperties.getAllowedPublicOnly(), dsProcessor);
        DynamicDataSourceAnnotationAdvisor advisor = new DynamicDataSourceAnnotationAdvisor(interceptor, DS.class);
        advisor.setOrder(aopProperties.getOrder());
        return advisor;
    }

DynamicDataSourceAnnotationAdvisor#buildPointcut，構(gòu)造切面，對方法和類都攔截。

    private Pointcut buildPointcut() {
        Pointcut cpc = new AnnotationMatchingPointcut(annotation, true);
        Pointcut mpc = new AnnotationMethodPoint(annotation);
        return new ComposablePointcut(cpc).union(mpc);
    }

如果使用@Aspect來切面的話，對注解進(jìn)行切片，要注意@within和@annotation的區(qū)別。

 1.  @within 對象級別
 2.  @annotation 方法級別

DynamicDataSourceAnnotationInterceptor#invoke，獲取方法上或者類上的注解中的key

    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        String dsKey = determineDatasourceKey(invocation);
        DynamicDataSourceContextHolder.push(dsKey);
        try {
            return invocation.proceed();
        } finally {
            DynamicDataSourceContextHolder.poll();
        }
    }

DynamicDataSourceAnnotationInterceptor#determineDatasourceKey，如果key以#開頭，則返回dsProcessor.determineDatasource(invocation, key)，否則直接返回key。

    private String determineDatasourceKey(MethodInvocation invocation) {
        String key = dataSourceClassResolver.findKey(invocation.getMethod(), invocation.getThis());
        return key.startsWith(DYNAMIC_PREFIX) ? dsProcessor.determineDatasource(invocation, key) : key;
    }

DsProcessor

在DynamicDataSourceAutoConfiguration會注入DsProcessor，使用過濾器鏈的模式進(jìn)行處理。

    @Bean
    @ConditionalOnMissingBean
    public DsProcessor dsProcessor(BeanFactory beanFactory) {
        DsHeaderProcessor headerProcessor = new DsHeaderProcessor();
        DsSessionProcessor sessionProcessor = new DsSessionProcessor();
        DsSpelExpressionProcessor spelExpressionProcessor = new DsSpelExpressionProcessor();
        spelExpressionProcessor.setBeanResolver(new BeanFactoryResolver(beanFactory));
        headerProcessor.setNextProcessor(sessionProcessor);
        sessionProcessor.setNextProcessor(spelExpressionProcessor);
        return headerProcessor;
    }

DsHeaderProcessor#doDetermineDatasource，如果方法上的注解類似于@DS(#header=tenat_id)，那么切換路由的key是由header中tenat_id的值決定的。

    @Override
    public String doDetermineDatasource(MethodInvocation invocation, String key) {
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
        return request.getHeader(key.substring(8));
    }

spelExpressionProcessor是支持表達(dá)式的。

在注解中配置@DS("#header=tenantName")，則從header里面去尋找key；寫了@DS("#session=tenantName")，就從session里面獲取以tenantName為鍵的值。而@DS("#tenantName")和@DS("#user.tenantName")根據(jù)參數(shù)來獲取。

獲取數(shù)據(jù)源

獲取連接，AbstractRoutingDataSource#getConnection()。首先獲取數(shù)據(jù)源，從數(shù)據(jù)源中獲取Connection

    @Override
    public Connection getConnection() throws SQLException {
        String xid = TransactionContext.getXID();
        if (StringUtils.isEmpty(xid)) {
            return determineDataSource().getConnection();
        } else {
            String ds = DynamicDataSourceContextHolder.peek();
            ds = StringUtils.isEmpty(ds) ? "default" : ds;
            ConnectionProxy connection = ConnectionFactory.getConnection(ds);
            return connection == null ? getConnectionProxy(ds, determineDataSource().getConnection()) : connection;
        }
    }

DynamicRoutingDataSource#determineDataSource，獲取線程變量的數(shù)據(jù)，根據(jù)線程變量獲取數(shù)據(jù)源。

    @Override
    public DataSource determineDataSource() {
        String dsKey = DynamicDataSourceContextHolder.peek();
        return getDataSource(dsKey);
    }

DynamicRoutingDataSource#getDataSource，該key為空，獲取默認(rèn)數(shù)據(jù)源，優(yōu)先從groupDataSources里面獲取數(shù)據(jù)源，然后再從dataSourceMap里面獲取。

    public DataSource getDataSource(String ds) {
        if (StringUtils.isEmpty(ds)) {
            return determinePrimaryDataSource();
        } else if (!groupDataSources.isEmpty() && groupDataSources.containsKey(ds)) {
            log.debug("dynamic-datasource switch to the datasource named [{}]", ds);
            return groupDataSources.get(ds).determineDataSource();
        } else if (dataSourceMap.containsKey(ds)) {
            log.debug("dynamic-datasource switch to the datasource named [{}]", ds);
            return dataSourceMap.get(ds);
        }
        if (strict) {
            throw new CannotFindDataSourceException("dynamic-datasource could not find a datasource named" + ds);
        }
        return determinePrimaryDataSource();
    }

DynamicDataSourceStrategy，從群組里面獲取數(shù)據(jù)源需要配置獲取策略，從集合中決定是哪一個，有隨機(jī)和輪詢。

public class RandomDynamicDataSourceStrategy implements DynamicDataSourceStrategy {

    @Override
    public String determineKey(List<String> dsNames) {
        return dsNames.get(ThreadLocalRandom.current().nextInt(dsNames.size()));
    }
}

比對一下，spring-jdbc中的動態(tài)數(shù)據(jù)源切換。

AbstractRoutingDataSource#afterPropertiesSet，重寫了InitializingBean#afterPropertiesSet的方法。

    public void afterPropertiesSet() {
        if (this.targetDataSources == null) {
            throw new IllegalArgumentException("Property 'targetDataSources' is required");
        } else {
            this.resolvedDataSources = new HashMap(this.targetDataSources.size());
            this.targetDataSources.forEach((key, value) -> {
                Object lookupKey = this.resolveSpecifiedLookupKey(key);
                DataSource dataSource = this.resolveSpecifiedDataSource(value);
                this.resolvedDataSources.put(lookupKey, dataSource);
            });
            if (this.defaultTargetDataSource != null) {
                this.resolvedDefaultDataSource = this.resolveSpecifiedDataSource(this.defaultTargetDataSource);
            }

        }
    }

AbstractRoutingDataSource#getConnection()。獲取lookupKey的方式由子類決定。

    public Connection getConnection() throws SQLException {
        return this.determineTargetDataSource().getConnection();
    }

    protected DataSource determineTargetDataSource() {
        Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
        Object lookupKey = this.determineCurrentLookupKey();
        DataSource dataSource = (DataSource)this.resolvedDataSources.get(lookupKey);
        if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
            dataSource = this.resolvedDefaultDataSource;
        }

        if (dataSource == null) {
            throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
        } else {
            return dataSource;
        }
    }

    @Nullable
    protected abstract Object determineCurrentLookupKey();

多數(shù)據(jù)源事務(wù)

在DynamicDataSourceAutoConfiguration會注入dynamicTransactionAdvisor，主要是攔截處理有DSTransactional注解的方法。

    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    @Bean
    @ConditionalOnProperty(prefix = DynamicDataSourceProperties.PREFIX, name = "seata", havingValue = "false", matchIfMissing = true)
    public Advisor dynamicTransactionAdvisor() {
        DynamicLocalTransactionInterceptor interceptor = new DynamicLocalTransactionInterceptor();
        return new DynamicDataSourceAnnotationAdvisor(interceptor, DSTransactional.class);
    }

DynamicLocalTransactionInterceptor，開啟事務(wù)。

public class DynamicLocalTransactionInterceptor implements MethodInterceptor {

    @Override
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        if (!StringUtils.isEmpty(TransactionContext.getXID())) {
            return methodInvocation.proceed();
        }
        boolean state = true;
        Object o;
        LocalTxUtil.startTransaction();
        try {
            o = methodInvocation.proceed();
        } catch (Exception e) {
            state = false;
            throw e;
        } finally {
            if (state) {
                LocalTxUtil.commit();
            } else {
                LocalTxUtil.rollback();
            }
        }
        return o;
    }
}

LocalTxUtil#startTransaction

    public static void startTransaction() {
        if (!StringUtils.isEmpty(TransactionContext.getXID())) {
            log.debug("dynamic-datasource exist local tx [{}]", TransactionContext.getXID());
        } else {
            String xid = UUID.randomUUID().toString();
            TransactionContext.bind(xid);
            log.debug("dynamic-datasource start local tx [{}]", xid);
        }
    }

AbstractRoutingDataSource#getConnection()，判斷是否存在事務(wù)id，如果存在，則獲取連接，并封裝成ConnectionProxy。

    @Override
    public Connection getConnection() throws SQLException {
        String xid = TransactionContext.getXID();
        if (StringUtils.isEmpty(xid)) {
            return determineDataSource().getConnection();
        } else {
            String ds = DynamicDataSourceContextHolder.peek();
            ds = StringUtils.isEmpty(ds) ? "default" : ds;
            ConnectionProxy connection = ConnectionFactory.getConnection(ds);
            return connection == null ? getConnectionProxy(ds, determineDataSource().getConnection()) : connection;
        }
    }

    private Connection getConnectionProxy(String ds, Connection connection) {
        ConnectionProxy connectionProxy = new ConnectionProxy(connection, ds);
        ConnectionFactory.putConnection(ds, connectionProxy);
        return connectionProxy;
    }

ConnectionFactory#putConnection，存儲到線程變量中的concurrentHashMap。

    public static void putConnection(String ds, ConnectionProxy connection) {
        Map<String, ConnectionProxy> concurrentHashMap = CONNECTION_HOLDER.get();
        if (!concurrentHashMap.containsKey(ds)) {
            try {
                connection.setAutoCommit(false);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            concurrentHashMap.put(ds, connection);
        }
    }

提交事務(wù)，LocalTxUtil#commit

    public static void commit() {
        ConnectionFactory.notify(true);
        log.debug("dynamic-datasource commit local tx [{}]", TransactionContext.getXID());
        TransactionContext.remove();
    }

ConnectionFactory#notify，對于線程變量中的連接全部處理（回滾或者提交），并清空線程變量。

    public static void notify(Boolean state) {
        try {
            Map<String, ConnectionProxy> concurrentHashMap = CONNECTION_HOLDER.get();
            for (ConnectionProxy connectionProxy : concurrentHashMap.values()) {
                connectionProxy.notify(state);
            }
        } finally {
            CONNECTION_HOLDER.remove();
        }
    }

配置文件加密

在DynamicDataSourceAutoConfiguration會注入EncDataSourceInitEvent

    @Bean
    @ConditionalOnMissingBean
    public DataSourceInitEvent dataSourceInitEvent() {
        return new EncDataSourceInitEvent();
    }

EncDataSourceInitEvent#beforeCreate，對加密的字符串進(jìn)行解密

    @Override
    public void beforeCreate(DataSourceProperty dataSourceProperty) {
        String publicKey = dataSourceProperty.getPublicKey();
        if (StringUtils.hasText(publicKey)) {
            dataSourceProperty.setUrl(decrypt(publicKey, dataSourceProperty.getUrl()));
            dataSourceProperty.setUsername(decrypt(publicKey, dataSourceProperty.getUsername()));
            dataSourceProperty.setPassword(decrypt(publicKey, dataSourceProperty.getPassword()));
        }
    }

EncDataSourceInitEvent#decrypt，匹配正則表達(dá)式則進(jìn)行解密。 Pattern ENC_PATTERN = Pattern.compile("^ENC\$(.*)\$$");

    private String decrypt(String publicKey, String cipherText) {
        if (StringUtils.hasText(cipherText)) {
            Matcher matcher = ENC_PATTERN.matcher(cipherText);
            if (matcher.find()) {
                try {
                    return CryptoUtils.decrypt(publicKey, matcher.group(1));
                } catch (Exception e) {
                    log.error("DynamicDataSourceProperties.decrypt error ", e);
                }
            }
        }
        return cipherText;
    }

腳本執(zhí)行器

AbstractDataSourceCreator#runScrip，用對應(yīng)的數(shù)據(jù)源執(zhí)行腳本

    private void runScrip(DataSource dataSource, DataSourceProperty dataSourceProperty) {
        DatasourceInitProperties initProperty = dataSourceProperty.getInit();
        String schema = initProperty.getSchema();
        String data = initProperty.getData();
        if (StringUtils.hasText(schema) || StringUtils.hasText(data)) {
            ScriptRunner scriptRunner = new ScriptRunner(initProperty.isContinueOnError(), initProperty.getSeparator());
            if (StringUtils.hasText(schema)) {
                scriptRunner.runScript(dataSource, schema);
            }
            if (StringUtils.hasText(data)) {
                scriptRunner.runScript(dataSource, data);
            }
        }
    }

主從插件

MasterSlaveAutoRoutingPlugin。當(dāng)進(jìn)行查詢的時候，切換數(shù)據(jù)源SLAVE；當(dāng)進(jìn)行更新的時候，切換數(shù)據(jù)源，MASTER。

@Intercepts({
        @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
        @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class, CacheKey.class, BoundSql.class}),
        @Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class})})
@Slf4j
public class MasterSlaveAutoRoutingPlugin implements Interceptor {

    @Autowired
    protected DataSource dynamicDataSource;

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Object[] args = invocation.getArgs();
        MappedStatement ms = (MappedStatement) args[0];
        String pushedDataSource = null;
        try {
            String dataSource = SqlCommandType.SELECT == ms.getSqlCommandType() ? DdConstants.SLAVE : DdConstants.MASTER;
            pushedDataSource = DynamicDataSourceContextHolder.push(dataSource);
            return invocation.proceed();
        } finally {
            if (pushedDataSource != null) {
                DynamicDataSourceContextHolder.poll();
            }
        }
    }

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

    @Override
    public void setProperties(Properties properties) {
    }
}

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