nacos只支持mysql的原因分析

什么是Nacos

英文全称Dynamic Naming and Configuration Service，Na为naming/nameServer即注册中心,co为configuration即注册中心，service是指该注册/配置中心都是以服务为核心。服务在nacos是一等公民

没看源码之前,觉得很离谱,为啥只能限制数据库为mysql,按道理来说,nacos用了JdbcTemplate,可以适配很多数据库才是

最近看了nacos的源码,发现其中有很多硬编码,才明白原因

nacos的数据源获取都是通过com.alibaba.nacos.config.server.service.datasource.DynamicDataSource来获取的

在获取数据源时,根据配置判断你到底是使用内置的本地数据库还是外部的数据库(mysql)

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public synchronized DataSourceService getDataSource() {      try {            // Embedded storage is used by default in stand-alone mode          // In cluster mode, external databases are used by default          // 根据System.getProperty("nacos.standalone")来判断你到底是不是standalone模式          // standalone模式,使用内置数据库          if (PropertyUtil.isEmbeddedStorage()) {              if (localDataSourceService == null ) {                  localDataSourceService = new LocalDataSourceServiceImpl();                  localDataSourceService.init();              }              return localDataSourceService;          } else {              // 如果不是standalone,直接创建外部的数据源              if (basicDataSourceService == null ) {                  basicDataSourceService = new ExternalDataSourceServiceImpl();                  basicDataSourceService.init();              }              return basicDataSourceService;          }      } catch (Exception e) {          throw new RuntimeException(e);      } }

外部数据源com.alibaba.nacos.config.server.service.datasource.ExternalDataSourceServiceImpl.init()

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@Override public void init() {      queryTimeout = ConvertUtils.toInt(System.getProperty( "QUERYTIMEOUT" ), 3 );      jt = new JdbcTemplate();      // Set the maximum number of records to prevent memory expansion      jt.setMaxRows( 50000 );      jt.setQueryTimeout(queryTimeout);      testMasterJT = new JdbcTemplate();      testMasterJT.setQueryTimeout(queryTimeout);      testMasterWritableJT = new JdbcTemplate();      // Prevent the login interface from being too long because the main library is not available      testMasterWritableJT.setQueryTimeout( 1 );      //  Database health check      testJtList = new ArrayList<JdbcTemplate>();      isHealthList = new ArrayList<Boolean>();      tm = new DataSourceTransactionManager();      tjt = new TransactionTemplate(tm);      // Transaction timeout needs to be distinguished from ordinary operations.      tjt.setTimeout(TRANSACTION_QUERY_TIMEOUT);      // 判断到底是是不是用外部数据库      // 这个可以在com.alibaba.nacos.config.server.utils.PropertyUtil#loadSetting中看到      // setUseExternalDB("mysql".equalsIgnoreCase(getString("spring.datasource.platform", "")));      // 好家伙,直接判断配置的是不是mysql,是mysql那就是外部数据库,进行reload,不是,那就不管了      if (PropertyUtil.isUseExternalDB()) {          try {              reload();          } catch (IOException e) {              e.printStackTrace();              throw new RuntimeException(DB_LOAD_ERROR_MSG);          }          if ( this .dataSourceList.size() > DB_MASTER_SELECT_THRESHOLD) {              ConfigExecutor.scheduleConfigTask( new SelectMasterTask(), 10 , 10 , TimeUnit.SECONDS);          }          ConfigExecutor.scheduleConfigTask( new CheckDbHealthTask(), 10 , 10 , TimeUnit.SECONDS);      } }

在com.alibaba.nacos.config.server.service.datasource.ExternalDataSourceServiceImpl#reload中,我们可以看到

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@Override public synchronized void reload() throws IOException {      try {          // 根据配置文件,构建数据源集合          dataSourceList = new ExternalDataSourceProperties()              .build(EnvUtil.getEnvironment(), (dataSource) -> {                  JdbcTemplate jdbcTemplate = new JdbcTemplate();                  jdbcTemplate.setQueryTimeout(queryTimeout);                  jdbcTemplate.setDataSource(dataSource);                  testJtList.add(jdbcTemplate);                  isHealthList.add(Boolean.TRUE);              });          new SelectMasterTask().run();          new CheckDbHealthTask().run();      } catch (RuntimeException e) {          FATAL_LOG.error(DB_LOAD_ERROR_MSG, e);          throw new IOException(e);      } }

在com.alibaba.nacos.config.server.service.datasource.ExternalDataSourceProperties#build中

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List<HikariDataSource> build(Environment environment, Callback<HikariDataSource> callback) {      List<HikariDataSource> dataSources = new ArrayList<>();      // 把胚子信息绑定到当前的ExternalDataSourceProperties对象,赋值操作      // 因为外面是直接new出来的,需要对属性根据文件进行赋值      Binder.get(environment).bind( "db" , Bindable.ofInstance( this ));      Preconditions.checkArgument(Objects.nonNull(num), "db.num is null" );      Preconditions.checkArgument(CollectionUtils.isNotEmpty(user), "db.user or db.user.[index] is null" );      Preconditions.checkArgument(CollectionUtils.isNotEmpty(password), "db.password or db.password.[index] is null" );      // 可以配置多个数据库      for ( int index = 0 ; index < num; index++) {          int currentSize = index + 1 ;          Preconditions.checkArgument(url.size() >= currentSize, "db.url.%s is null" , index);          // 拿到spring.datasource.xxx一堆,这个针对所有的数据源都适用          DataSourcePoolProperties poolProperties = DataSourcePoolProperties.build(environment);          // 为每一个数据源进行单独的url,user,password进行替换          poolProperties.setDriverClassName(JDBC_DRIVER_NAME);          poolProperties.setJdbcUrl(url.get(index).trim());          poolProperties.setUsername(getOrDefault(user, index, user.get( 0 )).trim());          poolProperties.setPassword(getOrDefault(password, index, password.get( 0 )).trim());          HikariDataSource ds = poolProperties.getDataSource();          ds.setConnectionTestQuery(TEST_QUERY);          dataSources.add(ds);          callback.accept(ds);      }      Preconditions.checkArgument(CollectionUtils.isNotEmpty(dataSources), "no datasource available" );      return dataSources; }

这个整体还行,但是为啥JDBC_DRIVER_NAME是硬编码呢,代码中清晰看到

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1	private static final String JDBC_DRIVER_NAME = "com.mysql.cj.jdbc.Driver" ;

到这已经一目了然,代码中硬编码了mysql,driver也没法改,所以根本没法更换数据库驱动,有点骚,而且com.mysql.cj.jdbc.Driver是mysql8的驱动,对mysql版本是有要求的

再看其他部分,也可以发现大量的硬编码,例如com.alibaba.nacos.config.server.auth.ExternalUserPersistServiceImpl

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public class ExternalUserPersistServiceImpl implements UserPersistService {           @Autowired      private ExternalStoragePersistServiceImpl persistService;           private JdbcTemplate jt;           @PostConstruct      protected void init() {          jt = persistService.getJdbcTemplate();      }           /**       * Execute create user operation.       *       * @param username username string value.       * @param password password string value.       */      public void createUser(String username, String password) {          String sql = "INSERT into users (username, password, enabled) VALUES (?, ?, ?)" ;                   try {              jt.update(sql, username, password, true );          } catch (CannotGetJdbcConnectionException e) {              LogUtil.FATAL_LOG.error( "[db-error] " + e.toString(), e);              throw e;          }      }           /**       * Execute delete user operation.       *       * @param username username string value.       */      public void deleteUser(String username) {          String sql = "DELETE from users WHERE username=?" ;          try {              jt.update(sql, username);          } catch (CannotGetJdbcConnectionException e) {              LogUtil.FATAL_LOG.error( "[db-error] " + e.toString(), e);              throw e;          }      }           /**       * Execute update user password operation.       *       * @param username username string value.       * @param password password string value.       */      public void updateUserPassword(String username, String password) {          try {              jt.update( "UPDATE users SET password = ? WHERE username=?" , password, username);          } catch (CannotGetJdbcConnectionException e) {              LogUtil.FATAL_LOG.error( "[db-error] " + e.toString(), e);              throw e;          }      }           /**       * Execute find user by username operation.       *       * @param username username string value.       * @return User model.       */      public User findUserByUsername(String username) {          String sql = "SELECT username,password FROM users WHERE username=? " ;          try {              return this .jt.queryForObject(sql, new Object[] {username}, USER_ROW_MAPPER);          } catch (CannotGetJdbcConnectionException e) {              LogUtil.FATAL_LOG.error( "[db-error] " + e.toString(), e);              throw e;          } catch (EmptyResultDataAccessException e) {              return null ;          } catch (Exception e) {              LogUtil.FATAL_LOG.error( "[db-other-error]" + e.getMessage(), e);              throw new RuntimeException(e);          }      }           public Page<User> getUsers( int pageNo, int pageSize) {                   PaginationHelper<User> helper = persistService.createPaginationHelper();                   String sqlCountRows = "select count(*) from users where " ;          String sqlFetchRows = "select username,password from users where " ;                   String where = " 1=1 " ;                   try {              Page<User> pageInfo = helper                      .fetchPage(sqlCountRows + where, sqlFetchRows + where, new ArrayList<String>().toArray(), pageNo,                              pageSize, USER_ROW_MAPPER);              if (pageInfo == null ) {                  pageInfo = new Page<>();                  pageInfo.setTotalCount( 0 );                  pageInfo.setPageItems( new ArrayList<>());              }              return pageInfo;          } catch (CannotGetJdbcConnectionException e) {              LogUtil.FATAL_LOG.error( "[db-error] " + e.toString(), e);              throw e;          }      }      @Override      public List<String> findUserLikeUsername(String username) {          String sql = "SELECT username FROM users WHERE username like '%' ? '%'" ;          List<String> users = this .jt.queryForList(sql, new String[]{username}, String. class );          return users;      } }

几乎所有的sql都是硬编码....所以要改造成其他数据库工作量还是非常大的

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原文链接：https://www.cnblogs.com/xixisix/p/15821706.html