在SASS的大潮流下，相信依然存在很多使用一个数据库为多个租户提供服务的场景，这个情况下一般是多个租户共用同一套表通过sql语句级别来隔离不同租户的资源，比如设置一个租户标识字段，每次查询的时候在后面附加一个筛选条件：TenantId=xxx。这样能低代价、简单地实现多租户服务，但是每次执行sql的时候需要附加字段隔离，否则会出现数据错乱。
此隔离过程应该自动标识完成，所以我今天借助于Mybatis的插件机制来完成一个多租户sql隔离插件。
一、设计需求
1、首先，我们需要一种方案来识别哪些表需要使用多租户隔离，并且确定多租户隔离字段名称。
2、然后拦截mybatis执行过程中的prepare方法，通过改写加入多租户隔离条件，然后替换为我们新的sql。
3、寻找一种方法能多层次的智能的为识别到的数据表添加condition，毕竟CRUD过程都会存在子查询，并且不会丢失原有的where条件。
二、设计思路
对于需求1，我们可以定义一个条件字段决策器，用来决策某个表是否需要添加多租户过滤条件，比如定义一个接口：ITableFieldConditionDecision
/** * 表字段条件决策器 * 用于决策某个表是否需要添加某个字段过滤条件 * * @author liushuishang@gmail.com * @date 2017/12/23 15:49 **/ public interface ITableFieldConditionDecision { /** * 条件字段是否运行null值 * @return */ boolean isAllowNullValue(); /** * 判决某个表是否需要添加某个字段过滤 * * @param tableName 表名称 * @param fieldName 字段名称 * @return */ boolean adjudge(String tableName, String fieldName); }
然后在使用插件的地方填写必要的参数来初始化决策器
<!--多租户隔离插件-->
<bean class="com.smartdata360.smartfx.dao.plugin.MultiTenantPlugin">
<property name="properties">
<value>
<!--当前数据库方言-->
dialect=postgresql
<!--多租户隔离字段名称-->
tenantIdField=domain
<!--需要隔离的表名称java正则表达式-->
tablePattern=uam_*
<!--需要隔离的表名称，逗号分隔-->
tableSet=uam_user,uam_role
</value>
</property>
</bean>对于需求2，我们开发一个Mybatis的拦截器：MultiTenantPlugin。抽取出将要预编译的sql语句，加工后再替换，然后Mybatis最终执行的是我们加工过的sql语句。
/** * 多租户数据隔离插件 * * @author liushuishang@gmail.com * @date 2017/12/21 11:58 **/ @Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class})}) public class MultiTenantPlugin extends BasePlugin
对于需求3，我使用阿里Druid的sql parser模块来实现sql解析和condition附加。其大致过程如下：
（1）把sql解析成一颗AST，基本每个部分都会有一个对象与之对应。
（2）遍历AST，获取select、query和SQLExpr，抽取出表名称和别名，交给决策器判断是否需要添加多租户隔离条件。如果需要添加，则扩展原有condition加上多租户筛选条件；否则不做处理
（3）把修改后的AST重新转成sql语句
执行结果：
三、代码参考
import com.alibaba.druid.sql.SQLUtils; import com.alibaba.druid.sql.ast.SQLStatement; import com.smartdata360.smartfx.dao.extension.MultiTenantContent; import com.smartdata360.smartfx.dao.sqlparser.ITableFieldConditionDecision; import com.smartdata360.smartfx.dao.sqlparser.SqlConditionHelper; import org.apache.commons.lang3.StringUtils; import org.apache.ibatis.executor.statement.StatementHandler; import org.apache.ibatis.mapping.BoundSql; import org.apache.ibatis.plugin.Intercepts; import org.apache.ibatis.plugin.Invocation; import org.apache.ibatis.plugin.Signature; import org.apache.ibatis.reflection.MetaObject; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.sql.Connection; import java.util.*; import java.util.regex.Pattern; /** * 多租户数据隔离插件 * * @author liushuishang@gmail.com * @date 2017/12/21 11:58 **/ @Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class})}) public class MultiTenantPlugin extends BasePlugin { private final Logger logger = LoggerFactory.getLogger(MultiTenantPlugin.class); /** * 当前数据库的方言 */ private String dialect; /** * 多租户字段名称 */ private String tenantIdField; /** * 需要识别多租户字段的表名称的正则表达式 */ private Pattern tablePattern; /** * 需要识别多租户字段的表名称列表 */ private Set<String> tableSet; private SqlConditionHelper conditionHelper; @Override public Object intercept(Invocation invocation) throws Throwable { String tenantId = MultiTenantContent.getCurrentTenantId(); //租户id为空时不做处理 if (StringUtils.isBlank(tenantId)) { return invocation.proceed(); } StatementHandler statementHandler = (StatementHandler) invocation.getTarget(); BoundSql boundSql = statementHandler.getBoundSql(); String newSql = addTenantCondition(boundSql.getSql(), tenantId); MetaObject boundSqlMeta = getMetaObject(boundSql); //把新sql设置到boundSql boundSqlMeta.setValue("sql", newSql); return invocation.proceed(); } @Override public void setProperties(Properties properties) { dialect = properties.getProperty("dialect"); if (StringUtils.isBlank(dialect)) throw new IllegalArgumentException("MultiTenantPlugin need dialect property value"); tenantIdField = properties.getProperty("tenantIdField"); if (StringUtils.isBlank(tenantIdField)) throw new IllegalArgumentException("MultiTenantPlugin need tenantIdField property value"); String tableRegex = properties.getProperty("tableRegex"); if (!StringUtils.isBlank(tableRegex)) tablePattern = Pattern.compile(tableRegex); String tableNames = properties.getProperty("tableNames"); if (!StringUtils.isBlank(tableNames)) { tableSet = new HashSet<String>(Arrays.asList(StringUtils.split(tableNames))); } if (tablePattern == null || tableSet == null) throw new IllegalArgumentException("MultiTenantPlugin tableRegex and tableNames must have one"); /** * 多租户条件字段决策器 */ ITableFieldConditionDecision conditionDecision = new ITableFieldConditionDecision() { @Override public boolean isAllowNullValue() { return false; } @Override public boolean adjudge(String tableName, String fieldName) { if (tableRegex != null && tableRegex.matches(tableName)) return true; if (tableSet != null && tableSet.contains(tableName)) return true; return false; } }; conditionHelper = new SqlConditionHelper(conditionDecision); } /** * 给sql语句where添加租户id过滤条件 * * @param sql 要添加过滤条件的sql语句 * @param tenantId 当前的租户id * @return 添加条件后的sql语句 */ private String addTenantCondition(String sql, String tenantId) { if (StringUtils.isBlank(sql) || StringUtils.isBlank(tenantIdField)) return sql; List<SQLStatement> statementList = SQLUtils.parseStatements(sql, dialect); if (statementList == null || statementList.size() == 0) return sql; SQLStatement sqlStatement = statementList.get(0); conditionHelper.addStatementCondition(sqlStatement, tenantIdField, tenantId); return SQLUtils.toSQLString(statementList, dialect); } }
import com.alibaba.druid.sql.SQLUtils; import com.alibaba.druid.sql.ast.SQLExpr; import com.alibaba.druid.sql.ast.SQLStatement; import com.alibaba.druid.sql.ast.expr.*; import com.alibaba.druid.sql.ast.statement.*; import com.alibaba.druid.util.JdbcConstants; import org.apache.commons.lang3.NotImplementedException; import org.apache.commons.lang3.StringUtils; import java.util.List; /** * sql语句where条件处理辅助类 * * @author liushuishang@gmail.com * @date 2017/12/21 15:05 **/ public class SqlConditionHelper { private ITableFieldConditionDecision conditionDecision; public SqlConditionHelper(ITableFieldConditionDecision conditionDecision) { this.conditionDecision = conditionDecision; } /** * 为sql'语句添加指定where条件 * * @param sqlStatement * @param fieldName * @param fieldValue */ public void addStatementCondition(SQLStatement sqlStatement, String fieldName, String fieldValue) { if (sqlStatement instanceof SQLSelectStatement) { SQLSelectQueryBlock queryObject = (SQLSelectQueryBlock) ((SQLSelectStatement) sqlStatement).getSelect().getQuery(); addSelectStatementCondition(queryObject, queryObject.getFrom(), fieldName, fieldValue); } else if (sqlStatement instanceof SQLUpdateStatement) { SQLUpdateStatement updateStatement = (SQLUpdateStatement) sqlStatement; addUpdateStatementCondition(updateStatement, fieldName, fieldValue); } else if (sqlStatement instanceof SQLDeleteStatement) { SQLDeleteStatement deleteStatement = (SQLDeleteStatement) sqlStatement; addDeleteStatementCondition(deleteStatement, fieldName, fieldValue); } else if (sqlStatement instanceof SQLInsertStatement) { SQLInsertStatement insertStatement = (SQLInsertStatement) sqlStatement; addInsertStatementCondition(insertStatement, fieldName, fieldValue); } } /** * 为insert语句添加where条件 * * @param insertStatement * @param fieldName * @param fieldValue */ private void addInsertStatementCondition(SQLInsertStatement insertStatement, String fieldName, String fieldValue) { if (insertStatement != null) { SQLInsertInto sqlInsertInto = insertStatement; SQLSelect sqlSelect = sqlInsertInto.getQuery(); if (sqlSelect != null) { SQLSelectQueryBlock selectQueryBlock = (SQLSelectQueryBlock) sqlSelect.getQuery(); addSelectStatementCondition(selectQueryBlock, selectQueryBlock.getFrom(), fieldName, fieldValue); } } } /** * 为delete语句添加where条件 * * @param deleteStatement * @param fieldName * @param fieldValue */ private void addDeleteStatementCondition(SQLDeleteStatement deleteStatement, String fieldName, String fieldValue) { SQLExpr where = deleteStatement.getWhere(); //添加子查询中的where条件 addSQLExprCondition(where, fieldName, fieldValue); SQLExpr newCondition = newEqualityCondition(deleteStatement.getTableName().getSimpleName(), deleteStatement.getTableSource().getAlias(), fieldName, fieldValue, where); deleteStatement.setWhere(newCondition); } /** * where中添加指定筛选条件 * * @param where 源where条件 * @param fieldName * @param fieldValue */ private void addSQLExprCondition(SQLExpr where, String fieldName, String fieldValue) { if (where instanceof SQLInSubQueryExpr) { SQLInSubQueryExpr inWhere = (SQLInSubQueryExpr) where; SQLSelect subSelectObject = inWhere.getSubQuery(); SQLSelectQueryBlock subQueryObject = (SQLSelectQueryBlock) subSelectObject.getQuery(); addSelectStatementCondition(subQueryObject, subQueryObject.getFrom(), fieldName, fieldValue); } else if (where instanceof SQLBinaryOpExpr) { SQLBinaryOpExpr opExpr = (SQLBinaryOpExpr) where; SQLExpr left = opExpr.getLeft(); SQLExpr right = opExpr.getRight(); addSQLExprCondition(left, fieldName, fieldValue); addSQLExprCondition(right, fieldName, fieldValue); } else if (where instanceof SQLQueryExpr) { SQLSelectQueryBlock selectQueryBlock = (SQLSelectQueryBlock) (((SQLQueryExpr) where).getSubQuery()).getQuery(); addSelectStatementCondition(selectQueryBlock, selectQueryBlock.getFrom(), fieldName, fieldValue); } } /** * 为update语句添加where条件 * * @param updateStatement * @param fieldName * @param fieldValue */ private void addUpdateStatementCondition(SQLUpdateStatement updateStatement, String fieldName, String fieldValue) { SQLExpr where = updateStatement.getWhere(); //添加子查询中的where条件 addSQLExprCondition(where, fieldName, fieldValue); SQLExpr newCondition = newEqualityCondition(updateStatement.getTableName().getSimpleName(), updateStatement.getTableSource().getAlias(), fieldName, fieldValue, where); updateStatement.setWhere(newCondition); } /** * 给一个查询对象添加一个where条件 * * @param queryObject * @param fieldName * @param fieldValue */ private void addSelectStatementCondition(SQLSelectQueryBlock queryObject, SQLTableSource from, String fieldName, String fieldValue) { if (StringUtils.isBlank(fieldName) || from == null || queryObject == null) return; SQLExpr originCondition = queryObject.getWhere(); if (from instanceof SQLExprTableSource) { String tableName = ((SQLIdentifierExpr) ((SQLExprTableSource) from).getExpr()).getName(); String alias = from.getAlias(); SQLExpr newCondition = newEqualityCondition(tableName, alias, fieldName, fieldValue, originCondition); queryObject.setWhere(newCondition); } else if (from instanceof SQLJoinTableSource) { SQLJoinTableSource joinObject = (SQLJoinTableSource) from; SQLTableSource left = joinObject.getLeft(); SQLTableSource right = joinObject.getRight(); addSelectStatementCondition(queryObject, left, fieldName, fieldValue); addSelectStatementCondition(queryObject, right, fieldName, fieldValue); } else if (from instanceof SQLSubqueryTableSource) { SQLSelect subSelectObject = ((SQLSubqueryTableSource) from).getSelect(); SQLSelectQueryBlock subQueryObject = (SQLSelectQueryBlock) subSelectObject.getQuery(); addSelectStatementCondition(subQueryObject, subQueryObject.getFrom(), fieldName, fieldValue); } else { throw new NotImplementedException("未处理的异常"); } } /** * 根据原来的condition创建一个新的condition * * @param tableName 表名称 * @param tableAlias 表别名 * @param fieldName * @param fieldValue * @param originCondition * @return */ private SQLExpr newEqualityCondition(String tableName, String tableAlias, String fieldName, String fieldValue, SQLExpr originCondition) { //如果不需要设置条件 if (!conditionDecision.adjudge(tableName, fieldName)) return originCondition; //如果条件字段不允许为空 if (fieldValue == null && !conditionDecision.isAllowNullValue()) return originCondition; String filedName = StringUtils.isBlank(tableAlias) ? fieldName : tableAlias + "." + fieldName; SQLExpr condition = new SQLBinaryOpExpr(new SQLIdentifierExpr(filedName), new SQLCharExpr(fieldValue), SQLBinaryOperator.Equality); return SQLUtils.buildCondition(SQLBinaryOperator.BooleanAnd, condition, false, originCondition); } public static void main(String[] args) { // String sql = "select * from user s "; // String sql = "select * from user s where s.name='333'"; // String sql = "select * from (select * from tab t where id = 2 and name = 'wenshao') s where s.name='333'"; // String sql="select u.*,g.name from user u join user_group g on u.groupId=g.groupId where u.name='123'"; // String sql = "update user set name=? where id =(select id from user s)"; // String sql = "delete from user where id = ( select id from user s )"; // String sql = "insert into user (id,name) select g.id,g.name from user_group g where id=1"; String sql = "select u.*,g.name from user u join (select * from user_group g join user_role r on g.role_code=r.code ) g on u.groupId=g.groupId where u.name='123'"; List<SQLStatement> statementList = SQLUtils.parseStatements(sql, JdbcConstants.POSTGRESQL); SQLStatement sqlStatement = statementList.get(0); //决策器定义 SqlConditionHelper helper = new SqlConditionHelper(new ITableFieldConditionDecision() { @Override public boolean adjudge(String tableName, String fieldName) { return true; } @Override public boolean isAllowNullValue() { return false; } }); //添加多租户条件，domain是字段ignc，yay是筛选值 helper.addStatementCondition(sqlStatement, "domain", "yay"); System.out.println("源sql：" + sql); System.out.println("修改后sql:" + SQLUtils.toSQLString(statementList, JdbcConstants.POSTGRESQL)); } }
因为时间和环境限制，仅仅提供一个基础版本，可能测试不够充分，欢迎提出修正意见。
仅此而已
