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本文次要钻研一下ShardingSphere进行sql重写的原理
prepareStatement
org/apache/shardingsphere/driver/jdbc/core/connection/ShardingSphereConnection.java
public final class ShardingSphereConnection extends AbstractConnectionAdapter { @Override public PreparedStatement prepareStatement(final String sql) throws SQLException { return new ShardingSpherePreparedStatement(this, sql); } //......} ShardingSphereConnection的prepareStatement创立的是ShardingSpherePreparedStatement
ShardingSpherePreparedStatement
org/apache/shardingsphere/driver/jdbc/core/statement/ShardingSpherePreparedStatement.java
public final class ShardingSpherePreparedStatement extends AbstractPreparedStatementAdapter { @Getter private final ShardingSphereConnection connection; public ShardingSpherePreparedStatement(final ShardingSphereConnection connection, final String sql) throws SQLException { this(connection, sql, ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY, ResultSet.HOLD_CURSORS_OVER_COMMIT, false, null); } private ShardingSpherePreparedStatement(final ShardingSphereConnection connection, final String sql, final int resultSetType, final int resultSetConcurrency, final int resultSetHoldability, final boolean returnGeneratedKeys, final String[] columns) throws SQLException { if (Strings.isNullOrEmpty(sql)) { throw new EmptySQLException().toSQLException(); } this.connection = connection; metaDataContexts = connection.getContextManager().getMetaDataContexts(); SQLParserRule sqlParserRule = metaDataContexts.getMetaData().getGlobalRuleMetaData().getSingleRule(SQLParserRule.class); hintValueContext = sqlParserRule.isSqlCommentParseEnabled() ? new HintValueContext() : SQLHintUtils.extractHint(sql).orElseGet(HintValueContext::new); this.sql = sqlParserRule.isSqlCommentParseEnabled() ? sql : SQLHintUtils.removeHint(sql); statements = new ArrayList<>(); parameterSets = new ArrayList<>(); SQLParserEngine sqlParserEngine = sqlParserRule.getSQLParserEngine( DatabaseTypeEngine.getTrunkDatabaseTypeName(metaDataContexts.getMetaData().getDatabase(connection.getDatabaseName()).getProtocolType())); sqlStatement = sqlParserEngine.parse(this.sql, true); sqlStatementContext = SQLStatementContextFactory.newInstance(metaDataContexts.getMetaData(), sqlStatement, connection.getDatabaseName()); parameterMetaData = new ShardingSphereParameterMetaData(sqlStatement); statementOption = returnGeneratedKeys ? new StatementOption(true, columns) : new StatementOption(resultSetType, resultSetConcurrency, resultSetHoldability); executor = new DriverExecutor(connection); JDBCExecutor jdbcExecutor = new JDBCExecutor(connection.getContextManager().getExecutorEngine(), connection.getDatabaseConnectionManager().getConnectionContext()); batchPreparedStatementExecutor = new BatchPreparedStatementExecutor(metaDataContexts, jdbcExecutor, connection.getDatabaseName()); kernelProcessor = new KernelProcessor(); statementsCacheable = isStatementsCacheable(metaDataContexts.getMetaData().getDatabase(connection.getDatabaseName()).getRuleMetaData()); trafficRule = metaDataContexts.getMetaData().getGlobalRuleMetaData().getSingleRule(TrafficRule.class); selectContainsEnhancedTable = sqlStatementContext instanceof SelectStatementContext && ((SelectStatementContext) sqlStatementContext).isContainsEnhancedTable(); statementManager = new StatementManager(); } //......} ShardingSpherePreparedStatement继承了AbstractPreparedStatementAdapter，其结构器次要是通过SQLParserEngine解析sql失去SQLStatement，创立DriverExecutor、BatchPreparedStatementExecutor、KernelProcessor、StatementManager；这里即便useServerPrepStmts=true，也不会触发mysql server的prepare操作
executeUpdate
public int executeUpdate() throws SQLException { try { if (statementsCacheable && !statements.isEmpty()) { resetParameters(); return statements.iterator().next().executeUpdate(); } clearPrevious(); QueryContext queryContext = createQueryContext(); trafficInstanceId = getInstanceIdAndSet(queryContext).orElse(null); if (null != trafficInstanceId) { JDBCExecutionUnit executionUnit = createTrafficExecutionUnit(trafficInstanceId, queryContext); return executor.getTrafficExecutor().execute(executionUnit, (statement, sql) -> ((PreparedStatement) statement).executeUpdate()); } executionContext = createExecutionContext(queryContext); if (hasRawExecutionRule()) { Collection<ExecuteResult> executeResults = executor.getRawExecutor().execute(createRawExecutionGroupContext(), executionContext.getQueryContext(), new RawSQLExecutorCallback()); return accumulate(executeResults); } return isNeedImplicitCommitTransaction(connection, executionContext) ? executeUpdateWithImplicitCommitTransaction() : useDriverToExecuteUpdate(); // CHECKSTYLE:OFF } catch (final RuntimeException ex) { // CHECKSTYLE:ON handleExceptionInTransaction(connection, metaDataContexts); throw SQLExceptionTransformEngine.toSQLException(ex, metaDataContexts.getMetaData().getDatabase(connection.getDatabaseName()).getProtocolType().getType()); } finally { clearBatch(); } } private void clearPrevious() { statements.clear(); parameterSets.clear(); generatedValues.clear(); } private ExecutionContext createExecutionContext(final QueryContext queryContext) { ShardingSphereRuleMetaData globalRuleMetaData = metaDataContexts.getMetaData().getGlobalRuleMetaData(); ShardingSphereDatabase currentDatabase = metaDataContexts.getMetaData().getDatabase(connection.getDatabaseName()); SQLAuditEngine.audit(queryContext.getSqlStatementContext(), queryContext.getParameters(), globalRuleMetaData, currentDatabase, null, queryContext.getHintValueContext()); ExecutionContext result = kernelProcessor.generateExecutionContext( queryContext, currentDatabase, globalRuleMetaData, metaDataContexts.getMetaData().getProps(), connection.getDatabaseConnectionManager().getConnectionContext()); findGeneratedKey(result).ifPresent(optional -> generatedValues.addAll(optional.getGeneratedValues())); return result; }这里executeUpdate会先执行clearPrevious办法，清空statements、parameterSets、generatedValues，而后createExecutionContext，这里有一步是kernelProcessor.generateExecutionContext
KernelProcessor
generateExecutionContext
shardingsphere-infra-context-5.4.0-sources.jar!/org/apache/shardingsphere/infra/connection/kernel/KernelProcessor.java
public ExecutionContext generateExecutionContext(final QueryContext queryContext, final ShardingSphereDatabase database, final ShardingSphereRuleMetaData globalRuleMetaData, final ConfigurationProperties props, final ConnectionContext connectionContext) { RouteContext routeContext = route(queryContext, database, globalRuleMetaData, props, connectionContext); SQLRewriteResult rewriteResult = rewrite(queryContext, database, globalRuleMetaData, props, routeContext, connectionContext); ExecutionContext result = createExecutionContext(queryContext, database, routeContext, rewriteResult); logSQL(queryContext, props, result); return result; }KernelProcessor的generateExecutionContext办法先创立routeContext，而后执行rewrite，最初执行createExecutionContext
rewrite
private SQLRewriteResult rewrite(final QueryContext queryContext, final ShardingSphereDatabase database, final ShardingSphereRuleMetaData globalRuleMetaData, final ConfigurationProperties props, final RouteContext routeContext, final ConnectionContext connectionContext) { SQLRewriteEntry sqlRewriteEntry = new SQLRewriteEntry(database, globalRuleMetaData, props); return sqlRewriteEntry.rewrite(queryContext.getSql(), queryContext.getParameters(), queryContext.getSqlStatementContext(), routeContext, connectionContext, queryContext.getHintValueContext()); }rewrite次要是通过SQLRewriteEntry的rewrite办法进行的
SQLRewriteEntry
shardingsphere-infra-rewrite-5.4.0-sources.jar!/org/apache/shardingsphere/infra/rewrite/SQLRewriteEntry.java
/** * Rewrite. * * @param sql SQL * @param params SQL parameters * @param sqlStatementContext SQL statement context * @param routeContext route context * @param connectionContext connection context * @param hintValueContext hint value context * * @return route unit and SQL rewrite result map */ public SQLRewriteResult rewrite(final String sql, final List<Object> params, final SQLStatementContext sqlStatementContext, final RouteContext routeContext, final ConnectionContext connectionContext, final HintValueContext hintValueContext) { SQLRewriteContext sqlRewriteContext = createSQLRewriteContext(sql, params, sqlStatementContext, routeContext, connectionContext, hintValueContext); SQLTranslatorRule rule = globalRuleMetaData.getSingleRule(SQLTranslatorRule.class); DatabaseType protocolType = database.getProtocolType(); Map<String, DatabaseType> storageTypes = database.getResourceMetaData().getStorageTypes(); return routeContext.getRouteUnits().isEmpty() ? new GenericSQLRewriteEngine(rule, protocolType, storageTypes).rewrite(sqlRewriteContext) : new RouteSQLRewriteEngine(rule, protocolType, storageTypes).rewrite(sqlRewriteContext, routeContext); } private SQLRewriteContext createSQLRewriteContext(final String sql, final List<Object> params, final SQLStatementContext sqlStatementContext, final RouteContext routeContext, final ConnectionContext connectionContext, final HintValueContext hintValueContext) { SQLRewriteContext result = new SQLRewriteContext(database.getName(), database.getSchemas(), sqlStatementContext, sql, params, connectionContext, hintValueContext); decorate(decorators, result, routeContext, hintValueContext); result.generateSQLTokens(); return result; } private void decorate(final Map<ShardingSphereRule, SQLRewriteContextDecorator> decorators, final SQLRewriteContext sqlRewriteContext, final RouteContext routeContext, final HintValueContext hintValueContext) { if (hintValueContext.isSkipSQLRewrite()) { return; } for (Entry<ShardingSphereRule, SQLRewriteContextDecorator> entry : decorators.entrySet()) { entry.getValue().decorate(entry.getKey(), props, sqlRewriteContext, routeContext); } }SQLRewriteEntry的rewrite办法，先通过createSQLRewriteContext来创立SQLRewriteContext，这里通过decorate办法遍历decorators，挨个执行SQLRewriteContextDecorator的decorate办法；最初通过GenericSQLRewriteEngine或者RouteSQLRewriteEngine进行rewrite
SQLRewriteContextDecorator
org/apache/shardingsphere/infra/rewrite/context/SQLRewriteContextDecorator.java
@SingletonSPIpublic interface SQLRewriteContextDecorator<T extends ShardingSphereRule> extends OrderedSPI<T> { /** * Decorate SQL rewrite context. * * @param rule rule * @param props ShardingSphere properties * @param sqlRewriteContext SQL rewrite context to be decorated * @param routeContext route context */ void decorate(T rule, ConfigurationProperties props, SQLRewriteContext sqlRewriteContext, RouteContext routeContext);}SQLRewriteContextDecorator定义了decorate办法，它有诸如ShardingSQLRewriteContextDecorator、EncryptSQLRewriteContextDecorator的实现类
EncryptSQLRewriteContextDecorator
org/apache/shardingsphere/encrypt/rewrite/context/EncryptSQLRewriteContextDecorator.java
/** * SQL rewrite context decorator for encrypt. */public final class EncryptSQLRewriteContextDecorator implements SQLRewriteContextDecorator<EncryptRule> { @Override public void decorate(final EncryptRule encryptRule, final ConfigurationProperties props, final SQLRewriteContext sqlRewriteContext, final RouteContext routeContext) { SQLStatementContext sqlStatementContext = sqlRewriteContext.getSqlStatementContext(); if (!containsEncryptTable(encryptRule, sqlStatementContext)) { return; } Collection<EncryptCondition> encryptConditions = createEncryptConditions(encryptRule, sqlRewriteContext); if (!sqlRewriteContext.getParameters().isEmpty()) { Collection<ParameterRewriter> parameterRewriters = new EncryptParameterRewriterBuilder(encryptRule, sqlRewriteContext.getDatabaseName(), sqlRewriteContext.getSchemas(), sqlStatementContext, encryptConditions).getParameterRewriters(); rewriteParameters(sqlRewriteContext, parameterRewriters); } Collection<SQLTokenGenerator> sqlTokenGenerators = new EncryptTokenGenerateBuilder(encryptRule, sqlStatementContext, encryptConditions, sqlRewriteContext.getDatabaseName()).getSQLTokenGenerators(); sqlRewriteContext.addSQLTokenGenerators(sqlTokenGenerators); } private Collection<EncryptCondition> createEncryptConditions(final EncryptRule encryptRule, final SQLRewriteContext sqlRewriteContext) { SQLStatementContext sqlStatementContext = sqlRewriteContext.getSqlStatementContext(); if (!(sqlStatementContext instanceof WhereAvailable)) { return Collections.emptyList(); } Collection<WhereSegment> whereSegments = ((WhereAvailable) sqlStatementContext).getWhereSegments(); Collection<ColumnSegment> columnSegments = ((WhereAvailable) sqlStatementContext).getColumnSegments(); return new EncryptConditionEngine(encryptRule, sqlRewriteContext.getSchemas()) .createEncryptConditions(whereSegments, columnSegments, sqlStatementContext, sqlRewriteContext.getDatabaseName()); } private boolean containsEncryptTable(final EncryptRule encryptRule, final SQLStatementContext sqlStatementContext) { for (String each : sqlStatementContext.getTablesContext().getTableNames()) { if (encryptRule.findEncryptTable(each).isPresent()) { return true; } } return false; } private void rewriteParameters(final SQLRewriteContext sqlRewriteContext, final Collection<ParameterRewriter> parameterRewriters) { for (ParameterRewriter each : parameterRewriters) { each.rewrite(sqlRewriteContext.getParameterBuilder(), sqlRewriteContext.getSqlStatementContext(), sqlRewriteContext.getParameters()); } } @Override public int getOrder() { return EncryptOrder.ORDER; } @Override public Class<EncryptRule> getTypeClass() { return EncryptRule.class; }}rewriteParameters是通过ParameterRewriter进行rewrite，次要是批改ParameterBuilder；而具体sql语句的批改则通过sqlTokenGenerators进行
SQLToken
@RequiredArgsConstructor@Getterpublic abstract class SQLToken implements Comparable<SQLToken> { private final int startIndex; @Override public final int compareTo(final SQLToken sqlToken) { return startIndex - sqlToken.startIndex; }}SQLToken它有诸如InsertValuesToken、SubstitutableColumnNameToken、InsertColumnsToken之类的实现类
RouteSQLRewriteEngine
/** * Rewrite SQL and parameters. * * @param sqlRewriteContext SQL rewrite context * @param routeContext route context * @return SQL rewrite result */ public RouteSQLRewriteResult rewrite(final SQLRewriteContext sqlRewriteContext, final RouteContext routeContext) { Map<RouteUnit, SQLRewriteUnit> sqlRewriteUnits = new LinkedHashMap<>(routeContext.getRouteUnits().size(), 1F); for (Entry<String, Collection<RouteUnit>> entry : aggregateRouteUnitGroups(routeContext.getRouteUnits()).entrySet()) { Collection<RouteUnit> routeUnits = entry.getValue(); if (isNeedAggregateRewrite(sqlRewriteContext.getSqlStatementContext(), routeUnits)) { sqlRewriteUnits.put(routeUnits.iterator().next(), createSQLRewriteUnit(sqlRewriteContext, routeContext, routeUnits)); } else { addSQLRewriteUnits(sqlRewriteUnits, sqlRewriteContext, routeContext, routeUnits); } } return new RouteSQLRewriteResult(translate(sqlRewriteContext.getSqlStatementContext().getSqlStatement(), sqlRewriteUnits)); } private void addSQLRewriteUnits(final Map<RouteUnit, SQLRewriteUnit> sqlRewriteUnits, final SQLRewriteContext sqlRewriteContext, final RouteContext routeContext, final Collection<RouteUnit> routeUnits) { for (RouteUnit each : routeUnits) { sqlRewriteUnits.put(each, new SQLRewriteUnit(new RouteSQLBuilder(sqlRewriteContext, each).toSQL(), getParameters(sqlRewriteContext.getParameterBuilder(), routeContext, each))); } } private Map<RouteUnit, SQLRewriteUnit> translate(final SQLStatement sqlStatement, final Map<RouteUnit, SQLRewriteUnit> sqlRewriteUnits) { Map<RouteUnit, SQLRewriteUnit> result = new LinkedHashMap<>(sqlRewriteUnits.size(), 1F); for (Entry<RouteUnit, SQLRewriteUnit> entry : sqlRewriteUnits.entrySet()) { DatabaseType storageType = storageTypes.get(entry.getKey().getDataSourceMapper().getActualName()); String sql = translatorRule.translate(entry.getValue().getSql(), sqlStatement, protocolType, storageType); SQLRewriteUnit sqlRewriteUnit = new SQLRewriteUnit(sql, entry.getValue().getParameters()); result.put(entry.getKey(), sqlRewriteUnit); } return result; }addSQLRewriteUnits是往sqlRewriteUnits增加SQLRewriteUnit，最初translate办法构建SQLRewriteUnit；SQLRewriteUnit蕴含了更改之后的sql以及对应改变后的参数
useDriverToExecuteUpdate
org/apache/shardingsphere/driver/jdbc/core/statement/ShardingSpherePreparedStatement.java
private int useDriverToExecuteUpdate() throws SQLException { ExecutionGroupContext<JDBCExecutionUnit> executionGroupContext = createExecutionGroupContext(); cacheStatements(executionGroupContext.getInputGroups()); return executor.getRegularExecutor().executeUpdate(executionGroupContext, executionContext.getQueryContext(), executionContext.getRouteContext().getRouteUnits(), createExecuteUpdateCallback()); } private ExecutionGroupContext<JDBCExecutionUnit> createExecutionGroupContext() throws SQLException { DriverExecutionPrepareEngine<JDBCExecutionUnit, Connection> prepareEngine = createDriverExecutionPrepareEngine(); return prepareEngine.prepare(executionContext.getRouteContext(), executionContext.getExecutionUnits(), new ExecutionGroupReportContext(connection.getDatabaseName())); } private void cacheStatements(final Collection<ExecutionGroup<JDBCExecutionUnit>> executionGroups) throws SQLException { for (ExecutionGroup<JDBCExecutionUnit> each : executionGroups) { each.getInputs().forEach(eachInput -> { statements.add((PreparedStatement) eachInput.getStorageResource()); parameterSets.add(eachInput.getExecutionUnit().getSqlUnit().getParameters()); }); } replay(); } private void replay() throws SQLException { replaySetParameter(); for (Statement each : statements) { getMethodInvocationRecorder().replay(each); } } private void replaySetParameter() throws SQLException { for (int i = 0; i < statements.size(); i++) { replaySetParameter(statements.get(i), parameterSets.get(i)); } } protected final void replaySetParameter(final PreparedStatement preparedStatement, final List<Object> params) throws SQLException { setParameterMethodInvocations.clear(); addParameters(params); for (PreparedStatementInvocationReplayer each : setParameterMethodInvocations) { each.replayOn(preparedStatement); } } private void addParameters(final List<Object> params) { int i = 0; for (Object each : params) { int index = ++i; setParameterMethodInvocations.add(preparedStatement -> preparedStatement.setObject(index, each)); } }useDriverToExecuteUpdate办法会执行createExecutionGroupContext(会执行prepare办法)，cacheStatements这里次要是把eachInput.getStorageResource()真正的PrepareStatement赋值到ShardingSpherePreparedStatement的statements变量中，把eachInput.getExecutionUnit().getSqlUnit().getParameters()赋值到parameterSets，而后执行replay办法通过PreparedStatementInvocationReplayer把批改后的变量replay到真正的PrepareStatement
该办法委托给executor.getRegularExecutor().executeUpdate，最初一个参数为callback，即createExecuteUpdateCallback
DriverExecutionPrepareEngine.prepare
org/apache/shardingsphere/infra/executor/sql/prepare/AbstractExecutionPrepareEngine.java
public final ExecutionGroupContext<T> prepare(final RouteContext routeContext, final Collection<ExecutionUnit> executionUnits, final ExecutionGroupReportContext reportContext) throws SQLException { return prepare(routeContext, Collections.emptyMap(), executionUnits, reportContext); } public final ExecutionGroupContext<T> prepare(final RouteContext routeContext, final Map<String, Integer> connectionOffsets, final Collection<ExecutionUnit> executionUnits, final ExecutionGroupReportContext reportContext) throws SQLException { Collection<ExecutionGroup<T>> result = new LinkedList<>(); for (Entry<String, List<SQLUnit>> entry : aggregateSQLUnitGroups(executionUnits).entrySet()) { String dataSourceName = entry.getKey(); List<SQLUnit> sqlUnits = entry.getValue(); List<List<SQLUnit>> sqlUnitGroups = group(sqlUnits); ConnectionMode connectionMode = maxConnectionsSizePerQuery < sqlUnits.size() ? ConnectionMode.CONNECTION_STRICTLY : ConnectionMode.MEMORY_STRICTLY; result.addAll(group(dataSourceName, connectionOffsets.getOrDefault(dataSourceName, 0), sqlUnitGroups, connectionMode)); } return decorate(routeContext, result, reportContext); } protected List<ExecutionGroup<T>> group(final String dataSourceName, final int connectionOffset, final List<List<SQLUnit>> sqlUnitGroups, final ConnectionMode connectionMode) throws SQLException { List<ExecutionGroup<T>> result = new LinkedList<>(); List<C> connections = databaseConnectionManager.getConnections(dataSourceName, connectionOffset, sqlUnitGroups.size(), connectionMode); int count = 0; for (List<SQLUnit> each : sqlUnitGroups) { result.add(createExecutionGroup(dataSourceName, each, connections.get(count++), connectionMode)); } return result; } private ExecutionGroup<T> createExecutionGroup(final String dataSourceName, final List<SQLUnit> sqlUnits, final C connection, final ConnectionMode connectionMode) throws SQLException { List<T> result = new LinkedList<>(); for (SQLUnit each : sqlUnits) { result.add((T) sqlExecutionUnitBuilder.build(new ExecutionUnit(dataSourceName, each), statementManager, connection, connectionMode, option, databaseTypes.get(dataSourceName))); } return new ExecutionGroup<>(result); }group办法调用遍历SQLUnit执行createExecutionGroup，而后者则执行sqlExecutionUnitBuilder.build；这里databaseConnectionManager.getConnections获取的connection是通过真正driver获取的connection(com.mysql.jdbc.Driver)PreparedStatementExecutionUnitBuilder
org/apache/shardingsphere/infra/executor/sql/prepare/driver/jdbc/builder/PreparedStatementExecutionUnitBuilder.java
public JDBCExecutionUnit build(final ExecutionUnit executionUnit, final ExecutorJDBCStatementManager statementManager, final Connection connection, final ConnectionMode connectionMode, final StatementOption option, final DatabaseType databaseType) throws SQLException { PreparedStatement preparedStatement = createPreparedStatement( executionUnit, statementManager, connection, connectionMode, option, databaseType); return new JDBCExecutionUnit(executionUnit, connectionMode, preparedStatement); } private PreparedStatement createPreparedStatement(final ExecutionUnit executionUnit, final ExecutorJDBCStatementManager statementManager, final Connection connection, final ConnectionMode connectionMode, final StatementOption option, final DatabaseType databaseType) throws SQLException { return (PreparedStatement) statementManager.createStorageResource(executionUnit, connection, connectionMode, option, databaseType); }PreparedStatementExecutionUnitBuilder的build办法这里才真正创立PreparedStatement
StatementManager
org/apache/shardingsphere/driver/jdbc/core/statement/StatementManager.java
public Statement createStorageResource(final ExecutionUnit executionUnit, final Connection connection, final ConnectionMode connectionMode, final StatementOption option, final DatabaseType databaseType) throws SQLException { Statement result = cachedStatements.get(new CacheKey(executionUnit, connectionMode)); if (null == result || result.isClosed() || result.getConnection().isClosed()) { String sql = executionUnit.getSqlUnit().getSql(); if (option.isReturnGeneratedKeys()) { result = null == option.getColumns() || 0 == option.getColumns().length ? connection.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS) : connection.prepareStatement(sql, option.getColumns()); } else { result = connection.prepareStatement(sql, option.getResultSetType(), option.getResultSetConcurrency(), option.getResultSetHoldability()); } cachedStatements.put(new CacheKey(executionUnit, connectionMode), result); } return result; }createStorageResource则是通过connection.prepareStatement来创立真正的PrepareStatement，而此时传入的sql也是通过重写之后的sql
createExecuteUpdateCallback
org/apache/shardingsphere/driver/jdbc/core/statement/ShardingSpherePreparedStatement.java
private JDBCExecutorCallback<Integer> createExecuteUpdateCallback() { boolean isExceptionThrown = SQLExecutorExceptionHandler.isExceptionThrown(); return new JDBCExecutorCallback<Integer>(metaDataContexts.getMetaData().getDatabase(connection.getDatabaseName()).getProtocolType(), metaDataContexts.getMetaData().getDatabase(connection.getDatabaseName()).getResourceMetaData().getStorageTypes(), sqlStatement, isExceptionThrown) { @Override protected Integer executeSQL(final String sql, final Statement statement, final ConnectionMode connectionMode, final DatabaseType storageType) throws SQLException { return ((PreparedStatement) statement).executeUpdate(); } @Override protected Optional<Integer> getSaneResult(final SQLStatement sqlStatement, final SQLException ex) { return Optional.empty(); } }; }createExecuteUpdateCallback创立的JDBCExecutorCallback，其executeSQL办法则是通过((PreparedStatement) statement).executeUpdate()来执行，即委托给了真正的PreparedStatement
小结
- ShardingSphereConnection的prepareStatement创立的是ShardingSpherePreparedStatement，它在ShardingSpherePreparedStatement的executeUpdate的时候进行sql重写，而后prepare，最初执行的时候是通过JDBCExecutorCallback，其executeSQL办法则是通过((PreparedStatement) statement).executeUpdate()来执行，即委托给了真正的PreparedStatement
- rewriteParameters是通过ParameterRewriter进行rewrite，次要是批改ParameterBuilder；而具体sql语句的批改则通过sqlTokenGenerators进行
- PreparedStatementExecutionUnitBuilder的build办法这里才真正创立PreparedStatement：它通过StatementManager.createStorageResource则是通过connection.prepareStatement来创立真正的PrepareStatement，而此时传入的sql也是通过重写之后的sql
useDriverToExecuteUpdate办法会执行createExecutionGroupContext(
会执行prepare办法)，cacheStatements这里次要是把eachInput.getStorageResource()真正的PrepareStatement赋值到ShardingSpherePreparedStatement的statements变量中，把eachInput.getExecutionUnit().getSqlUnit().getParameters()赋值到parameterSets，而后执行replay办法通过PreparedStatementInvocationReplayer把批改后的变量replay到真正的PrepareStatementShardingSpherePreparedStatement实现了java.sql.PreparedStatement接口，其sql属性是用户传入的sql，即未通过重写的sql，而理论execute的时候，会触发sql重写(包含重写sql语句及参数)，最初会通过connection.prepareStatement(传入重写之后的sql)来创立真正的PrepareStatement，而后有一步replay操作，把重写后的参数作用到真正的PrepareStatement，最初通过((PreparedStatement) statement).executeUpdate()来触发执行
至此咱们能够失去sql重写的一个基本思路：通过实现java.sql.PreparedStatement接口假装一个PreparedStatement类，其创立和set参数先内存缓存起来，之后在execute的时候进行sql重写，创立真正的PreparedStatement，replay参数，执行execute办法