Druid LogFilter输出可执行的SQL-编程知识

配置

测试代码：

DruidDataSource dataSource = new DruidDataSource();
dataSource.setUrl("xxx");
dataSource.setUsername("xxx");
dataSource.setPassword("xxx");
dataSource.setFilters("slf4j");
dataSource.setValidationQuery("SELECT 1");
dataSource.setTestOnBorrow(true);
dataSource.setTestWhileIdle(true);Connection connection = dataSource.getConnection();PreparedStatement stmt = connection.prepareStatement("select * from tb_order where id=?");
stmt.setInt(1,1);
stmt.execute();

在配置输出可执行的SQL之前，看下Druid的日志输出：

SQL占位符和参数分开打印

配置输出可执行的SQL

Java启动参数配置方式

-Ddruid.log.stmt.executableSql=true

logFilter参数直接配置：

<bean id="log-filter" class="com.alibaba.druid.filter.logging.Log4jFilter"><property name="statementExecutableSqlLogEnable" value="true" /></bean>

在配置输出可执行的SQL之后，看下Druid的日志输出：

打印出了可执行的SQL

源码

调用栈是DruidPooledPreparedStatement.execute->StatementProxyImpl.execute-> FilterChainImpl.preparedStatement_execute->FilterEventAdapter.preparedStatement_execute（所有Filter都继承了FilterEventAdapter）-> LogFilter.statementExecuteAfter->LogFilter.logExecutableSql。源码如下：

// DruidPooledPreparedStatement.execute
public boolean execute() throws SQLException {checkOpen();incrementExecuteCount();transactionRecord(sql);oracleSetRowPrefetch();conn.beforeExecute();try {//这个stmt是一个StatementProxyImpl实例return stmt.execute();} catch (Throwable t) {errorCheck(t);throw checkException(t);} finally {conn.afterExecute();}
}

StatementProxyImpl.execute：

// StatementProxyImpl.execute
public boolean execute() throws SQLException {updateCount = null;lastExecuteSql = sql;lastExecuteType = StatementExecuteType.Execute;lastExecuteStartNano = -1L;lastExecuteTimeNano = -1L;//调用过滤器链的preparedStatement_executefirstResultSet = createChain().preparedStatement_execute(this);return firstResultSet;
}

FilterChainImpl.preparedStatement_execute：

public boolean preparedStatement_execute(PreparedStatementProxy statement) throws SQLException {if (this.pos < filterSize) {// 调用过滤器的preparedStatement_execute方法return nextFilter().preparedStatement_execute(this, statement);}return statement.getRawObject().execute();
}

所有过滤器都继承了FilterEventAdapter，看名字是个和事件有关的类，这个父类里面实现了preparedStatement_execute方法：

// FilterEventAdapter.preparedStatement_execute
public boolean preparedStatement_execute(FilterChain chain, PreparedStatementProxy statement) throws SQLException {try {statementExecuteBefore(statement, statement.getSql());// 递归调用配置的所有过滤器的preparedStatement_execute方法，直到真正执行完statementboolean firstResult = chain.preparedStatement_execute(statement);// 在执行完statement后执行，这是个空方法，具体的逻辑在子类里面实现，即LogFilterthis.statementExecuteAfter(statement, statement.getSql(), firstResult);return firstResult;} catch (SQLException error) {statement_executeErrorAfter(statement, statement.getSql(), error);throw error;} catch (RuntimeException error) {statement_executeErrorAfter(statement, statement.getSql(), error);throw error;} catch (Error error) {statement_executeErrorAfter(statement, statement.getSql(), error);throw error;}}

LogFilter.statementExecuteAfter方法：

protected void statementExecuteAfter(StatementProxy statement, String sql, boolean firstResult) {// 打印可执行的SQLlogExecutableSql(statement, sql);// 统计SQL执行的时间if (statementExecuteAfterLogEnable && isStatementLogEnabled()) {statement.setLastExecuteTimeNano();double nanos = statement.getLastExecuteTimeNano();double millis = nanos / (1000 * 1000);statementLog("{conn-" + statement.getConnectionProxy().getId() + ", " + stmtId(statement) + "} executed. "+ millis + " millis. " + sql);}
}

LogFilter.logExecutableSql：

private void logExecutableSql(StatementProxy statement, String sql) {// 没有配置输出可执行SQL，直接返回if ((!isStatementExecutableSqlLogEnable()) || !isStatementLogEnabled()) {return;}// 获取SQL参数数量int parametersSize = statement.getParametersSize();if (parametersSize == 0) {statementLog("{conn-" + statement.getConnectionProxy().getId() + ", " + stmtId(statement) + "} executed. "+ sql);return;}// 获取SQL的参数，存到parameters中List<Object> parameters = new ArrayList<Object>(parametersSize);for (int i = 0; i < parametersSize; ++i) {JdbcParameter jdbcParam = statement.getParameter(i);parameters.add(jdbcParam != null? jdbcParam.getValue(): null);}DbType dbType = DbType.of(statement.getConnectionProxy().getDirectDataSource().getDbType());// 最终由SQLUtils根据参数列表和预执行SQL，转换为可执行SQLString formattedSql = SQLUtils.format(sql, dbType, parameters, this.statementSqlFormatOption);// statementLog是个抽象方法，由具体的日志过滤器类实现（如Slf4jLogFilter）statementLog("{conn-" + statement.getConnectionProxy().getId() + ", " + stmtId(statement) + "} executed. "+ formattedSql);
}

总结

输出可执行SQL在日常排查SQL执行错误还是很实用的。其原理是在PreparedStatement.execute执行之后，调用SQLUtils.format打印出可执行的SQL。FilterEventAdapter这个类很关键，它会在SQL执行之前或者之后，调用扩展的处理，具体的处理逻辑又委派给子类实现。

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