mysql 5.1.39
mysql-connector-j 5.1.11
测试代码
public static void main(String[] args) throws Exception { Connection conn = getConnection(); PreparedStatement ps = conn .prepareStatement("select * from test where name=?"); ps.setInt(1, 1); ps.execute(); Statement stmt = conn.createStatement(); stmt.execute("select * from test where name=1"); conn.commit(); conn.close(); } private static Connection getConnection() throws Exception { Class.forName("com.mysql.jdbc.Driver"); Connection conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/db_test?useServerPrepStmts=false", "db_test", "db_test"); conn.setAutoCommit(false); return conn; }
在mysql驱动url中如果设置useServerPrepStmts=false,那么上面两条语句执行时,向服务器发送的数据包一样(用wireshark抓包工具加断点看到)。
如果设置useServerPrepStmts=true,那么执行conn.prepareStatement("select * from test where name=?");语句时,会向服务器发送命令,告知这条语句,执行ps.execute();时则只发送参数和语句编号。此时在服务器端
mysql> show global status like 'Com_stmt%' ;
可以看到 Com_stmt_prepare数量增加。