Php 函数中的PDO try catch用法
我正在考虑在我未来的所有网络应用程序中使用PDO。目前(使用到目前为止我从中学到的知识),我在我的站点中处理数据库连接的是这样一个单例类:Php 函数中的PDO try catch用法,php,pdo,Php,Pdo,我正在考虑在我未来的所有网络应用程序中使用PDO。目前(使用到目前为止我从中学到的知识),我在我的站点中处理数据库连接的是这样一个单例类: class DB { private static $instance = NULL; private static $dsn = "mysql:host=localhost;dbname=mydatabase;"; private static $db_user = 'root'; private static
class DB {
private static $instance = NULL;
private static $dsn = "mysql:host=localhost;dbname=mydatabase;";
private static $db_user = 'root';
private static $db_pass = '0O0ooIl1';
private function __construct()
{
}
private function __clone()
{
}
public static function getInstance() {
if (!self::$instance)
{
self::$instance = new PDO(self::$dsn, self::$db_user, self::$db_pass);
self::$instance-> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
return self::$instance;
}
}
还有另一个文件(functions.php),其中包含特定于内容的函数,看起来与此完全相同:
function get_recent_activities ()
{
try
{
$db = DB::getInstance();
// --prepare and execute query here, fetch the result--
return $my_list_of_recent_activities;
}
catch (PDOException $e)
{
return "some fail-messages";
}
}
...
这意味着我必须重复try。。所有函数中的catch
部分
我的问题是:
try..catch
,但仍然能够在每个函数上返回不同的“失败消息”)如果这看起来不清楚或太长,我很抱歉。提前感谢。这里有几个注意事项:
- 编写此代码是为了考虑一些遗留问题,例如数据库日志记录和数据库配置管理李>
- 我强烈建议您在构建自己的解决方案之前先查看现有的解决方案。很多人一开始会想,他们不想使用现有的框架或库,因为它们太大,需要太多的时间来学习,等等,但是在成为这些人中的一员之后,我无法强调我将离开我的自定义框架和包装类,转而使用框架。我想搬到Zend,但是有很多很好的选择
class DB extends PDO
{
// Allows implementation of the singleton pattern -- ndg 5/24/2008
private static $instance;
// Public static variables for configuring the DB class for a particular database -- ndg 6/16/2008
public static $error_table;
public static $host_name;
public static $db_name;
public static $username;
public static $password;
public static $driver_options;
public static $db_config_path;
function __construct($dsn="", $username="", $password="", $driver_options=array())
{
if(isset(self::$db_config_path))
{
try
{
if(!require_once self::$db_config_path)
{
throw new error('Failed to require file: ' . self::$db_config_path);
}
}
catch(error $e)
{
$e->emailAdmin();
}
}
elseif(isset($_ENV['DB']))
{
self::$db_config_path = 'config.db.php';
try
{
if(!require_once self::$db_config_path)
{
throw new error('Failed to require file: ' . self::$db_config_path);
}
}
catch(error $e)
{
$e->emailAdmin();
}
}
parent::__construct("mysql:host=" . self::$host_name . ";dbname=" .self::$db_name, self::$username, self::$password, self::$driver_options);
$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('QueryStatement', array($this)));
if(!isset(self::$error_table))
{
self::$error_table = 'errorlog_rtab';
}
}
/**
* Return a DB Connection Object
*
* @return DB
*/
public static function connect()
{
// New PDO Connection to be used in NEW development and MAINTENANCE development
try
{
if(!isset(self::$instance))
{
if(!self::$instance = new DB())
{
throw new error('PDO DB Connection failed with error: ' . self::errorInfo());
}
}
return self::$instance;
}
catch(error $e)
{
$e->printErrMsg();
}
}
/**
* Returns a QueryBuilder object which can be used to build dynamic queries
*
* @return QueryBuilder
*
*/
public function createQuery()
{
return new QueryBuilder();
}
public function executeStatement($statement, $params = null, $FETCH_MODE = null)
{
if($FETCH_MODE == 'scalar')
{
return $this->executeScalar($statement, $params);
}
try {
try {
if(!empty($params))
{
$stmt = $this->prepare($statement);
$stmt->execute($params);
}
else
{
$stmt = $this->query($statement);
}
}
catch(PDOException $pdo_error)
{
throw new error("Failed to execute query:\n" . $statement . "\nUsing Parameters:\n" . print_r($params, true) . "\nWith Error:\n" . $pdo_error->getMessage());
}
}
catch(error $e)
{
$this->logDBError($e);
$e->emailAdmin();
return false;
}
try
{
if($FETCH_MODE == 'all')
{
$tmp = $stmt->fetchAll();
}
elseif($FETCH_MODE == 'column')
{
$arr = $stmt->fetchAll();
foreach($arr as $key => $val)
{
foreach($val as $var => $value)
{
$tmp[] = $value;
}
}
}
elseif($FETCH_MODE == 'row')
{
$tmp = $stmt->fetch();
}
elseif(empty($FETCH_MODE))
{
return true;
}
}
catch(PDOException $pdoError)
{
return true;
}
$stmt->closeCursor();
return $tmp;
}
public function executeScalar($statement, $params = null)
{
$stmt = $this->prepare($statement);
if(!empty($this->bound_params) && empty($params))
{
$params = $this->bound_params;
}
try {
try {
if(!empty($params))
{
$stmt->execute($params);
}
else
{
$stmt = $this->query($statement);
}
}
catch(PDOException $pdo_error)
{
throw new error("Failed to execute query:\n" . $statement . "\nUsing Parameters:\n" . print_r($params, true) . "\nWith Error:\n" . $pdo_error->getMessage());
}
}
catch(error $e)
{
$this->logDBError($e);
$e->emailAdmin();
}
$count = $stmt->fetchColumn();
$stmt->closeCursor();
//echo $count;
return $count;
}
protected function logDBError($e)
{
$error = $e->getErrorReport();
$sql = "
INSERT INTO " . self::$error_table . " (message, time_date)
VALUES (:error, NOW())";
$this->executeStatement($sql, array(':error' => $error));
}
}
class QueryStatement extends PDOStatement
{
public $conn;
protected function __construct()
{
$this->conn = DB::connect();
$this->setFetchMode(PDO::FETCH_ASSOC);
}
public function execute($bound_params = null)
{
return parent::execute($bound_params);
}
}
您的实现很好,在大多数情况下都能很好地工作 没有必要将每个查询都放在try/catch块中,事实上,在大多数情况下,您实际上不想这样做。原因是,如果查询生成异常,它是致命问题(如语法错误或数据库问题)的结果,而这些问题不应在您执行的每个查询中进行说明 例如:
try {
$rs = $db->prepare('SELECT * FROM foo');
$rs->execute();
$foo = $rs->fetchAll();
} catch (Exception $e) {
die("Oh noes! There's an error in the query!");
}
// We're handling a file upload here.
try {
$rs = $db->prepare('INSERT INTO files (fileID, filename) VALUES (?, ?)');
$rs->execute(array(1234, '/var/tmp/file1234.txt'));
} catch (Exception $e) {
unlink('/var/tmp/file1234.txt');
throw $e;
}
这里的查询要么正常工作,要么根本不工作。它根本不起作用的情况不应该在生产系统中有任何规律地发生,因此它们不是您应该在这里检查的条件。这样做实际上会适得其反,因为您的用户会收到一个永远不会更改的错误,并且您不会收到一条异常消息来提醒您这个问题
相反,只需写下以下内容:
$rs = $db->prepare('SELECT * FROM foo');
$rs->execute();
$foo = $rs->fetchAll();
通常,您希望捕获和处理查询异常的唯一时间是,如果查询失败,您希望执行其他操作。例如:
try {
$rs = $db->prepare('SELECT * FROM foo');
$rs->execute();
$foo = $rs->fetchAll();
} catch (Exception $e) {
die("Oh noes! There's an error in the query!");
}
// We're handling a file upload here.
try {
$rs = $db->prepare('INSERT INTO files (fileID, filename) VALUES (?, ?)');
$rs->execute(array(1234, '/var/tmp/file1234.txt'));
} catch (Exception $e) {
unlink('/var/tmp/file1234.txt');
throw $e;
}
您需要编写一个简单的异常处理程序,记录或通知生产环境中发生的数据库错误,并向用户显示友好的错误消息,而不是异常跟踪。有关如何执行此操作的信息,请参阅。要了解pd所说的内容,我使用自定义错误类只是将错误记录到db并向我发送电子邮件。最终用户从未看到堆栈跟踪或其他不友好的情况。这就是为什么如果出现错误,我会返回false,然后测试查询的返回值,以确定如果您更改了SELECT和/或其他查询更改了数据库,使SELECT不再起作用,那么应该告诉用户什么:在您自己测试页面之前,您永远不会知道这一点。这会适得其反。每个查询都需要try/catch!