Typecho_Db
Typecho 没有 Model 层，采用自建的 DB 类帮助开发者快速获取自己需要的数据。
一、初始化数据库
config.inc.php
# 这里的配置文件只作为参考，可能和你自己的配置文件有出入。
$db = new Typecho_Db('Pdo_Mysql', 'typecho_');
$db->addServer(array (
'host' => 'localhost',
'user' => 'username',
'charset' => 'utf8',
'port' => 'password',
'database' => 'typecho',
), Typecho_Db::READ | Typecho_Db::WRITE);
Typecho_Db::set($db);
typecho/var/Typecho/Db.php
class Typecho_Db
{
private static $_instance;
public function __construct($adapterName, $prefix = 'typecho_')
{
/** 获取适配器名称 */
$this->_adapterName = $adapterName;
/** 数据库适配器 */
$adapterName = 'Typecho_Db_Adapter_' . $adapterName;
if (!call_user_func(array($adapterName, 'isAvailable'))) {
throw new Typecho_Db_Exception("Adapter {$adapterName} is not available");
}
$this->_prefix = $prefix;
/** 初始化内部变量 */
$this->_pool = array();
$this->_connectedPool = array();
$this->_config = array();
//实例化适配器对象
$this->_adapter = new $adapterName();
}
public function addServer($config, $op)
{
$this->_config[] = Typecho_Config::factory($config);
$key = count($this->_config) - 1;
/** 将连接放入池中 */
switch ($op) {
case self::READ:
case self::WRITE:
$this->_pool[$op][] = $key;
break;
default:
$this->_pool[self::READ][] = $key;
$this->_pool[self::WRITE][] = $key;
break;
}
}
public static function get()
{
if (empty(self::$_instance)) {
/** Typecho_Db_Exception */
throw new Typecho_Db_Exception('Missing Database Object');
}
return self::$_instance;
}
public static function set(Typecho_Db $db)
{
self::$_instance = $db;
}
}
代码分析：
1. 初始化内部变量（$this->_pool, $this->_connectedPool、$this->_config）和实例化适配器对象,这里的适配器对象为：Typecho_Db_Adapter_Pdo_Mysql（$this->_adapter）。
2. 添加配置信息到 $this->_config 中。然后，将配置信息在 $this->_config 中的 key 保存到对应的连接池中。（这里假设数据库操作为读，$this->_pool[self::READ][] = $key）
3. 最后，将实例化后的 Typecho_Db 对象保存在 Typecho_Db::$_instance 中。
备注：上面的 $this 指的是 Typecho_Db 实例对象
二、Typecho如何实现数据库查询
$db = Typecho_Db::get();
$select = $db->select()->from("table.options")->where("user = 0");
$result = $db->fetchAll($select);
class Typecho_Db
{
private static $_instance;
public static function get()
{
if (empty(self::$_instance)) {
/** Typecho_Db_Exception */
throw new Typecho_Db_Exception('Missing Database Object');
}
return self::$_instance;
}
public function sql()
{
return new Typecho_Db_Query($this->_adapter, $this->_prefix);
}
public function select()
{
$args = func_get_args();
return call_user_func_array(array($this->sql(), 'select'), $args ? $args : array('*'));
}
public function query($query, $op = self::READ, $action = self::SELECT)
{
/** 在适配器中执行查询 */
if ($query instanceof Typecho_Db_Query) {
$action = $query->getAttribute('action');
$op = (self::UPDATE == $action || self::DELETE == $action
|| self::INSERT == $action) ? self::WRITE : self::READ;
} else if (!is_string($query)) {
/** 如果query不是对象也不是字符串,那么将其判断为查询资源句柄,直接返回 */
return $query;
}
/** 选择连接池 */
$handle = $this->selectDb($op);
/** 提交查询 */
$resource = $this->_adapter->query($query, $handle, $op, $action);
if ($action) {
//根据查询动作返回相应资源
switch ($action) {
case self::UPDATE:
case self::DELETE:
return $this->_adapter->affectedRows($resource, $handle);
case self::INSERT:
return $this->_adapter->lastInsertId($resource, $handle);
case self::SELECT:
default:
return $resource;
}
} else {
//如果直接执行查询语句则返回资源
return $resource;
}
}
public function selectDb($op)
{
if (!isset($this->_connectedPool[$op])) {
if (empty($this->_pool[$op])) {
/** Typecho_Db_Exception */
throw new Typecho_Db_Exception('Missing Database Connection');
}
//获取相应读或写服务器连接池中的一个
$selectConnection = rand(0, count($this->_pool[$op]) - 1);
//获取随机获得的连接池配置
$selectConnectionConfig = $this->_config[$this->_pool[$op][$selectConnection]];
$selectConnectionHandle = $this->_adapter->connect($selectConnectionConfig);
$this->_connectedPool[$op] = &$selectConnectionHandle;
}
return $this->_connectedPool[$op];
}
public function fetchAll($query, array $filter = NULL)
{
//执行查询
$resource = $this->query($query, self::READ);
$result = array();
/** 取出过滤器 */
if (!empty($filter)) {
list($object, $method) = $filter;
}
//取出每一行
while ($rows = $this->_adapter->fetch($resource)) {
//判断是否有过滤器
$result[] = $filter ? call_user_func(array(&$object, $method), $rows) : $rows;
}
return $result;
}
}
class Typecho_Db_Query
{
public function select($field = '*')
{
$this->_sqlPreBuild['action'] = Typecho_Db::SELECT;
$args = func_get_args();
$this->_sqlPreBuild['fields'] = $this->getColumnFromParameters($args);
return $this;
}
public function from($table)
{
$this->_sqlPreBuild['table'] = $this->filterPrefix($table);
return $this;
}
public function where()
{
$condition = func_get_arg(0);
$condition = str_replace('?', "%s", $this->filterColumn($condition));
$operator = empty($this->_sqlPreBuild['where']) ? ' WHERE ' : ' AND';
if (func_num_args() <= 1) {
$this->_sqlPreBuild['where'] .= $operator . ' (' . $condition . ')';
} else {
$args = func_get_args();
array_shift($args);
$this->_sqlPreBuild['where'] .= $operator . ' (' . vsprintf($condition, $this->quoteValues($args)) . ')';
}
return $this;
}
public function __toString()
{
switch ($this->_sqlPreBuild['action']) {
case Typecho_Db::SELECT:
return $this->_adapter->parseSelect($this->_sqlPreBuild);
case Typecho_Db::INSERT:
return 'INSERT INTO '
. $this->_sqlPreBuild['table']
. '(' . implode(' , ', array_keys($this->_sqlPreBuild['rows'])) . ')'
. ' VALUES '
. '(' . implode(' , ', array_values($this->_sqlPreBuild['rows'])) . ')'
. $this->_sqlPreBuild['limit'];
case Typecho_Db::DELETE:
return 'DELETE FROM '
. $this->_sqlPreBuild['table']
. $this->_sqlPreBuild['where'];
case Typecho_Db::UPDATE:
$columns = array();
if (isset($this->_sqlPreBuild['rows'])) {
foreach ($this->_sqlPreBuild['rows'] as $key => $val) {
$columns[] = "$key = $val";
}
}
return 'UPDATE '
. $this->_sqlPreBuild['table']
. ' SET ' . implode(' , ', $columns)
. $this->_sqlPreBuild['where'];
default:
return NULL;
}
}
}
代码分析：
1. 获取数据库对象实例（Typecho_Db::get()）
2. 使用 Typecho_Db_Query 构造 SQL 语句。其中 $db->select() 返回 Typecho_Db_Query 实例化对象。
3. 执行查询操作
如果对这部分有兴趣，请深入代码了解。