CodeIgniter框架源码解析十七之异常处理类文件Exceptions.php

2018-04-09

前言

CI框架的异常处理类通常使用以下几个函数处理错误：

function show_error($heading, $message, $template = ‘error_general’, $status_code = 500)；由于用户操作不当，比如找不到控制器，指定方法之类的，触发的错误。
function show_404($page = ‘’, $log_error = TRUE)；show_error()中的一种特殊情况，表示请求不存在。
function show_php_error($severity, $message, $filepath, $line);PHP原生错误，来着代码本身的一些错误，例如变量未定义之类的。
log_exception($severity, $message, $filepath, $line)；

我们先来看下Exception类的实现框架：

//Nesting level of the output buffering mechanism
public $ob_level;
//List of available error levels
public $levels = array(
  E_ERROR			=>	'Error',
  E_WARNING		=>	'Warning',
  E_PARSE			=>	'Parsing Error',
  E_NOTICE		=>	'Notice',
  E_CORE_ERROR		=>	'Core Error',
  E_CORE_WARNING		=>	'Core Warning',
  E_COMPILE_ERROR		=>	'Compile Error',
  E_COMPILE_WARNING	=>	'Compile Warning',
  E_USER_ERROR		=>	'User Error',
  E_USER_WARNING		=>	'User Warning',
  E_USER_NOTICE		=>	'User Notice',
  E_STRICT		=>	'Runtime Notice'
);

public function __construct(){...}
public function log_exception($severity, $message, $filepath, $line){...}
public function show_404($page = '', $log_error = TRUE){...}
public function show_error($heading, $message, $template = 'error_general', $status_code = 500){...}
public function show_exception($exception){...}
public function show_php_error($severity, $message, $filepath, $line){...}

构造函数 construct()

public function __construct(){
  $this->ob_level = ob_get_level();
  // Note: Do not log messages from this constructor.
}

记录异常 log_exception($severity, $message, $filepath, $line)

public function log_exception($severity, $message, $filepath, $line){
  $severity = isset($this->levels[$severity]) ? $this->levels[$severity] : $severity;
  log_message('error', 'Severity: '.$severity.' --> '.$message.' '.$filepath.' '.$line);
}

show_404($page = ‘’, $log_error = TRUE)

public function show_404($page = '', $log_error = TRUE){
  if (is_cli()){
    $heading = 'Not Found';
    $message = 'The controller/method pair you requested was not found.';
  }else{
    $heading = '404 Page Not Found';
    $message = 'The page you requested was not found.';
  }
  // By default we log this, but allow a dev to skip it
  if ($log_error){
    log_message('error', $heading.': '.$page);
  }
  echo $this->show_error($heading, $message, 'error_404', 404);
  exit(4); // EXIT_UNKNOWN_FILE
}

show_error($heading, $message, $template = ‘error_general’, $status_code = 500)

Displays the error message((either as a string or an array)) using the specified template.

public function show_error($heading, $message, $template = 'error_general', $status_code = 500){
  $templates_path = config_item('error_views_path');
  if (empty($templates_path)){
    $templates_path = VIEWPATH.'errors'.DIRECTORY_SEPARATOR;
  }

  if (is_cli()){
    $message = "\t".(is_array($message) ? implode("\n\t", $message) : $message);
    $template = 'cli'.DIRECTORY_SEPARATOR.$template;
  }else{
    set_status_header($status_code);
    $message = '<p>'.(is_array($message) ? implode('</p><p>', $message) : $message).'</p>';
    $template = 'html'.DIRECTORY_SEPARATOR.$template;
  }

  if (ob_get_level() > $this->ob_level + 1){
    //如果是在视图文件发生错误，则就会出现缓冲级别相差1的情况，此时先把输出的内容给flush出来，然后再把错误信息输出。
    ob_end_flush();
  }
  ob_start();
  include($templates_path.$template.'.php');
  $buffer = ob_get_contents();
  ob_end_clean();
  return $buffer;
}

show_exception($exception)

雷同上个函数，只是获取错误的级别和方式不一样。

public function show_exception($exception){
  $templates_path = config_item('error_views_path');
  if (empty($templates_path)){
    $templates_path = VIEWPATH.'errors'.DIRECTORY_SEPARATOR;
  }

  $message = $exception->getMessage();
  if (empty($message)){
    $message = '(null)';
  }

  if (is_cli()){
    $templates_path .= 'cli'.DIRECTORY_SEPARATOR;
  }else{
    $templates_path .= 'html'.DIRECTORY_SEPARATOR.$template;
  }

  if (ob_get_level() > $this->ob_level + 1){
    ob_end_flush();
  }
  ob_start();
  include($templates_path.'error_exception.php');
  $buffer = ob_get_contents();
  ob_end_clean();
  echo $buffer;
}

show_php_error($severity, $message, $filepath, $line)

public function show_php_error($severity, $message, $filepath, $line){
  $templates_path = config_item('error_views_path');
  if (empty($templates_path)){
    $templates_path = VIEWPATH.'errors'.DIRECTORY_SEPARATOR;
  }

  $severity = isset($this->levels[$severity]) ? $this->levels[$severity] : $severity;
  // For safety reasons we don't show the full file path in non-CLI requests，最后两段路径信息
  if ( ! is_cli()){
    $filepath = str_replace('\\', '/', $filepath);
    if (FALSE !== strpos($filepath, '/')){
      $x = explode('/', $filepath);
      $filepath = $x[count($x)-2].'/'.end($x);
    }
    $template = 'html'.DIRECTORY_SEPARATOR.'error_php';
  }else{
    $template = 'cli'.DIRECTORY_SEPARATOR.'error_php';
  }

  if (ob_get_level() > $this->ob_level + 1){
    ob_end_flush();
  }
  ob_start();
  include($templates_path.$template.'.php');
  $buffer = ob_get_contents();
  ob_end_clean();
  echo $buffer;
}

总结

CI框架的异常处理类文件Exceptions.php，能记录错误日志，将异常信息以既定的模版展示出来。