LWP::UserAgent(3) User Contributed Perl Documentation LWP::UserAgent(3)
NAME
LWP::UserAgent - Web user agent class
SYNOPSIS
require LWP::UserAgent;
my $ua = LWP::UserAgent->new;
$ua->timeout(10);
$ua->env_proxy;
my $response = $ua->get('http://search.cpan.org/');
if ($response->is_success) {
print $response->decoded_content; # or whatever
}
else {
die $response->status_line;
}
DESCRIPTION
The "LWP::UserAgent" is a class implementing a web user agent. "LWP::UserAgent" objects can be used to dispatch web requests.
“LWP:：UserAgent”是实现Web用户代理。”LWP:：UserAgent”对象可以用来发送Web请求
In normal use the application creates an "LWP::UserAgent" object, and then configures it with values for timeouts, proxies, name, etc. It then creates an instance of
"HTTP::Request" for the request that needs to be performed.
This request is then passed to one of the request method the UserAgent, which dispatches it using the relevant
protocol, and returns a "HTTP::Response" object. There are convenience methods for sending the most common request types: get(), head() and post(). When using these methods
then the creation of the request object is hidden as shown in the synopsis above.
在正常使用的应用程序创建的一个"LWP::UserAgent" object, 然后配置它的参数 比如timeouts, proxies, name, etc.
然后创建一个 "HTTP::Request"的实例用于执行需要的请求,
这些请求被处理到一个请求的方法,它将使用相关协议, "HTTP::Response" object. 这是最常见的类型的请求发送,常见的请求类型:
get(), head() and post().
The basic approach of the library is to use HTTP style communication for all protocol schemes. This means that you will construct "HTTP::Request" objects and receive
"HTTP::Response" objects even for non-HTTP resources like gopher and ftp. In order to achieve even more similarity to HTTP style communications, gopher menus and file
directories are converted to HTML documents.
library 的最基本的使用方法是使用HTTP协议通信的所有风格, 这意味着你将构建"HTTP::Request" objects 和 接收
"HTTP::Response" objects 即使非 HTTP的资源 像gopher and ftp,为了实现更相似的HTTP通信,gopher menus and file 目录转为为HTML documents
CONSTRUCTOR METHODS
构造方法:
The following constructor methods are available:
$ua = LWP::UserAgent->new( %options )
This method constructs a new "LWP::UserAgent" object and returns it. Key/value pair arguments may be provided to set up the initial state. The following options
该方法构造了一个新的 "LWP::UserAgent" 对象和返回它,键值对参数可以设置为初始状态 下面是选项:
correspond to attribute methods described below:
KEY DEFAULT
----------- --------------------
agent "libwww-perl/#.###"
from undef
conn_cache undef
cookie_jar undef
default_headers HTTP::Headers->new
max_size undef
max_redirect 7
parse_head 1
protocols_allowed undef
protocols_forbidden undef
requests_redirectable ['GET', 'HEAD']
timeout 180
The following additional options are also accepted: If the "env_proxy" option is passed in with a TRUE value, then proxy settings are read from environment variables (see
env_proxy() method below). If the "keep_alive" option is passed in, then a "LWP::ConnCache" is set up (see conn_cache() method below). The "keep_alive" value is passed
on as the "total_capacity" for the connection cache.
以下附加选项也接受:如果"env_proxy" 选项 赋了一个真值,那么代理设置就从环境变量(见
env_proxy()方法如下）
如果 "keep_alive" 选项被传入, "LWP::ConnCache" 设置(see conn_cache() method below)
$ua->clone
Returns a copy of the LWP::UserAgent object.
返回一个 LWP::UserAgent object对象的复制
ATTRIBUTES
The settings of the configuration attributes modify the behaviour of the "LWP::UserAgent" when it dispatches requests. Most of these can also be initialized by options passed
to the constructor method.
配置的设置属性 修改"LWP::UserAgent" 的行为:当它被调度请求,大部分这些也可以通过选项进行初始化来构造方法。
The following attribute methods are provided. The attribute value is left unchanged if no argument is given. The return value from each method is the old attribute value.
下面提供的属性方法,如果没有给给出任何参数,则该属性将保持不变,返回值从每一种方法都是旧的属性的值。
$ua->agent
$ua->agent( $product_id )
Get/set the product token that is used to identify the user agent on the network. The agent value is sent as the "User-Agent" header in the requests. The default is the
string returned by the _agent() method (see below).
Get/get 提供了签名 用于定位user agent,agent 的值是发送作为 "User-Agent" header 在请求里,默认是_agent()返回的字符串
If the $product_id ends with space then the _agent() string is appended to it.
如果$product_id 是空值, _agent() string is appended to it.
The user agent string should be one or more simple product identifiers with an optional version number separated by the "/" character. Examples are:
use agent 字符串可以使一个或者多个简单的产品标示,用一个可选的版本号分隔的“/”字符
$ua->agent('Checkbot/0.4 ' . $ua->_agent);
$ua->agent('Checkbot/0.4 '); # same as above
$ua->agent('Mozilla/5.0');
$ua->agent(""); # don't identify
$ua->_agent
Returns the default agent identifier. This is a string of the form "libwww-perl/#.###", where "#.###" is substituted with the version number of this library.
返回默认的agent identifier, 这个字符串的格式为"libwww-perl/#.###", 这里的“#.# # #”与版本号这个库取代
[root@dr-mysql01 test]# cat a6.pl
use LWP::UserAgent;
my $ua = LWP::UserAgent->new;
$ua->_agent;
print $ua->_agent ;
[root@dr-mysql01 test]# perl a6.pl
libwww-perl/5.833[root@dr-mysql01 test]#
$ua->from
$ua->from( $email_address )
Get/set the e-mail address for the human user who controls the requesting user agent. The address should be machine-usable, as defined in RFC 822. The "from" value is
send as the "From" header in the requests. Example:
$ua->from('[email protected]');
The default is to not send a "From" header. See the default_headers() method for the more general interface that allow any header to be defaulted.
Get/set e-mail address 用于人们使用,控制请求的用户代理, 这个地址必须是machine-usable "form" 值是作为"Form" header 在请求里发送的
默认是不发送"From" header
$ua->cookie_jar
$ua->cookie_jar( $cookie_jar_obj )
Get/set the cookie jar object to use. The only requirement is that the cookie jar object must implement the extract_cookies($request) and add_cookie_header($response)
methods. These methods will then be invoked by the user agent as requests are sent and responses are received. Normally this will be a "HTTP::Cookies" object or some
subclass.
The default is to have no cookie_jar, i.e. never automatically add "Cookie" headers to the requests.
Shortcut: If a reference to a plain hash is passed in as the $cookie_jar_object, then it is replaced with an instance of "HTTP::Cookies" that is initialized based on the
hash. This form also automatically loads the "HTTP::Cookies" module. It means that:
Get/set the cookie jar object to use，
唯一需要的是 cookie jar object 必须实现 extract_cookies($request) 和 add_cookie_header($response) 方法。
那些模块会通过user agent 作为请求被发送和接收响应。通常这是一个 "HTTP::Cookies" object 或者 一些子类
默认是没有cookie_jar, i.e. 不会自动增加 "Cookie" headers to the requests.
快捷: 这个 form 也自动的加载"HTTP::Cookies" module. 它意味着:
$ua->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });
is really just a shortcut for:
require HTTP::Cookies;
$ua->cookie_jar(HTTP::Cookies->new(file => "$ENV{HOME}/.cookies.txt"));
[root@dr-mysql01 test]# cat cookie
#LWP-Cookies-1.0
Set-Cookie3: usertrack="c+5+hVWcjK1OAGeUFim/Ag=="; path="/"; domain=.163.com; path_spec; expires="2016-07-07 02:36:29Z"; version=0
Set-Cookie3: NTESBLOGSI=F52C85755C5C1A52870634794962A86A.app-86-8010; path="/"; domain=blog.163.com; path_spec; discard; version=0
一般现在的cookie都不会， 只记录服务器session的id， 所有的记录都留在服务器了。
$ua->default_headers
$ua->default_headers( $headers_obj )
Get/set the headers object that will provide default header values for any requests sent. By default this will be an empty "HTTP::Headers" object.
设置或返回每一次请求的headers值，缺省是一个空的HTTP::Headers 对象
$ua->default_header( $field )
$ua->default_header( $field => $value )
This is just a short-cut for $ua->default_headers->header( $field => $value ). Example:
$ua->default_header('Accept-Encoding' => scalar HTTP::Message::decodable());
$ua->default_header('Accept-Language' => "no, en");
$ua->conn_cache
$ua->conn_cache( $cache_obj )
Get/set the "LWP::ConnCache" object to use. See LWP::ConnCache for details.
$ua->credentials( $netloc, $realm )
$ua->credentials( $netloc, $realm, $uname, $pass )
Get/set the user name and password to be used for a realm.
The $netloc is a string of the form "<host>:<port>". The username and password will only be passed to this server. Example:
$ua->credentials("www.example.com:80", "Some Realm", "foo", "secret");
$ua->max_size
$ua->max_size( $bytes )
Get/set the size limit for response content. The default is "undef", which means that there is no limit. If the returned response content is only partial, because the
size limit was exceeded, then a "Client-Aborted" header will be added to the response. The content might end up longer than "max_size" as we abort once appending a chunk
of data makes the length exceed the limit. The "Content-Length" header, if present, will indicate the length of the full content and will normally not be the same as
"length($res->content)".
$ua->max_redirect
$ua->max_redirect( $n )
This reads or sets the object’s limit of how many times it will obey redirection responses in a given request cycle.
By default, the value is 7. This means that if you call request() method and the response is a redirect elsewhere which is in turn a redirect, and so on seven times, then
LWP gives up after that seventh request.
$ua->parse_head
$ua->parse_head( $boolean )
Get/set a value indicating whether we should initialize response headers from the <head> section of HTML documents. The default is TRUE. Do not turn this off, unless you
know what you are doing.
$ua->protocols_allowed
$ua->protocols_allowed( \@protocols )
This reads (or sets) this user agent’s list of protocols that the request methods will exclusively allow. The protocol names are case insensitive.
For example: "$ua->protocols_allowed( [ 'http', 'https'] );" means that this user agent will allow only those protocols, and attempts to use this user agent to access URLs
with any other schemes (like "ftp://...") will result in a 500 error.
To delete the list, call: "$ua->protocols_allowed(undef)"
By default, an object has neither a "protocols_allowed" list, nor a "protocols_forbidden" list.
Note that having a "protocols_allowed" list causes any "protocols_forbidden" list to be ignored.
$ua->protocols_forbidden
$ua->protocols_forbidden( \@protocols )
This reads (or sets) this user agent’s list of protocols that the request method will not allow. The protocol names are case insensitive.
For example: "$ua->protocols_forbidden( [ 'file', 'mailto'] );" means that this user agent will not allow those protocols, and attempts to use this user agent to access
URLs with those schemes will result in a 500 error.
To delete the list, call: "$ua->protocols_forbidden(undef)"
$ua->requests_redirectable
$ua->requests_redirectable( \@requests )
This reads or sets the object’s list of request names that "$ua->redirect_ok(...)" will allow redirection for. By default, this is "['GET', 'HEAD']", as per RFC 2616. To
change to include ’POST’, consider:
push @{ $ua->requests_redirectable }, 'POST';
$ua->show_progress
$ua->show_progress( $boolean )
Get/set a value indicating whether a progress bar should be displayed on on the terminal as requests are processed. The default is FALSE.
$ua->timeout
$ua->timeout( $secs )
Get/set the timeout value in seconds. The default timeout() value is 180 seconds, i.e. 3 minutes.
The requests is aborted if no activity on the connection to the server is observed for "timeout" seconds. This means that the time it takes for the complete transaction
and the request() method to actually return might be longer.
Proxy attributes
The following methods set up when requests should be passed via a proxy server.
$ua->proxy(\@schemes, $proxy_url)
$ua->proxy($scheme, $proxy_url)
Set/retrieve proxy URL for a scheme:
$ua->proxy(['http', 'ftp'], 'http://proxy.sn.no:8001/');
$ua->proxy('gopher', 'http://proxy.sn.no:8001/');
The first form specifies that the URL is to be used for proxying of access methods listed in the list in the first method argument, i.e. ’http’ and ’ftp’.
The second form shows a shorthand form for specifying proxy URL for a single access scheme.
$ua->no_proxy( $domain, ... )
Do not proxy requests to the given domains. Calling no_proxy without any domains clears the list of domains. Eg:
$ua->no_proxy('localhost', 'example.com');
$ua->env_proxy
Load proxy settings from *_proxy environment variables. You might specify proxies like this (sh-syntax):
gopher_proxy=http://proxy.my.place/
wais_proxy=http://proxy.my.place/
no_proxy="localhost,example.com"
export gopher_proxy wais_proxy no_proxy
csh or tcsh users should use the "setenv" command to define these environment variables.
On systems with case insensitive environment variables there exists a name clash between the CGI environment variables and the "HTTP_PROXY" environment variable normally
picked up by env_proxy(). Because of this "HTTP_PROXY" is not honored for CGI scripts. The "CGI_HTTP_PROXY" environment variable can be used instead.
Handlers
Handlers are code that injected at various phases during the processing of requests. The following methods are provided to manage the active handlers:
$ua->add_handler( $phase => \&cb, %matchspec )
Add handler to be invoked in the given processing phase. For how to specify %matchspec see "Matching" in HTTP::Config.
The possible values $phase and the corresponding callback signatures are:
request_preprepare => sub { my($request, $ua, $h) = @_; ... }
The handler is called before the "request_prepare" and other standard initialization of of the request. This can be used to set up headers and attributes that the
"request_prepare" handler depends on. Proxy initialization should take place here; but in general don’t register handlers for this phase.
request_prepare => sub { my($request, $ua, $h) = @_; ... }
The handler is called before the request is sent and can modify the request any way it see fit. This can for instance be used to add certain headers to specific
requests.
The method can assign a new request object to $_[0] to replace the request that is sent fully.
The return value from the callback is ignored. If an exceptions is raised it will abort the request and make the request method return a "400 Bad request" response.
request_send => sub { my($request, $ua, $h) = @_; ... }
This handler get a chance of handling requests before it’s sent to the protocol handlers. It should return an HTTP::Response object if it wishes to terminate the
processing; otherwise it should return nothing.
The "response_header" and "response_data" handlers will not be invoked for this response, but the "response_done" will be.
response_header => sub { my($response, $ua, $h) = @_; ... }
This handler is called right after the response headers have been received, but before any content data. The handler might set up handlers for data and might croak to
abort the request.
The handler might set the $response->{default_add_content} value to control if any received data should be added to the response object directly. This will initially
be false if the $ua->request() method was called with a ’:content_filename’ or ’:content_callbak’ argument; otherwise true.
response_data => sub { my($response, $ua, $h, $data) = @_; ... }
This handlers is called for each chunk of data received for the response. The handler might croak to abort the request.
This handler need to return a TRUE value to be called again for subsequent chunks for the same request.
response_done => sub { my($response, $ua, $h) = @_; ... }
The handler is called after the response has been fully received, but before any redirect handling is attempted. The handler can be used to extract information or
modify the response.
response_redirect => sub { my($response, $ua, $h) = @_; ... }
The handler is called in $ua->request after "response_done". If the handler return an HTTP::Request object we’ll start over with processing this request instead.
$ua->remove_handler( undef, %matchspec )
$ua->remove_handler( $phase, %matchspec )
Remove handlers that match the given %matchspec. If $phase is not provided remove handlers from all phases.
Be careful as calling this function with %matchspec that is not not specific enough can remove handlers not owned by you. It’s probably better to use the set_my_handler()
method instead.
The removed handlers are returned.
$ua->set_my_handler( $phase, $cb, %matchspec )
Set handlers private to the executing subroutine. Works by defaulting an "owner" field to the %matchhspec that holds the name of the called subroutine. You might pass an
explicit "owner" to override this.
If $cb is passed as "undef", remove the handler.
$ua->get_my_handler( $phase, %matchspec )
$ua->get_my_handler( $phase, %matchspec, $init )
Will retrieve the matching handler as hash ref.
If $init is passed passed as a TRUE value, create and add the handler if it’s not found. If $init is a subroutine reference, then it’s called with the created handler
hash as argument. This sub might populate the hash with extra fields; especially the callback. If $init is a hash reference, merge the hashes.
$ua->handlers( $phase, $request )
$ua->handlers( $phase, $response )
Returns the handlers that apply to the given request or response at the given processing phase.
REQUEST METHODS
The methods described in this section are used to dispatch requests via the user agent. The following request methods are provided:
$ua->get( $url )
$ua->get( $url , $field_name => $value, ... )
This method will dispatch a "GET" request on the given $url. Further arguments can be given to initialize the headers of the request. These are given as separate
name/value pairs. The return value is a response object. See HTTP::Response for a description of the interface it provides.
There will still be a response object returned when LWP can’t connect to the server specified in the URL or when other failures in protocol handlers occur. These internal
responses use the standard HTTP status codes, so the responses can’t be differentiated by testing the response status code alone. Error responses that LWP generates
internally will have the "Client-Warning" header set to the value "Internal response". If you need to differentiate these internal responses from responses that a remote
server actually generates, you need to test this header value.
Fields names that start with ":" are special. These will not initialize headers of the request but will determine how the response content is treated. The following
special field names are recognized:
:content_file => $filename
:content_cb => \&callback
:read_size_hint => $bytes
If a $filename is provided with the ":content_file" option, then the response content will be saved here instead of in the response object. If a callback is provided with
the ":content_cb" option then this function will be called for each chunk of the response content as it is received from the server. If neither of these options are
given, then the response content will accumulate in the response object itself. This might not be suitable for very large response bodies. Only one of ":content_file" or
":content_cb" can be specified. The content of unsuccessful responses will always accumulate in the response object itself, regardless of the ":content_file" or
":content_cb" options passed in.
The ":read_size_hint" option is passed to the protocol module which will try to read data from the server in chunks of this size. A smaller value for the
":read_size_hint" will result in a higher number of callback invocations.
The callback function is called with 3 arguments: a chunk of data, a reference to the response object, and a reference to the protocol object. The callback can abort the
request by invoking die(). The exception message will show up as the "X-Died" header field in the response returned by the get() function.
$ua->head( $url )
$ua->head( $url , $field_name => $value, ... )
This method will dispatch a "HEAD" request on the given $url. Otherwise it works like the get() method described above.
$ua->post( $url, \%form )
$ua->post( $url, \@form )
$ua->post( $url, \%form, $field_name => $value, ... )
$ua->post( $url, $field_name => $value,... Content => \%form )
$ua->post( $url, $field_name => $value,... Content => \@form )
$ua->post( $url, $field_name => $value,... Content => $content )
This method will dispatch a "POST" request on the given $url, with %form or @form providing the key/value pairs for the fill-in form content. Additional headers and
content options are the same as for the get() method.
This method will use the POST() function from "HTTP::Request::Common" to build the request. See HTTP::Request::Common for a details on how to pass form content and other
advanced features.
$ua->mirror( $url, $filename )
This method will get the document identified by $url and store it in file called $filename. If the file already exists, then the request will contain an "If-Modified-
Since" header matching the modification time of the file. If the document on the server has not changed since this time, then nothing happens. If the document has been
updated, it will be downloaded again. The modification time of the file will be forced to match that of the server.
The return value is the the response object.
$ua->request( $request )
$ua->request( $request, $content_file )
$ua->request( $request, $content_cb )
$ua->request( $request, $content_cb, $read_size_hint )
This method will dispatch the given $request object. Normally this will be an instance of the "HTTP::Request" class, but any object with a similar interface will do. The
return value is a response object. See HTTP::Request and HTTP::Response for a description of the interface provided by these classes.
The request() method will process redirects and authentication responses transparently. This means that it may actually send several simple requests via the
simple_request() method described below.
The request methods described above; get(), head(), post() and mirror(), will all dispatch the request they build via this method. They are convenience methods that
simply hides the creation of the request object for you.
The $content_file, $content_cb and $read_size_hint all correspond to options described with the get() method above.
You are allowed to use a CODE reference as "content" in the request object passed in. The "content" function should return the content when called. The content can be
returned in chunks. The content function will be invoked repeatedly until it return an empty string to signal that there is no more content.
$ua->simple_request( $request )
$ua->simple_request( $request, $content_file )
$ua->simple_request( $request, $content_cb )
$ua->simple_request( $request, $content_cb, $read_size_hint )
This method dispatches a single request and returns the response received. Arguments are the same as for request() described above.
The difference from request() is that simple_request() will not try to handle redirects or authentication responses. The request() method will in fact invoke this method
for each simple request it sends.
$ua->is_protocol_supported( $scheme )
You can use this method to test whether this user agent object supports the specified "scheme". (The "scheme" might be a string (like ’http’ or ’ftp’) or it might be an
URI object reference.)
Whether a scheme is supported, is determined by the user agent’s "protocols_allowed" or "protocols_forbidden" lists (if any), and by the capabilities of LWP. I.e., this
will return TRUE only if LWP supports this protocol and it’s permitted for this particular object.
Callback methods
The following methods will be invoked as requests are processed. These methods are documented here because subclasses of "LWP::UserAgent" might want to override their
behaviour.
$ua->prepare_request( $request )
This method is invoked by simple_request(). Its task is to modify the given $request object by setting up various headers based on the attributes of the user agent. The
return value should normally be the $request object passed in. If a different request object is returned it will be the one actually processed.
The headers affected by the base implementation are; "User-Agent", "From", "Range" and "Cookie".
$ua->redirect_ok( $prospective_request, $response )
This method is called by request() before it tries to follow a redirection to the request in $response. This should return a TRUE value if this redirection is
permissible. The $prospective_request will be the request to be sent if this method returns TRUE.
The base implementation will return FALSE unless the method is in the object’s "requests_redirectable" list, FALSE if the proposed redirection is to a "file://..." URL,
and TRUE otherwise.
$ua->get_basic_credentials( $realm, $uri, $isproxy )
This is called by request() to retrieve credentials for documents protected by Basic or Digest Authentication. The arguments passed in is the $realm provided by the
server, the $uri requested and a boolean flag to indicate if this is authentication against a proxy server.
The method should return a username and password. It should return an empty list to abort the authentication resolution attempt. Subclasses can override this method to
prompt the user for the information. An example of this can be found in "lwp-request" program distributed with this library.
The base implementation simply checks a set of pre-stored member variables, set up with the credentials() method.
$ua->progress( $status, $request_or_response )
This is called frequently as the response is received regardless of how the content is processed. The method is called with $status "begin" at the start of processing the
request and with $state "end" before the request method returns. In between these $status will be the fraction of the response currently received or the string "tick" if
the fraction can’t be calculated.
When $status is "begin" the second argument is the request object, otherwise it is the response object.
SEE ALSO
See LWP for a complete overview of libwww-perl5. See lwpcook and the scripts lwp-request and lwp-download for examples of usage.
See HTTP::Request and HTTP::Response for a description of the message objects dispatched and received. See HTTP::Request::Common and HTML::Form for other ways to build
request objects.
See WWW::Mechanize and WWW::Search for examples of more specialized user agents based on "LWP::UserAgent".
COPYRIGHT
Copyright 1995-2009 Gisle Aas.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
perl v5.10.1 2009-10-07 LWP::UserAgent(3)
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