Spider Dart Reference Documentation
CkSpider
Current Version: 11.6.1
Chilkat.Spider
Initialize the spider with a domain and crawl only URLs that belong to
that same domain.
Add starting URLs, crawl the next queued URL, skip selected URLs, and
inspect unspidered, spidered, failed, and outbound URL lists.
Add wildcard avoid patterns, must-match patterns, and outbound-link
avoid patterns to control which URLs are crawled or collected.
Read the last fetched HTML, page title, meta description, meta keywords,
final redirect URL, and last-modified timestamp.
Fetch pages from a Chilkat-managed cache, update the cache, detect when a
page was redirected, and inspect whether the last page came from cache.
Configure user-agent, proxy settings, connect/read timeouts, IPv6
preference, maximum URL length, maximum response size, and abort support.
Crawl a website domain, manage URL queues, filter links, cache pages, and inspect fetched HTML.
Chilkat.Spider crawls pages within a single initialized domain.
It maintains internal lists of unspidered, spidered, failed, and outbound
URLs; fetches one page at a time; extracts same-domain links for continued
crawling; collects outbound links separately; respects robots.txt;
supports wildcard include and avoid patterns; can use a dedicated cache
directory; and exposes the last fetched HTML, title, meta description,
keywords, redirect information, cache status, and last-modified date.
Domain-limited crawling
URL queue management
Filtering rules
Page metadata
Caching and redirects
Network controls
Initialize with the target domain, add one or more starting
URLs with AddUnspidered, optionally add filtering patterns, then
repeatedly call CrawlNext. After each successful crawl, inspect
LastUrl, LastHtml, page metadata, redirect state,
and the URL-list counts to decide whether to continue, skip, recrawl, or
process the page.
Spider is intended for controlled, domain-oriented crawling and
link discovery. Use Chilkat.Http or Chilkat.Rest
when the task is a single HTTP request, API call, form post, or download
rather than a crawl of discovered links.
Object Creation
// pubspec.yaml:
// dependencies:
// chilkat: ^11.6.1
import 'package:chilkat/chilkat.dart';
// Once per process, before any other Chilkat call:
Chilkat.unlockBundle('Anything for 30-day trial'); // shorthand for CkGlobal().unlockBundle(..)
final spider = CkSpider();
// ... the native object is released when `spider` is garbage collected, or now with spider.dispose().Creates the underlying native Chilkat object. Use a CkSpider only from the isolate that created it: Chilkat objects cannot be sent between isolates. Every call is synchronous; in a Flutter app, run long operations (network, large files) inside Isolate.run, creating the Chilkat objects inside the isolate.
Releases the native object immediately instead of waiting for garbage collection (useful for a large CkBinData or an open socket). Calling it more than once is harmless; any other use of the object afterwards throws a StateError. isDisposed tells whether it has been called.
Errors
A method that can fail throws a ChilkatException: a method whose only outcome is success or failure returns void and throws on failure; a method producing a String or an object returns it and throws where Chilkat would have returned null. The exception carries the object's LastErrorText at the time of the failure (lastErrorText), the class and method names (className, methodName) and a one-line message. Properties never throw, and methods that answer a question (has..., is..., ...) return a plain bool.
try {
spider.someMethod(...);
} on ChilkatException catch (e) {
print(e); // CkSpider.someMethod failed: <reason>
print(e.lastErrorText); // the full Chilkat log of the failed call
}Properties
AbortCurrent
bool get abortCurrent
set abortCurrent(bool value)
When set to true, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to false when the next method is called. When the abort occurs, this property is reset to false. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)
AvoidHttps
bool get avoidHttps
set avoidHttps(bool value)
If set the 1 (true) the spider will avoid all HTTPS URLs. The default is 0 (false).
topCacheDir
String get cacheDir
set cacheDir(String value)
Specifies a cache directory to use for spidering. If either of the FetchFromCache or UpdateCache properties are true, this is the location of the cache to be used. Note: the Internet Explorer, Netscape, and FireFox caches are completely separate from the Chilkat Spider cache directory. You should specify a new and empty directory.
ChopAtQuery
bool get chopAtQuery
set chopAtQuery(bool value)
If equal to 1 (true), then the query portion of all URLs are automatically removed when adding to the unspidered list. The default value is 0 (false).
topConnectTimeout
int get connectTimeout
set connectTimeout(int value)
The maximum number of seconds to wait while connecting to an HTTP server.
topDebugLogFilePath
String get debugLogFilePath
set debugLogFilePath(String value)
If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.
Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.
Possible causes of hangs include:
- A timeout property set to 0, indicating an infinite timeout.
- A hang occurring within an event callback in the application code.
- An internal bug in the Chilkat code causing the hang.
Domain
String get domain
The domain name that is being spidered. This is the domain previously set in the Initialize method.
topFetchFromCache
bool get fetchFromCache
set fetchFromCache(bool value)
If equal to 1 (true) then pages are fetched from cache when possible. If 0, the cache is ignored. The default value is 1. Regardless, if no CacheDir is set then the cache is not used.
FinalRedirectUrl
String get finalRedirectUrl
If the last URL crawled was redirected (as indicated by the WasRedirected property), this property will contain the final redirect URL.
topHeartbeatMs
int get heartbeatMs
set heartbeatMs(int value)
The interval in milliseconds between each AbortCheck event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0, meaning no AbortCheck event callbacks will trigger.
LastErrorHtml
String get lastErrorHtml
Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastErrorText
String get lastErrorText
Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
LastErrorXml
String get lastErrorXml
Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastFromCache
bool get lastFromCache
Equal to 1 if the last page spidered was fetched from the cache. Otherwise equal to 0.
topLastHtml
String get lastHtml
The HTML text of the last paged fetched by the spider.
topLastHtmlDescription
String get lastHtmlDescription
The HTML META description from the last page fetched by the spider.
LastHtmlKeywords
String get lastHtmlKeywords
LastHtmlTitle
String get lastHtmlTitle
LastMethodSuccess
bool get lastMethodSuccess
set lastMethodSuccess(bool value)
Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.
LastModDateStr
String get lastModDateStr
The last modification date/time (RFC822 format) from the last page fetched by the spider.
topLastUrl
String get lastUrl
The URL of the last page spidered.
topMaxResponseSize
int get maxResponseSize
set maxResponseSize(int value)
The maximum HTTP response size allowed. The spider will automatically fail any pages larger than this size. The default value is 250,000 bytes.
MaxUrlLen
int get maxUrlLen
set maxUrlLen(int value)
The maximum URL length allowed. URLs longer than this are not added to the unspidered list. The default value is 200.
NumAvoidPatterns
int get numAvoidPatterns
The number of avoid patterns previously set by calling AddAvoidPattern.
topNumFailed
int get numFailed
The number of URLs in the object's failed URL list.
topNumOutboundLinks
int get numOutboundLinks
The number of URLs in the object's outbound links URL list.
topNumSpidered
int get numSpidered
The number of URLs in the object's already-spidered URL list.
topNumUnspidered
int get numUnspidered
PreferIpv6
bool get preferIpv6
set preferIpv6(bool value)
If true, then use IPv6 over IPv4 when both are supported for a particular domain. The default value of this property is false, which will choose IPv4 over IPv6.
ProxyDomain
String get proxyDomain
set proxyDomain(String value)
The domain name of a proxy host if an HTTP proxy is used.
topProxyLogin
String get proxyLogin
set proxyLogin(String value)
If an HTTP proxy is used and it requires authentication, this property specifies the HTTP proxy login.
topProxyPassword
String get proxyPassword
set proxyPassword(String value)
If an HTTP proxy is used and it requires authentication, this property specifies the HTTP proxy password.
topProxyPort
int get proxyPort
set proxyPort(int value)
The port number of a proxy server if an HTTP proxy is used.
topReadTimeout
int get readTimeout
set readTimeout(int value)
The maximum number of seconds to wait when reading from an HTTP server.
topUpdateCache
bool get updateCache
set updateCache(bool value)
If equal to 1 (true) then pages saved to the cache. If 0, the cache is ignored. The default value is 1. Regardless, if no CacheDir is set then the cache is not used.
UserAgent
String get userAgent
set userAgent(String value)
The value of the HTTP user-agent header field to be sent with HTTP requests. This can be set to any desired value, but be aware that some websites may reject requests from unknown user agents.
topVerboseLogging
bool get verboseLogging
set verboseLogging(bool value)
If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
String get version
WasRedirected
bool get wasRedirected
Indicates whether the last URL crawled was redirected. (true = yes, false = no)
WindDownCount
int get windDownCount
set windDownCount(int value)
The wind-down phase begins when this number of URLs has been spidered. When in the wind-down phase, no new URLs are added to the unspidered list. The default value is 0 which means that there is NO wind-down phase.
Methods
AddAvoidOutboundLinkPattern
Adds a wildcarded pattern to prevent collecting matching outbound link URLs. For example, if *google* is added, then any outbound links containing the word google will be ignored. The * character matches zero or more of any character.
AddAvoidPattern
Adds a wildcarded pattern to prevent spidering matching URLs. For example, if *register* is added, then any url containing the word register is not spidered. The * character matches zero or more of any character.
AddMustMatchPattern
Adds a wildcarded pattern to limit spidering to only URLs that match the pattern. For example, if */products/* is added, then only URLs containing /products/ are spidered. This is helpful for only spidering a portion of a website. The * character matches zero or more of any character.
AddUnspidered
To begin spidering you must call this method one or more times to provide starting points. It adds a single URL to the object's internal queue of URLs to be spidered.
CanonicalizeUrl
Canonicalizes a URL by doing the following:
- Drops username/password if present.
- Drops fragment if present.
- Converts domain to lowercase.
- Removes port 80 or 443
- Remove default.asp, index.html, index.htm, default.html, index.htm, default.htm, index.php, index.asp, default.php, .cfm, .aspx, ,php3, .pl, .cgi, .txt, .shtml, .phtml
- Remove www. from the domain if present.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
ClearFailedUrls
Clears the object's internal list of URLs that could not be downloaded.
topClearOutboundLinks
Clears the object's internal list of outbound URLs that will automatically accumulate while spidering.
topClearSpideredUrls
Clears the object's internal list of already-spidered URLs that will automatically accumulate while spidering.
topCrawlNext
Crawls the next URL in the internal list of unspidered URLs. The URL is moved from the unspidered list to the spidered list. Any new links within the same domain and not yet spidered are added to the unspidered list. (providing that they do not match avoid patterns, etc.) Any new outbound links are added to the outbound URL list.
If successful, the HTML of the downloaded page is available in the LastHtml property. If there are no more URLs left unspidered, the method returns false. Information about the URL crawled is available in the properties LastUrl, LastFromCache, and LastModDate.
Returns normally on success; throws a ChilkatException on failure.
FetchRobotsText
Returns the contents of the robots.txt file from the domain being crawled. This spider object will not crawl URLs excluded by robots.txt. If you believe the spider is not behaving correctly, please notify us at support@chilkatsoft.com and provide information detailing a case that allows us to reproduce the problem.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetAvoidPattern
Returns the Nth avoid pattern previously added by calling AddAvoidPattern. Indexing begins at 0.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetBaseDomain
Returns the second-level + top-level domain of the domain. For example, if domain is xyz.example.com, this returns example.com. For some domains, such as xyz.example.co.uk, the top 3 levels are returned, such as example.co.uk.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetFailedUrl
Returns the Nth URL in the failed URL list. Indexing begins at 0.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetOutboundLink
Returns the Nth URL in the outbound link URL list. Indexing begins at 0.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetSpideredUrl
Returns the Nth URL in the already-spidered URL list. Indexing begins at 0.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetUnspideredUrl
Returns the Nth URL in the unspidered URL list. Indexing begins at 0.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
GetUrlDomain
Returns the domain name part of a URL. For example, if the URL is https://www.chilkatsoft.com/test.asp, then www.chilkatsoft.com is returned.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
Initialize
Initializes the object to begin spidering a domain. Calling Initialize clears any patterns added via the AddAvoidOutboundLinkPattern, AddAvoidPattern, and AddMustMatchPattern methods. The domain name passed to this method is what is returned by the Domain property. The spider only crawls URLs within the same domain.
RecrawlLast
Re-crawls the last URL spidered. This helpful when cookies set in a previous page load cause the page to be loaded differently the next time.
Returns normally on success; throws a ChilkatException on failure.
SkipUnspidered
Moves a URL from the unspidered list to the spidered list. This allows an application to skip a specific URL.
topSleepMs
Suspends the execution of the current thread until the time-out interval elapses.
topEvents
All Chilkat methods are synchronous: the call returns when the work is done. During a call, CkSpider raises three events so your application can show progress and offer a way out. Each event is a nullable callback property on the object; assign a function to receive it, or null to stop receiving it:
final spider = CkSpider();
spider.onPercentDone = (pct) {
print('$pct%');
return false; // return true to abort the method in progress
};
spider.onProgressInfo = (name, value) => print('$name: $value');
spider.heartbeatMs = 250; // raise onAbortCheck 4 times per second during Chilkat calls
spider.onAbortCheck = () => _userPressedCancel;AbortCheck fires at regular intervals controlled by the HeartbeatMs property (0, the default, disables it); PercentDone fires when an operation's completion percentage is known; ProgressInfo delivers named progress values. Returning true from onAbortCheck or onPercentDone aborts the running method, which then throws a ChilkatException.
Events fire on the thread that called the method, before that method returns. An exception thrown inside a callback aborts the running method and is rethrown from it once the native library has returned. In a Flutter app the callbacks run inside the worker isolate that owns the object; forward progress to the UI through a SendPort, and let onAbortCheck read a flag the UI sets the same way.
AbortCheck
bool Function()? onAbortCheck
Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.
Example:
spider.heartbeatMs = 250; // call onAbortCheck 4 times per second
var cancelRequested = false;
spider.onAbortCheck = () => cancelRequested;
// ... set cancelRequested = true (e.g. from a message received on a ReceivePort) to abort the method in progressPercentDone
bool Function(int pctDone)? onPercentDone
This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).
The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.
To abort the operation, set the abort output argument to true. This will cause the method to terminate and return a failure status or corresponding failure value.
Example:
spider.onPercentDone = (pct) {
// pct ranges from 1 to 100.
print('Percent done: $pct');
return false; // return true to abort the method in progress
};ProgressInfo
void Function(String name, String value)? onProgressInfo
This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.
Note: Some Chilkat methods don't fire any ProgressInfo events.
Example:
spider.onProgressInfo = (name, value) => print('$name: $value');