java.lang.Object
- com.norconex.collector.http.canon.impl.GenericCanonicalLinkDetector

All Implemented Interfaces:

ICanonicalLinkDetector, IXMLConfigurable
```
public class GenericCanonicalLinkDetector
extends Object
implements ICanonicalLinkDetector, IXMLConfigurable
```
Generic canonical link detector. It detects links from the HTTP headers as well as HTML files. Good canonical reference documentation can be found on this Google Webmaster Tools help page.

HTTP Headers

This detector will look for a metadata field (normally obtained from the HTTP Headers) name called "Link" with a value following this pattern:
```
 <http://www.example.com/sample.pdf> rel="canonical"
 
```
All documents will be verified for a canonical link (not just HTML).

Document content

This detector will look within the HTML <head> tags for a <link> tag following this pattern:
```
 <link rel="canonical" href="https://www.example.com/sample" />
 
```
Only HTML documents will be verified for a canonical link. By default, these content-types are considered HTML:
```
 text/html, application/xhtml+xml, vnd.wap.xhtml+xml, x-asp
 
```
You can specify your own content types as long as they contain HTML text.

XML configuration usage:
```
<canonicalLinkDetector
    class="com.norconex.collector.http.canon.impl.GenericCanonicalLinkDetector"
    ignore="(false|true)">
  <contentTypes>
    (CSV list of content types on which to perform canonical link
    detection. Leave blank or remove this tag to use defaults.)
  </contentTypes>
</canonicalLinkDetector>
```
XML usage example:
```
<canonicalLinkDetector
    ignore="true"/>
```
The above example ignores canonical link resolution.
Since:

2.2.0

Author:

Pascal Essiembre

Constructor Summary

Constructors
Constructor Description

GenericCanonicalLinkDetector()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`String`	`detectFromContent(String reference, InputStream is, ContentType contentType)`	Detects from a document content the presence of a canonical URL.
`String`	`detectFromMetadata(String reference, Properties metadata)`	Detects from metadata gathered so far, which when invoked, is normally the HTTP header values.
`boolean`	`equals(Object other)`
`List<ContentType>`	`getContentTypes()`
`int`	`hashCode()`
`void`	`loadFromXML(XML xml)`
`void`	`saveToXML(XML xml)`
`void`	`setContentTypes(ContentType... contentTypes)`	Sets the content types on which to perform canonical link detection.
`void`	`setContentTypes(List<ContentType> contentTypes)`	Sets the content types on which to perform canonical link detection.
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - GenericCanonicalLinkDetector
```
public GenericCanonicalLinkDetector()
```
- Method Detail
  - getContentTypes
```
public List<ContentType> getContentTypes()
```
  - setContentTypes
```
public void setContentTypes(ContentType... contentTypes)
```
    Sets the content types on which to perform canonical link detection.
    
    Parameters:
    
    contentTypes - content types
  - setContentTypes
```
public void setContentTypes(List<ContentType> contentTypes)
```
    Sets the content types on which to perform canonical link detection.
    
    Parameters:
    
    contentTypes - content types
    
    Since:
    
    3.0.0
  - detectFromMetadata
```
public String detectFromMetadata(String reference,
                                 Properties metadata)
```
    Description copied from interface: ICanonicalLinkDetector
    
    Detects from metadata gathered so far, which when invoked, is normally the HTTP header values.
    
    Specified by:
    
    detectFromMetadata in interface ICanonicalLinkDetector
    
    Parameters:
    
    reference - document reference
    
    metadata - metadata object containing HTTP headers
    
    Returns:
    
    the detected canonical URL or null if none is found.
  - detectFromContent
```
public String detectFromContent(String reference,
                                InputStream is,
                                ContentType contentType)
                         throws IOException
```
    Description copied from interface: ICanonicalLinkDetector
    
    Detects from a document content the presence of a canonical URL. This occur before a document gets parsed and may apply to only a few content types.
    
    Specified by:
    
    detectFromContent in interface ICanonicalLinkDetector
    
    Parameters:
    
    reference - document reference
    
    is - the document content input stream
    
    contentType - the document content type
    
    Returns:
    
    the detected canonical URL or null if none is found.
    
    Throws:
    
    IOException - problem reading content
  - loadFromXML
```
public void loadFromXML(XML xml)
```
    Specified by:
    
    loadFromXML in interface IXMLConfigurable
  - saveToXML
```
public void saveToXML(XML xml)
```
    Specified by:
    
    saveToXML in interface IXMLConfigurable
  - equals
```
public boolean equals(Object other)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class GenericCanonicalLinkDetector

HTTP Headers

Document content

XML configuration usage:

XML usage example:

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

GenericCanonicalLinkDetector

Method Detail

getContentTypes

setContentTypes

setContentTypes

detectFromMetadata

detectFromContent

loadFromXML

saveToXML

equals

hashCode

toString