Tag (Jericho HTML Parser 3.4)

java.lang.Object
- Segment
- - Tag

All Implemented Interfaces:

java.lang.CharSequence, java.lang.Comparable<Segment>

Direct Known Subclasses:

EndTag, StartTag
```
public abstract class Tag
extends Segment
```
Represents either a StartTag or EndTag in a specific source document.
Take the following HTML segment as an example:
<p>This is a sample paragraph.</p>
The "<p>" is represented by a StartTag object, and the "</p>" is represented by an EndTag object, both of which are subclasses of the Tag class. The whole segment, including the start tag, its corresponding end tag and all of the content in between, is represented by an Element object.
Tag Parsing Process
The following process describes how each tag is identified by the parser:
1. Every '<' character found in the source document is considered to be the start of a tag. The characters following it are compared with the start delimiters of all the registered tag types, and a list of matching tag types is determined.
2. A more detailed analysis of the source is performed according to the features of each matching tag type from the first step, in order of precedence, until a valid tag is able to be constructed.
  The analysis performed in relation to each candidate tag type is a two-stage process:
  1. The position of the tag is checked to determine whether it is valid. In theory, a server tag is valid in any position, but a non-server tag is not valid inside any other tag, nor inside elements with CDATA content such as SCRIPT and STYLE elements. Theory dictates therefore that comments and explicit CDATA sections inside script elements should not be recognised as tags. The behaviour of the parser however does not always strictly adhere to the theory, to maintain compatability with major browsers and also for efficiency reasons.
    The TagType.isValidPosition(Source, int pos, int[] fullSequentialParseData) method is responsible for this check and has a common default implementation for all tag types (although custom tag types can override it if necessary). Its behaviour differs depending on whether or not a full sequential parse is peformed. See the documentation of the isValidPosition method for full details.
  2. A final analysis is performed by the TagType.constructTagAt(Source, int pos) method of the candidate tag type. This method returns a valid Tag object if all conditions of the candidate tag type are met, otherwise it returns null and the process continues with the next candidate tag type.
3. If the source does not match the start delimiter or syntax of any registered tag type, the segment spanning it and the next '>' character is taken to be an unregistered tag. Some tag search methods ignore unregistered tags. See the isUnregistered() method for more information.
See the documentation of the TagType class for more details on how tags are recognised.
Tag Search Methods

Methods that get tags in a source document are collectively referred to as Tag Search Methods. They are found mostly in the Source and Segment classes, and can be generally categorised as follows:
Open Search:
These methods search for tags of any name and type.
Named Search:
These methods include a parameter called name which is used to specify the name of the tag to search for. Specifying a name that ends in a colon (:) searches for all elements or tags in the specified XML namespace.
Tag Type Search:
These methods typically include a parameter called tagType which is used to specify the type of the tag to search for. In some methods the search parameter is restricted to the StartTagType or EndTagType subclass of TagType.
Attribute Search:
These methods perform the search based on an attribute name and value.

Method Summary

Methods
Modifier and Type	Method and Description
`abstract Element`	`getElement()` Returns the element that is started or ended by this tag.
`java.lang.String`	`getName()` Returns the name of this tag, always in lower case.
`Segment`	`getNameSegment()` Returns the segment spanning the name of this tag.
`Tag`	`getNextTag()` Returns the next tag in the source document.
`Tag`	`getPreviousTag()` Returns the previous tag in the source document.
`abstract TagType`	`getTagType()` Returns the type of this tag.
`java.lang.Object`	`getUserData()` Returns the general purpose user data object that has previously been associated with this tag via the `setUserData(Object)` method.
`abstract boolean`	`isUnregistered()` Indicates whether this tag has a syntax that does not match any of the registered tag types.
`static boolean`	`isXMLName(java.lang.CharSequence text)` Indicates whether the specified text is a valid XML Name.
`static boolean`	`isXMLNameChar(char ch)` Indicates whether the specified character is valid anywhere in an XML Name.
`static boolean`	`isXMLNameStartChar(char ch)` Indicates whether the specified character is valid at the start of an XML Name.
`void`	`setUserData(java.lang.Object userData)` Associates the specified general purpose user data object with this tag.
`abstract java.lang.String`	`tidy()` Returns an XML representation of this tag.

Methods inherited from class Segment
charAt, compareTo, encloses, encloses, equals, getAllCharacterReferences, getAllElements, getAllElements, getAllElements, getAllElements, getAllElements, getAllElementsByClass, getAllStartTags, getAllStartTags, getAllStartTags, getAllStartTags, getAllStartTags, getAllStartTagsByClass, getAllTags, getAllTags, getBegin, getChildElements, getDebugInfo, getEnd, getFirstElement, getFirstElement, getFirstElement, getFirstElement, getFirstElementByClass, getFirstStartTag, getFirstStartTag, getFirstStartTag, getFirstStartTag, getFirstStartTag, getFirstStartTagByClass, getFormControls, getFormFields, getMaxDepthIndicator, getNodeIterator, getRenderer, getRowColumnVector, getSource, getStyleURISegments, getTextExtractor, getURIAttributes, hashCode, ignoreWhenParsing, isWhiteSpace, isWhiteSpace, length, parseAttributes, subSequence, toString

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

- Method Detail
  - getElement
```
public abstract Element getElement()
```
    Returns the element that is started or ended by this tag.
    StartTag.getElement() is guaranteed not null.
    EndTag.getElement() can return null if the end tag is not properly matched to a start tag.
    
    Returns:
    the element that is started or ended by this tag.
  - getName
```
public final java.lang.String getName()
```
    Returns the name of this tag, always in lower case.
    The name always starts with the name prefix defined in this tag's type. For some tag types, the name consists only of this prefix, while in others it must be followed by a valid XML name (see StartTagType.isNameAfterPrefixRequired()).
    If the name is equal to one of the constants defined in the HTMLElementName interface, this method is guaranteed to return the constant itself. This allows comparisons to be performed using the == operator instead of the less efficient String.equals(Object) method.
    For example, the following expression can be used to test whether a StartTag is from a SELECT element:
    startTag.getName()==HTMLElementName.SELECT
    To get the name of this tag in its original case, use getNameSegment().toString().
    
    Returns:
    the name of this tag, always in lower case.
  - getNameSegment
```
public Segment getNameSegment()
```
    Returns the segment spanning the name of this tag.
    The code getNameSegment().toString() can be used to retrieve the name of this tag in its original case.
    Every call to this method constructs a new Segment object.
    
    Returns:
    the segment spanning the name of this tag.
    See Also:
    getName()
  - getTagType
```
public abstract TagType getTagType()
```
    Returns the type of this tag.
    
    Returns:
    the type of this tag.
  - getUserData
```
public java.lang.Object getUserData()
```
    Returns the general purpose user data object that has previously been associated with this tag via the setUserData(Object) method.
    If setUserData(Object) has not been called, this method returns null.
    
    Returns:
    the generic data object that has previously been associated with this tag via the setUserData(Object) method.
  - setUserData
```
public void setUserData(java.lang.Object userData)
```
    Associates the specified general purpose user data object with this tag.
    This property can be useful for applications that need to associate extra information with tags. The object can be retrieved later via the getUserData() method.
    
    Parameters:
    userData - general purpose user data of any type.
  - getNextTag
```
public Tag getNextTag()
```
    Returns the next tag in the source document.
    This method also returns server tags.
    The result of a call to this method is cached. Performing a full sequential parse prepopulates this cache.
    If the result is not cached, a call to this method is equivalent to source.getNextTag(getBegin()+1).
    See the Tag class documentation for more details about the behaviour of this method.
    
    Returns:
    the next tag in the source document, or null if this is the last tag.
  - getPreviousTag
```
public Tag getPreviousTag()
```
    Returns the previous tag in the source document.
    This method also returns server tags.
    The result of a call to this method is cached. Performing a full sequential parse prepopulates this cache.
    If the result is not cached, a call to this method is equivalent to source.getPreviousTag(getBegin()-1).
    See the Tag class documentation for more details about the behaviour of this method.
    
    Returns:
    the previous tag in the source document, or null if this is the first tag.
  - isUnregistered
```
public abstract boolean isUnregistered()
```
    Indicates whether this tag has a syntax that does not match any of the registered tag types.
    The only requirement of an unregistered tag type is that it starts with '<' and there is a closing '>' character at some position after it in the source document.
    The absence or presence of a '/' character after the initial '<' determines whether an unregistered tag is respectively a StartTag with a type of StartTagType.UNREGISTERED or an EndTag with a type of EndTagType.UNREGISTERED.
    There are no restrictions on the characters that might appear between these delimiters, including other '<' characters. This may result in a '>' character that is identified as the closing delimiter of two separate tags, one an unregistered tag, and the other a tag of any type that begins in the middle of the unregistered tag. As explained below, unregistered tags are usually only found when specifically looking for them, so it is up to the user to detect and deal with any such nonsensical results.
    Unregistered tags are only returned by the Source.getTagAt(int pos) method, named search methods, where the specified name matches the first characters inside the tag, and by tag type search methods, where the specified tagType is either StartTagType.UNREGISTERED or EndTagType.UNREGISTERED.
    Open tag searches and other searches always ignore unregistered tags, although every discovery of an unregistered tag is logged by the parser.
    The logic behind this design is that unregistered tag types are usually the result of a '<' character in the text that was mistakenly left unencoded, or a less-than operator inside a script, or some other occurrence which is of no interest to the user. By returning unregistered tags in named and tag type search methods, the library allows the user to specifically search for tags with a certain syntax that does not match any existing TagType. This expediency feature avoids the need for the user to create a custom tag type to define the syntax before searching for these tags. By not returning unregistered tags in the less specific search methods, it is providing only the information that most users are interested in.
    
    Returns:
    true if this tag has a syntax that does not match any of the registered tag types, otherwise false.
  - tidy
```
public abstract java.lang.String tidy()
```
    Returns an XML representation of this tag.
    This is an abstract method which is implemented in the StartTag and EndTag subclasses. See the documentation of the StartTag.tidy() and EndTag.tidy() methods for details.
    
    Returns:
    an XML representation of this tag.
  - isXMLName
```
public static final boolean isXMLName(java.lang.CharSequence text)
```
    Indicates whether the specified text is a valid XML Name.
    This implementation first checks that the first character of the specified text is a valid XML Name start character as defined by the isXMLNameStartChar(char) method, and then checks that the rest of the characters are valid XML Name characters as defined by the isXMLNameChar(char) method.
    Note that this implementation does not exactly adhere to the formal definition of an XML Name, but the differences are unlikely to be significant in real-world XML or HTML documents.
    
    Parameters:
    text - the text to test.
    
    Returns:
    true if the specified text is a valid XML Name, otherwise false.
    See Also:
    Source.getNameEnd(int pos)
  - isXMLNameStartChar
```
public static final boolean isXMLNameStartChar(char ch)
```
    Indicates whether the specified character is valid at the start of an XML Name.
    The XML 1.0 specification section 2.3 defines a Name as starting with one of the characters
    (Letter | '_' | ':').
    This method uses the expression
    Character.isLetter(ch) || ch=='_' || ch==':'.
    Note that there are many differences between the Character.isLetter() definition of a Letter and the XML definition of a Letter, but these differences are unlikely to be significant in real-world XML or HTML documents.
    
    Parameters:
    ch - the character to test.
    
    Returns:
    true if the specified character is valid at the start of an XML Name, otherwise false.
    See Also:
    Source.getNameEnd(int pos)
  - isXMLNameChar
```
public static final boolean isXMLNameChar(char ch)
```
    Indicates whether the specified character is valid anywhere in an XML Name.
    The XML 1.0 specification section 2.3 uses the entity NameChar to represent this set of characters, which is defined as
    (Letter | Digit | '.' | '-' | '_' | ':' | CombiningChar | Extender).
    This method uses the expression
    Character.isLetterOrDigit(ch) || ch=='.' || ch=='-' || ch=='_' || ch==':'.
    Note that there are many differences between these definitions, but these differences are unlikely to be significant in real-world XML or HTML documents.
    
    Parameters:
    ch - the character to test.
    
    Returns:
    true if the specified character is valid anywhere in an XML Name, otherwise false.
    See Also:
    Source.getNameEnd(int pos)

Class Tag

Tag Parsing Process

Tag Search Methods

Method Summary

Methods inherited from class Segment

Methods inherited from class java.lang.Object

Method Detail

getElement

getName

getNameSegment

getTagType

getUserData

setUserData

getNextTag

getPreviousTag

isUnregistered

tidy

isXMLName

isXMLNameStartChar

isXMLNameChar