sunlabs.brazil.handler
public class HtmlRewriter extends Object
The user can sequentially examine and rewrite each token in the source HTML document. As each token in the document is seen, the user has two choices:
Parsing is implemented lazily, meaning, for example, that unless the user actually asks for attributes of an HTML tag, this parser does not have to spend the time breaking up the attributes.
This class is used by HTML filters to maintain the state of the document and allow the filters to perform arbitrary rewriting.
Version: @(#)HtmlRewriter.java 2.6
Field Summary | |
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LexHTML | lex
The parser for the source HTML document. |
StringBuffer | sb
Storage holding the resultant HTML document. |
Constructor Summary | |
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HtmlRewriter(LexHTML lex)
Creates a new HtmlRewriter from the given HTML parser.
| |
HtmlRewriter(String str)
Creates a new HtmlRewriter that will operate on the given
string.
|
Method Summary | |
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boolean | accumulate(boolean accumulate)
Turns on or off the automatic accumulation of each token.
|
void | append(String str)
Instead of modifying an existing token, this method allows the user
to completely replace the current token with arbitrary new content.
|
void | appendToken()
Appends the current token to the resultant HTML document.
|
String | get(String key)
Returns the value that the specified case-insensitive key maps
to in the attributes for the current tag. |
String | getArgs()
Gets the arguments of the current token as a string.
|
String | getBody()
Gets the body of the current token as a string.
|
StringMap | getMap()
Return a copy of the StringMap of attributes. |
String | getTag()
Gets the current tag's name. |
String | getToken()
Gets the raw string making up the entire current token, including
the angle brackets or comment delimiters, if applicable.
|
int | getType()
Gets the type of the current token.
|
boolean | isSingleton()
See if the current tag a singleton. |
Enumeration | keys()
Returns an enumeration of the keys in the current tag's attributes.
|
void | killToken()
Tells this HtmlRewriter not to append the current token
to the resultant HTML document. |
boolean | nextTag()
A convenence method built on top of nextToken .
|
boolean | nextToken()
Advances to the next token in the source HTML document.
|
void | pushback()
Puts the current token back. |
void | put(String key, String value)
Maps the given case-insensitive key to the specified value in the
current tag's attributes.
|
static String | quote(String str)
Helper class to quote a attribute's value when the value is being
written to the resultant HTML document. |
void | remove(String key)
Removes the given case-insensitive key and its corresponding value
from the current tag's attributes. |
void | reset()
Forgets all the tokens that have been appended to the resultant
HTML document so far, including the current token. |
void | setSingleton(boolean singleton)
Make the current tag a singleton. |
void | setTag(String tag)
Changes the current tag's name. |
void | setType(int type)
Sets the type of the current token. |
int | tagCount()
Return count of tags seen so far |
int | tokenCount()
Return count of tokens seen so far |
String | toString()
Returns the "new" rewritten HTML document. |
HtmlRewriter
from the given HTML parser.
Parameters: lex The HTML parser.
HtmlRewriter
that will operate on the given
string.
Parameters: str The HTML document.
After each token is processed, the current token is appended to
to the resultant HTML document unless the user has already appended
something else. By setting accumulate
to
false
, this behavior is turned off. The user must then
explicitly call appendToken
to cause the current token
to be appended.
Turning off accumulation takes effect immediately, while turning
on accumulation takes effect on the next token. In other words,
whether the user turns this setting off or on, the current token
will not be added to the resultant HTML document unless the user
explicitly calls appendToken
.
Following is sample code that illustrates how to use this method
to extract the contents of the <head>
of the
source HTML document.
HtmlRewriter hr = new HtmlRewriter(str); // Don't accumulate tokens until we see the <head> below. hr.accumulate(false); while (hr.nextTag()) { if (hr.getTag().equals("head")) { // Start remembering the contents of the HTML document, // not including the <head> tag itself. hr.accumulate(true); } else if (hr.getTag().equals("/head")) { // Return everything accumulated so far. return hr.toString(); } }This method can be called any number of times while processing the source HTML document.
Parameters: accumulate
true
to automatically accumulate tokens in the
resultant HTML document, false
to require
that the user explicitly accumulate them.
Returns: The previous accumulate setting
See Also: HtmlRewriter
This method may be called multiple times while processing the current
token to add more and more data to the resultant HTML document.
Before and/or after calling this method, the appendToken
method may also be called explicitly in order to add the current token
to the resultant HTML document.
Following is sample code illustrating how to use this method
to put bold tags around all the <a>
tags.
HtmlRewriter hr = new HtmlRewriter(str); while (hr.nextTag()) { if (hr.getTag().equals("a")) { hr.append("<b>"); hr.appendToken(); } else if (hr.getTag().equals("/a")) { hr.appendToken(); hr.append("</b>"); } }The calls to
appendToken
are necessary. Otherwise,
the HtmlRewriter
could not know where and when to
append the existing token in addition to the new content provided
by the user.
Parameters: str
The new content to append. May be null
,
in which case no new content is appended (the equivalent
of appending "").
See Also: appendToken HtmlRewriter
setTag
, set
, or remove
methods, those changes will be reflected.
By default, this method is automatically called after each token is processed unless the user has already appended something to the resultant HTML document. Therefore, if the user appends something and also wants to append the current token, or if the user wants to append the current token a number of times, this method must be called.
See Also: HtmlRewriter HtmlRewriter
<table border rows=2>
: get("border")
returns the empty string "".
get("rows")
returns 2.
Surrounding single and double quote marks that occur in the literal
tag are removed from the values reported. So, for the tag
<a href="/foo.html" target=_top onclick='alert("hello")'>
:
get("href")
returns /foo.html .
get("target")
returns _top .
get("onclick")
returns alert("hello") .
Parameters: The key to lookup in the current tag's attributes.
Returns: The value to which the specified key is mapped, or
null
if the key was not in the attributes.
See Also: LexHTML
Returns: The body.
See Also: LexHTML
Returns: The body.
See Also: LexHTML
Returns: The lower-cased tag name, or null
if the
current token does not have a tag name
See Also: LexHTML
Returns: The current token.
See Also: LexHTML
Returns: The type.
See Also: LexHTML
<
.get
to get the values of the attributes.
Returns: An enumeration of the keys.
HtmlRewriter
not to append the current token
to the resultant HTML document. Even if the user hasn't appended
anything else, the current token will be ignored rather than appended.
See Also: HtmlRewriter HtmlRewriter
nextToken
.
Advances to the next HTML tag. All intervening strings and comments
between the last tag and the new current tag are copied through
unchanged. This method can be used when the caller wants to process
only HTML tags, without having to manually check the type of each
token to see if it is actually a tag.
Returns: true
if there are tokens left to process,
false
otherwise.
The other purpose of this function is to "do the right thing", which is to append the token we just processed to the resultant HTML document, unless the user has already appended something else.
A sample program follows. This program changes all
<img>
tags to <form>
tags,
deletes all <table>
tags, capitalizes
and bolds each string token, and passes all other tokens through
unchanged, to illustrate how nextToken
interacts with
some of the other methods in this class.
HtmlRewriter hr = new HtmlRewriter(str); while (hr.nextToken()) { switch (hr.getType()) { case LexHTML.TAG: if (hr.getTag().equals("img")) { // Change the tag name w/o affecting the attributes. hr.setTag("form"); } else if (hr.getTag().equals("table")) { // Eliminate the entire "table" token. hr.killToken(); } break; case LexHTML.STRING: // Append a new sequence in place of the existing token. hr.append("<b>" + hr.getToken().toUpperCase() + "</b>"); break; } // Any tokens we didn't modify get copied through unchanged. }
Returns: true
if there are tokens left to process,
false
otherwise.
nextToken
is called, it will be the current token again, rather than
advancing to the next token in the source HTML document.
This is useful when a code fragment needs to read an indefinite number of tokens, but that once some distinguished token is found, needs to push that token back so that normal processing can occur on that token.
The value can be retrieved by calling get
with a
key that is case-insensitive equal to the given key.
If the attributes already contained a mapping for the given key, the old value is forgotten and the new specified value is used. The case of the prior key is retained in that case. Otherwise the case of the new key is used and a new mapping is made.
Parameters: key
The new key. May not be null
.
value
The new value. May be not be null
.
put
method are automatically quoted as needed. This
method is provided in case the user is dynamically constructing a new
tag to be appended with append
and needs to quote some
arbitrary values.
The quoting algorithm is as follows:
If the string contains double-quotes, put single quotes around it.
If the string contains any "special" characters, put double-quotes
around it.
This algorithm is, of course, insufficient for complicated
strings that include both single and double quotes. In that case,
it is the user's responsibility to escape the special characters
in the string using the HTML special symbols like
"
or "
Returns: The quoted string, or the original string if it did not need to be quoted.
Parameters: key
The key that needs to be removed. Must not be
null
.
<
.Parameters: tag New tag name
At any time, this method can be called to return the current state of the HTML document. The return value is the result of processing the source document up to this point in time; the unprocessed remainder of the source document is not considered.
Due to the implementation, calling this method may be expensive.
Specifically, calling this method a second (or further) time for
a given HtmlRewriter
may involve copying temporary
strings around. The pessimal case would be to call this method
every time a new token is appended.
Returns: The rewritten HTML document, up to this point in time.