HtmlToXml Lua Reference Documentation
chilkat.HtmlToXml
Current Version: 11.7.0
Markdown version of this page for AI tools (v 11.7.0) · all AI docs
Chilkat.HtmlToXml
Convert real-world HTML into well-formed XML that can be loaded into
Supply HTML from strings, files, byte arrays,
Remove specific tag types from the output when the application wants a
cleaner XML result focused on relevant content.
Drop common formatting tags when the structure matters more than visual
presentation.
Control how non-breaking spaces are represented, converted, removed, or
preserved in the XML output.
Choose the XML charset and write the converted XML directly to a file
when a persisted result is needed.
For an extended overview, see
HtmlToXml Class Overview.
Convert HTML into well-formed XML for structured parsing and searching.
Chilkat.HtmlToXml converts HTML into well-formed XML so the
content can be parsed, searched, transformed, or processed programmatically
with XML tools. It can accept HTML from strings, files, byte arrays,
BinData, or StringBuilder, and provides options for
dropping selected tags, removing common text-formatting tags, controlling
non-breaking spaces, choosing the XML charset, and saving the converted XML
to a file.
HTML to XML conversion
Chilkat.Xml or other XML processing tools.
Flexible input sources
BinData, or
StringBuilder depending on how the content is received or
built.
Drop selected tags
Text-formatting cleanup
NBSP handling
Charset and file output
Nbsp behavior, and
XmlCharset, then call the conversion method and parse the result
as XML. Use HtmlToXml when structured extraction is needed; use
HtmlToText when the goal is readable plain text.
Object Creation
local chilkat = require("chilkat")
local html_to_xml = chilkat.HtmlToXml.new()Creates the object (chilkat.HtmlToXml() does the same). Lua's garbage collector frees it when it is no longer referenced; html_to_xml:dispose() frees it at once, and in Lua 5.4 and later local html_to_xml <close> = chilkat.HtmlToXml.new() frees it when the block ends. Calling a method of a disposed object raises an error.
Errors
A method that fails returns nil followed by the error text, as io.open does: local body, err = html_to_xml:method(...), where err is the object's last_error_text. Wrap the call in assert() to raise an error with that text instead. Methods that answer a question return true or false, numbers are returned as they are (check last_method_success where the description says a value means failure), and property reads and writes never fail for Chilkat reasons.
Misuse raises a Lua error: a wrong argument type or a missing argument (bad argument #1 to ...), an unknown property name, a write to a read-only property, an out-of-range integer, or an object of the wrong class.
Names are Chilkat's in snake_case: QuickGetStr is quick_get_str, LastErrorText is last_error_text. Properties are fields (html_to_xml.verbose_logging = true) and methods use the colon (html_to_xml:method(...)). Strings are UTF-8; binary data is a Lua string of bytes. Indexes are 0-based, as in every Chilkat API. Unlocking: call chilkat.unlock_bundle("...") once at startup.
Properties
DebugLogFilePath
local strVal = html_to_xml.debug_log_file_path
html_to_xml.debug_log_file_path = strVal
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.
DropCustomTags
local boolVal = html_to_xml.drop_custom_tags
html_to_xml.drop_custom_tags = boolVal
Controls whether tags that Chilkat does not recognize as standard HTML elements are omitted from the generated XML.
true when custom or application-specific tags would add noise to the XML structure. Leave it false when those tags are meaningful to the application and should remain represented in the converted output.Html
local strVal = html_to_xml.html
html_to_xml.html = strVal
The HTML source to be converted. Set this property to an HTML string, configure any conversion options, and then call ToXml, Xml, or ToXmlSb.
Assigning this property replaces the current in-memory HTML source. For file-to-file conversion, use ConvertFile. To load HTML from a file, BinData, or StringBuilder, use the corresponding SetHtml* method.
<text> elements to simplify programmatic extraction.LastErrorHtml
local strVal = html_to_xml.last_error_html
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
local strVal = html_to_xml.last_error_text
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
local strVal = html_to_xml.last_error_xml
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.
topLastMethodSuccess
local boolVal = html_to_xml.last_method_success
html_to_xml.last_method_success = boolVal
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.
Nbsp
local intVal = html_to_xml.nbsp
html_to_xml.nbsp = intVal
Controls how HTML non-breaking-space entities are handled during conversion. The default value is 0.
| Value | Behavior for |
|---|---|
0 | Convert to a normal space character (U+0020). |
1 | Convert to the numeric character reference   (U+00A0). |
2 | Drop the non-breaking-space entity. |
3 | Leave the entity unconverted by this option. |
This setting applies specifically to the HTML entity ; it does not define general whitespace normalization.
VerboseLogging
local boolVal = html_to_xml.verbose_logging
html_to_xml.verbose_logging = boolVal
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
local strVal = html_to_xml.version
XmlCharset
local strVal = html_to_xml.xml_charset
html_to_xml.xml_charset = strVal
Specifies the character encoding to identify for the generated XML, such as utf-8 or iso-8859-1. If this property is empty, Chilkat uses the character encoding of the HTML input. Otherwise, the converted XML uses the specified charset.
ToXml or Xml is a string in the programming language's native string representation, while the XML declaration reflects XmlCharset. When writing that string to a file, use the same charset so the file bytes agree with the XML declaration. ConvertFile performs the file conversion directly.Methods
ConvertFile
-- dest_xml_path is a string
-- ok is true, or nil and err on failure
local ok, err = html_to_xml:convert_file(in_html_path, dest_xml_path)
Converts the HTML file at inHtmlPath to a well-formed XML file at destXmlPath. The output encoding is controlled by XmlCharset; if XmlCharset is empty, Chilkat uses the HTML source encoding.
Returns true on success and false on failure.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
DropTagType
html_to_xml:drop_tag_type(tag_name)
Marks the specified HTML tag type to be dropped from the generated XML. To drop multiple tag types, call this method once for each tag name.
The setting remains in effect for subsequent conversions performed by this HtmlToXml object. Use UndropTagType to reverse the setting for a particular tag type.
DropTextFormattingTags
Configures the converter to drop common text-formatting tags from the generated XML. The affected tag names are:
b, font, i, u, br, center, em, strong, big, tt, s, small, strike, sub, and sup.
This is useful when the formatting markup is not relevant to later XML parsing and the application wants a simpler structural representation. Call UndropTextFormattingTags to keep these tags instead.
SetHtmlBd
-- ok is true, or nil and err on failure
local ok, err = html_to_xml:set_html_bd(bd)
Replaces the current HTML source with the complete contents of bd.
The data is copied from the supplied BinData object and becomes the input for a later call to ToXml, Xml, or ToXmlSb. Returns true on success and false on failure.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetHtmlFromFile
-- ok is true, or nil and err on failure
local ok, err = html_to_xml:set_html_from_file(filename)
Loads HTML from filename and replaces the current Html input with the file contents.
Returns true on success and false if the file cannot be read or the HTML input cannot be loaded. Call ToXml, Xml, or ToXmlSb afterward to perform the conversion.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetHtmlSb
-- ok is true, or nil and err on failure
local ok, err = html_to_xml:set_html_sb(sb)
Replaces the current HTML source with the complete contents of sb.
The text is copied from the supplied StringBuilder and becomes the input for a later call to ToXml, Xml, or ToXmlSb. Returns true on success and false on failure.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToXml
local str, err = html_to_xml:to_xml()
Converts the current Html input to well-formed XML and returns the XML string. The generated XML uses the conversion settings currently configured on this object, including DropCustomTags, dropped tag types, Nbsp, and XmlCharset.
<text> elements to make extraction with XML tools straightforward.Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToXmlSb
-- ok is true, or nil and err on failure
local ok, err = html_to_xml:to_xml_sb(sb)
Converts the current Html input to well-formed XML and appends the generated XML to sb.
Returns true on success and false on failure. Because the result is appended, clear the destination StringBuilder first when replacement rather than concatenation is desired.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
UndropTagType
html_to_xml:undrop_tag_type(tag_name)
Reverses a previous DropTagType setting for the specified tag name so that tag type is no longer intentionally dropped from subsequent XML output.
This affects only the named tag type. Other tag types previously configured to be dropped remain unchanged.
topUndropTextFormattingTags
Configures the converter to retain the common text-formatting tags that are otherwise dropped by default:
b, font, i, u, br, center, em, strong, big, tt, s, small, strike, sub, and sup.
Call DropTextFormattingTags to return to dropping these formatting tags.
Xml
local str, err = html_to_xml:xml()
Equivalent to ToXml. Converts the current Html input to well-formed XML and returns the XML string using the object's current conversion settings.
This method is provided as an alternate name for ToXml; it does not perform a different conversion.
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.