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[7.8] [DOCS] Reformat html_strip charfilter (#57764) #57811

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Jun 8, 2020
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[7.8] [DOCS] Reformat html_strip charfilter (#57764) #57811

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157 changes: 80 additions & 77 deletions docs/reference/analysis/charfilters/htmlstrip-charfilter.asciidoc
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Original file line number Diff line number Diff line change
@@ -1,29 +1,44 @@
[[analysis-htmlstrip-charfilter]]
=== HTML Strip Char Filter
=== HTML strip character filter
++++
<titleabbrev>HTML strip</titleabbrev>
++++

The `html_strip` character filter strips HTML elements from the text and
replaces HTML entities with their decoded value (e.g. replacing `&amp;` with
`&`).
Strips HTML elements from a text and replaces HTML entities with their decoded
value (e.g, replaces `&amp;` with `&`).

[float]
=== Example output
The `html_strip` filter uses Lucene's
{lucene-analysis-docs}/charfilter/HTMLStripCharFilter.html[HTMLStripCharFilter].

[[analysis-htmlstrip-charfilter-analyze-ex]]
==== Example

The following <<indices-analyze,analyze API>> request uses the
`html_strip` filter to change the text `<p>I&apos;m so <b>happy</b>!</p>` to
`\nI'm so happy!\n`.

[source,console]
---------------------------
POST _analyze
----
GET /_analyze
{
"tokenizer": "keyword", <1>
"char_filter": [ "html_strip" ],
"tokenizer": "keyword",
"char_filter": [
"html_strip"
],
"text": "<p>I&apos;m so <b>happy</b>!</p>"
}
---------------------------
----

<1> The <<analysis-keyword-tokenizer,`keyword` tokenizer>> returns a single term.
The filter produces the following text:

/////////////////////
[source,text]
----
[ \nI'm so happy!\n ]
----

////
[source,console-result]
----------------------------
----
{
"tokens": [
{
Expand All @@ -35,93 +50,81 @@ POST _analyze
}
]
}
----------------------------

/////////////////////

----
////

The above example returns the term:
[[analysis-htmlstrip-charfilter-analyzer-ex]]
==== Add to an analyzer

[source,text]
---------------------------
[ \nI'm so happy!\n ]
---------------------------

The same example with the `standard` tokenizer would return the following terms:
The following <<indices-create-index,create index API>> request uses the
`html_strip` filter to configure a new
<<analysis-custom-analyzer,custom analyzer>>.

[source,text]
---------------------------
[ I'm, so, happy ]
---------------------------

[float]
=== Configuration
[source,console]
----
PUT /my_index
{
"settings": {
"analysis": {
"analyzer": {
"my_analyzer": {
"tokenizer": "keyword",
"char_filter": [
"html_strip"
]
}
}
}
}
}
----

The `html_strip` character filter accepts the following parameter:
[[analysis-htmlstrip-charfilter-configure-parms]]
==== Configurable parameters

[horizontal]
`escaped_tags`::
(Optional, array of strings)
Array of HTML elements without enclosing angle brackets (`< >`). The filter
skips these HTML elements when stripping HTML from the text. For example, a
value of `[ "p" ]` skips the `<p>` HTML element.

An array of HTML tags which should not be stripped from the original text.
[[analysis-htmlstrip-charfilter-customize]]
==== Customize

[float]
=== Example configuration
To customize the `html_strip` filter, duplicate it to create the basis
for a new custom token filter. You can modify the filter using its configurable
parameters.

In this example, we configure the `html_strip` character filter to leave `<b>`
tags in place:
The following <<indices-create-index,create index API>> request
configures a new <<analysis-custom-analyzer,custom analyzer>> using a custom
`html_strip` filter, `my_custom_html_strip_char_filter`.

The `my_custom_html_strip_char_filter` filter skips the removal of the `<b>`
HTML element.

[source,console]
----------------------------
----
PUT my_index
{
"settings": {
"analysis": {
"analyzer": {
"my_analyzer": {
"tokenizer": "keyword",
"char_filter": ["my_char_filter"]
"char_filter": [
"my_custom_html_strip_char_filter"
]
}
},
"char_filter": {
"my_char_filter": {
"my_custom_html_strip_char_filter": {
"type": "html_strip",
"escaped_tags": ["b"]
"escaped_tags": [
"b"
]
}
}
}
}
}

POST my_index/_analyze
{
"analyzer": "my_analyzer",
"text": "<p>I&apos;m so <b>happy</b>!</p>"
}
----------------------------

/////////////////////

[source,console-result]
----------------------------
{
"tokens": [
{
"token": "\nI'm so <b>happy</b>!\n",
"start_offset": 0,
"end_offset": 32,
"type": "word",
"position": 0
}
]
}
----------------------------

/////////////////////


The above example produces the following term:

[source,text]
---------------------------
[ \nI'm so <b>happy</b>!\n ]
---------------------------
----