jsoup select 选择器

问题

采用CSS或类似jquery 选择器（selector）语法来处理HTML文档中的数据。

方法

利用方法：Element.select(String selector)和Elements.select(String selector)。

File input = new File("/tmp/input.html");
Document doc = Jsoup.parse(input, "UTF-8", "http://example.com/");
Elements links = doc.select("a[href]"); // a with href
Elements pngs = doc.select("img[src$=.png]");  // img with src ending .png
Element masthead = doc.select("div.masthead").first();
  // div with class=masthead
Elements resultLinks = doc.select("h3.r > a"); // direct a after h3

描述

Jsoup的元素支持类似CSS或（jquery）的选择器语法的查找匹配的元素，可实现功能强大且鲁棒性好的查询。

jsoup elements support a CSS(or jquery) like selector syntax to find matching elements, that allows very powerful and robust queries.

Select方法可作用于Document、Element或Elements，且是上下文相关的，因此可实现指定元素的过滤，或者链式选择访问。

The selectmethod is available in a Document, Element, or in Elements. It is contextual, so you can filter by selecting from a specific element, or by chaining select calls.

选择（操作）返回元素列表（Elements），并提供一组方法来提取或处理结果。

Select returns a list of Elements (as Elements), which provides a range of methods to extract and manipulate the results.

选择器概要（Selector overview）

• Tagname：通过标签查找元素（例如：a）
• ns|tag：通过标签在命名空间查找元素，例如：fb|name查找<fb:name>元素
• #id：通过ID查找元素，例如#logo
• .class：通过类型名称查找元素，例如.masthead
• [attribute]：带有属性的元素，例如[href]
• [^attr]：带有名称前缀的元素，例如[^data-]查找HTML5带有数据集（dataset）属性的元素
• [attr=value]：带有属性值的元素，例如[width=500]
• [attr^=value]，[attr$=value]，[attr*=value]：包含属性且其值以value开头、结尾或包含value的元素，例如[href*=/path/]
• [attr~=regex]：属性值满足正则表达式的元素，例如img[src~=(?i)\.(png|jpe?g)]
• *：所有元素，例如*

选择器组合方法

• el#id:：带有ID的元素ID，例如div#logo
• el.class：带类型的元素，例如. div.masthead
• el[attr]：包含属性的元素，例如a[href]
• 任意组合：例如a[href].highlight
• ancestor child：继承自某祖（父）元素的子元素，例如.body p查找“body”块下的p元素
• parent > child：直接为父元素后代的子元素，例如: div.content > pf查找p元素，body > * 查找body元素的直系子元素
• siblingA + siblingB：查找由同级元素A前导的同级元素，例如div.head + div
• siblingA ~ siblingX：查找同级元素A前导的同级元素X例如h1 ~ p
• el, el, el：多个选择器组合，查找匹配任一选择器的唯一元素，例如div.masthead, div.logo

伪选择器（Pseudo selectors）

• :lt(n)：查找索引值（即DOM树中相对于其父元素的位置）小于n的同级元素，例如td:lt(3)
• :gt(n)：查找查找索引值大于n的同级元素，例如div p:gt(2)
• :eq(n) ：查找索引值等于n的同级元素，例如form input:eq(1)
• :has(seletor)：查找匹配选择器包含元素的元素，例如div:has(p)
• :not(selector)：查找不匹配选择器的元素，例如div:not(.logo)
• :contains(text)：查找包含给定文本的元素，大小写铭感，例如p:contains(jsoup)
• :containsOwn(text)：查找直接包含给定文本的元素
• :matches(regex)：查找其文本匹配指定的正则表达式的元素，例如div:matches((?i)login)
• :matchesOwn(regex)：查找其自身文本匹配指定的正则表达式的元素
• 注意：上述伪选择器是0-基数的，亦即第一个元素索引值为0，第二个元素index为1等

详见SelectorAPI 参考资料所列全部信息和细节。

【原文】http://jsoup.org/cookbook/extracting-data/selector-syntax

-------------------------------------------------------------------------------------------------------------------------------

CSS-like element selector, that finds elements matching a query.

Selector syntax

A selector is a chain of simple selectors, separated by combinators. Selectors are case insensitive (including against elements, attributes, and attribute values).

The universal selector (*) is implicit when no element selector is supplied (i.e. *.header and .header is equivalent).

PatternMatchesExample*any element*tagelements with the given tag namedivns|Eelements of type E in the namespace nsfb|name finds <fb:name> elements#idelements with attribute ID of "id"div#wrap, #logo.classelements with a class name of "class"div.left, .result[attr]elements with an attribute named "attr" (with any value)a[href], [title][^attrPrefix]elements with an attribute name starting with "attrPrefix". Use to find elements with HTML5 datasets[^data-], div[^data-][attr=val]elements with an attribute named "attr", and value equal to "val"img[width=500], a[rel=nofollow][attr^=valPrefix]elements with an attribute named "attr", and value starting with "valPrefix"a[href^=http:][attr$=valSuffix]elements with an attribute named "attr", and value ending with "valSuffix"img[src$=.png][attr*=valContaining]elements with an attribute named "attr", and value containing "valContaining"a[href*=/search/][attr~=regex]elements with an attribute named "attr", and value matching the regular expressionimg[src~=(?i)\\.(png|jpe?g)] The above may be combined in any orderdiv.header[title] 

Combinators

E Fan F element descended from an E elementdiv a, .logo h1E > Fan F direct child of Eol > liE + Fan F element immediately preceded by sibling Eli + li, div.head + divE ~ Fan F element preceded by sibling Eh1 ~ pE, F, Gall matching elements E, F, or Ga[href], div, h3 

Pseudo selectors

:lt(n)elements whose sibling index is less than ntd:lt(3) finds the first 2 cells of each row:gt(n)elements whose sibling index is greater than ntd:gt(1) finds cells after skipping the first two:eq(n)elements whose sibling index is equal to ntd:eq(0) finds the first cell of each row:has(selector)elements that contains at least one element matching the selectordiv:has(p) finds divs that contain p elements:not(selector)elements that do not match the selector. See also Elements.not(String)div:not(.logo) finds all divs that do not have the "logo" class.
div:not(:has(div)) finds divs that do not contain divs.:contains(text)elements that contains the specified text. The search is case insensitive. The text may appear in the found element, or any of its descendants.p:contains(jsoup) finds p elements containing the text "jsoup".:matches(regex)elements whose text matches the specified regular expression. The text may appear in the found element, or any of its descendants.td:matches(\\d+) finds table cells containing digits. div:matches((?i)login) finds divs containing the text, case insensitively.:containsOwn(text)elements that directly contain the specified text. The search is case insensitive. The text must appear in the found element, not any of its descendants.p:containsOwn(jsoup) finds p elements with own text "jsoup".:matchesOwn(regex)elements whose own text matches the specified regular expression. The text must appear in the found element, not any of its descendants.td:matchesOwn(\\d+) finds table cells directly containing digits.div:matchesOwn((?i)login) finds divs containing the text, case insensitively. The above may be combined in any order and with other selectors.light:contains(name):eq(0)

Structural pseudo selectors

:rootThe element that is the root of the document. In HTML, this is the html element:root:nth-child(an+b)

elements that have an+b-1 siblings before it in the document tree, for any positive integer or zero value of n, and has a parent element. For values of a and b greater than zero, this effectively divides the element's children into groups of a elements (the last group taking the remainder), and selecting the bth element of each group. For example, this allows the selectors to address every other row in a table, and could be used to alternate the color of paragraph text in a cycle of four. The a and b values must be integers (positive, negative, or zero). The index of the first child of an element is 1.

In addition to this, :nth-child() can take odd and even as arguments instead. odd has the same signification as 2n+1, and even has the same signification as 2n.tr:nth-child(2n+1) finds every odd row of a table. :nth-child(10n-1) the 9th, 19th, 29th, etc, element. li:nth-child(5) the 5h li:nth-last-child(an+b)elements that have an+b-1 siblings after it in the document tree. Otherwise like :nth-child()tr:nth-last-child(-n+2) the last two rows of a table:nth-of-type(an+b)pseudo-class notation represents an element that has an+b-1 siblings with the same expanded element name before it in the document tree, for any zero or positive integer value of n, and has a parent elementimg:nth-of-type(2n+1):nth-last-of-type(an+b)pseudo-class notation represents an element that has an+b-1 siblings with the same expanded element name after it in the document tree, for any zero or positive integer value of n, and has a parent elementimg:nth-last-of-type(2n+1):first-childelements that are the first child of some other element.div > p:first-child:last-childelements that are the last child of some other element.ol > li:last-child:first-of-typeelements that are the first sibling of its type in the list of children of its parent elementdl dt:first-of-type:last-of-typeelements that are the last sibling of its type in the list of children of its parent elementtr > td:last-of-type:only-childelements that have a parent element and whose parent element hasve no other element children :only-of-typean element that has a parent element and whose parent element has no other element children with the same expanded element name :emptyelements that have no children at all