如何获取具有最小属性值的节点？

Question

我的 xml 结构是这样的：

<page height="777" width="777">
    <block r="777" l="778" blockType="Text">
        <region/>
        <separator/>
    </block>
    <block r="777" l="790" blockType="Text">
        <region/>
        <separator/>
    </block>
    <block r="777" l="688" blockType="Text">
        <region/>
        <text/>
    </block>
</page>

我想要 select 具有最小 "l" 值的块节点，即“688”

我知道 XPath 2.0 中有一个 min() 函数，但我使用的是 Xpath1.0。

我试过了

     //XPathExpression pattern2TextExpr = 
xPath.compile("//page/block[not(preceding-sibling::block/@l < = @l) and not(following-sibling::block/@l >@l)]/@l");

How can I use XPath to find the minimum value of an attribute in a set of elements?

但这给了我多个节点列表。如果它是最小的，它应该只有一个节点。任何其他可能和有效的解决方案？请建议。谢谢

Answer 1

更新 2：

根据更新后的 XML 示例，假设您想要找到 line 元素的 l 属性的最小值，请尝试以下方式：

//page/block/text/par/line[not(preceding::line/@l <= @l) and not(following::line/@l<@l)]/@l

输出：

Attribute='l="253"'

更新：

实际上，通过 preceding-sibling::block/@l <= @l 和 following-sibling::block/@l < @l 的组合，无论如何你都不可能得到重复的。由于 <=，xpath returns 只有第一个最小值，以防存在重复值。我在你的 xpath 中发现的真正问题是，你在 following-sibling 评估中使用 > 而不是使用 <.

 //page/block[
        not(preceding-sibling::block/@l <= @l) 
            and 
        not(following-sibling::block/@l < @l)
    ]/@l

But this gives me multiple nodelist. if it's min it should be only one node.

如果唯一的问题是你的 xpath 可能 return 多个值，那么你可以简单地用 ()[1] 包装整个 xpath 以将结果限制为单个值，例如（格式化为可读性) :

(
 //page/block[
        not(preceding-sibling::block/@l <= @l) 
            and 
        not(following-sibling::block/@l > @l)
    ]/@l
)[1]

在xpath tester中输出：

Attribute='l="688"'

Answer 2

这是我正在使用的 Xml。上面的 xpath 总是 returns 第一个元素。

line b="240" r="1148" t="208" l="1026"

<page originalCoords="1" resolution="300" height="3641" width="2656">
-<block b="246" r="1154" t="207" l="1020" blockName="" blockType="Text">
-<text>
-<par lineSpacing="890">
-<line b="240" r="1148" t="208" l="1026" baseline="280">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="259" r="1540" t="215" l="1336" blockName="" blockType="Text">
-<text>
-<par lineSpacing="890">
-<line b="252" r="1534" t="217" l="1342" baseline="282">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="303" r="2510" t="235" l="2075" blockName="" blockType="Text">
-<region>
<rect b="236" r="2104" t="235" l="2076"/>
<rect b="237" r="2142" t="236" l="2076"/>
<rect b="238" r="2180" t="237" l="2076"/>
</region>
-<text>
-<par lineSpacing="1000">
-<line b="289" r="2504" t="237" l="2081" baseline="283">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="966" r="1607" t="191" l="232" blockName="" blockType="Text">
-<text>
-<par lineSpacing="890" align="Justified">
-<line b="252" r="790" t="198" l="258" baseline="287">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
-<text>
-<par lineSpacing="1230" align="Justified" leftIndent="900">
-<line b="298" r="841" t="243" l="272" baseline="339">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="984">
-<line b="370" r="1479" t="299" l="255" baseline="394">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
-<line b="424" r="1605" t="343" l="253" baseline="435">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1224" align="Justified" leftIndent="900">
-<line b="467" r="1581" t="395" l="282" baseline="489">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1224" align="Justified" leftIndent="900">
-<line b="521" r="1580" t="446" l="281" baseline="540">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1224" align="Justified" leftIndent="900">
-<line b="565" r="1578" t="497" l="282" baseline="591">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified" leftIndent="900">
-<line b="618" r="1577" t="546" l="278" baseline="638">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified" leftIndent="900">
-<line b="667" r="1576" t="596" l="278" baseline="688">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified" leftIndent="900">
-<line b="718" r="1573" t="644" l="277" baseline="738">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified" leftIndent="900">
-<line b="758" r="1481" t="695" l="276" baseline="788">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified" leftIndent="900">
-<line b="818" r="1583" t="744" l="274" baseline="837">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified" leftIndent="900">
-<line b="870" r="1587" t="794" l="273" baseline="889">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="950" align="Justified" leftIndent="900">
-<line b="916" r="1580" t="842" l="272" baseline="934">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="950" align="Justified" leftIndent="900">
-<line b="960" r="1579" t="892" l="269" baseline="983">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="756" r="1748" t="428" l="1686" blockName="" blockType="Text">
-<text>
-<par lineSpacing="1360" align="Justified">
-<line b="477" r="1748" t="434" l="1694" baseline="499">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1060" align="Justified">
-<line b="516" r="1740" t="484" l="1700" baseline="541">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="950" align="Justified">
-<line b="563" r="1737" t="532" l="1699" baseline="587">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1176" align="Justified">
-<line b="608" r="1738" t="578" l="1697" baseline="632">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
-<line b="666" r="1743" t="627" l="1696" baseline="680">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="950" align="Justified">
-<line b="714" r="1742" t="672" l="1688" baseline="738">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="950" align="Justified">
-<line b="750" r="1732" t="720" l="1694" baseline="774">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="575" r="2129" t="355" l="1797" blockName="" blockType="Text">
-<text>
-<par lineSpacing="1170" leftIndent="1100">
-<line b="405" r="2055" t="362" l="1847" baseline="414">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified">
-<line b="466" r="2003" t="421" l="1800" baseline="481">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Justified">
-<line b="522" r="2120" t="471" l="1802" baseline="534">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1200" align="Right">
-<line b="569" r="2119" t="522" l="1883" baseline="579">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="421" r="2436" t="367" l="2215" blockName="" blockType="Text">
-<text>
-<par lineSpacing="950">
-<line b="415" r="2430" t="373" l="2221" baseline="414">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="585" r="2494" t="496" l="2403" blockName="" blockType="Text">
-<text>
-<par lineSpacing="890">
-<line b="531" r="2488" t="502" l="2412" baseline="535">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="890">
-<line b="579" r="2487" t="552" l="2409" baseline="582">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="766" r="2125" t="563" l="1894" blockName="" blockType="Text">
-<text>
-<par lineSpacing="890" align="Justified">
-<line b="616" r="2117" t="568" l="1904" baseline="624">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1128" align="Justified">
-<line b="676" r="2117" t="625" l="1897" baseline="676">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1128" align="Right">
-<line b="712" r="2117" t="665" l="1980" baseline="725">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
-<line b="760" r="2115" t="718" l="1900" baseline="770">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="776" r="2493" t="591" l="2399" blockName="" blockType="Text">
-<text>
-<par lineSpacing="1120" align="Justified">
-<line b="640" r="2485" t="597" l="2403" baseline="631">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1152" align="Justified">
-<line b="675" r="2484" t="646" l="2408" baseline="677">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1152" align="Justified">
-<line b="722" r="2483" t="693" l="2407" baseline="726">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1152" align="Justified">
-<line b="770" r="2483" t="742" l="2407" baseline="774">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
-<block b="935" r="2336" t="775" l="2185" blockName="" blockType="Text">
-<text>
-<par lineSpacing="1360" align="Justified">
-<line b="838" r="2328" t="780" l="2202" baseline="846">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
-<par lineSpacing="1296" align="Justified">
-<line b="889" r="2326" t="841" l="2199" baseline="886">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
-<line b="935" r="2327" t="877" l="2208" baseline="938">
<formatting lang="EnglishUnitedStates">data scrambled</formatting>
</line>
</par>
</text>
</block>
</page>

Answer 3

请使用下面的代码和已知的 xpath 1.0 解决方案，请参阅 link 此处 How can I use XPath to find the minimum value of an attribute in a set of elements?

/page/block[not(preceding-sibling::block/@l &lt;= @l) and not(following-sibling::block/@l &lt; @l)]/@l

如何获取具有最小属性值的节点？

How to get the node with min attribute value?

xml

xpath

min

nodelist