用Java讀取XML文件

Question

我是Java的新手，我想解析一個xml文件

我有一個這樣的xml文件格式

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <metadonnees>
        <factory type="factory1">
            <icones>
                <icone type="empty" path="src/ressources/UMP0%.png"/>
                <icone type="half" path="src/ressources/UMP33%.png"/>
                <icone type="full" path="src/ressources/UMP100%.png"/>
            </icones>
            <out type = "materiel1"/>
            <interval>100</interval>
        </factory>
        <factory type="factory2">
            <icones>
                <icone type="empty" path="src/ressources/UT0%.png"/>
                <icone type="half" path="src/ressources/UT33%.png"/>
                <icone type="full" path="src/ressources/UT100%.png"/>
            </icones>
            <enter type="materiel1" quantite="2"/>
            <out type="materiel2"/>
            <interval> 2 </interval>
        </factory>

    </metadonnees>

    <simulation>
        <factory type="factoty1" id="11" x="32" y="32"/>
        <factory type="factory2" id="21" x="320" y="32"/>

        <paths>
            <path de="11" vers="21" />
            <path de="21" vers="41" />
            <path de="41" vers="51" />
            </paths>
    </simulation>

</configuration>

我嘗試使用Java讀取它，但遇到了麻煩

NodeList config = document.getElementsByTagName("metadonnees");

for(int j = 0;j<config.getLength();j++) {

    NodeList usineList = document.getElementsByTagName("factory");
    for (int i = 0; i < usineList.getLength(); i++) {
        Node usine = usineList.item(i);
        if (usine.getNodeType() == Node.ELEMENT_NODE) {
            Element type = (Element) usine;
            String typeUsine = type.getAttribute("type");

            System.out.println(typeUsine);
        }
    }
}

此列表僅列出我的工廠類型

• 工廠1
• 工廠2
• 工廠1
• 工廠2

我只想在metadonnee部分中列出數據，所以我可以獲取出廠設置以及如何分別獲取圖標

我該如何解決？

Answer 1

在您的代碼中， document.getElementsByTagName("factory"); 返回所有帶有標簽<factory>元素。 如果要限制在元數據metadonnees部分中的選擇，則可以使用XPath（XML路徑語言）。

獲取元素

獲取元數據中的所有factory元素：

//metadonnees/factory

Java代碼：

XPath xPath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xPath.compile("//metadonnees/factory");
NodeList usineList = (NodeList) expr.evaluate(document, XPathConstants.NODESET);
for (int i = 0; i < usineList.getLength(); i++) {
  Element usine = (Element) usineList.item(i);
  String typeUsine = usine.getAttribute("type");
  System.out.println(typeUsine);
}

獲取屬性

獲取元數據中factory元素的所有type屬性：

//metadonnees/factory/@type

Java代碼：

XPath xPath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xPath.compile("//metadonnees/factory/@type");
NodeList typeList = (NodeList) expr.evaluate(document, XPathConstants.NODESET);
for (int i = 0; i < typeList.getLength(); i++) {
  Attr type = (Attr) typeList.item(i);
  System.out.println(type.getValue());
}

獲取子節點

查詢factory的子節點時，您需要以下xpath，這意味着查詢從當前節點（ . ）開始，一直持續到元素<icone>為止：

.//icone

Java代碼：

XPath xPath = XPathFactory.newInstance().newXPath();
NodeList usineList =
    (NodeList) xPath.evaluate("//metadonnees/factory", document, XPathConstants.NODESET);
for (int i = 0; i < usineList.getLength(); i++) {
  Element usine = (Element) usineList.item(i);
  NodeList icons = (NodeList) xPath.evaluate(".//icone", usine, XPathConstants.NODESET);
  System.out.println(usine.getAttribute("type"));

  for (int j = 0; j < icons.getLength(); j++) {
    Element icon = (Element) icons.item(j);
    String type = icon.getAttribute("type");
    String path = icon.getAttribute("path");
    String msg = "type=" + type + ", path=" + path;
    System.out.println(msg);
  }
}

結果：

factory1
type=empty, path=src/ressources/UMP0%.png
type=half, path=src/ressources/UMP33%.png
type=full, path=src/ressources/UMP100%.png
factory2
type=empty, path=src/ressources/UT0%.png
type=half, path=src/ressources/UT33%.png
type=full, path=src/ressources/UT100%.png

Answer 2

SimpleXml可以做到這一點：

final String data = ...
final SimpleXml simple = new SimpleXml();
final Element element = simple.fromXml(data);
for (final Element factory : element.children.get(0).children) {
    for (final Element icone : factory.children.get(0).children) {
        System.out.println(String.format("Factory: %s, Icone: %s", factory.attributes.get("type"), icone.attributes.get("type")));
    }
}

將輸出：

Factory: factory1, Icone: empty
Factory: factory1, Icone: half
Factory: factory1, Icone: full
Factory: factory2, Icone: empty
Factory: factory2, Icone: half
Factory: factory2, Icone: full

從Maven Central：

<dependency>
    <groupId>com.github.codemonstur</groupId>
    <artifactId>simplexml</artifactId>
    <version>1.4.0</version>
</dependency>