Java 解析 XML

标簽： Java基礎

XML解析技術有兩種

DOM

SAX

DOM方式

根據XML的層級結構在記憶體中配置設定一個樹形結構,把XML的标簽,屬性和文本等元素都封裝成樹的節點對象
- 優點: 便于實作 增 删 改 查
- 缺點: XML檔案過大可能造成記憶體溢出
SAX方式

采用事件驅動模型邊讀邊解析:從上到下一行行解析,解析到某一進制素, 調用相應解析方法
- 優點: 不會造成記憶體溢出,
- 缺點: 查詢不友善,但不能實作 增 删 改

不同的公司群組織提供了針對DOM和SAX兩種方式的解析器

SUN的 jaxp
Dom4j組織的 dom4j (最常用:如Spring)
JDom組織的 jdom 關于這三種解析器淵源可以參考java解析xml檔案四種方式.

JAXP 解析

JAXP是JavaSE的一部分,在

javax.xml.parsers

包下,分别針對dom與sax提供了如下解析器:

Dom
- DocumentBuilder
- DocumentBuilderFactory
SAX
- SAXParser
- SAXParserFactory

示例XML如下,下面我們會使用JAXP對他進行

增

删

改

查

操作

config.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE beans SYSTEM "constraint.dtd">
<beans>
    <bean id="id1" class="com.fq.domain.Bean">
        <property name="isUsed" value="true"/>
    </bean>
    <bean id="id2" class="com.fq.domain.ComplexBean">
        <property name="refBean" ref="id1"/>
    </bean>
</beans>

constraint.dtd

<!ELEMENT beans (bean*) >
        <!ELEMENT bean (property*)>
        <!ATTLIST bean
                id CDATA #REQUIRED
                class CDATA #REQUIRED
                >

        <!ELEMENT property EMPTY>
        <!ATTLIST property
                name CDATA #REQUIRED
                value CDATA #IMPLIED
                ref CDATA #IMPLIED>

JAXP-Dom

/**
 * @author jifang
 * @since 16/1/13下午11:24.
 */
public class XmlRead {

    @Test
    public void client() throws ParserConfigurationException, IOException, SAXException {
        // 生成一個Dom解析器
        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();

        // 解析XML檔案
        Document document = builder.parse(ClassLoader.getSystemResourceAsStream("config.xml"));

        // ...
    }
}

DocumentBuilder

的

parse(String/File/InputSource/InputStream param)

方法可以将一個XML檔案解析為一個

Document

對象,代表整個文檔.

Document

(

org.w3c.dom

包下)是一個接口,其父接口為

Node

Node

的其他子接口還有

Element

Attr

Text

等.

Node

`Node` 常用方法	釋義
`Node appendChild(Node newChild)`	Adds the node newChild to the end of the list of children of this node.
`Node removeChild(Node oldChild)`	Removes the child node indicated by oldChild from the list of children, and returns it.
`NodeList getChildNodes()`	A NodeList that contains all children of this node.
`NamedNodeMap getAttributes()`	A NamedNodeMap containing the attributes of this node (if it is an Element) or null otherwise.
`String getTextContent()`	This attribute returns the text content of this node and its descendants.

Document

`Document` 常用方法	釋義
`NodeList getElementsByTagName(String tagname)`	Returns a NodeList of all the Elements in document order with a given tag name and are contained in the document.
`Element createElement(String tagName)`	Creates an element of the type specified.
`Text createTextNode(String data)`	Creates a Text node given the specified string.
`Attr createAttribute(String name)`	Creates an Attr of the given name.

Dom查詢

解析 <bean/> 标簽上的所有屬性

public class XmlRead {

    private Document document;

    @Before
    public void setUp() throws ParserConfigurationException, IOException, SAXException {
        document = DocumentBuilderFactory.newInstance().newDocumentBuilder()
                .parse(ClassLoader.getSystemResourceAsStream("config.xml"));
    }

    @Test
    public void client() throws ParserConfigurationException, IOException, SAXException {
        NodeList beans = document.getElementsByTagName("bean");
        for (int i = ; i < beans.getLength(); ++i) {
            NamedNodeMap attributes = beans.item(i).getAttributes();
            scanNameNodeMap(attributes);
        }
    }

    private void scanNameNodeMap(NamedNodeMap attributes) {
        for (int i = ; i < attributes.getLength(); ++i) {
            Attr attribute = (Attr) attributes.item(i);
            System.out.printf("%s -> %s%n", attribute.getName(), attribute.getValue());
            // System.out.println(attribute.getNodeName() + " -> " + attribute.getTextContent());
        }
    }
}

列印XML檔案所有标簽名

@Test
public void client() {
    list(document, );
}

private void list(Node node, int depth) {
    if (node.getNodeType() == Node.ELEMENT_NODE) {
        for (int i = ; i < depth; ++i)
            System.out.print("\t");
        System.out.println("<" + node.getNodeName() + ">");
    }

    NodeList childNodes = node.getChildNodes();
    for (int i = ; i < childNodes.getLength(); ++i) {
        list(childNodes.item(i), depth + );
    }
}

Dom添加節點

在第一個 <bean/> 标簽下添加一個 <property/> 标簽,最終結果形式:

<bean id="id1" class="com.fq.domain.Bean">
    <property name="isUsed" value="true"/>
    <property name="name" value="simple-bean">新添加的</property>
</bean>

/**
 * @author jifang
 * @since 16/1/17 下午5:56.
 */
public class XmlAppend {

    // 文檔回寫器
    private Transformer transformer;

    // xml文檔
    private Document document;

    @Before
    public void setUp() throws ParserConfigurationException, IOException, SAXException {
        document = DocumentBuilderFactory.newInstance().newDocumentBuilder()
                .parse(ClassLoader.getSystemResourceAsStream("config.xml"));
    }

    @Test
    public void client() {
        // 得到第一bean标簽
        Node firstBean = document.getElementsByTagName("bean").item();

        /** 建立一個property标簽 **/
        Element property = document.createElement("property");

        // 為property标簽添加屬性
        // property.setAttribute("name", "name");
        // property.setAttribute("value", "feiqing");
        Attr name = document.createAttribute("name");
        name.setValue("name");
        property.setAttributeNode(name);
        Attr value = document.createAttribute("value");
        value.setValue("simple-bean");
        property.setAttributeNode(value);

        // 為property标簽添加内容
        //property.setTextContent("新添加的");
        property.appendChild(document.createTextNode("新添加的"));

        // 将property标簽添加到bean标簽下
        firstBean.appendChild(property);
    }

    @After
    public void tearDown() throws TransformerException {
        transformer = TransformerFactory.newInstance().newTransformer();

        // 寫回XML
        transformer.transform(new DOMSource(document),
                new StreamResult("src/main/resources/config.xml"));
    }
}

注意: 必須将記憶體中的DOM寫回XML文檔才能生效

Dom更新節點

将剛剛添加的 <property/> 修改如下

<property name="name" value="new-simple-bean">simple-bean是新添加的</property>

@Test
public void client() {
    NodeList properties = document.getElementsByTagName("property");
    for (int i = ; i < properties.getLength(); ++i) {
        Element property = (Element) properties.item(i);
        if (property.getAttribute("value").equals("simple-bean")) {
            property.setAttribute("value", "new-simple-bean");
            property.setTextContent("simple-bean是新添加的");
            break;
        }
    }
}

Dom删除節點

删除剛剛修改的

<property/>

标簽

@Test
public void client() {
    NodeList properties = document.getElementsByTagName("property");
    for (int i = ; i < properties.getLength(); ++i) {
        Element property = (Element) properties.item(i);
        if (property.getAttribute("value").equals("new-simple-bean")) {
            property.getParentNode().removeChild(property);
            break;
        }
    }
}

JAXP-SAX

SAXParser

執行個體需要從

SAXParserFactory

執行個體的

newSAXParser()

方法獲得, 用于解析XML檔案的

parse(String uri, DefaultHandler dh)

方法沒有傳回值,但比DOM方法多了一個事件處理器參數

DefaultHandler

解析到開始标簽,自動調用 DefaultHandler 的 startElement() 方法;
解析到标簽内容(文本),自動調用 DefaultHandler 的 characters() 方法;
解析到結束标簽,自動調用 DefaultHandler 的 endElement() 方法.

Sax查詢

列印整個XML文檔

/**
 * @author jifang
 * @since 16/1/17 下午9:16.
 */
public class SaxRead {

    @Test
    public void client() throws ParserConfigurationException, IOException, SAXException {
        SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
        parser.parse(ClassLoader.getSystemResourceAsStream("config.xml"), new SaxHandler());
    }

    private class SaxHandler extends DefaultHandler {

        @Override
        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            System.out.print("<" + qName);
            for (int i = ; i < attributes.getLength(); ++i) {
                String attrName = attributes.getQName(i);
                String attrValue = attributes.getValue(i);
                System.out.print(" " + attrName + "=" + attrValue);
            }
            System.out.print(">");
        }

        @Override
        public void characters(char[] ch, int start, int length) throws SAXException {
            System.out.print(new String(ch, start, length));
        }

        @Override
        public void endElement(String uri, String localName, String qName) throws SAXException {
            System.out.print("</" + qName + ">");
        }
    }
}

列印所有 property 标簽内容的 Handler

private class SaxHandler extends DefaultHandler {
    // 用互斥鎖保護isProperty變量
    private boolean isProperty = false;
    private Lock mutex = new ReentrantLock();

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if (qName.equals("property")) {
            mutex.lock();
            isProperty = true;
        }
    }

    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        // 隻有被鎖定之後才有可能是true
        if (isProperty) {
            System.out.println(new String(ch, start, length));
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (qName.equals("property")) {
            try {
                isProperty = false;
            } finally {
                mutex.unlock();
            }
        }
    }
}

注: SAX方式不能實作 增 删 改 操作.

Dom4j解析

Dom4j是JDom的一種智能分支,從原先的JDom組織中分離出來,提供了比JDom功能更加強大,性能更加卓越的Dom4j解析器(比如提供對XPath支援).

使用Dom4j需要在pom中添加如下依賴:

<dependency>
    <groupId>dom4j</groupId>
    <artifactId>dom4j</artifactId>
    <version>1.6.1</version>
</dependency>

示例XML如下,下面我們會使用Dom4j對他進行

增

删

改

查

操作:

config.xml

<?xml version="1.0" encoding="utf-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.fq.me/context"
       xsi:schemaLocation="http://www.fq.me/context http://www.fq.me/context/context.xsd">
    <bean id="id1" class="com.fq.benz">
        <property name="name" value="benz"/>
    </bean>
    <bean id="id2" class="com.fq.domain.Bean">
        <property name="isUsed" value="true"/>
        <property name="complexBean" ref="id1"/>
    </bean>
</beans>

context.xsd

<?xml version="1.0" encoding="utf-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
        targetNamespace="http://www.fq.me/context"
        elementFormDefault="qualified">
    <element name="beans">
        <complexType>
            <sequence>
                <element name="bean" maxOccurs="unbounded">
                    <complexType>
                        <sequence>
                            <element name="property" maxOccurs="unbounded">
                                <complexType>
                                    <attribute name="name" type="string" use="required"/>
                                    <attribute name="value" type="string" use="optional"/>
                                    <attribute name="ref" type="string" use="optional"/>
                                </complexType>
                            </element>
                        </sequence>
                        <attribute name="id" type="string" use="required"/>
                        <attribute name="class" type="string" use="required"/>
                    </complexType>
                </element>
            </sequence>
        </complexType>
    </element>
</schema>

/**
 * @author jifang
 * @since 16/1/18下午4:02.
 */
public class Dom4jRead {

    @Test
    public void client() throws DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(ClassLoader.getSystemResource("config.xml"));
        // ...
    }
}

與JAXP類似

Document

也是一個接口(

org.dom4j

包下),其父接口是

Node

Node

的子接口還有

Element

Attribute

Document

Text

CDATA

Branch

等

Node

`Node` 常用方法	釋義
`Element getParent()`	getParent returns the parent Element if this node supports the parent relationship or null if it is the root element or does not support the parent relationship.

Document

`Document` 常用方法	釋義
`Element getRootElement()`	Returns the root Elementfor this document.

Element

`Element` 常用方法	釋義
`void add(Attribute/Text param)`	Adds the given Attribute/Text to this element.
`Element addAttribute(String name, String value)`	Adds the attribute value of the given local name.
`Attribute attribute(int index)`	Returns the attribute at the specified indexGets the
`Attribute attribute(String name)`	Returns the attribute with the given name
`Element element(String name)`	Returns the first element for the given local name and any namespace.
`Iterator elementIterator()`	Returns an iterator over all this elements child elements.
`Iterator elementIterator(String name)`	Returns an iterator over the elements contained in this element which match the given local name and any namespace.
`List elements()`	Returns the elements contained in this element.
`List elements(String name)`	Returns the elements contained in this element with the given local name and any namespace.

Branch

`Branch` 常用方法	釋義
`Element addElement(String name)`	Adds a new Element node with the given name to this branch and returns a reference to the new node.
`boolean remove(Node node)`	Removes the given Node if the node is an immediate child of this branch.

Dom4j查詢

列印所有屬性資訊:

/**
 * @author jifang
 * @since 16/1/18下午4:02.
 */
public class Dom4jRead {

    private Document document;

    @Before
    public void setUp() throws DocumentException {
        document = new SAXReader()
                .read(ClassLoader.getSystemResource("config.xml"));
    }

    @Test
    @SuppressWarnings("unchecked")
    public void client() {
        Element beans = document.getRootElement();

        for (Iterator iterator = beans.elementIterator(); iterator.hasNext(); ) {
            Element bean = (Element) iterator.next();
            String id = bean.attributeValue("id");
            String clazz = bean.attributeValue("class");
            System.out.println("id: " + id + ", class: " + clazz);

            scanProperties(bean.elements());
        }
    }

    public void scanProperties(List<? extends Element> properties) {
        for (Element property : properties) {
            System.out.print("name: " + property.attributeValue("name"));
            Attribute value = property.attribute("value");
            if (value != null) {
                System.out.println("," + value.getName() + ": " + value.getValue());
            }
            Attribute ref = property.attribute("ref");
            if (ref != null) {
                System.out.println("," + ref.getName() + ": " + ref.getValue());
            }
        }
    }
}

Dom4j添加節點

在第一個

<bean/>

标簽末尾添加

<property/>

标簽

<bean id="id1" class="com.fq.benz"> 
    <property name="name" value="benz"/>  
    <property name="refBean" ref="id2">新添加的标簽</property>
</bean>

/**
 * @author jifang
 * @since 16/1/19上午9:50.
 */
public class Dom4jAppend {

    //...

    @Test
    public void client() {
        Element beans = document.getRootElement();
        Element firstBean = beans.element("bean");
        Element property = firstBean.addElement("property");
        property.addAttribute("name", "refBean");
        property.addAttribute("ref", "id2");
        property.setText("新添加的标簽");
    }

    @After
    public void tearDown() throws IOException {
        // 回寫XML
        OutputFormat format = OutputFormat.createPrettyPrint();
        XMLWriter writer = new XMLWriter(new FileOutputStream("src/main/resources/config.xml"), format);
        writer.write(document);
    }
}

我們可以将擷取讀寫XML操作封裝成一個工具, 以後調用時會友善些:

/**
 * @author jifang
 * @since 16/1/19下午2:12.
 */
public class XmlUtils {

    public static Document getXmlDocument(String config) {
        try {
            return new SAXReader().read(ClassLoader.getSystemResource(config));
        } catch (DocumentException e) {
            throw new RuntimeException(e);
        }
    }

    public static void writeXmlDocument(String path, Document document) {
        try {
            new XMLWriter(new FileOutputStream(path), OutputFormat.createPrettyPrint()).write(document);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

在第一個 <bean/> 的第一個 <property/> 後面添加一個 <property/> 标簽

<bean id="id1" class="com.fq.benz"> 
    <property name="name" value="benz"/>  
    <property name="rate" value="3.14"/>
    <property name="refBean" ref="id2">新添加的标簽</property> 
</bean>

public class Dom4jAppend {

    private Document document;

    @Before
    public void setUp() {
        document = XmlUtils.getXmlDocument("config.xml");
    }

    @Test
    @SuppressWarnings("unchecked")
    public void client() {
        Element beans = document.getRootElement();
        Element firstBean = beans.element("bean");
        List<Element> properties = firstBean.elements();

        //Element property = DocumentHelper
        // .createElement(QName.get("property", firstBean.getNamespaceURI()));
        Element property = DocumentFactory.getInstance()
                .createElement("property", firstBean.getNamespaceURI());
        property.addAttribute("name", "rate");
        property.addAttribute("value", "3.14");
        properties.add(, property);
    }

    @After
    public void tearDown() {
        XmlUtils.writeXmlDocument("src/main/resources/config.xml", document);
    }
}

Dom4j修改節點

将 id1 bean 的第一個 <property/> 修改如下:

<property name="name" value="翡青"/>

@Test
@SuppressWarnings("unchecked")
public void client() {
    Element beans = document.getRootElement();
    Element firstBean = beans.element("bean");
    List<Element> properties = firstBean.elements();

    Element property = DocumentFactory.getInstance()
            .createElement("property", firstBean.getNamespaceURI());
    property.addAttribute("name", "rate");
    property.addAttribute("value", "3.14");
    properties.add(, property);
}

Dom4j 删除節點

删除剛剛修改的節點

@Test
@SuppressWarnings("unchecked")
public void delete() {
    List<Element> beans = document.getRootElement().elements("bean");
    for (Element bean : beans) {
        if (bean.attributeValue("id").equals("id1")) {
            List<Element> properties = bean.elements("property");
            for (Element property : properties) {
                if (property.attributeValue("name").equals("name")) {
                    // 執行删除動作
                    property.getParent().remove(property);
                    break;
                }
            }
            break;
        }
    }
}

Dom4j執行個體

在Java 反射一文中我們實作了根據

JSON

配置檔案來加載

bean

的對象池,現在我們可以為其添加根據XML配置(XML檔案同前):

/**
 * @author jifang
 * @since 16/1/18下午9:18.
 */
public class XmlParse {

    private static final ObjectPool POOL = ObjectPoolBuilder.init(null);

    public static Element parseBeans(String config) {
        try {
            return new SAXReader().read(ClassLoader.getSystemResource(config)).getRootElement();
        } catch (DocumentException e) {
            throw new RuntimeException(e);
        }
    }

    public static void processObject(Element bean, List<? extends Element> properties)
            throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchFieldException {
        Class<?> clazz = Class.forName(bean.attributeValue(CommonConstant.CLASS));
        Object targetObject = clazz.newInstance();

        for (Element property : properties) {
            String fieldName = property.attributeValue(CommonConstant.NAME);
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            // 含有value屬性
            if (property.attributeValue(CommonConstant.VALUE) != null) {
                SimpleValueSetUtils.setSimpleValue(field, targetObject, property.attributeValue(CommonConstant.VALUE));
            } else if (property.attributeValue(CommonConstant.REF) != null) {
                String refId = property.attributeValue(CommonConstant.REF);
                Object object = POOL.getObject(refId);
                field.set(targetObject, object);
            } else {
                throw new RuntimeException("neither value nor ref");
            }
        }

        POOL.putObject(bean.attributeValue(CommonConstant.ID), targetObject);
    }
}

注: 上面代碼隻是對象池項目的XML解析部分,完整項目可參考[email protected]:feiqing/commons-frame.git

XPath

XPath是一門在XML文檔中查找資訊的語言,XPath可用來在XML文檔中對元素和屬性進行周遊.

表達式	描述
`/`	從根節點開始擷取( `/beans` :比對根下的 `<beans/>` ; `/beans/bean` :比對 `<beans/>` 下面的 `<bean/>` )
`//`	從目前文檔中搜尋,而不用考慮它們的位置( `//property` : 比對目前文檔中所有 `<property/>` )
`*`	比對任何元素節點( `/*` : 比對所有标簽)
`@`	比對屬性(例: `//@name` : 比對所有 `name` 屬性)
`[position]`	位置謂語比對(例: `//property[1]` : 比對第一個 `<property/>` ; `//property[last()]` : 比對最後一個 `<property/>` )
`[@attr]`	屬性謂語比對(例: `//bean[@id]` : 比對所有帶id屬性的标簽; `//bean[@id='id1']` : 比對所有id屬性值為’id1’的标簽)

謂語: 謂語用來查找某個特定的節點或者包含某個指定的值的節點.

XPath的文法詳細内容可以參考W3School XPath 教程.

Dom4j對XPath的支援

預設的情況下Dom4j并不支援XPath, 需要在pom下添加如下依賴:

<dependency>
    <groupId>jaxen</groupId>
    <artifactId>jaxen</artifactId>
    <version>1.1.6</version>
</dependency>

Dom4j

Node

接口提供了方法對XPath支援:

方法
`List selectNodes(String xpathExpression)`
`List selectNodes(String xpathExpression, String comparisonXPathExpression)`
`List selectNodes(String xpathExpression, String comparisonXPathExpression, boolean removeDuplicates)`
`Object selectObject(String xpathExpression)`
`Node selectSingleNode(String xpathExpression)`

XPath實作查詢

查詢所有 bean 标簽上的屬性值

/**
 * @author jifang
 * @since 16/1/20上午9:28.
 */
public class XPathRead {

    private Document document;

    @Before
    public void setUp() throws DocumentException {
        document = XmlUtils.getXmlDocument("config.xml");
    }

    @Test
    @SuppressWarnings("unchecked")
    public void client() {
        List<Element> beans = document.selectNodes("//bean");
        for (Element bean : beans) {
            System.out.println("id: " + bean.attributeValue("id") +
                    ", class: " + bean.attributeValue("class"));
        }
    }
}

XPath實作更新

删除id=”id2”的 <bean/>

@Test
public void client() {
    Node bean = document.selectSingleNode("//bean[@id=\"id2\"]");
    bean.getParent().remove(bean);
}

參考:

Dom4j的使用

Java 處理 XML 的三種主流技術及介紹

Java 解析 XML Java 解析 XML

Java 解析 XML

JAXP 解析

JAXP-Dom

Dom查詢

Dom添加節點

Dom更新節點

Dom删除節點

JAXP-SAX

Sax查詢

Dom4j解析

Dom4j查詢

Dom4j添加節點

Dom4j修改節點

Dom4j 删除節點

Dom4j執行個體

XPath

Dom4j對XPath的支援

XPath實作查詢

XPath實作更新

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