Android 建立與解析XML（五）——詳解Dom4j方式_Android

1、Dom4j概述

dom4j is an easy to use, open source library for working with XML, XPath and XSLT on the Java platform using the Java Collections Framework and with full support for DOM, SAX and JAXP.

dom4j官方網址：dom4j 

dom4j源碼下載：dom4j download

本樣本中，需要匯入dom4j.jar包，才能引用dom4j相關類，dom4j源碼和jar包，請見本樣本【源碼下載】或訪問 dom4j

org.dom4j包，不僅包含建立xml的構建器類DocumentHelper、Element，而且還包含解析xml的解析器SAXReader、Element，包含類如下：

org.dom4j

• org.dom4j.DocumentHelper;
• org.dom4j.Element;
• org.dom4j.io.SAXReader;
• org.dom4j.io.XMLWriter;
• org.dom4j.DocumentException;

建立和解析xml的效果圖：

2、Dom4j 建立 XML

Dom4j，建立xml主要用到了org.dom4j.DocumentHelper、org.dom4j.Document、org.dom4j.io.OutputFormat、org.dom4j.io.XMLWriter

首先，DocumentHelper.createDocument()，建立 org.dom4j.Document 的執行個體 doc

接著，通過doc，設定xml屬性doc.setXMLEncoding("utf-8")、doc.addElement("root")根節點，以及子節點等

然後，定義xml格式並輸出，new XMLWriter(xmlWriter, outputFormat)

/** Dom4j方式，建立 XML */ public String dom4jXMLCreate(){   StringWriter xmlWriter = new StringWriter();    Person []persons = new Person[3];    // 建立節點Person對象   persons[0] = new Person(1, "sunboy_2050", "http://blogcsdnnet/sunboy_2050");   persons[1] = new Person(2, "baidu", "http://wwwbaiducom");   persons[2] = new Person(3, "google", "http://wwwgooglecom");      try {     orgdom4jDocument doc = DocumentHelpercreateDocument();          docsetXMLEncoding("utf-8");          orgdom4jElement eleRoot = docaddElement("root");     eleRootaddAttribute("author", "homer");     eleRootaddAttribute("date", "2012-04-25");     eleRootaddComment("dom4j test");          int personsLen = personslength;     for(int i=0; i<personsLen; i++){              Element elePerson = eleRootaddElement("person");  // 建立person節點，引用類為 orgdom4jElement              Element eleId = elePersonaddElement("id");       eleIdaddText(persons[i]getId()+"");              Element eleName = elePersonaddElement("name");       eleNameaddText(persons[i]getName());              Element eleBlog = elePersonaddElement("blog");       eleBlogaddText(persons[i]getBlog());     }      orgdom4jioOutputFormat outputFormat = new orgdom4jioOutputFormat();  // 設定xml輸出格式     outputFormatsetEncoding("utf-8");     outputFormatsetIndent(false);     outputFormatsetNewlines(true);     outputFormatsetTrimText(true);          orgdom4jioXMLWriter output = new XMLWriter(xmlWriter, outputFormat);   // 儲存xml     outputwrite(doc);     outputclose();   } catch (Exception e) {     eprintStackTrace();   }      savedXML(fileName, xmlWritertoString());   return xmlWritertoString(); } 

運行結果：

3、Dom4j 解析 XML

Dom4j，解析xml主要用到了org.dom4j.io.SAXReader、org.dom4j.Document、doc.getRootElement()，以及ele.getName()、ele.getText()等

首先，建立SAXReader的執行個體reader，讀入xml位元組流 reader.read(is)

接著，通過doc.getRootElement()得到root根節點，利用迭代器取得root下一級的子節點eleRoot.elementIterator()等

然後，得到解析的xml內容xmlWriter.append(xmlHeader)、xmlWriter.append(personsList.get(i).toString())

解析一：標準解析（Iterator 迭代）

/** Dom4j方式，解析 XML */ public String dom4jXMLResolve(){   StringWriter xmlWriter = new StringWriter();      InputStream is = readXML(fileName);   try {     SAXReader reader = new SAXReader();     orgdom4jDocument doc = readerread(is);      List<Person> personsList = null;     Person person = null;     StringBuffer xmlHeader = new StringBuffer();               Element eleRoot = docgetRootElement();   // 獲得root根節點，引用類為 orgdom4jElement     String attrAuthor = eleRootattributeValue("author");     String attrDate = eleRootattributeValue("date");     xmlHeaderappend("root")append("\t\t");     xmlHeaderappend(attrAuthor)append("\t");     xmlHeaderappend(attrDate)append("\n");     personsList = new ArrayList<Person>();          // 擷取root子節點，即person     Iterator<Element> iter = eleRootelementIterator();     for(; iterhasNext(); ) {       Element elePerson = (Element)iternext();              if("person"equals(elePersongetName())){         person = new Person();                  // 擷取person子節點，即id、name、blog         Iterator<Element> innerIter = elePersonelementIterator();         for(; innerIterhasNext();) {           Element ele = (Element)innerIternext();                      if("id"equals(elegetName())) {             String id = elegetText();             personsetId(IntegerparseInt(id));           } else if("name"equals(elegetName())) {             String name = elegetText();             personsetName(name);           } else if("blog"equals(elegetName())) {             String blog = elegetText();             personsetBlog(blog);           }         }                  personsListadd(person);         person = null;       }     }          xmlWriterappend(xmlHeader);     int personsLen = personsListsize();     for(int i=0; i<personsLen; i++) {       xmlWriterappend(personsListget(i)toString());     }        } catch (DocumentException e) {     eprintStackTrace();   } catch (Exception e) {     eprintStackTrace();   }      return xmlWritertoString(); } 

運行結果：

解析二：選擇性解析（XPath路徑）

Dom4j+XPath，選擇性只解析id，doc.selectNodes("//root//person//id")

/** Dom4j方式，解析 XML（方式二） */ public String dom4jXMLResolve2(){   StringWriter xmlWriter = new StringWriter();      InputStream is = readXML(fileName);   try {     orgdom4jioSAXReader reader = new orgdom4jioSAXReader();     orgdom4jDocument doc = readerread(is);      List<Person> personsList = null;     Person person = null;     StringBuffer xmlHeader = new StringBuffer();               Element eleRoot = docgetRootElement();   // 獲得root根節點，引用類為 orgdom4jElement     String attrAuthor = eleRootattributeValue("author");     String attrDate = eleRootattributeValue("date");     xmlHeaderappend("root")append("\t\t");     xmlHeaderappend(attrAuthor)append("\t");     xmlHeaderappend(attrDate)append("\n");     personsList = new ArrayList<Person>();          @SuppressWarnings("unchecked")     List<Element> idList = (List<Element>) docselectNodes("//root//person//id");  // 選擇性擷取全部id     Iterator<Element> idIter = idListiterator();     while(idIterhasNext()){       person = new Person();              Element idEle = (Element)idIternext();       String id = idElegetText();       personsetId(IntegerparseInt(id));              personsListadd(person);     }      xmlWriterappend(xmlHeader);     int personsLen = personsListsize();     for(int i=0; i<personsLen; i++) {       xmlWriterappend("id = ")append(personsListget(i)getId()+"")append("\n");     }        } catch (DocumentException e) {     eprintStackTrace();   } catch (Exception e) {     eprintStackTrace();   }      return xmlWritertoString(); } 

註：藉助 XPath 解析 XML 時，需要匯入 jaxen；

Jaxen is an open source XPath library written in Java. It is adaptable to many different object models, including DOM, XOM, dom4j, and JDOM. Is it also possible to write adapters that treat non-XML trees such as compiled Java byte code or Java beans as XML, thus enabling you to query these trees with XPath too.

運行結果：

4、Person類

請參見前面部落格 Android 建立與解析XML（二）—— Dom方式 【4、Person類】

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