一、關于xml解析

　　XML在java應用程序里變得越來越重要, 廣泛應用于數據存儲和交換. 比如我們常見的配置文件,都是以XML方式存儲的. XML還應用于Java Message Service和Web Services等技術作為數據交換.因此,正確讀寫XML文檔是XML應用的基礎.

　　Java提供了SAX和DOM兩種方式用于解析XML,但即便如此,要讀寫一個稍微復雜的XML,也不是一件容易的事.

　　二、XMLBean簡介

　　Hibernate已經成為目前流行的面向Java環境的對象/關系數據庫映射工具.在Hibernate等對象/關系數據庫映射工具出現之前,對數據庫的操作是通過JDBC來實現的,對數據庫的任何操作,開發人員都要自己寫SQL語句來實現. 對象/關系數據庫映射工具出現后,對數據庫的操作轉成對JavaBean的操作,極大方便了數據庫開發. 所以如果有一個類似的工具能夠實現將對XML的讀寫轉成對JavaBean的操作,將會簡化XML的讀寫,即使對XML不熟悉的開發人員也能方便地讀寫XML. 這個工具就是XMLBean.

　　三、準備XMLBean和XML文檔

　　XMLBean是Apache的一個開源項目,可以從http://www.apache.org下載,最新的版本是2.0. 解壓后目錄如下:

xmlbean2.0.0
     +---bin
     +---docs
     +---lib
     +---samples
     +---schemas

　　另外還要準備一個XML文檔(customers.xml),

　　在本文的例子里,我們將對這個文檔進行讀寫操作. 文檔源碼如下:

<?xml version="1.0" encoding="UTF-8"?>
<Customers>
    <customer>
            <id>1</id>
            <gender>female</gender>
            <firstname>Jessica</firstname>
            <lastname>Lim</lastname>
            <phoneNumber>1234567</phoneNumber>
            <address>
                <PRimaryAddress>
                        <postalCode>350106</postalCode>
                        <addressLine1>#25-1</addressLine1>
                        <addressLine2>SHINSAYAMA 2-CHOME</addressLine2>
                </primaryAddress>
                <billingAddress>
                        <receiver>Ms Danielle</receiver>
                        <postalCode>350107</postalCode>
                        <addressLine1>#167</addressLine1>
                        <addressLine2>NORTH TOWER HARBOUR CITY</addressLine2>
                </billingAddress>
            </address>
    </customer>
    <customer>
            <id>2</id>
            <gender>male</gender>
            <firstname>David</firstname>
            <lastname>Bill</lastname>
            <phoneNumber>808182</phoneNumber>
            <address>
                <primaryAddress>
                        <postalCode>319087</postalCode>
                        <addressLine1>1033 WS St.</addressLine1>
                        <addressLine2>Tima Road</addressLine2>
                </primaryAddress>
                <billingAddress>
                        <receiver>Mr William</receiver>
                        <postalCode>672993</postalCode>
                        <addressLine1>1033 WS St.</addressLine1>
                        <addressLine2>Tima Road</addressLine2>
                </billingAddress>
            </address>
    </customer>
</Customers>

　　這是一個客戶的數據模型,每個客戶都有客戶編號(ID),姓名,性別(gender),電話號碼(phoneNumber)和地址,其中地址有兩個: 首要地址(PrimaryAddress)和帳單地址(BillingAddress),每個地址有郵編,地址1,和地址2組成.其中帳單地址還有收件人(receiver).此外,還要準備一個配置文件(文件名customer.xsdconfig),這個文件的作用我后面會講,它的內容如下:

<xb:config xmlns:xb="

  <xb:namespace>
    <xb:package>sample.xmlbean</xb:package>
  </xb:namespace>

</xb:config>

　　四、XMLBean使用步驟

　　和其他面向Java環境的對象/關系數據庫映射工具的使用步驟一樣,在正式使用XMLBean前,我們要作兩個準備.

　　1. 生成XML Schema文件

　　什么是XML Schema文件? 正常情況下,每個XML文件都有一個Schema文件,XML Schema文件是一個XML的約束文件,它定義了XML文件的結構和元素.以及對元素和結構的約束. 通俗地講,如果說XML文件是數據庫里的記錄,那么Schema就是表結構定義.

　　為什么需要這個文件? XMLBean需要通過這個文件知道一個XML文件的結構以及約束,比如數據類型等. 利用這個Schema文件,XMLBean將會產生一系列相關的Java Classes來實現對XML的操作. 而作為開發人員,則是利用XMLBean產生的Java Classes來完成對XML的操作而不需要SAX或DOM.怎樣產生這個Schema文件呢? 如果對于熟悉XML的開發人員,可以自己來寫這個Schema文件,對于不熟悉XML的開發人員,可以通過一些工具來完成.比較有名的如XMLSPY和Stylus Studio都可以通過XML文件來生成Schema文件. 加入我們已經生成這個Schema文件(customer.xsd):

       <?xml version="1.0" encoding="UTF-8"?>
       <xs:schema xmlns:xs="                  elementFormDefault="qualified">
         <xs:element name="Customers">
           <xs:complexType>
             <xs:sequence>
               <xs:element maxOccurs="unbounded" name="customer"
                           type="customerType"/>
             </xs:sequence>
           </xs:complexType>
         </xs:element>
       <xs:complexType name="customerType">
             <xs:sequence>
               <xs:element name="id" type="xs:int"/>
               <xs:element name="gender" type="xs:string"/>
               <xs:element name="firstname" type="xs:string"/>
               <xs:element name="lastname" type="xs:string"/>
               <xs:element name="phoneNumber" type="xs:string"/>
               <xs:element name="address" type="addressType"/>
             </xs:sequence>
       </xs:complexType>
         <xs:complexType name="addressType">
             <xs:sequence>
               <xs:element name="primaryAddress" type="primaryAddressType"/>
               <xs:element name="billingAddress" type="billingAddressType"/>
             </xs:sequence>
         </xs:complexType>

         <xs:complexType name="primaryAddressType">
             <xs:sequence>
               <xs:element name="postalCode" type="xs:string"/>
               <xs:element name="addressLine1" type="xs:string"/>
               <xs:element name="addressLine2" type="xs:string"/>
             </xs:sequence>
         </xs:complexType>
         <xs:complexType name="billingAddressType">
             <xs:sequence>
                   <xs:element name="receiver" type="xs:string"/>
               <xs:element name="postalCode" type="xs:string"/>
               <xs:element name="addressLine1" type="xs:string"/>
               <xs:element name="addressLine2" type="xs:string"/>
             </xs:sequence>
         </xs:complexType>
       </xs:schema>

　　2. 利用scomp來生成Java Classes

　　scomp是XMLBean提供的一個編譯工具,它在bin的目錄下. 通過這個工具,我們可以將以上的Schema文件生成Java Classes.scomp的語法如下:-

　　scomp [options] [dirs]* [schemaFile.xsd]* [service.wsdl]* [config.xsdconfig]*

　　主要參數說明:

　　-src [dir] -- 生成的Java Classes存放目錄

　　-srconly -- 不編譯Java Classes,不產生Jar文件

　　-out [jarFileName] -- 生成的Jar文件,缺省是xmltypes.jar

　　-compiler -- Java編譯器的路徑,即Javac的位置

　　schemaFile.xsd -- XML Schema文件位置

　　config.xsdconfig -- xsdconfig文件的位置, 這個文件主要用來制定生成的Java Class的一些文件名規則和Package的名稱,在本文,package是sample.xmlbean

　　在本文,我是這樣運行的:

      scomp -src build/src  -out build/customerXmlBean.jar schema/customer.xsd
             -compiler C:/jdk142_04/bin/javac customer.xsdconfig

　　這個命令行的意思是告訴scomp生成customerXmlBean.jar,放在build目錄下,同時生成源代碼放在build/src下, Schema文件是customer.xsd,xsdconfig文件是customer.xsdconfig.其實, 生成的Java源代碼沒有多大作用,我們要的是jar文件.我們先看一下build/src/sample/xmlbean下生成的Classes.

　　CustomersDocument.java -- 整個XML文檔的Java Class映射

　　CustomerType.java -- 節點sustomer的映射

　　AddressType.java -- 節點address的映射

　　BillingAddressType.java -- 節點billingAddress的映射

　　PrimaryAddressType.java -- 節點primaryAddress的映射

　　好了,到此我們所有的準備工作已經完成了. 下面就開始進入重點:利用剛才生成的jar文件讀寫XML.

　　五、利用XMLBean讀XML文件

　　新建一個Java Project,將XMLBean2.0.0/lib/下的Jar文件和剛才我們生成的customerXmlBean.jar加入到Project的ClassPath.

　　新建一個Java Class: CustomerXMLBean. 源碼如下:

    package com.sample.reader;

    import java.io.File;
   
    import sample.xmlbean.*;
    import org.apache.commons.beanutils.BeanUtils;
    import org.apache.xmlbeans.XmlOptions;
    public class CustomerXMLBean {
    private String filename = null;
   
    public CustomerXMLBean(String filename) {
            super();
            this.filename = filename;
    }

    public void customerReader() {
            try {
              File xmlFile = new File(filename);
              CustomersDocument doc = CustomersDocument.Factory.parse(xmlFile);
              CustomerType[] customers = doc.getCustomers().getCustomerArray();
         
              for (int i = 0; i < customers.length; i++) {
                CustomerType customer = customers[i];
                println("Customer#" + i);
                println("Customer ID:" + customer.getId());
                println("First name:" + customer.getFirstname());
                println("Last name:" + customer.getLastname());
                println("Gender:" + customer.getGender());
                println("PhoneNumber:" + customer.getPhoneNumber());
                // Primary address
                PrimaryAddressType primaryAddress = customer.getAddress().getPrimaryAddress();
                println("PrimaryAddress:");
                println("PostalCode:" + primaryAddress.getPostalCode());
                println("AddressLine1:" + primaryAddress.getAddressLine1());
                println("AddressLine2:" + primaryAddress.getAddressLine2());
                // Billing address
                BillingAddressType billingAddress = customer.getAddress().getBillingAddress();
                println("BillingAddress:");
                println("Receiver:" + billingAddress.getReceiver());
                println("PostalCode:" + billingAddress.getPostalCode());
                println("AddressLine1:" + billingAddress.getAddressLine1());
                println("AddressLine2:" + billingAddress.getAddressLine2());
           
              }
            } catch (Exception ex) {
                    ex.printStackTrace();
            }
    }
    private void println(String str) {
          System.out.println(str);
    }
   public static void main(String[] args) {
      String filename = "F://JavaTest//Ecl                  
     CustomerXMLBean customerXMLBean = new CustomerXMLBean(filename);
                   customerXMLBean.customerReader();
    }

    }

　　運行它,參看輸出結果:

       Customer#0
       Customer ID:1
       First name:Jessica
       Last name:Lim
       Gender:female
       PhoneNumber:1234567
       PrimaryAddress:
       PostalCode:350106
       AddressLine1:#25-1
       AddressLine2:SHINSAYAMA 2-CHOME
       BillingAddress:
       Receiver:Ms Danielle
       PostalCode:350107
       AddressLine1:#167
       AddressLine2:NORTH TOWER HARBOUR CITY

       Customer#1
       Customer ID:2
       First name:David
       Last name:Bill
       Gender:male
       PhoneNumber:808182
       PrimaryAddress:
       PostalCode:319087
       AddressLine1:1033 WS St.
       AddressLine2:Tima Road
       BillingAddress:
       Receiver:Mr William
       PostalCode:672993
       AddressLine1:1033 WS St.
       AddressLine2:Tima Road

　　怎么樣,是不是很輕松? XMLBean的威力.

　　六、利用XMLBean寫XML文件

　　利用XMLBean創建一個XML文檔也是一件輕而易舉的事.我們再增加一個Method,

　　請看一下的Java Class:

    public void createCustomer() {
    try {
        // Create Document
        CustomersDocument doc = CustomersDocument.Factory.newInstance();
        // Add new customer
        CustomerType customer = doc.addNewCustomers().addNewCustomer();
        // set customer info
        customer.setId(3);
        customer.setFirstname("Jessica");
        customer.setLastname("Lim");
        customer.setGender("female");
        customer.setPhoneNumber("1234567");
        // Add new address
        AddressType address = customer.addNewAddress();
        // Add new PrimaryAddress
        PrimaryAddressType primaryAddress = address.addNewPrimaryAddress();
        primaryAddress.setPostalCode("350106");
        primaryAddress.setAddressLine1("#25-1");
        primaryAddress.setAddressLine2("SHINSAYAMA 2-CHOME");

        // Add new BillingAddress
        BillingAddressType billingAddress = address.addNewBillingAddress();
        billingAddress.setReceiver("Ms Danielle");
        billingAddress.setPostalCode("350107");
        billingAddress.setAddressLine1("#167");
        billingAddress.setAddressLine2("NORTH TOWER HARBOUR CITY");

        File xmlFile = new File(filename);
        doc.save(xmlFile);
        } catch (Exception ex) {
                ex.printStackTrace();
        }

  }

　　修改main method.

    public static void main(String[] args) {
    String filename = "F://JavaTest//Eclipse//XMLBean//xml//customers_new.xml";
        CustomerXMLBean customerXMLBean = new CustomerXMLBean(filename);
        customerXMLBean.createCustomer();
    }

　　運行,打開customers_new.xml:

    <?xml version="1.0" encoding="UTF-8"?>
    <Customers>
    <customer>
            <id>3</id>
            <gender>female</gender>
            <firstname>Jessica</firstname>
            <lastname>Lim</lastname>
            <phoneNumber>1234567</phoneNumber>
            <address>
                    <primaryAddress>
                         <postalCode>350106</postalCode>
                         <addressLine1>#25-1</addressLine1>
                                       <addressLine2>SHINSAYAMA 2-CHOME</addressLine2>
                    </primaryAddress>
                    <billingAddress>
                        <receiver>Ms Danielle</receiver>
                        <postalCode>350107</postalCode>
                       <addressLine1>#167</addressLine1>
                       <addressLine2>NORTH TOWER HARBOUR CITY</addressLine2>
                    </billingAddress>
                    </address>
            </customer>
    </Customers>

　　七、利用XMLBean修改XML文件

　　我們再增加一個Method:

      public void updateCustomer(int id,String lastname) {
         try {
        File xmlFile = new File(filename);
        CustomersDocument doc = CustomersDocument.Factory.parse(xmlFile);
        CustomerType[] customers = doc.getCustomers().getCustomerArray();
     
        for (int i = 0; i < customers.length; i++) {
           CustomerType customer = customers[i];
          if(customer.getId()==id){
                customer.setLastname(lastname);
                break;
            }
        }
        doc.save(xmlFile);
         } catch (Exception ex) {
          ex.printStackTrace();
         }
           }

　　main method:

    public static void main(String[] args) {
     String filename = "F://JavaTest//Eclipse//XMLBean//xml//customers_new.xml";
                   
    CustomerXMLBean customerXMLBean = new CustomerXMLBean(filename);
                   
    customerXMLBean.updateCustomer(3,"last");
    }

　　運行之后,我們將會看到客戶編號為3的客戶的lastname已經改為last.

　　八、利用XMLBean刪除一個customer

　　再增加一個Method:

    public void deleteCustomer(int id) {
     try {
      File xmlFile = new File(filename);
     CustomersDocument doc = CustomersDocument.Factory.parse(xmlFile);
    CustomerType[] customers = doc.getCustomers().getCustomerArray();

   for (int i = 0; i < customers.length; i++) {
        CustomerType customer = customers[i];
        if(customer.getId()==id){
                        customer.setNil() ;
                        break;
               }
   }
   doc.save(xmlFile);
   } catch (Exception ex) {
        ex.printStackTrace();
        }
   }

　　main method:

    public static void main(String[] args) {
    String filename = "F://JavaTest//Eclipse//XMLBean//xml//customers_new.xml";
                   
    CustomerXMLBean customerXMLBean = new CustomerXMLBean(filename);
                   
    customerXMLBean.deleteCustomer(3);
    }

　　運行,我們將會看到客戶編號為3的客戶的資料已經被刪除.

　　九、查詢XML

　　除了本文在以上講述的,利用XMLBean能輕輕松松完成XML的讀寫操作外,結合XPath和XQuery,XMLBean還能完成象SQL查詢數據庫一樣方便地查詢XML數據. 關于XML查詢以及如何創建XML數據庫, 我將在另一篇文章里討論.

　　十、結束語

　　XMLBean能幫助我們輕易讀寫XML,這將有助于我們降低XML的學習和使用,有了這個基礎,開發人員將為學習更多地XML相關技術和Web Services,JMS等其他J2EE技術打下良好地基礎.

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作者:葉楓(http://blog.matrix.org.cn/page/葉楓)
原文地址:http://www.matrix.org.cn/resource/article/44/44027_XMLBean.html