一、关于XML解析
  XML在Java应用程序里变得越来越重要, 广泛应用于数据存储和
交换. 比如我们常见的配置文件,都是以XML方式存储的. XML还应用
于Java Message Service和Web Services等技术作为数据交换.
因此,正确读写XML文档是XML应用的基础.
  Java提供了SAX和DOM两种方式用于解析XML,但即便如此,要读写一个
稍微复杂的XML,也不是一件容易的事.
二、XMLBean简介
    Hibernate已经成为目前流行的面向Java环境的对象/关系数据库映射工具.
在Hibernate等对象/关系数据库映射工具出现之前,对数据库的操作是
通过JDBC来实现的,对数据库的任何操作,开发人员都要自己写SQL语句
来实现. 对象/关系数据库映射工具出现后,对数据库的操作转成对
JavaBean的操作,极大方便了数据库开发. 所以如果有一个类似的工具能够
实现将对XML的读写转成对JavaBean的操作,将会简化XML的读写,即使对XML
不熟悉的开发人员也能方便地读写XML. 这个工具就是XMLBean.
三、准备XMLBean和XML文档
   XMLBean是Apache的一个开源项目,可以从http://www.apache.org下载,
最新的版本是2.0. 解压后目录如下:
xmlbean2.0.0
     +---bin
     +---docs
     +---lib
     +---samples
     +---schemas
另外还要准备一个XML文档(customers.xml),
在本文的例子里,我们将对这个文档进行读写操作. 文档源码如下:
<?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>


这是一个客户的数据模型,每个客户都有客户编号(ID),姓名,性别(gender),
电话号码(phoneNumber)和地址,其中地址有两个: 首要地址(PrimaryAddress)
和帐单地址(BillingAddress),每个地址有邮编,地址1,和地址2组成.
其中帐单地址还有收件人(receiver).
    此外,还要准备一个配置文件(文件名customer.xsdconfig),这个文件的
作用我后面会讲,它的内容如下:
<xb:config xmlns:xb="http://xml.apache.org/xmlbeans/2004/02/xbean/config">
  <xb:namespace>
    <xb:package>sample.xmlbean</xb:package>
  </xb:namespace>
</xb:config>


四、XMLBean使用步骤
    和其他面向Java环境的对象/关系数据库映射工具的使用步骤一样,
在正式使用XMLBean前,我们要作两个准备.
    1. 生成XML Schema文件
       什么是XML Schema文件? 正常情况下,每个XML文件都有一个Schema文件,
       XML Schema文件是一个XML的约束文件,它定义了XML文件的结构和元素.
       以及对元素和结构的约束. 通俗地讲,如果说XML文件是数据库里的记录,
       那么Schema就是表结构定义.
       为什么需要这个文件? XMLBean需要通过这个文件知道一个XML文件的
       结构以及约束,比如数据类型等. 利用这个Schema文件,XMLBean将会产生
       一系列相关的Java Classes来实现对XML的操作. 而作为开发人员,则是
       利用XMLBean产生的Java Classes来完成对XML的操作而不需要SAX或DOM.
       怎样产生这个Schema文件呢? 如果对于熟悉XML的开发人员,可以自己来
       写这个Schema文件,对于不熟悉XML的开发人员,可以通过一些工具来完成.
       比较有名的如XMLSPY和Stylus Studio都可以通过XML文件来生成Schema
       文件. 加入我们已经生成这个Schema文件(customer.xsd):
      
       <?xml version="1.0" encoding="UTF-8"?>
       <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
                  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来生成Java Classes
       scomp是XMLBean提供的一个编译工具,它在bin的目录下. 通过这个工具,
       我们可以将以上的Schema文件生成Java Classes.
       scomp的语法如下:-
      
       scomp [options] [dirs]* [schemaFile.xsd]* [service.wsdl]* [config.xsdconfig]*
      


       主要参数说明:
       -src [dir]                  -- 生成的Java Classes存放目录
     -srconly                  -- 不编译Java Classes,不产生Jar文件
     -out [jarFileName]  -- 生成的Jar文件,缺省是xmltypes.jar
       -compiler                 -- Java编译器的路径,即Javac的位置
       schemaFile.xsd    -- XML Schema文件位置
       config.xsdconfig   -- xsdconfig文件的位置, 这个文件主要用来制定生成的Java Class
                              的一些文件名规则和Package的名称,在本文,package是sample.xmlbean
       在本文,我是这样运行的:
      
       scomp -src build\src  -out build\customerXmlBean.jar schema\customer.xsd
             -compiler C:\jdk142_04\bin\javac customer.xsdconfig
      


       这个命令行的意思是告诉scomp生成customerXmlBean.jar,放在build目录下,同时
       生成源代码放在build\src下, Schema文件是customer.xsd,xsdconfig文件是customer.xsdconfig.
       其实, 生成的Java源代码没有多大作用,我们要的是jar文件.我们先看一下build\src\sample\xmlbean下生成的Classes.
      
          CustomersDocument.java    -- 整个XML文档的Java Class映射
       CustomerType.java              -- 节点sustomer的映射
       AddressType.java                 -- 节点address的映射
       BillingAddressType.java        -- 节点billingAddress的映射
       PrimaryAddressType.java      -- 节点primaryAddress的映射
    


       好了,到此我们所有的准备工作已经完成了. 下面就开始进入重点：利用刚才生成的jar文件读写XML.
五、利用XMLBean读XML文件
    新建一个Java Project,将XMLBean2.0.0\lib\下的Jar文件和刚才我们生成的customerXmlBean.jar加入
    到Project的ClassPath.
    新建一个Java Class: CustomerXMLBean.  源码如下:
    
    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//Eclipse//XMLBean//xml//customers.xml";
                  
     CustomerXMLBean customerXMLBean = new CustomerXMLBean(filename);
                   customerXMLBean.customerReader();
    }
    }
    
    运行它,参看输出结果:
    
       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
    
    怎么样,是不是很轻松? XMLBean的威力.
六、利用XMLBean写XML文件
    利用XMLBean创建一个XML文档也是一件轻而易举的事.我们再增加一个Method,
    请看一下的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();
    }
    
    运行,打开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
    我们再增加一个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");
    }
    
    运行之后,我们将会看到客户编号为3的客户的lastname已经改为last.
八、利用XMLBean删除一个customer
    再增加一个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);
    }
       
运行,我们将会看到客户编号为3的客户的资料已经被删除.
九、查询XML
    除了本文在以上讲述的,利用XMLBean能轻轻松松完成XML的读写操作外,结合XPath和XQuery,
   XMLBean还能完成象SQL查询数据库一样方便地查询XML数据. 关于XML查询以及如何创建XML数据库, 我将在另一篇文章里讨论.

十、结束语
    XMLBean能帮助我们轻易读写XML,这将有助于我们降低XML的学习和使用,有了这个基础,
    开发人员将为学习更多地XML相关技术和Web Services,JMS等其他J2EE技术打下良好地基础.