利用XMLBean轻轻松松读写XML

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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2.3.0. 解压后目录如下:
xmlbean2.3.0
     +---bin
     +---docs
     +---lib
     +---samples
     +---schemas
其他设置参照前一篇：使用Eclipse开发XMLBeans项目
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 xmlns="http://xmlbeans.apache.org/samples/template/xmlbean"> <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).

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 targetNamespace="http://xmlbeans.apache.org/samples/template/xmlbean" xmlns:po="http://xmlbeans.apache.org/samples/template/xmlbean" 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="po: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="po:addressType" /> </xs:sequence> </xs:complexType> <xs:complexType name="addressType"> <xs:sequence> <xs:element name="primaryAddress" type="po:primaryAddressType" /> <xs:element name="billingAddress" type="po: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ANT工具来生成Java Classes
ANT文件可以参照下面文件作成：
 <project name="SampleTemplate" default="build"> <property environment="env"/> <path id="SampleTemplate.path"> <path refid="xmlbeans.path"/> <fileset dir="lib" includes="*.jar"/> <pathelement path="build/classes"/> </path> <target name="init" depends = "clean"> <property name="xmlbeans.home" value="${env.XMLBEANS_HOME}"/> <echo message="xmlbeans.home: ${xmlbeans.home}"/>  <available property="xmlbeans.lib" value="${xmlbeans.home}/lib" file="${xmlbeans.home}/lib/xbean.jar" />  <available property="xmlbeans.lib" value="${xmlbeans.home}/build/lib" file="${xmlbeans.home}/build/lib/xbean.jar" /> <fail message="Set XMLBEANS_HOME in your enviornment." unless="xmlbeans.lib"/> <echo message="xmlbeans.lib: ${xmlbeans.lib}"/> <path id="xmlbeans.path"> <fileset dir="${xmlbeans.lib}" includes="*.jar"/> </path> <taskdef name="xmlbean" classname="org.apache.xmlbeans.impl.tool.XMLBean" classpathref="xmlbeans.path"/> </target>  <target name="clean"> <delete dir="build"/> <delete file="lib/schemas.jar"/> <delete dir="XMLBeansSrc"/> <mkdir dir="XMLBeansSrc"/> </target>  <target name="build" depends="init,schemas.jar,SampleTemplate.classes"> </target> <target name="schemas.check"> <uptodate property="schemas.notRequired" targetfile="lib/schemas.jar"> <srcfiles dir="schemas" includes="**/*.xsd"/> </uptodate> </target> <target name="schemas.jar" depends="init,schemas.check" unless="schemas.notRequired"> <xmlbean schema="schemas" destfile="lib/schemas.jar" srcgendir="XMLBeansSrc" classpathref="xmlbeans.path" debug="on" /> </target> <target name="SampleTemplate.classes" depends="init"> <mkdir dir="build/classes"/> <javac srcdir="src" destdir="build/classes" classpathref="SampleTemplate.path" debug="on" source="1.5" /> </target>  <target name="run" depends="init,build"> <echo message="============================== running SampleTemplate"/> <java classname="org.apache.xmlbeans.samples.template.SampleTemplate" classpathref="SampleTemplate.path" fork="true"> <arg line="xml/hello.xml"/> <arg line="xml/bad.xml"/> </java> </target>  <target name="test" depends="init,build"> <echo message="============================== testing SampleTemplate"/> <java classname="org.apache.xmlbeans.samples.template.SampleTemplateTest" classpathref="SampleTemplate.path" fork="true"> <arg line="xml/hello.xml"/> <arg line="xml/bad.xml"/> </java> </target> </project>

其实, 生成的Java源代码没有多大作用,我们要的是jar文件.我们先看一下生成文件一览：
XMLBeansSrc/org/apache/xmlbeans/samples/template/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
XMLBeansSrc/org/apache/xmlbeans/samples/template/xmlbean/impl下生成的Classes是上面文件的接口类.

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
六、利用XMLBean写XML文件
七、利用XMLBean修改XML文件
八、利用XMLBean删除一个customer

新建一个Java Class: CustomerXMLBean. 源码如下:

package com.sample.reader; import java.io.File; import org.apache.xmlbeans.XmlOptions; import org.apache.xmlbeans.samples.template.xmlbean.AddressType; import org.apache.xmlbeans.samples.template.xmlbean.BillingAddressType; import org.apache.xmlbeans.samples.template.xmlbean.CustomerType; import org.apache.xmlbeans.samples.template.xmlbean.CustomersDocument; import org.apache.xmlbeans.samples.template.xmlbean.PrimaryAddressType; 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(); } } 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(); } } private void insertCustomer() ...{ try ...{ File xmlFile = new File(filename); // Create Document CustomersDocument doc = CustomersDocument.Factory.parse(xmlFile); // Add new customer CustomersDocument.Customers customer = doc.getCustomers(); CustomerType importCustomer = customer.addNewCustomer(); // set customer info importCustomer.setId(3); importCustomer.setFirstname("Jessica3"); importCustomer.setLastname("Lim"); importCustomer.setGender("female"); importCustomer.setPhoneNumber("1234567"); // Add new address AddressType address = importCustomer.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"); importCustomer = customer.insertNewCustomer(1); // set customer info importCustomer.setId(4); importCustomer.setFirstname("Jessica4"); importCustomer.setLastname("Lim"); importCustomer.setGender("female"); importCustomer.setPhoneNumber("1234567"); // Add new address address = importCustomer.addNewAddress(); // Add new PrimaryAddress primaryAddress = address.addNewPrimaryAddress(); primaryAddress.setPostalCode("350106"); primaryAddress.setAddressLine1("#25-1"); primaryAddress.setAddressLine2("SHINSAYAMA 2-CHOME"); // Add new BillingAddress billingAddress = address.addNewBillingAddress(); billingAddress.setReceiver("Ms Danielle"); billingAddress.setPostalCode("350107"); billingAddress.setAddressLine1("#167"); billingAddress.setAddressLine2("NORTH TOWER HARBOUR CITY"); XmlOptions xmlOptions = new XmlOptions(); xmlOptions.setSavePrettyPrint(); doc.save(xmlFile, xmlOptions); } catch (Exception ex) ...{ ex.printStackTrace(); } } 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(); } } 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(); } } private void println(String str) ...{ System.out.println(str); } public static void main(String[] args) ...{ String filename = "xml/customers.xml"; CustomerXMLBean customerXMLBean = new CustomerXMLBean(filename); customerXMLBean.customerReader(); filename = "xml/customers2.xml"; customerXMLBean = new CustomerXMLBean(filename); customerXMLBean.createCustomer(); filename = "xml/customersForUpdate.xml"; customerXMLBean = new CustomerXMLBean(filename); customerXMLBean.updateCustomer(2, "test"); filename = "xml/customersForDeleteAndInsert.xml"; customerXMLBean = new CustomerXMLBean(filename); customerXMLBean.deleteCustomer(2); customerXMLBean.insertCustomer(); } }

怎么样,是不是很轻松? XMLBean的威力.

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.

本文参考文献：叶枫利用XMLBean轻轻松松读写XML
http://blog.matrix.org.cn/page/叶枫