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利用XMLBean轻轻松松读写XML

　　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.

版权声明：techtarget获matrix授权发布,如需转载请联系matrix
作者:叶枫(http://blog.matrix.org.cn/page/叶枫)
原文地址:http://www.matrix.org.cn/resource/article/44/44027_xmlbean.html

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