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="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="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//Eclipse//XMLBean//xml//customers.xml";
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.