XMLBeans处理xml数据的好帮手 - 编译、测试和应用实例

3  编译schema

3.1 定义schema
<xs:schema targetNamespace="http://openuri.org/easypo"
    xmlns:po="http://openuri.org/easypo"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="qualified">

    <xs:element name="purchase-order">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="customer" type="po:customer"/>
                <xs:element name="date" type="xs:dateTime"/>
                <xs:element name="line-item" type="po:line-item" minOccurs="0" maxOccurs="unbounded"/>
                <xs:element name="shipper" type="po:shipper" minOccurs="0"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:complexType name="customer">
        <xs:sequence>
            <xs:element name="name" type="xs:string"/>
            <xs:element name="address" type="xs:string"/>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="line-item">
        <xs:sequence>
            <xs:element name="description" type="xs:string"/>
            <xs:element name="per-unit-ounces" type="xs:decimal"/>
            <xs:element name="price" type="xs:double"/>
            <xs:element name="quantity" type="xs:int"/>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="shipper">
        <xs:sequence>
            <xs:element name="name" type="xs:string"/>
            <xs:element name="per-ounce-rate" type="xs:decimal"/>
        </xs:sequence>
    </xs:complexType>
</xs:schema>

3.2 schema解释
1）我们在这里定义了三种复杂类型（complex types）客户，商品列表、以及卖家。他们都是purchase-order的子元素。在schema中复杂元素通常包含子元素和属性。他的子元素被sequence包含，并且嵌套在复杂类型中。同时purchase-order又是global类型因为他们在schema的根元素下。这就意味着它可以在schema中的任何地方引用。
2）在复杂类型中使用了简单类型（simple types）如：姓名、地址、商品描述。它们都是xs:string类型，这种类型schema的内置类型，共有46种内置类型。如：xs:double 、xs:int、xs:decimal等等。
3）全局元素（global element）purchase-order，它是由多个复杂子元素构成的，注意这种复杂元素引用了在schema中定义的复杂元素。
然后你就可以用XMLBean通过这个XSD文件编译出我们所需要的jar文件。这个jar包含了根据schema产生的一系列接口。

3.3 通过这个.xsd文件编译出xmlbeans
Scomp 它是Schema Compiler的缩写，顾名思义就是schema编译器的意思。

进入命令行运行命令：
C:\xmlbeans2.2\schemas>scomp -out biz.jar  biz.xsd
很不幸你十有八九会碰到这种情况

不要着这其实是XMLBeans需要制定一个额外的java 编译器。我们加上一个编译器的参数就可以了。
 

Ok,我们最终编译jar文件成功！

4 测试XMLBeans

4.1 工程结构


4.2 必要的Jar 包
注意不要忘记把必要的Jar加入你的工程。注意我们这里用的是easypo.jar,而不是biz.jar。这个jar的名字无所谓，只要是你刚才通过scomp编译出来的jar就可以了。你可以自己定义jar的名字。
[img]http://yangyang.iteye.com/upload/picture/pic/6447/1452634c-1e79-48c9-8bca-2d2a8a122e6c.bmp [/img]

4.3 测试代码
我们来写一个类来测试一下easypo.jar：
package xmlbeans.test;

import java.io.File;

import org.openuri.easypo.LineItem;
import org.openuri.easypo.PurchaseOrderDocument;
import org.openuri.easypo.PurchaseOrderDocument.PurchaseOrder;

public class POHandler
{
    public static void printItems(File po) throws Exception
    {
        /*
         * All XMLBeans schema types provide a nested Factory class you can
         * use to bind XML to the type, or to create new instances of the type.
         * Note that a "Document" type such as this one is an XMLBeans
         * construct for representing a global element. It provides a way
         * for you to get and set the contents of the entire element.
         *
         * Also, note that the parse method will only succeed if the
         * XML you're parsing appears to conform to the schema.
         */
        PurchaseOrderDocument poDoc =
            PurchaseOrderDocument.Factory.parse(po);

        /*
         * The PurchaseOrder type represents the purchase-order element's
         * complex type.
         */
        PurchaseOrder po1 = poDoc.getPurchaseOrder();

        /*
         * When an element may occur more than once as a child element,
         * the schema compiler will generate methods that refer to an
         * array of that element. The line-item element is defined with
         * a maxOccurs attribute value of "unbounded", meaning that
         * it may occur as many times in an instance document as needed.
         * So there are methods such as getLineItemArray and setLineItemArray.
         */
        LineItem[] lineitems = po1.getLineItemArray();
        System.out.println("Purchase order has " + lineitems.length + " line items.");

        double totalAmount = 0.0;
        int numberOfItems = 0;

        /*
         * Loop through the line-item elements, using generated accessors to
         * get values for child elements such a description, quantity, and
         * price.
         */
        for (int j = 0; j < lineitems.length; j++)
        {
            System.out.println(" Line item: " + j);
            System.out.println(
                "   Description: " + lineitems[j].getDescription());
            System.out.println("   Quantity: " + lineitems[j].getQuantity());
            System.out.println("   Price: " + lineitems[j].getPrice());
            //numberOfItems += lineitems[j].getQuantity();
            //totalAmount += lineitems[j].getPrice() * lineitems[j].getQuantity();
        }
       // System.out.println("Total items: " + numberOfItems);
       // System.out.println("Total amount: " + totalAmount);
    }
    public static void main(String args[]){
    try {
POHandler.printItems(new File("xml/order.xml"));
} catch (Exception e) {
e.printStackTrace();
}
    }
}


Order.xml文件内容：
<purchase-order xmlns="http://openuri.org/easypo">
    <customer>
        <name>Gladys Kravitz</name>
        <address>Anytown, PA</address>
    </customer>
    <date>2003-01-07T14:16:00-05:00</date>
    <line-item>
        <description>Burnham's Celestial Handbook, Vol 1</description>
        <per-unit-ounces>5</per-unit-ounces>
        <price>21.79</price>
        <quantity>2</quantity>
    </line-item>
    <line-item>
        <description>Burnham's Celestial Handbook, Vol 2</description>
        <per-unit-ounces>5</per-unit-ounces>
        <price>19.89</price>
        <quantity>2</quantity>
    </line-item>
    <shipper>
        <name>ZipShip</name>
        <per-ounce-rate>0.74</per-ounce-rate>
    </shipper>
</purchase-order>
运行后得到结果：


That’s all !  下面一张我们会进一步讨论XMlBeans的使用。

5 几个XMLBeans 使用的例子

5.1 验证xml 数据
XMLBeans 是根据编译时的schema 来验证xml 数据的。
public static boolean validate( File file){

    PurchaseOrderDocument myDoc = null;
try {
myDoc = PurchaseOrderDocument.Factory.parse(file);
} catch (XmlException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

//    Set up the validation error listener.
    ArrayList validationErrors = new ArrayList();
    XmlOptions validationOptions = new XmlOptions();
    validationOptions.setErrorListener(validationErrors);


//    Do some editing to myDoc.

//    During validation, errors are added to the ArrayList for
//    retrieval and printing by the printErrors method.
    boolean isValid = myDoc.validate(validationOptions);

//    Print the errors if the XML is invalid.
    if (!isValid)
    {
        Iterator iter = validationErrors.iterator();
        while (iter.hasNext())
        {
            System.out.println(">> " + iter.next() + "\n");
        }
    }
    return isValid;
    }
注：file是一个xml数据文件。

5.2 读取xml数据
使用XMLBeans来将xml 数据包装成对象，并且通过对象读取信息。
public static void printItems(File file) throws Exception
    {
        PurchaseOrderDocument poDoc =
            PurchaseOrderDocument.Factory.parse(file);
     
        PurchaseOrder po1 = poDoc.getPurchaseOrder();
       
        LineItem[] lineitems = po1.getLineItemArray();
        Customer c =  po1.getCustomer();
        c.getAddress();
        c.getAge();
        System.out.println("Purchase order has " + lineitems.length + " line items.");

        for (int j = 0; j < lineitems.length; j++)
        {
            System.out.println(" Line item: " + j);
            System.out.println(
                "   Description: " + lineitems[j].getDescription());
            System.out.println("   Quantity: " + lineitems[j].getQuantity());
            System.out.println("   Price: " + lineitems[j].getPrice());
        }
    }
注：file是一个xml数据文件。

5.3 创建xml 数据
创建新的xml数据并保存到xml文件中。
public static void createPO()
    {
        PurchaseOrderDocument newPODoc = PurchaseOrderDocument.Factory.newInstance();
        PurchaseOrder newPO = newPODoc.addNewPurchaseOrder();
        Customer newCustomer = newPO.addNewCustomer();
        newCustomer.setName("Doris Kravitz");
        newCustomer.setAddress("Bellflower, CA");
        newPODoc .save( new File("xml/newOrder.xml") );
}
除了这些基本的功能以外，XMLBeans还提供了xpath查询，指定位置插入删除xml数据元素等强大功能，值得我们深入研究。