java - JAXB で XML を切り取る

Question

私は次のxmlを持っています:

        <Package>
        <PackageHeader>
            <name>External Vendor File</name>
            <description>External vendor file for some purpose</description>
            <version>3.141694baR3</version>
        </PackageHeader>
        <PackageBody>
            <Characteristic id="1">
                <Size>
                    <value>1.68</value>
                    <scale>Meters</scale>
                    <comment>Size can vary, depending on temperature</comment>
                </Size>
                <Weight>
                    <value>9</value>
                    <scale>M*Tons</scale>
                    <comment>His mama is so fat, we had to use another scale</comment>
                </Weight>
                <rating>  
                    <ratingCompany>ISO</ratingCompany>
                    <rating:details xmlns:rating="http://www.w3schools.com/ratingDetails">
                        <rating:value companyDepartment="Finance">A</rating:value>
                        <rating:expirationDate update="1/12/2010">1/1/2014</rating:expirationDate>
                        <rating:comment userID="z94234">You're not Silvia.</rating:comment>
                        <rating:comment userID="r24942">You're one of the Kung-Fu Creatures On The Rampage</rating:comment>
                        <rating:comment userID="i77880">TWO!</rating:comment>
                        <rating:priority>3</rating:priority>
                    </rating:details>
                </rating>
            </Characteristic>
            <Characteristic id="2">
                <Size/>               
                <Weight/>
                <rating/>
            </Characteristic>
            ...
            <Characteristic id="n"/>
        </PackageBody>
    </Package>

そして、次の Java コード:

    public class XMLTest {

        public static void main(String[] args) throws Exception {

            Package currentPackage = new Package();     
            Package sourcePackage = new Package();
            int totalCharacteristics;

            PackageBody currentPackageBody = new PackageBody();     
            Characteristic currentCharacteristic = new Characteristic();        
            rating currentRating = new rating();

            FileInputStream fis = new FileInputStream("sourceFile.xml");

            JAXBContext myCurrentContext = JAXBContext.newInstance(Package.class);
            Marshaller m = myCurrentContext.createMarshaller();
            Unmarshaller um = myCurrentContext.createUnmarshaller();

            sourcePackage = (Package)um.unmarshal(fis);

            currentPackage.setPackageHeader(sourcePackage.getPackageHeader());

            totalCharacteristics = sourcePackage.getPackageBody().getCharacteristics().size();
            for (int i = 0; i < totalCharacteristics; i++)
            {
                currentRating = sourcePackage.getPackageBody().getCharacteristics().get(i).getrating();
            }       

            currentCharacteristic.setrating(currentRating);
            currentPackageBody.getCharacteristics().add(currentCharacteristic);

            currentPackage.setPackageBody(currentPackageBody);      
            m.marshal(currentPackage, new File("targetFile.xml"));
            fis.close();
        }
    }

これにより、次の XML が得られます。

    <Package>
        <PackageHeader>
            <name>External Vendor File</name>
            <description>External vendor file for some purpose</description>
            <version>3.141694baR3</version>
        </PackageHeader>
        <PackageBody>
            <Characteristic id="1">           
                <rating>
                    <ratingCompany>ISO</ratingCompany>
                    <rating:details xmlns:rating="http://www.w3schools.com/ratingDetails">
                        <rating:value companyDepartment="Finance">A</rating:value>
                        <rating:expirationDate update="1/12/2010">1/1/2014</rating:expirationDate>
                        <rating:comment userID="z94234">You're not Silvia.</rating:comment>
                        <rating:comment userID="r24942">You're one of the Kung-Fu Creatures On The Rampage</rating:comment>
                        <rating:comment userID="i77880">TWO!</rating:comment>
                        <rating:priority>3</rating:priority>
                    </rating:details>
                </rating>
            </Characteristic>
            <Characteristic id="2">           
                <rating/>         
            </Characteristic>
            ...
            <Characteristic id="n"/>
        </PackageBody>
    </Package>

そして、これが私が必要とするものです：

    <Package>
        <PackageHeader>
            <name>External Vendor File</name>
            <description>External vendor file for some purpose</description>
            <version>3.141694baR3</version>
        </PackageHeader>
        <PackageBody>
            <Characteristic>
                <rating id="1">
                    <ratingCompany>ISO</ratingCompany>
                    <rating:details xmlns:rating="http://www.w3schools.com/ratingDetails">                    
                        <rating:comment userID="z94234">You're not Silvia.</rating:comment>
                        <rating:comment userID="r24942">You're one of the Kung-Fu Creatures On The Rampage</rating:comment>
                        <rating:comment userID="i77880">TWO!</rating:comment>
                        <rating:priority>3</rating:priority>
                    </rating:details>
                </rating>
            </Characteristic>
            <Characteristic>
                <rating id="2"/>
            </Characteristic>
            ...
            <Characteristic/>
        </PackageBody>
    </Package>

しかし、いくつか質問があります。

• 4GB のファイルを読み取る方法を実装するにはどうすればよいですか? (たとえば、StAX で読み取る)。

• いくつかのタグをソースからターゲットにフィルターをかけたい場合 (最後の xml のように)、それらを 1 つずつ targetFile に割り当てる必要がありますか? すべてのサブノードを調べて割り当てることができる反復子はありますか?

• sourceFile が変更された場合、xjc を再実行してプロジェクト全体を再コンパイルする必要がありますか?

ありがとう。