Question

Okay, so I have been looking at the sample code below from the Ephesoft Developer’s Guide…

//import java.io.File;
//
//import javax.xml.transform.Result;
//import javax.xml.transform.Source;
//import javax.xml.transform.Transformer;
//import javax.xml.transform.TransformerConfigurationException;
//import javax.xml.transform.TransformerException;
//import javax.xml.transform.TransformerFactory;
//import javax.xml.transform.TransformerFactoryConfigurationError;
//import javax.xml.transform.dom.DOMSource;
//import javax.xml.transform.stream.StreamResult;
//
//import org.w3c.dom.Document;
//import org.w3c.dom.Element;
//import org.w3c.dom.Node;
//import org.w3c.dom.NodeList;

import com.ephesoft.dcma.script.IScripts;
//--------------------------------------

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.output.XMLOutputter;

//import com.ephesoft.dcma.script.IJDomScript;


/**
 * The <code>ScriptDocumentAssembler</code> class represents the script execute structure. Writer of scripts plug-in should implement this IScript
 * interface to execute it from the scripting plug-in. Via implementing this interface writer can change its java file at run time.
 * Before the actual call of the java Scripting plug-in will compile the java and run the new class file.
 * 
 * @author Ephesoft
 * @version 1.0
 */

public class ScriptDocumentAssembler 
{

    private static final String BATCH_LOCAL_PATH = "BatchLocalPath";

    private static final String BATCH_INSTANCE_ID = "BatchInstanceIdentifier";

    private static final String EXT_BATCH_XML_FILE = "_batch.xml";

    private static final String DOCUMENTS = "Documents";

    private static final String DOCUMENT = "Document";

    private static final String PAGES = "Pages";

    private static final String PAGE = "Page";

    private static String ZIP_FILE_EXT = ".zip";

    /**
     * The <code>execute</code> method will execute the script written by the writer at run time with new compilation of java file. It
     * will execute the java file dynamically after new compilation.
     * 
     * @param document {@link Document}
     */
    public void execute(Document document, String fieldName, String docIdentifier) {
        System.out.println("*************  Inside ScriptDocumentAssembler scripts.");
        System.out.println("*************  Start execution of the ScriptDocumentAssembler scripts.");
        System.out.println("Custom ScriptDocumentAssembler, removing Document seperator sheets...");
        removeFirstPageOfDoc(document);
        boolean isWrite = true;
        //boolean isWrite = false;
        // write the document object to the XML file.
        if (isWrite) {
            writeToXML(document);
            System.out.println("*************  Successfully write the xml file for the ScriptDocumentAssembler scripts.");
        } else {
            System.out.println("************** No changes performed by ScriptDocumentAssembler scripts.");
        }
        System.out.println("*************  End execution of the ScriptDocumentAssembler scripts.");
    }

    private void removeFirstPageOfDoc(Document documentFile) {
        Element documentsList = (Element) documentFile.getChildren(DOCUMENTS).get(0);
        List<?> documentList = documentsList.getChildren(DOCUMENT);
        for (int documentIndex = 0; documentIndex < documentList.size(); documentIndex++) {
            Element document = (Element) documentList.get(documentIndex);
            System.out.println("Processing Document - " + document.getChildren("Identifier").get(0).getText());
            Element pages = (Element) document.getChildren(PAGES).get(0);
            List<?> pageList = pages.getChildren(PAGE);         
            Element page = (Element)pageList.get(0);            

            System.out.println(document.getChildren("Identifier").get(0).getText() + " Page Count = " + pageList.size());
            System.out.println("Removing page node " + page.getChildren("Identifier").get(0).getText() + " from " +
                    document.getChildren("Identifier").get(0).getText());
            pages.remove(page);             
            System.out.println(document.getChildren("Identifier").get(0).getText() + " Page Count = " + pageList.size());           
        }
    }

    private void writeToXML(Document document) {
        String batchLocalPath = null;
        List<?> batchLocalPathList = document.getRootElement().getChildren(BATCH_LOCAL_PATH);
        if (null != batchLocalPathList) {
            batchLocalPath = ((Element) batchLocalPathList.get(0)).getText();
        }
        if (null == batchLocalPath) {
                System.err.println("Unable to find the local folder path in batch xml file.");
            return;
        }
        String batchInstanceID = null;
        List<?> batchInstanceIDList = document.getRootElement().getChildren(BATCH_INSTANCE_ID);
        if (null != batchInstanceIDList) {
            batchInstanceID = ((Element) batchInstanceIDList.get(0)).getText();
        }
        if (null == batchInstanceID) {
            System.err.println("Unable to find the batch instance ID in batch xml file.");
            return;
        }
        String batchXMLPath = batchLocalPath.trim() + File.separator + batchInstanceID + File.separator + batchInstanceID
        + EXT_BATCH_XML_FILE;
        String batchXMLZipPath = batchXMLPath + ZIP_FILE_EXT;
        System.out.println("batchXMLZipPath************" + batchXMLZipPath);
        OutputStream outputStream = null;
        File zipFile = new File(batchXMLZipPath);
        FileWriter writer = null;
        XMLOutputter out = new XMLOutputter();
        try {
            if (zipFile.exists()) {
                System.out.println("Found the batch xml zip file.");
                outputStream = getOutputStreamFromZip(batchXMLPath, batchInstanceID + EXT_BATCH_XML_FILE);
                out.output(document, outputStream);
            } else {
                writer = new java.io.FileWriter(batchXMLPath);
                out.output(document, writer);
                writer.flush();
                writer.close();
            }
        } catch (Exception e) {
            System.err.println(e.getMessage());
        } finally {
            if (outputStream != null) {
                try {
                    outputStream.close();
                } catch (IOException e) {
                }
            }
        }
    }

    public static OutputStream getOutputStreamFromZip(final String zipName, final String fileName) throws FileNotFoundException, IOException {
        ZipOutputStream stream = null;
        stream = new ZipOutputStream(new FileOutputStream(new File(zipName + ZIP_FILE_EXT)));
        ZipEntry zipEntry = new ZipEntry(fileName);
        stream.putNextEntry(zipEntry);
        return stream;
    }

}

Note I have not changed anything from the original code, but I added the jdom and ephesoft jars to my build path. However, within the removeFirstPageOfDoc method, I am still getting a bunch of errors related to the casting.For example, the line Element documentsList = (Element) documentFile.getChildren(DOCUMENTS).get(0); should allow documentFile to gain access to the methods of Element, right? However, it still seems to only have access to the methods of type document. I was just wondering what the issue might be here and how I might go about resolving it?

Answer 1

For example, the line Element documentsList = (Element) documentFile.getChildren(DOCUMENTS).get(0); should allow documentFile to gain access to the methods of Element, right?

No, because casting has lower precedence than the dot operator. To cast documentFile to type Element, you would write this:

Element documentsList = ((Element) documentFile).getChildren(DOCUMENTS).get(0);

with parentheses around (Element) documentFile.

Edited to add (incorporating information from the comments below):

However, according to the Javadoc for org.jdom.Document and that for org.jdom.Element, they’re both actual classes — neither one is an interface — and neither is a subtype of the other. This means that you can’t actually cast from one to the other. (In Java, a cast doesn’t let you convert an instance of one type into another type; in order for ((Type) reference) to work, reference has to refer to an object that really does belong to type Type. Since an object can never be an instance of both Element and Document, the compiler won’t even allow this sort of cast here.)

Instead, the person who wrote this sample-code probably should have written this:

Element documentsList =
    documentFile.getRootElement().getChildren(DOCUMENTS).get(0);

which uses the getRootElement() method (which returns the document’s root element) rather than casting to Element (which would try to convince the compiler that the document simply is an element).