Implementation

The JAXB Insurance Profile System (JAXBIPS) sample application implements several features defined in the Oracle JAXB specifications, including:

• Usage of the JAXB class generator
• Usage of the Marshaler and Unmarshaler classes
• Marshaling and Unmarshaling from File and StreamSource
• Using JAXB in conjunction with XMLType
• Binding of XML Schema and Complex types
• Using collection types in schema definition (Multiple claim information)
• Unmarshal-time validation

This tutorial highlights one of the most important features of JAXB - Unmarshaling and Marshaling Data. In this section we will look at how the design decisions for the JAXBIPS are implemented in the application, by looking at related code snippets.Before writing code, we need to generate support classes with the help of the Oracle JAXB compiler that is part of the oracle.xml.jaxb package. In order for us to use this, we need to have the xmlparserv2.jar in the CLASSPATH:

     On the command / shell prompt execute following command:

     $java oracle.xml.jaxb.orajaxb -schema profile.xsd -targetPkg oracle.otnsamples.orajaxb -outputDir ../src

To describe the XML document structure, we need to have a schema definition file. Using profile.xsd we build the classes that allow us to marshal, unmarshal and validate XML document instances against the schema definition file. The Schema definition file in our case is the profile.xsd.  

Marshaling and Unmarshaling - FileSystem

We will now look at the code that marshals the Java instances into the File System:

public void saveRecord(Record rec) { try { //Create a JAXBContext instance JAXBContext jc = JAXBContext.newInstance( "jaxbderived.profile" ); String filename = null; if ( !dirPath.endsWith(".xml")) filename = dirPath + "/" + currentRecord.getCustomerID() +".xml"; else filename = dirPath; textArea.append(" Saving file " + filename + "\n"); File f = new File(filename); f.delete(); //Create a marshaler object Marshaller m = jc.createMarshaller(); StringWriter swriter = new StringWriter(); //Marshal the record object m.marshal(rec, swriter); //Store the marshaled object in the String String s = swriter.toString(); //Output this String to a file FileOutputStream fout = new FileOutputStream(filename); PrintWriter pw = new PrintWriter(fout); pw.write(s); //Flush and close file and printWriter pw.flush(); if (pw != null) { pw.close(); } if (fout != null) { fout.close(); } textArea.append("Record saved... \n"); } catch (Exception e) { e.printStackTrace(); } }

Here's the code that unmarshals the document instances from the File System:

public void loadSingleRecord() { textArea.append("This may take some time. Please wait... \n"); try { //Create a JAXBContext instance JAXBContext jc = JAXBContext.newInstance( "jaxbderived.profile" ); //Create an unmarshaler instance Unmarshaller u = jc.createUnmarshaller(); u.setValidating(true); textArea.append("\nReading file " + dirPath + "\n"); //Unmarshal the Record object from FileInputStream Record rec = (Record) u.unmarshal(fileToURL(dirPath)); //Store the object in the list list.add(rec); textArea.append("One record loaded.\n Size of the list is " + list.size() + " \n" ); } catch (Exception ex) { textArea.append("There was an error while parsing \n" + dirPath + "\nThis file will be ignored. \n" ); textArea.append( "Please note that this error is thrown when the source XML does not " ); textArea.append( "confirm to the Profile Record \nSchema definition. The error is given below \n" ); textArea.append(ex.toString() +"\n\n"); } finally { } }

Marshaling and Unmarshaling - Database

Here's the code to marshal and save the records into the database:

public void saveRecord(Record rec) {
        Statement st = null;
        JAXBContext jc = null;
        Marshaller m = null;
        OraclePreparedStatement stmt = null;

        try {
            st = con.createStatement();
            textArea.append("Saving record with customer id " +
                rec.getCustomerID() + " \n"
            );

            //Delete previous record if any
            st.execute(
                "DELETE profile_tab pt WHERE  pt.c1.extract('//Record/@CustomerID').getStringVal() ='" +
                rec.getCustomerID() + "'"
            );

            if (st != null) {
                st.close();
            }

            //Insert updated record
            stmt = (OraclePreparedStatement) con.prepareStatement(
                    "INSERT INTO profile_tab VALUES 
                    (XMLType.CreateXML(?).CreateSchemaBasedXML('http://jaxbderived.profile/profile.xsd'))"
                );

            //Create JAXBContext instance
            jc = JAXBContext.newInstance("jaxbderived.profile");

            //Create Marshaler instance
            m = jc.createMarshaller();

            StringWriter swriter = new StringWriter();

            //Marshal record object to a StringWriter
            m.marshal(rec, swriter);

            //Set the parameter
            stmt.setString(1, swriter.toString());

            //Execute the insert statement
            stmt.execute();
            con.commit();
            textArea.append("One record has been added / updated \n");
        } catch (Exception e) {
            textArea.append(
                "There was problem while adding / updating profile record in the database\n"
            );
            textArea.append("Error message is \n");
            textArea.append(e.toString() + "\n");
        } finally {
            try {
                if (st != null) {
                    st.close();
                }
            } catch (Exception e1) {
            }
        }
    }

Here is the code that unmarshals the document instances from the database:

private void createListFromDatabase() {
        // Create a list instance
        list = Collections.synchronizedList(new ArrayList());

        Statement st = null;
        ResultSet rs = null;
        Unmarshaller u = null;
        JAXBContext jc = null;

        try {
            //Create a JAXBContext instance
            jc = JAXBContext.newInstance("jaxbderived.profile");

            //Create unmarshaler object
            u = jc.createUnmarshaller();
            u.setValidating(false);
            textArea.append("Reading records from the database \n");
            st = con.createStatement();

            //Select all records from profile_tab
            rs = st.executeQuery(
                    "SELECT pt.c1.getStringVal() FROM profile_tab pt"
                );

            int i = 0;

            while (rs.next()) {
                //Retrieve the XMLType object as a String
                String s = rs.getString(1);

                //Get byte array from the String object
                byte[] bytes = s.getBytes();

                //Create ByteArrayInputStream object
                ByteArrayInputStream bais = new ByteArrayInputStream(bytes);

                try {
                    //Unmarshal the record
                    Record rec = (Record) u.unmarshal(new StreamSource(bais));
                    //Add the record to the list
                    list.add(rec);
                } catch (Exception e1) {
                    textArea.append("There was an error while parsing " + i +
                        " th record from the result set \n" +
                        " This record has been skipped"
                    );
                }

                i++;
            }

            textArea.append("Number of records retrieved from the database :  " +
                list.size() + "\n"
            );
            listiterator = list.listIterator(0);

            try {
                listiterator.next();
            } catch (Exception ex) {
            }

            if (st != null) {
                st.close();
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                if (st != null) {
                    st.close();
                }
            } catch (Exception ex1) {
            }
        }
    }