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Basic Examples

This section describes five basic examples (Unmarshal Read, Modify Marshal, Create Marshal, Unmarshal Validate, Validate-On-Demand) that demonstrate how to:

Unmarshal Read Example

The purpose of the Unmarshal Read example is to demonstrate how to unmarshal an XML document into a Java content tree and access the data contained within it.

  1. The <JWSDP_HOME>/jaxb/samples/unmarshal-read/
    Main.java     class declares imports for four standard Java classes plus three JAXB binding framework classes and the primer.po package:

    2. import java.io.FileInputStream
    import java.io.IOException
    import java.util.Iterator
    import java.util.List
    import javax.xml.bind.JAXBContext
    import javax.xml.bind.JAXBException
    import javax.xml.bind.Unmarshaller
    import primer.po.*;

  2. A JAXBContext instance is created for handling classes generated in primer.po.

    3. JAXBContext jc = JAXBContext.newInstance( "primer.po" );

  3. An Unmarshaller instance is created.

    4. Unmarshaller u = jc.createUnmarshaller();

  4. po.xml is unmarshalled into a Java content tree comprising objects generated by the JAXB binding compiler into the primer.po package.

    5. PurchaseOrder po =
      (PurchaseOrder)u.unmarshal(
        new FileInputStream( "po.xml" ) );

  5. A simple string is printed to system.out to provide a heading for the purchase order invoice.

    6. System.out.println( "Ship the following items to: " );

  6. get and display methods are used to parse XML content in preparation for output.

    7. USAddress address = po.getShipTo();
    displayAddress(address);
    Items items = po.getItems();
    displayItems(items);

  7. Basic error handling is implemented.

    8. } catch( JAXBException je ) {
      je.printStackTrace();
    } catch( IOException ioe ) {
      ioe.printStackTrace();

  8. The USAddress branch of the Java tree is walked, and address information is printed to system.out.

    9. public static void displayAddress( USAddress address ) {
      // display the address
      System.out.println( "\t" + address.getName() );
      System.out.println( "\t" + address.getStreet() );
      System.out.println( "\t" + address.getCity() +
        ", " + address.getState() +
        " " + address.getZip() );
      System.out.println( "\t" + address.getCountry() + "\n");
    }

  9. The Items list branch is walked, and item information is printed to system.out.

    10. public static void displayItems( Items items ) {
      // the items object contains a List of
      //primer.po.ItemType objects
      List itemTypeList = items.getItem();

  10. Walking of the Items branch is iterated until all items have been printed.

    11. for(Iterator iter = itemTypeList.iterator();
        iter.hasNext();) {
      Items.ItemType item = (Items.ItemType)iter.next();
      System.out.println( "\t" + item.getQuantity() +
        " copies of \"" + item.getProductName() +
        "\"" );
    }

Sample Output

Running java Main for this example produces the following output: 

Ship the following items to:
   Alice Smith
   123 Maple Street
   Cambridge, MA 12345
   US

   5 copies of "Nosferatu - Special Edition (1929)"
   3 copies of "The Mummy (1959)"
   3 copies of "Godzilla and Mothra: Battle for Earth/Godzilla
     vs. King Ghidora"

Modify Marshal Example

The purpose of the Modify Marshal example is to demonstrate how to modify a Java content tree.

  1. The <JWSDP_HOME>/jaxb/samples/modify-marshal/
    Main.java     class declares imports for three standard Java classes plus four JAXB binding framework classes and primer.po package:

    2. import java.io.FileInputStream;
    import java.io.IOException;
    import java.math.BigDecimal;
    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Marshaller;
    import javax.xml.bind.Unmarshaller;
    import primer.po.*;

  2. A JAXBContext instance is created for handling classes generated in primer.po.

    3. JAXBContext jc = JAXBContext.newInstance( "primer.po" );

  3. An Unmarshaller instance is created, and po.xml is unmarshalled.

    4. Unmarshaller u = jc.createUnmarshaller();
    PurchaseOrder po =
      (PurchaseOrder)u.unmarshal(
        new FileInputStream( "po.xml" ) );

  4. set methods are used to modify information in the address branch of the content tree.

    5. USAddress address = po.getBillTo();
    address.setName( "John Bob" );
    address.setStreet( "242 Main Street" );
    address.setCity( "Beverly Hills" );
    address.setState( "CA" );
    address.setZip( new BigDecimal( "90210" ) );

  5. A Marshaller instance is created, and the updated XML content is marshalled to system.out. The setProperty API is used to specify output encoding; in this case formatted (human readable) XML format.

    6. Marshaller m = jc.createMarshaller();
    m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,
      Boolean.TRUE);
    m.marshal( po, System.out );

Sample Output

Running java Main for this example produces the following output: 

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<purchaseOrder orderDate="1999-10-20-05:00">
<shipTo country="US">
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Cambridge</city>
<state>MA</state>
<zip>12345</zip>
</shipTo>
<billTo country="US">
<name>John Bob</name>
<street>242 Main Street</street>
<city>Beverly Hills</city>
<state>CA</state>
<zip>90210</zip>
</billTo>
<items>
<item partNum="242-NO">
<productName>Nosferatu - Special Edition (1929)</productName>
<quantity>5</quantity>
<USPrice>19.99</USPrice>
</item>
<item partNum="242-MU">
<productName>The Mummy (1959)</productName>
<quantity>3</quantity>
<USPrice>19.98</USPrice>
</item>
<item partNum="242-GZ">
<productName>
Godzilla and Mothra: Battle for Earth/Godzilla vs. King Ghidora
</productName>
<quantity>3</quantity>
<USPrice>27.95</USPrice>
</item>
</items>
</purchaseOrder>

Create Marshal Example

The Create Marshal example demonstrates how to use the ObjectFactory class to create a Java content tree from scratch and then marshal it to XML data.

  1. The <JWSDP_HOME>/jaxb/samples/create-marshal/
    Main.java     class declares imports for four standard Java classes plus three JAXB binding framework classes and the primer.po package:

    2. import java.math.BigDecimal;
    import java.math.BigInteger;
    import java.util.Calendar;
    import java.util.List;
    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Marshaller;
    import primer.po.*;

  2. A JAXBContext instance is created for handling classes generated in primer.po.

    3. JAXBContext jc = JAXBContext.newInstance( "primer.po" );

  3. The ObjectFactory class is used to instantiate a new empty PurchaseOrder object.

    4. // creating the ObjectFactory
    ObjectFactory objFactory = new ObjectFactory();

    // create an empty PurchaseOrder
    PurchaseOrder po = objFactory.createPurchaseOrder();

  4. Per the constraints in the po.xsd schema, the PurchaseOrder object requires a value for the orderDate attribute. To satisfy this constraint, the orderDate is set using the standard Calendar.getInstance() method from java.util.Calendar.

    5. po.setOrderDate( Calendar.getInstance() );

  5. The ObjectFactory is used to instantiate new empty USAddress objects, and the required attributes are set.

    6. USAddress shipTo = createUSAddress( "Alice Smith",
                                  "123 Maple Street",
                                  "Cambridge",
                                  "MA",
                                  "12345" );
      po.setShipTo( shipTo );

    USAddress billTo = createUSAddress( "Robert Smith",
                                  "8 Oak Avenue",
                                  "Cambridge",
                                  "MA",
                                  "12345" );
    po.setBillTo( billTo );

  6. The ObjectFactory class is used to instantiate a new empty Items object.

    7. Items items = objFactory.createItems();

  7. A get method is used to get a reference to the ItemType list.

    8. List itemList = items.getItem();

  8. ItemType objects are created and added to the Items list.

    9. itemList.add( createItemType(
              "Nosferatu - Special Edition (1929)",
              new BigInteger( "5" ),
              new BigDecimal( "19.99" ),
              null,
              null,
              "242-NO" ) );
    itemList.add( createItemType( "The Mummy (1959)",
              new BigInteger( "3" ),
              new BigDecimal( "19.98" ),
              null,
              null,
              "242-MU" ) );
    itemList.add( createItemType(
              "Godzilla and Mothra: Battle for Earth/Godzilla
                vs. King Ghidora",
              new BigInteger( "3" ),
              new BigDecimal( "27.95" ),
              null,
              null,
              "242-GZ" ) );

  9. The items object now contains a list of ItemType objects and can be added to the po object.

    10. po.setItems( items );

  10. A Marshaller instance is created, and the updated XML content is marshalled to system.out. The setProperty API is used to specify output encoding; in this case formatted (human readable) XML format.

    11. Marshaller m = jc.createMarshaller();
    m.setProperty( Marshaller.JAXB_FORMATTED_OUTPUT,
      Boolean.TRUE );
    m.marshal( po, System.out );

  11. An empty USAddress object is created and its properties set to comply with the schema constraints.

    12. public static USAddress createUSAddress(
              ObjectFactory objFactory,
              String name, String street,
              String city,
              String state,
              String zip )
        throws JAXBException {

      // create an empty USAddress objects
      USAddress address = objFactory.createUSAddress();

      // set properties on it
      address.setName( name );
      address.setStreet( street );
      address.setCity( city );
      address.setState( state );
      address.setZip( new BigDecimal( zip ) );

      // return it
      return address;
    }

  12. Similar to the previous step, an empty ItemType object is created and its properties set to comply with the schema constraints.

    13. public static Items.ItemType createItemType(ObjectFactory
        objFactory,
              String productName,
              BigInteger quantity,
              BigDecimal price,
              String comment,
              Calendar shipDate,
              String partNum )
        throws JAXBException {

      // create an empty ItemType object
      Items.ItemType itemType =
      objFactory.createItemsItemType();

      // set properties on it
      itemType.setProductName( productName );
      itemType.setQuantity( quantity );
      itemType.setUSPrice( price );
      itemType.setComment( comment );
      itemType.setShipDate( shipDate );
      itemType.setPartNum( partNum );

      // return it
      return itemType;
    }

Sample Output

Running java Main for this example produces the following output: 

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<purchaseOrder orderDate="2002-09-24-05:00">
<shipTo>
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Cambridge</city>
<state>MA</state>
<zip>12345</zip>
</shipTo>
<billTo>
<name>Robert Smith</name>
<street>8 Oak Avenue</street>
<city>Cambridge</city>
<state>MA</state>
<zip>12345</zip>
</billTo>
<items>
<item partNum="242-NO">
<productName>Nosferatu - Special Edition (1929)</productName>
<quantity>5</quantity
<USPrice>19.99</USPrice>
</item>
<item partNum="242-MU">
<productName>The Mummy (1959)</productName>
<quantity>3</quantity>
<USPrice>19.98</USPrice>
</item>
<item partNum="242-GZ">
<productName>Godzilla and Mothra: Battle for Earth/Godzilla vs. 
King Ghidora</productName>
<quantity>3</quantity>
<USPrice>27.95</USPrice>
</item>
</items>
</purchaseOrder>

Unmarshal Validate Example

The Unmarshal Validate example demonstrates how to enable validation during unmarshalling (Unmarshal-Time Validation). Note that JAXB provides functions for validation during unmarshalling but not during marshalling. Validation is explained in more detail in More About Validation.

  1. The <JWSDP_HOME>/jaxb/samples/unmarshal-validate/Main.java
    class declares imports for three standard Java classes plus seven JAXB binding framework classes and the primer.po package:

    2. import java.io.FileInputStream;
    import java.io.IOException;
    import java.math.BigDecimal;
    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Marshaller;
    import javax.xml.bind.UnmarshalException;
    import javax.xml.bind.Unmarshaller;
    import javax.xml.bind.ValidationEvent;
    import javax.xml.bind.util.ValidationEventCollector;
    import primer.po.*;

  2. A JAXBContext instance is created for handling classes generated in primer.po.

    3. JAXBContext jc = JAXBContext.newInstance( "primer.po" );

  3. An Unmarshaller instance is created.

    4. Unmarshaller u = jc.createUnmarshaller();

  4. The default JAXB Unmarshaller ValidationEventHandler is enabled to send to validation warnings and errors to system.out. The default configuration causes the unmarshal operation to fail upon encountering the first validation error.

    5. u.setValidating( true );

  5. An attempt is made to unmarshal po.xml into a Java content tree. For the purposes of this example, the po.xml contains a deliberate error.

    6. PurchaseOrder po =
      (PurchaseOrder)u.unmarshal(
        new FileInputStream("po.xml"));

  6. The default validation event handler processes a validation error, generates output to system.out, and then an exception is thrown.

    7. } catch( UnmarshalException ue ) {
      System.out.println( "Caught UnmarshalException" );
    } catch( JAXBException je ) {
      je.printStackTrace();
    } catch( IOException ioe ) {
      ioe.printStackTrace();

Sample Output

Running java Main for this example produces the following output: 

DefaultValidationEventHandler: [ERROR]: "-1" does not satisfy 
the "positiveInteger" type
Caught UnmarshalException

Validate-On-Demand Example

The Validate-On-Demand example demonstrates how to validate a Java content tree at runtime (On-Demand Validation). At any point, client applications can call the Validator.validate method on the Java content tree (or any subtree of it). All JAXB Providers are required to support this operation. Validation is explained in more detail in More About Validation.

  1. The <JWSDP_HOME>/jaxb/samples/ondemand-validate/Main.java
    class declares imports for five standard Java classes plus nine JAXB Java classes and the primer.po package:

    2. import java.io.FileInputStream;
    import java.io.IOException;
    import java.math.BigDecimal;
    import java.math.BigInteger;
    import java.util.List;
    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Marshaller;
    import javax.xml.bind.UnmarshalException;
    import javax.xml.bind.Unmarshaller;
    import javax.xml.bind.ValidationEvent;
    import javax.xml.bind.ValidationException;
    import javax.xml.bind.Validator;
    import javax.xml.bind.util.ValidationEventCollector;
    import primer.po.*;

  2. A JAXBContext instance is created for handling classes generated in primer.po.

    3. JAXBContext jc = JAXBContext.newInstance( "primer.po" );

  3. An Unmarshaller instance is created, and a valid po.xml document is unmarshalled into a Java content tree. Note that po.xml is valid at this point; invalid data will be added later in this example.

    4. Unmarshaller u = jc.createUnmarshaller();
    PurchaseOrder po =
      (PurchaseOrder)u.unmarshal( new FileInputStream( "po.xml" ) );

  4. A reference is obtained for the first item in the purchase order.

    5. Items items = po.getItems();
    List itemTypeList = items.getItem();
    Items.ItemType item = (Items.ItemType)itemTypeList.get( 0 );

  5. Next, the item quantity is set to an invalid number. When validation is enabled later in this example, this invalid quantity will throw an exception.

    6. item.setQuantity( new BigInteger( "-5" ) );

Note: If @enableFailFastCheck was "true" and the optional FailFast validation method was supported by an implementation, a TypeConstraintException would be thrown here. Note that the JAXB implementation does not support the FailFast feature. Refer to the JAXB Specification for more information about FailFast validation.

  1. A Validator instance is created, and the content tree is validated. Note that the Validator class is responsible for managing On-Demand validation, whereas the Unmarshaller class is responsible for managing Unmarshal-Time validation during unmarshal operations.

    2. Validator v = jc.createValidator();
    boolean valid = v.validateRoot( po );
    System.out.println( valid );

  2. The default validation event handler processes a validation error, generates output to system.out, and then an exception is thrown.

    3. } catch( ValidationException ue ) {
      System.out.println( "Caught ValidationException" );
    } catch( JAXBException je ) {
      je.printStackTrace();
    } catch( IOException ioe ) {
      ioe.printStackTrace();
    }

Sample Output

Running java Main for this example produces the following output: 

DefaultValidationEventHandler: [ERROR]: "-5" does not satisfy 
the "positiveInteger" type
Caught ValidationException
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