http://javaee.github.io/javamail/javax.mail-api: JavaMail API jar (Oracle)
  • Bill Shannon (Oracle) 
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package javax.mail;

import java.util.Vector;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import javax.activation.DataSource;


Multipart is a container that holds multiple body parts. Multipart
provides methods to retrieve and set its subparts. 

Multipart also acts as the base class for the content object returned 
by most Multipart DataContentHandlers. For example, invoking getContent()
on a DataHandler whose source is a "multipart/signed" data source may
return an appropriate subclass of Multipart. 

Some messaging systems provide different subtypes of Multiparts. For
example, MIME specifies a set of subtypes that include "alternative", 
"mixed", "related", "parallel", "signed", etc. 

Multipart is an abstract class.  Subclasses provide actual implementations.

Author:John Mani
/**
 * Multipart is a container that holds multiple body parts. Multipart
 * provides methods to retrieve and set its subparts. <p>
 * 
 * Multipart also acts as the base class for the content object returned 
 * by most Multipart DataContentHandlers. For example, invoking getContent()
 * on a DataHandler whose source is a "multipart/signed" data source may
 * return an appropriate subclass of Multipart. <p>
 *
 * Some messaging systems provide different subtypes of Multiparts. For
 * example, MIME specifies a set of subtypes that include "alternative", 
 * "mixed", "related", "parallel", "signed", etc. <p>
 *
 * Multipart is an abstract class.  Subclasses provide actual implementations.
 *
 * @author John Mani
 */

public abstract class Multipart {

    
Vector of BodyPart objects.

/**
     * Vector of BodyPart objects.
     */
    protected Vector<BodyPart> parts = new Vector<>(); // Holds BodyParts

    
This field specifies the content-type of this multipart
object. It defaults to "multipart/mixed".

/**
     * This field specifies the content-type of this multipart
     * object. It defaults to "multipart/mixed".
     */
    protected String contentType = "multipart/mixed"; // Content-Type

    
The Part containing this Multipart,
if known.

Since:	JavaMail 1.1
/**
     * The <code>Part</code> containing this <code>Multipart</code>,
     * if known.
     * @since	JavaMail 1.1
     */
    protected Part parent;

    
Default constructor. An empty Multipart object is created.

/** 
     * Default constructor. An empty Multipart object is created.
     */
    protected Multipart() { }

    
Setup this Multipart object from the given MultipartDataSource. 

The method adds the MultipartDataSource's BodyPart 
objects into this Multipart. This Multipart's contentType is
set to that of the MultipartDataSource. 

This method is typically used in those cases where one 
has a multipart data source that has already been pre-parsed into
the individual body parts (for example, an IMAP datasource), but 
needs to create an appropriate Multipart subclass that represents
a specific multipart subtype. 

Params:
  • mp – 	Multipart datasource
Throws:
/**
     * Setup this Multipart object from the given MultipartDataSource. <p>
     *
     * The method adds the MultipartDataSource's BodyPart 
     * objects into this Multipart. This Multipart's contentType is
     * set to that of the MultipartDataSource. <p>
     *
     * This method is typically used in those cases where one 
     * has a multipart data source that has already been pre-parsed into
     * the individual body parts (for example, an IMAP datasource), but 
     * needs to create an appropriate Multipart subclass that represents
     * a specific multipart subtype. 
     * 
     * @param	mp	Multipart datasource
     * @exception       MessagingException for failures
     */
    protected synchronized void setMultipartDataSource(MultipartDataSource mp)
			throws MessagingException {
	contentType = mp.getContentType();

	int count = mp.getCount();
	for (int i = 0; i < count; i++)
	    addBodyPart(mp.getBodyPart(i));
    }

    
Return the content-type of this Multipart. 

This implementation just returns the value of the
contentType field.

See Also:
Returns:	content-type
/**
     * Return the content-type of this Multipart. <p>
     *
     * This implementation just returns the value of the
     * <code>contentType</code> field.
     *
     * @return 	content-type
     * @see	#contentType
     */
    public synchronized String getContentType() {
	return contentType;
    }

    
Return the number of enclosed BodyPart objects. 


Throws:
See Also:
Returns:		number of parts
/**
     * Return the number of enclosed BodyPart objects. <p>
     *
     * @return		number of parts
     * @exception       MessagingException for failures
     * @see		#parts
     */
    public synchronized int getCount() throws MessagingException {
	if (parts == null)
	    return 0;

	return parts.size();
    }

    
Get the specified Part.  Parts are numbered starting at 0.

Params:
  • index – 	the index of the desired Part
Throws:
Returns:		the Part
/**
     * Get the specified Part.  Parts are numbered starting at 0.
     *
     * @param index	the index of the desired Part
     * @return		the Part
     * @exception       IndexOutOfBoundsException if the given index
     *			is out of range.
     * @exception       MessagingException for other failures
     */
    public synchronized BodyPart getBodyPart(int index)
				throws MessagingException {
	if (parts == null)
	    throw new IndexOutOfBoundsException("No such BodyPart");

	return parts.elementAt(index);
    }

    
Remove the specified part from the multipart message.
Shifts all the parts after the removed part down one.

Params:
  • part – 	The part to remove
Throws:
Returns:		true if part removed, false otherwise
/**
     * Remove the specified part from the multipart message.
     * Shifts all the parts after the removed part down one.
     *
     * @param   part	The part to remove
     * @return		true if part removed, false otherwise
     * @exception	MessagingException if no such Part exists
     * @exception	IllegalWriteException if the underlying
     *			implementation does not support modification
     *			of existing values
     */
    public synchronized boolean removeBodyPart(BodyPart part)
				throws MessagingException {
	if (parts == null)
	    throw new MessagingException("No such body part");

	boolean ret = parts.removeElement(part);
	part.setParent(null);
	return ret;
    }

    
Remove the part at specified location (starting from 0).
Shifts all the parts after the removed part down one.

Params:
  • index – 	Index of the part to remove
Throws:
/**
     * Remove the part at specified location (starting from 0).
     * Shifts all the parts after the removed part down one.
     *
     * @param   index	Index of the part to remove
     * @exception       IndexOutOfBoundsException if the given index
     *			is out of range.
     * @exception	IllegalWriteException if the underlying
     *			implementation does not support modification
     *			of existing values
     * @exception	MessagingException for other failures
     */
    public synchronized void removeBodyPart(int index)
				throws MessagingException {
	if (parts == null)
	    throw new IndexOutOfBoundsException("No such BodyPart");

	BodyPart part = parts.elementAt(index);
	parts.removeElementAt(index);
	part.setParent(null);
    }

    
Adds a Part to the multipart.  The BodyPart is appended to 
the list of existing Parts.

Params:
  • part –  The Part to be appended
Throws:
/**
     * Adds a Part to the multipart.  The BodyPart is appended to 
     * the list of existing Parts.
     *
     * @param  part  The Part to be appended
     * @exception	IllegalWriteException if the underlying
     *			implementation does not support modification
     *			of existing values
     * @exception       MessagingException for other failures
     */
    public synchronized void addBodyPart(BodyPart part) 
		throws MessagingException {
	if (parts == null)
	    parts = new Vector<>();

	parts.addElement(part);
	part.setParent(this);
    }

    
Adds a BodyPart at position index.
If index is not the last one in the list,
the subsequent parts are shifted up. If index
is larger than the number of parts present, the
BodyPart is appended to the end.

Params:
  • part –  The BodyPart to be inserted
  • index – Location where to insert the part
Throws:
/**
     * Adds a BodyPart at position <code>index</code>.
     * If <code>index</code> is not the last one in the list,
     * the subsequent parts are shifted up. If <code>index</code>
     * is larger than the number of parts present, the
     * BodyPart is appended to the end.
     *
     * @param  part  The BodyPart to be inserted
     * @param  index Location where to insert the part
     * @exception	IllegalWriteException if the underlying
     *			implementation does not support modification
     *			of existing values
     * @exception       MessagingException for other failures
     */
    public synchronized void addBodyPart(BodyPart part, int index) 
				throws MessagingException {
	if (parts == null)
	    parts = new Vector<>();

	parts.insertElementAt(part, index);
	part.setParent(this);
    }

    
Output an appropriately encoded bytestream to the given
OutputStream. The implementation subclass decides the
appropriate encoding algorithm to be used. The bytestream
is typically used for sending.

Params:
  • os – 	the stream to write to
Throws:
/**
     * Output an appropriately encoded bytestream to the given
     * OutputStream. The implementation subclass decides the
     * appropriate encoding algorithm to be used. The bytestream
     * is typically used for sending.
     * 
     * @param	os	the stream to write to
     * @exception       IOException if an IO related exception occurs
     * @exception       MessagingException for other failures
     */
    public abstract void writeTo(OutputStream os) 
		throws IOException, MessagingException;

    
Return the Part that contains this Multipart
object, or null if not known.

Returns:	the parent Part
Since:	JavaMail 1.1
/**
     * Return the <code>Part</code> that contains this <code>Multipart</code>
     * object, or <code>null</code> if not known.
     *
     * @return	the parent Part
     * @since	JavaMail 1.1
     */
    public synchronized Part getParent() {
	return parent;
    }

    
Set the parent of this Multipart to be the specified
Part.  Normally called by the Message
or BodyPart setContent(Multipart) method.
parent may be null if the
Multipart is being removed from its containing
Part.

Params:
  • parent – 	the parent Part
Since:	JavaMail 1.1
/**
     * Set the parent of this <code>Multipart</code> to be the specified
     * <code>Part</code>.  Normally called by the <code>Message</code>
     * or <code>BodyPart</code> <code>setContent(Multipart)</code> method.
     * <code>parent</code> may be <code>null</code> if the
     * <code>Multipart</code> is being removed from its containing
     * <code>Part</code>.
     *
     * @param	parent	the parent Part
     * @since	JavaMail 1.1
     */
    public synchronized void setParent(Part parent) {
	this.parent = parent;
    }
}