Part.java
/*
* Copyright (c) 1997, 2025 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.mail;
import jakarta.activation.DataHandler;
import jakarta.mail.util.StreamProvider;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.ServiceConfigurationError;
/**
* The <code>Part</code> interface is the common base interface for
* Messages and BodyParts. <p>
*
* Part consists of a set of attributes and a "Content".<p>
*
* <strong> Attributes: </strong> <p>
*
* The Jakarta Mail API defines a set of standard Part attributes that are
* considered to be common to most existing Mail systems. These
* attributes have their own settor and gettor methods. Mail systems
* may support other Part attributes as well, these are represented as
* name-value pairs where both the name and value are Strings.<p>
*
* <strong> Content: </strong> <p>
*
* The <strong>data type</strong> of the "content" is returned by
* the <code>getContentType()</code> method. The MIME typing system
* is used to name data types. <p>
*
* The "content" of a Part is available in various formats:
* <ul>
* <li> As a DataHandler - using the <code>getDataHandler()</code> method.
* The "content" of a Part is also available through a
* <code>jakarta.activation.DataHandler</code> object. The DataHandler
* object allows clients to discover the operations available on the
* content, and to instantiate the appropriate component to perform
* those operations.
*
* <li> As an input stream - using the <code>getInputStream()</code> method.
* Any mail-specific encodings are decoded before this stream is returned.
*
* <li> As a Java object - using the <code>getContent()</code> method.
* This method returns the "content" as a Java object.
* The returned object is of course dependent on the content
* itself. In particular, a "multipart" Part's content is always a
* Multipart or subclass thereof. That is, <code>getContent()</code> on a
* "multipart" type Part will always return a Multipart (or subclass) object.
* </ul>
*
* Part provides the <code>writeTo()</code> method that streams
* out its bytestream in mail-safe form suitable for transmission.
* This bytestream is typically an aggregation of the Part attributes
* and its content's bytestream. <p>
*
* Message and BodyPart implement the Part interface. Note that in
* MIME parlance, Part models an Entity (RFC 2045, Section 2.4).
*
* @author John Mani
*/
public interface Part {
/**
* Return the size of the content of this part in bytes.
* Return -1 if the size cannot be determined. <p>
*
* Note that the size may not be an exact measure of the content
* size and may or may not account for any transfer encoding
* of the content. The size is appropriate for display in a
* user interface to give the user a rough idea of the size
* of this part.
*
* @return size of content in bytes
* @throws MessagingException for failures
*/
int getSize() throws MessagingException;
/**
* Return the number of lines in the content of this part.
* Return -1 if the number cannot be determined.
*
* Note that this number may not be an exact measure of the
* content length and may or may not account for any transfer
* encoding of the content.
*
* @return number of lines in the content.
* @throws MessagingException for failures
*/
int getLineCount() throws MessagingException;
/**
* Returns the Content-Type of the content of this part.
* Returns null if the Content-Type could not be determined. <p>
*
* The MIME typing system is used to name Content-types.
*
* @return The ContentType of this part
* @throws MessagingException for failures
* @see jakarta.activation.DataHandler
*/
String getContentType() throws MessagingException;
/**
* Is this Part of the specified MIME type? This method
* compares <strong>only the <code>primaryType</code> and
* <code>subType</code></strong>.
* The parameters of the content types are ignored. <p>
*
* For example, this method will return <code>true</code> when
* comparing a Part of content type <strong>"text/plain"</strong>
* with <strong>"text/plain; charset=foobar"</strong>. <p>
*
* If the <code>subType</code> of <code>mimeType</code> is the
* special character '*', then the subtype is ignored during the
* comparison.
*
* @param mimeType the MIME type to test
* @return true if this part is of the specified type
* @throws MessagingException for failures
*/
boolean isMimeType(String mimeType) throws MessagingException;
/**
* This part should be presented as an attachment.
*
* @see #getDisposition
* @see #setDisposition
*/
String ATTACHMENT = "attachment";
/**
* This part should be presented inline.
*
* @see #getDisposition
* @see #setDisposition
*/
String INLINE = "inline";
/**
* Return the disposition of this part. The disposition
* describes how the part should be presented to the user.
* (See RFC 2183.) The return value should be considered
* without regard to case. For example:
* <blockquote><pre>
* String disp = part.getDisposition();
* if (disp == null || disp.equalsIgnoreCase(Part.ATTACHMENT))
* // treat as attachment if not first part
* </pre></blockquote>
*
* @return disposition of this part, or null if unknown
* @throws MessagingException for failures
* @see #ATTACHMENT
* @see #INLINE
* @see #getFileName
*/
String getDisposition() throws MessagingException;
/**
* Set the disposition of this part.
*
* @param disposition disposition of this part
* @throws IllegalWriteException if the underlying implementation
* does not support modification of this header
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
* @see #ATTACHMENT
* @see #INLINE
* @see #setFileName
*/
void setDisposition(String disposition) throws MessagingException;
/**
* Return a description String for this part. This typically
* associates some descriptive information with this part.
* Returns null if none is available.
*
* @return description of this part
* @throws MessagingException for failures
*/
String getDescription() throws MessagingException;
/**
* Set a description String for this part. This typically
* associates some descriptive information with this part.
*
* @param description description of this part
* @throws IllegalWriteException if the underlying implementation
* does not support modification of this header
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setDescription(String description) throws MessagingException;
/**
* Get the filename associated with this part, if possible.
* Useful if this part represents an "attachment" that was
* loaded from a file. The filename will usually be a simple
* name, not including directory components.
*
* @return Filename to associate with this part
* @throws MessagingException for failures
*/
String getFileName() throws MessagingException;
/**
* Set the filename associated with this part, if possible.
* Useful if this part represents an "attachment" that was
* loaded from a file. The filename will usually be a simple
* name, not including directory components.
*
* @param filename Filename to associate with this part
* @throws IllegalWriteException if the underlying implementation
* does not support modification of this header
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setFileName(String filename) throws MessagingException;
/**
* Return an input stream for this part's "content". Any
* mail-specific transfer encodings will be decoded before the
* input stream is provided. <p>
*
* This is typically a convenience method that just invokes
* the DataHandler's <code>getInputStream()</code> method.
*
* @return an InputStream
* @throws IOException this is typically thrown by the
* DataHandler. Refer to the documentation for
* jakarta.activation.DataHandler for more details.
* @throws MessagingException for other failures
* @see #getDataHandler
* @see jakarta.activation.DataHandler#getInputStream
*/
InputStream getInputStream()
throws IOException, MessagingException;
/**
* Return a DataHandler for the content within this part. The
* DataHandler allows clients to operate on as well as retrieve
* the content.
*
* @return DataHandler for the content
* @throws MessagingException for failures
*/
DataHandler getDataHandler() throws MessagingException;
/**
* Return the content as a Java object. The type of the returned
* object is of course dependent on the content itself. For example,
* the object returned for "text/plain" content is usually a String
* object. The object returned for a "multipart" content is always a
* Multipart subclass. For content-types that are unknown to the
* DataHandler system, an input stream is returned as the content <p>
*
* This is a convenience method that just invokes the DataHandler's
* getContent() method
*
* @return Object
* @throws IOException this is typically thrown by the
* DataHandler. Refer to the documentation for
* jakarta.activation.DataHandler for more details.
* @throws MessagingException for other failures
* @see jakarta.activation.DataHandler#getContent
*/
Object getContent() throws IOException, MessagingException;
/**
* This method provides the mechanism to set this part's content.
* The DataHandler wraps around the actual content.
*
* @param dh The DataHandler for the content.
* @throws IllegalWriteException if the underlying implementation
* does not support modification of existing values
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setDataHandler(DataHandler dh) throws MessagingException;
/**
* A convenience method for setting this part's content. The part
* internally wraps the content in a DataHandler. <p>
*
* Note that a DataContentHandler class for the specified type should
* be available to the Jakarta Mail implementation for this to work right.
* i.e., to do <code>setContent(foobar, "application/x-foobar")</code>,
* a DataContentHandler for "application/x-foobar" should be installed.
* Refer to the Java Activation Framework for more information.
*
* @param obj A java object.
* @param type MIME type of this object.
* @throws IllegalWriteException if the underlying implementation
* does not support modification of existing values
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setContent(Object obj, String type)
throws MessagingException;
/**
* A convenience method that sets the given String as this
* part's content with a MIME type of "text/plain".
*
* @param text The text that is the Message's content.
* @throws IllegalWriteException if the underlying
* implementation does not support modification of
* existing values
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setText(String text) throws MessagingException;
/**
* This method sets the given Multipart object as this message's
* content.
*
* @param mp The multipart object that is the Message's content
* @throws IllegalWriteException if the underlying
* implementation does not support modification of
* existing values
* @throws IllegalStateException if this Part is obtained
* from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setContent(Multipart mp) throws MessagingException;
/**
* Output a bytestream for this Part. This bytestream is
* typically an aggregration of the Part attributes and
* an appropriately encoded bytestream from its 'content'. <p>
*
* Classes that implement the Part interface decide on
* the appropriate encoding algorithm to be used. <p>
*
* The bytestream is typically used for sending.
*
* @param os the stream to write to
* @throws IOException if an error occurs writing to the
* stream or if an error is generated
* by the jakarta.activation layer.
* @throws MessagingException if an error occurs fetching the
* data to be written
* @see jakarta.activation.DataHandler#writeTo
*/
void writeTo(OutputStream os) throws IOException, MessagingException;
/**
* Get all the headers for this header name. Returns <code>null</code>
* if no headers for this header name are available.
*
* @param header_name the name of this header
* @return the value fields for all headers with
* this name
* @throws MessagingException for failures
*/
String[] getHeader(String header_name)
throws MessagingException;
/**
* Set the value for this header_name. Replaces all existing
* header values with this new value.
*
* @param header_name the name of this header
* @param header_value the value for this header
* @throws IllegalWriteException if the underlying
* implementation does not support modification
* of existing values
* @throws IllegalStateException if this Part is
* obtained from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void setHeader(String header_name, String header_value)
throws MessagingException;
/**
* Add this value to the existing values for this header_name.
*
* @param header_name the name of this header
* @param header_value the value for this header
* @throws IllegalWriteException if the underlying
* implementation does not support modification
* of existing values
* @throws IllegalStateException if this Part is
* obtained from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void addHeader(String header_name, String header_value)
throws MessagingException;
/**
* Remove all headers with this name.
*
* @param header_name the name of this header
* @throws IllegalWriteException if the underlying
* implementation does not support modification
* of existing values
* @throws IllegalStateException if this Part is
* obtained from a READ_ONLY folder
* @throws MessagingException for other failures
*/
void removeHeader(String header_name)
throws MessagingException;
/**
* Return all the headers from this part as an Enumeration of
* Header objects.
*
* @return enumeration of Header objects
* @throws MessagingException for failures
*/
Enumeration<Header> getAllHeaders() throws MessagingException;
/**
* Return matching headers from this part as an Enumeration of
* Header objects.
*
* @param header_names the headers to match
* @return enumeration of Header objects
* @throws MessagingException for failures
*/
Enumeration<Header> getMatchingHeaders(String[] header_names)
throws MessagingException;
/**
* Return non-matching headers from this envelope as an Enumeration
* of Header objects.
*
* @param header_names the headers to not match
* @return enumeration of Header objects
* @throws MessagingException for failures
*/
Enumeration<Header> getNonMatchingHeaders(String[] header_names)
throws MessagingException;
/**
* Obtains the {@link StreamProvider}.
* It defaults to {@link Session#getDefaultInstance(java.util.Properties, Authenticator)}.
*
* @return the StreamProvider.
* @throws MessagingException if errors.
*
* @since JavaMail 2.2
*/
default StreamProvider getStreamProvider() throws MessagingException {
try {
try {
return Session.getDefaultInstance(System.getProperties(), null).getStreamProvider();
} catch (ServiceConfigurationError sce) {
throw new IllegalStateException(sce);
}
} catch (RuntimeException re) {
throw new NoSuchProviderException("Unable to get " + StreamProvider.class.getName(), re);
}
}
}