JavaMail API - Folder Management
So far, we’ve worked in our previous chapters mostly with the INBOX folder. This is the default folder in which most mail resides. Some systems might call it as INBOX and some other might call it by some other name. But,you can always access it from the JavaMail API using the name INBOX.
The JavaMail API represents folders as instances of the abstract Folder class:
public abstract class Folder extends Object
This class declares methods for requesting named folders from servers, deleting messages from folders, searching for particular messages in folders, listing the messages in a folder, and so forth.
Opening a Folder
We can't create a folder directly as the only constructor in the Folder class is protected. We can get a Folder from:
a Session
a Store
or another Folder
All the above classes have a similar getFolder() method with similar signature:
public abstract Folder getFolder(String name) throws MessagingException
Some of the methods which help in getting the Folder object are:
| Method | Description |
|---|
| boolean exists() | Checks if the folder really exists. Use this method before getting the Folder object. |
| abstract void open(int mode) | When you get a Folder, its closed. Use this method to open it. mode
can be Folder.READ_ONLY or Folder.READ_WRITE. |
| abstract boolean isOpen() | This method returns true if the folder is open, false if it’s closed |
| abstract void close(boolean expunge) | Closes the folder. If the expunge argument is true, any deleted messages in the folder are deleted from the actual file on the server. Otherwise, they’re simply marked as deleted, but the messages can still be undeleted. |
Basic Folder Info
Following are some of the methods in Folder class which return basic information about a folder:
| Method | Description |
|---|
| abstract String getName() | Returns the name of the folder, such as "Howcodex Mail" |
| abstract String getFullName() | Returns the complete hierarchical name from the root such as “books/Manisha/Howcodex Mail”. |
| URLName getURLName() | Return a URLName representing this folder. |
| abstract Folder getParent() | Returns the name of the folder that contains this folder i.e the parent folder. E.g "Manisha" from the previous "Howcodex Mail" example. |
| abstract int getType() | Returns an int indicating whether the folder can contain messages and/or other folders. |
| int getMode() | It returns one of the two named constants Folder.READ_ONLY or Folder.READ_WRITE or -1 when the mode is unknown. |
| Store getStore() | Returns the Store object from which this folder was retrieved. |
| abstract char getSeparator() | Return the delimiter character that separates this Folder's pathname from the names of immediate subfolders. |
Managing Folder
Following are some of the methods which help manage the Folder:
| Method | Description |
|---|
| abstract boolean create(int type) | This creates a new folder in this folder’s Store. Where type would be:Folder.HOLDS_MESSAGES or Folder.HOLDS_FOLDERS. Returns true if folder is successfully created else returns false. |
| abstract boolean delete(boolean recurse) | This deletes the folder only if the folder is closed. Otherwise, it
throws an IllegalStateException. If recurse is true, then subfolders are deleted. |
| abstract boolean renameTo(Folder f) | This changes the name of this folder. A folder must be closed to be renamed. Otherwise, an IllegalStateException is thrown. |
Managing Messages in Folders
Following are some of the methods that help manage the messages in Folder:
| Method | Description |
|---|
| abstract void appendMessages(Message[] messages) | As the name implies, the messages in the array are placed at the end of this folder. |
| void copyMessages(Message[] messages, Folder destination) | This copies messages from this folder into a specified folder given as an argument. |
| abstract Message[] expunge() | To delete a message from a folder, set its Flags.Flag.DELETED flag to true. To physically remove deleted messages from a folder, you have to call this method. |
Listing the Contents of a Folder
There are four methods to list the folders that a folder contains:
| Method | Description |
|---|
| Folder[] list() | This returns an array listing the folders that this folder contains. |
| Folder[] listSubscribed() | This returns an array listing all the subscribed folders that this folder contains. |
| abstract Folder[] list(String pattern) | This is similar to the list() method except that it allows you to specify a
pattern. The pattern is a string giving the name of the folders that match. |
| Folder[] listSubscribed(String pattern) | This is similar to the listSubscribed() method except that it allows you to specify a pattern. The pattern is a string giving the name of the folders that match. |
Checking for Mail
| Method | Description |
|---|
| abstract int getMessageCount() | This method can be invoked on an open or closed folder. However, in the case of a closed
folder, this method may (or may not) return -1 to indicate that the exact number of messages isn’t easily available. |
| abstract boolean hasNewMessages() | This returns true if new messages have been added to the folder since it was last opened. |
| int getNewMessageCount() | It returns the new message count by checking messages in the folder whose RECENT flag is set. |
| int getUnreadMessageCount() | This can be invoked on either an open or a closed folder. However, in the case of a closed folder, it may return -1 to indicate that the real answer would be too expensive to obtain. |
Getting Messages from Folders
The Folder class provides four methods for retrieving messages from open folders:
| Method | Description |
|---|
| abstract Message getMessage(int messageNumber) | This returns the nth message in the folder. The first message in the folder is number 1. |
| Message[] getMessages() | This returns an array of Message objects representing all the messages in this folder. |
| Message[] getMessages(int start, int end) | This returns an array of Message objects from the folder, beginning with start and finishing with end, inclusive. |
| Message[] getMessages(int[] messageNumbers) | This returns an array containing only those messages specifically identified by number in the messageNumbers array. |
| void fetch(Message[] messages, FetchProfile fp) | Prefetch the items specified in the FetchProfile for the given Messages. The FetchProfile argument specifies which headers in the messages to prefetch. |
Searching Folders
If the server supports searching (as many IMAP servers do and most POP servers don’t), it’s easy to search a folder for the messages meeting certain criteria. The criteria are encoded in SearchTerm objects. Following are the two search methods:
| Method | Description |
|---|
| Message[] search(SearchTerm term) | Search this Folder for messages matching the specified search criterion. Returns an array containing the matching messages. Returns an empty array if no matches were found. |
| Message[] search(SearchTerm term, Message[] messages) | Search the given array of messages for those that match the specified search criterion. Returns an array containing the matching messages. Returns an empty array if no matches were found. The the specified Message objects must belong to this folder. |
Flags
Flag modification is useful when you need to change flags for the entire set of messages in a Folder. Following are the methods provided in the Folder class:
| Method | Description |
|---|
| void setFlags(Message[] messages, Flags flag, boolean value) | Sets the specified flags on the messages specified in the array. |
| void setFlags(int start, int end, Flags flag, boolean value) | Sets the specified flags on the messages numbered from start through end, both start and end inclusive. |
| void setFlags(int[] messageNumbers, Flags flag, boolean value) | Sets the specified flags on the messages whose message numbers are in the array. |
| abstract Flags getPermanentFlags() | Returns the flags that this folder supports for all messages. |
