Session (JavaMail API documentation)
Date: 2019-08-31

javax.mail

## Class Session

- java.lang.Object
- - javax.mail.Session

-     public final class Session
      extends java.lang.Object

  The Session class represents a mail session and is not subclassed. It collects together properties and defaults used by the mail API's. A single default session can be shared by multiple applications on the desktop. Unshared sessions can also be created.

  The Session class provides access to the protocol providers that implement the `Store`, `Transport`, and related classes. The protocol providers are configured using the following files:

  - `javamail.providers` and `javamail.default.providers`
  - `javamail.address.map` and `javamail.default.address.map`

  Each `javamail.`X resource file is searched for using three methods in the following order:

  1. `java.home/lib/javamail.`X
  2. `META-INF/javamail.`X
  3. `META-INF/javamail.default.`X

  The first method allows the user to include their own version of the resource file by placing it in the `lib` directory where the `java.home` property points. The second method allows an application that uses the JavaMail APIs to include their own resource files in their application's or jar file's `META-INF` directory. The `javamail.default.`X default files are part of the JavaMail `mail.jar` file.

  File location depends upon how the `ClassLoader` method `getResource` is implemented. Usually, the `getResource` method searches through CLASSPATH until it finds the requested file and then stops.

  The ordering of entries in the resource files matters. If multiple entries exist, the first entries take precedence over the later entries. For example, the first IMAP provider found will be set as the default IMAP implementation until explicitly changed by the application. The user- or system-supplied resource files augment, they do not override, the default files included with the JavaMail APIs. This means that all entries in all files loaded will be available.

  `javamail.providers` and `javamail.default.providers`

  These resource files specify the stores and transports that are available on the system, allowing an application to "discover" what store and transport implementations are available. The protocol implementations are listed one per line. The file format defines four attributes that describe a protocol implementation. Each attribute is an "="-separated name-value pair with the name in lowercase. Each name-value pair is semi-colon (";") separated. The following names are defined.

  Attribute Names in Providers Files
  Name | Description
  --- | ---
  protocol | Name assigned to protocol. For example, `smtp` for Transport.
  type | Valid entries are `store` and `transport`.
  class | Class name that implements this protocol.
  vendor | Optional string identifying the vendor.
  version | Optional string identifying the version.

  Here's an example of `META-INF/javamail.default.providers` file contents:

       protocol=imap; type=store; class=com.sun.mail.imap.IMAPStore; vendor=Oracle;
       protocol=smtp; type=transport; class=com.sun.mail.smtp.SMTPTransport; vendor=Oracle;

  `javamail.address.map` and `javamail.default.address.map`

  These resource files map transport address types to the transport protocol. The `getType` method of javax.mail.Address returns the address type. The `javamail.address.map` file maps the transport type to the protocol. The file format is a series of name-value pairs. Each key name should correspond to an address type that is currently installed on the system; there should also be an entry for each `javax.mail.Address` implementation that is present if it is to be used. For example, the `javax.mail.internet.InternetAddress` method `getType` returns "rfc822". Each referenced protocol should be installed on the system. For the case of `news`, below, the client should install a Transport provider supporting the nntp protocol.

  Here are the typical contents of a `javamail.address.map` file:

       rfc822=smtp
       news=nntp

- - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addProvider(Provider provider)` Add a provider to the session.
    `boolean` | `getDebug()` Get the debug setting for this Session.
    `java.io.PrintStream` | `getDebugOut()` Returns the stream to be used for debugging output.
    `static Session` | `getDefaultInstance(java.util.Properties props)` Get the default Session object.
    `static Session` | `getDefaultInstance(java.util.Properties props, Authenticator authenticator)` Get the default Session object.
    `Folder` | `getFolder(URLName url)` Get a closed Folder object for the given URLName.
    `static Session` | `getInstance(java.util.Properties props)` Get a new Session object.
    `static Session` | `getInstance(java.util.Properties props, Authenticator authenticator)` Get a new Session object.
    `PasswordAuthentication` | `getPasswordAuthentication(URLName url)` Return any saved PasswordAuthentication for this (store or transport) URLName.
    `java.util.Properties` | `getProperties()` Returns the Properties object associated with this Session
    `java.lang.String` | `getProperty(java.lang.String name)` Returns the value of the specified property.
    `Provider` | `getProvider(java.lang.String protocol)` Returns the default Provider for the protocol specified.
    `Provider[]` | `getProviders()` This method returns an array of all the implementations installed via the javamail.[default.]providers files that can be loaded using the ClassLoader available to this application.
    `Store` | `getStore()` Get a Store object that implements this user's desired Store protocol.
    `Store` | `getStore(Provider provider)` Get an instance of the store specified by Provider.
    `Store` | `getStore(java.lang.String protocol)` Get a Store object that implements the specified protocol.
    `Store` | `getStore(URLName url)` Get a Store object for the given URLName.
    `Transport` | `getTransport()` Get a Transport object that implements this user's desired Transport protcol.
    `Transport` | `getTransport(Address address)` Get a Transport object that can transport a Message of the specified address type.
    `Transport` | `getTransport(Provider provider)` Get an instance of the transport specified in the Provider.
    `Transport` | `getTransport(java.lang.String protocol)` Get a Transport object that implements the specified protocol.
    `Transport` | `getTransport(URLName url)` Get a Transport object for the given URLName.
    `PasswordAuthentication` | `requestPasswordAuthentication(java.net.InetAddress addr, int port, java.lang.String protocol, java.lang.String prompt, java.lang.String defaultUserName)` Call back to the application to get the needed user name and password.
    `void` | `setDebug(boolean debug)` Set the debug setting for this Session.
    `void` | `setDebugOut(java.io.PrintStream out)` Set the stream to be used for debugging output for this session.
    `void` | `setPasswordAuthentication(URLName url, PasswordAuthentication pw)` Save a PasswordAuthentication for this (store or transport) URLName.
    `void` | `setProtocolForAddress(java.lang.String addresstype, java.lang.String protocol)` Set the default transport protocol to use for addresses of the specified type.
    `void` | `setProvider(Provider provider)` Set the passed Provider to be the default implementation for the protocol in Provider.protocol overriding any previous values.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### getInstance

          public static Session getInstance(java.util.Properties props,
                                            Authenticator authenticator)

      Get a new Session object.
      Parameters:
        `props` - Properties object that hold relevant properties.
        It is expected that the client supplies values for the properties listed in Appendix A of the JavaMail spec (particularly mail.store.protocol, mail.transport.protocol, mail.host, mail.user, and mail.from) as the defaults are unlikely to work in all cases.
        `authenticator` - Authenticator object used to call back to the application when a user name and password is needed.
      Returns:
        a new Session object
      See Also:
        `Authenticator`

    - #### getInstance

          public static Session getInstance(java.util.Properties props)

      Get a new Session object.
      Parameters:
        `props` - Properties object that hold relevant properties.
        It is expected that the client supplies values for the properties listed in Appendix A of the JavaMail spec (particularly mail.store.protocol, mail.transport.protocol, mail.host, mail.user, and mail.from) as the defaults are unlikely to work in all cases.
      Returns:
        a new Session object
      Since:
        JavaMail 1.2

    - #### getDefaultInstance

          public static Session getDefaultInstance(java.util.Properties props,
                                                   Authenticator authenticator)

      Get the default Session object. If a default has not yet been setup, a new Session object is created and installed as the default.

      Since the default session is potentially available to all code executing in the same Java virtual machine, and the session can contain security sensitive information such as user names and passwords, access to the default session is restricted. The Authenticator object, which must be created by the caller, is used indirectly to check access permission. The Authenticator object passed in when the session is created is compared with the Authenticator object passed in to subsequent requests to get the default session. If both objects are the same, or are from the same ClassLoader, the request is allowed. Otherwise, it is denied.

      Note that if the Authenticator object used to create the session is null, anyone can get the default session by passing in null.

      Note also that the Properties object is used only the first time this method is called, when a new Session object is created. Subsequent calls return the Session object that was created by the first call, and ignore the passed Properties object. Use the `getInstance` method to get a new Session object every time the method is called.

      Additional security Permission objects may be used to control access to the default session.

      In the current implementation, if a SecurityManager is set, the caller must have the `RuntimePermission("setFactory")` permission.

      Parameters:
        `props` - Properties object. Used only if a new Session object is created.
        It is expected that the client supplies values for the properties listed in Appendix A of the JavaMail spec (particularly mail.store.protocol, mail.transport.protocol, mail.host, mail.user, and mail.from) as the defaults are unlikely to work in all cases.
        `authenticator` - Authenticator object. Used only if a new Session object is created. Otherwise, it must match the Authenticator used to create the Session.
      Returns:
        the default Session object

    - #### getDefaultInstance

          public static Session getDefaultInstance(java.util.Properties props)

      Get the default Session object. If a default has not yet been setup, a new Session object is created and installed as the default.

      Note that a default session created with no Authenticator is available to all code executing in the same Java virtual machine, and the session can contain security sensitive information such as user names and passwords.

      Parameters:
        `props` - Properties object. Used only if a new Session object is created.
        It is expected that the client supplies values for the properties listed in Appendix A of the JavaMail spec (particularly mail.store.protocol, mail.transport.protocol, mail.host, mail.user, and mail.from) as the defaults are unlikely to work in all cases.
      Returns:
        the default Session object
      Since:
        JavaMail 1.2

    - #### setDebug

          public void setDebug(boolean debug)

      Set the debug setting for this Session.

      Since the debug setting can be turned on only after the Session has been created, to turn on debugging in the Session constructor, set the property `mail.debug` in the Properties object passed in to the constructor to true. The value of the `mail.debug` property is used to initialize the per-Session debugging flag. Subsequent calls to the `setDebug` method manipulate the per-Session debugging flag and have no affect on the `mail.debug` property.

      Parameters:
        `debug` - Debug setting

    - #### getDebug

          public boolean getDebug()

      Get the debug setting for this Session.
      Returns:
        current debug setting

    - #### setDebugOut

          public void setDebugOut(java.io.PrintStream out)

      Set the stream to be used for debugging output for this session. If `out` is null, `System.out` will be used. Note that debugging output that occurs before any session is created, as a result of setting the `mail.debug` system property, will always be sent to `System.out`.
      Parameters:
        `out` - the PrintStream to use for debugging output
      Since:
        JavaMail 1.3

    - #### getDebugOut

          public java.io.PrintStream getDebugOut()

      Returns the stream to be used for debugging output. If no stream has been set, `System.out` is returned.
      Returns:
        the PrintStream to use for debugging output
      Since:
        JavaMail 1.3

    - #### getProviders

          public Provider[] getProviders()

      This method returns an array of all the implementations installed via the javamail.[default.]providers files that can be loaded using the ClassLoader available to this application.
      Returns:
        Array of configured providers

    - #### getProvider

          public Provider getProvider(java.lang.String protocol)
                               throws NoSuchProviderException

      Returns the default Provider for the protocol specified. Checks mail.<protocol>.class property first and if it exists, returns the Provider associated with this implementation. If it doesn't exist, returns the Provider that appeared first in the configuration files. If an implementation for the protocol isn't found, throws NoSuchProviderException
      Parameters:
        `protocol` - Configured protocol (i.e. smtp, imap, etc)
      Returns:
        Currently configured Provider for the specified protocol
      Throws:
        `NoSuchProviderException` - If a provider for the given protocol is not found.

    - #### setProvider

          public void setProvider(Provider provider)
                           throws NoSuchProviderException

      Set the passed Provider to be the default implementation for the protocol in Provider.protocol overriding any previous values.
      Parameters:
        `provider` - Currently configured Provider which will be set as the default for the protocol
      Throws:
        `NoSuchProviderException` - If the provider passed in is invalid.

    - #### getStore

          public Store getStore()
                         throws NoSuchProviderException

      Get a Store object that implements this user's desired Store protocol. The `mail.store.protocol` property specifies the desired protocol. If an appropriate Store object is not obtained, NoSuchProviderException is thrown
      Returns:
        a Store object
      Throws:
        `NoSuchProviderException` - If a provider for the given protocol is not found.

    - #### getStore

          public Store getStore(java.lang.String protocol)
                         throws NoSuchProviderException

      Get a Store object that implements the specified protocol. If an appropriate Store object cannot be obtained, NoSuchProviderException is thrown.
      Parameters:
        `protocol` -
      Returns:
        a Store object
      Throws:
        `NoSuchProviderException` - If a provider for the given protocol is not found.

    - #### getStore

          public Store getStore(URLName url)
                         throws NoSuchProviderException

      Get a Store object for the given URLName. If the requested Store object cannot be obtained, NoSuchProviderException is thrown. The "scheme" part of the URL string (Refer RFC 1738) is used to locate the Store protocol.

      Parameters:
        `url` - URLName that represents the desired Store
      Returns:
        a closed Store object
      Throws:
        `NoSuchProviderException` - If a provider for the given URLName is not found.
      See Also:
        `getFolder(URLName)`, `URLName`

    - #### getStore

          public Store getStore(Provider provider)
                         throws NoSuchProviderException

      Get an instance of the store specified by Provider. Instantiates the store and returns it.
      Parameters:
        `provider` - Store Provider that will be instantiated
      Returns:
        Instantiated Store
      Throws:
        `NoSuchProviderException` - If a provider for the given Provider is not found.

    - #### getFolder

          public Folder getFolder(URLName url)
                           throws MessagingException

      Get a closed Folder object for the given URLName. If the requested Folder object cannot be obtained, null is returned.

      The "scheme" part of the URL string (Refer RFC 1738) is used to locate the Store protocol. The rest of the URL string (that is, the "schemepart", as per RFC 1738) is used by that Store in a protocol dependent manner to locate and instantiate the appropriate Folder object.

      Note that RFC 1738 also specifies the syntax for the "schemepart" for IP-based protocols (IMAP4, POP3, etc.). Providers of IP-based mail Stores should implement that syntax for referring to Folders.

      Parameters:
        `url` - URLName that represents the desired folder
      Returns:
        Folder
      Throws:
        `NoSuchProviderException` - If a provider for the given URLName is not found.
        `MessagingException` - if the Folder could not be located or created.
      See Also:
        `getStore(URLName)`, `URLName`

    - #### getTransport

          public Transport getTransport()
                                 throws NoSuchProviderException

      Get a Transport object that implements this user's desired Transport protcol. The `mail.transport.protocol` property specifies the desired protocol. If an appropriate Transport object cannot be obtained, MessagingException is thrown.
      Returns:
        a Transport object
      Throws:
        `NoSuchProviderException` - If the provider is not found.

    - #### getTransport

          public Transport getTransport(java.lang.String protocol)
                                 throws NoSuchProviderException

      Get a Transport object that implements the specified protocol. If an appropriate Transport object cannot be obtained, null is returned.
      Returns:
        a Transport object
      Throws:
        `NoSuchProviderException` - If provider for the given protocol is not found.

    - #### getTransport

          public Transport getTransport(URLName url)
                                 throws NoSuchProviderException

      Get a Transport object for the given URLName. If the requested Transport object cannot be obtained, NoSuchProviderException is thrown. The "scheme" part of the URL string (Refer RFC 1738) is used to locate the Transport protocol.

      Parameters:
        `url` - URLName that represents the desired Transport
      Returns:
        a closed Transport object
      Throws:
        `NoSuchProviderException` - If a provider for the given URLName is not found.
      See Also:
        `URLName`

    - #### getTransport

          public Transport getTransport(Provider provider)
                                 throws NoSuchProviderException

      Get an instance of the transport specified in the Provider. Instantiates the transport and returns it.
      Parameters:
        `provider` - Transport Provider that will be instantiated
      Returns:
        Instantiated Transport
      Throws:
        `NoSuchProviderException` - If provider for the given provider is not found.

    - #### getTransport

          public Transport getTransport(Address address)
                                 throws NoSuchProviderException

      Get a Transport object that can transport a Message of the specified address type.
      Parameters:
        `address` -
      Returns:
        A Transport object
      Throws:
        `NoSuchProviderException` - If provider for the Address type is not found
      See Also:
        `Address`

    - #### setPasswordAuthentication

          public void setPasswordAuthentication(URLName url,
                                                PasswordAuthentication pw)

      Save a PasswordAuthentication for this (store or transport) URLName. If pw is null the entry corresponding to the URLName is removed.

      This is normally used only by the store or transport implementations to allow authentication information to be shared among multiple uses of a session.

    - #### getPasswordAuthentication

          public PasswordAuthentication getPasswordAuthentication(URLName url)

      Return any saved PasswordAuthentication for this (store or transport) URLName. Normally used only by store or transport implementations.
      Returns:
        the PasswordAuthentication corresponding to the URLName

    - #### requestPasswordAuthentication

          public PasswordAuthentication requestPasswordAuthentication(java.net.InetAddress addr,
                                                                      int port,
                                                                      java.lang.String protocol,
                                                                      java.lang.String prompt,
                                                                      java.lang.String defaultUserName)

      Call back to the application to get the needed user name and password. The application should put up a dialog something like:

           Connecting to <protocol> mail service on host <addr>, port <port>.
           <prompt>

           User Name: <defaultUserName>
           Password:

      Parameters:
        `addr` - InetAddress of the host. may be null.
        `protocol` - protocol scheme (e.g. imap, pop3, etc.)
        `prompt` - any additional String to show as part of the prompt; may be null.
        `defaultUserName` - the default username. may be null.
      Returns:
        the authentication which was collected by the authenticator; may be null.

    - #### getProperties

          public java.util.Properties getProperties()

      Returns the Properties object associated with this Session
      Returns:
        Properties object

    - #### getProperty

          public java.lang.String getProperty(java.lang.String name)

      Returns the value of the specified property. Returns null if this property does not exist.
      Returns:
        String that is the property value

    - #### addProvider

          public void addProvider(Provider provider)

      Add a provider to the session.
      Parameters:
        `provider` - the provider to add
      Since:
        JavaMail 1.4

    - #### setProtocolForAddress

          public void setProtocolForAddress(java.lang.String addresstype,
                                            java.lang.String protocol)

      Set the default transport protocol to use for addresses of the specified type. Normally the default is set by the `javamail.default.address.map` or `javamail.address.map` files or resources.
      Parameters:
        `addresstype` - type of address
        `protocol` - name of protocol
      Since:
        JavaMail 1.4
      See Also:
        `getTransport(Address)`

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