MidiSystem (Java 2 Platform SE 5.0) - JDK 5 Documentation v1.5.0, Java 2 SDK 英文文档

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javax.sound.midi
Class MidiSystem

java.lang.Object
  javax.sound.midi.MidiSystem

public class MidiSystem
extends Object
extends Object

The MidiSystem class provides access to the installed MIDI system resources, including devices such as synthesizers, sequencers, and MIDI input and output ports. A typical simple MIDI application might begin by invoking one or more MidiSystem methods to learn what devices are installed and to obtain the ones needed in that application.

The class also has methods for reading files, streams, and URLs that contain standard MIDI file data or soundbanks. You can query the MidiSystem for the format of a specified MIDI file.

You cannot instantiate a MidiSystem; all the methods are static.

Properties can be used to specify default MIDI devices. Both system properties and a properties file are considered. The properties file is "lib/sound.properties" in the JRE directory. If a property exists both as a system property and in the properties file, the system property takes precedence. If none is specified, a suitable default is chosen among the available devices. The syntax of the properties file is specified in Properties.load. The following table lists the available property keys and which methods consider them:

Property Key Interface Affected Method

javax.sound.midi.Receiver Receiver getReceiver()

javax.sound.midi.Sequencer Sequencer getSequencer()

javax.sound.midi.Synthesizer Synthesizer getSynthesizer()

javax.sound.midi.Transmitter Transmitter getTransmitter()

The property value consists of the provider class name and the device name, separated by the hash mark ("#"). The provider class name is the fully-qualified name of a concrete MIDI device provider class. The device name is matched against the String returned by the getName method of MidiDevice.Info. Either the class name, or the device name may be omitted. If only the class name is specified, the trailing hash mark is optional.

Property Key	Interface	Affected Method
`javax.sound.midi.Receiver`	`Receiver`	`getReceiver()`
`javax.sound.midi.Sequencer`	`Sequencer`	`getSequencer()`
`javax.sound.midi.Synthesizer`	`Synthesizer`	`getSynthesizer()`
`javax.sound.midi.Transmitter`	`Transmitter`	`getTransmitter()`

If the provider class is specified, and it can be successully retrieved from the installed providers, the list of MidiDevice.Info objects is retrieved from the provider. Otherwise, or when these devices do not provide a subsequent match, the list is retrieved from getMidiDeviceInfo() to contain all available MidiDevice.Info objects.

If a device name is specified, the resulting list of MidiDevice.Info objects is searched: the first one with a matching name, and whose MidiDevice implements the respective interface, will be returned. If no matching MidiDevice.Info object is found, or the device name is not specified, the first suitable device from the resulting list will be returned. For Sequencer and Synthesizer, a device is suitable if it implements the respective interface; whereas for Receiver and Transmitter, a device is suitable if it implements neither Sequencer nor Synthesizer and provides at least one Receiver or Transmitter, respectively. For example, the property javax.sound.midi.Receiver with a value "com.sun.media.sound.MidiProvider#SunMIDI1" will have the following consequences when getReceiver is called: if the class com.sun.media.sound.MidiProvider exists in the list of installed MIDI device providers, the first Receiver device with name "SunMIDI1" will be returned. If it cannot be found, the first Receiver from that provider will be returned, regardless of name. If there is none, the first Receiver with name "SunMIDI1" in the list of all devices (as returned by getMidiDeviceInfo) will be returned, or, if not found, the first Receiver that can be found in the list of all devices is returned. If that fails, too, a MidiUnavailableException is thrown.

Method Summary

static MidiDevice getMidiDevice(MidiDevice.Info info)
          Obtains the requested MIDI device.

static MidiDevice.Info[] getMidiDeviceInfo()
          Obtains an array of information objects representing the set of all MIDI devices available on the system.

static MidiFileFormat getMidiFileFormat(File file)
          Obtains the MIDI file format of the specified File.

static MidiFileFormat getMidiFileFormat(InputStream stream)
          Obtains the MIDI file format of the data in the specified input stream.

static MidiFileFormat getMidiFileFormat(URL url)
          Obtains the MIDI file format of the data in the specified URL.

static int[] getMidiFileTypes()
          Obtains the set of MIDI file types for which file writing support is provided by the system.

static int[] getMidiFileTypes(Sequence sequence)
          Obtains the set of MIDI file types that the system can write from the sequence specified.

static Receiver getReceiver()
          Obtains a MIDI receiver from an external MIDI port or other default device.

static Sequence getSequence(File file)
          Obtains a MIDI sequence from the specified File.

static Sequence getSequence(InputStream stream)
          Obtains a MIDI sequence from the specified input stream.

static Sequence getSequence(URL url)
          Obtains a MIDI sequence from the specified URL.

static Sequencer getSequencer()
          Obtains the default Sequencer, connected to a default device.

static Sequencer getSequencer(boolean connected)
          Obtains the default Sequencer, optionally connected to a default device.

static Soundbank getSoundbank(File file)
          Constructs a Soundbank by reading it from the specified File.

static Soundbank getSoundbank(InputStream stream)
          Constructs a MIDI sound bank by reading it from the specified stream.

static Soundbank getSoundbank(URL url)
          Constructs a Soundbank by reading it from the specified URL.

static Synthesizer getSynthesizer()
          Obtains the default synthesizer.

static Transmitter getTransmitter()
          Obtains a MIDI transmitter from an external MIDI port or other default source.

static boolean isFileTypeSupported(int fileType)
          Indicates whether file writing support for the specified MIDI file type is provided by the system.

static boolean isFileTypeSupported(int fileType, Sequence sequence)
          Indicates whether a MIDI file of the file type specified can be written from the sequence indicated.

static int write(Sequence in, int type, File out)
          Writes a stream of bytes representing a file of the MIDI file type indicated to the external file provided.

static int write(Sequence in, int fileType, OutputStream out)
          Writes a stream of bytes representing a file of the MIDI file type indicated to the output stream provided.

Methods inherited from class java.lang.Object

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

Method Summary
`static MidiDevice`	`getMidiDevice(MidiDevice.Info info)` Obtains the requested MIDI device.
`static MidiDevice.Info[]`	`getMidiDeviceInfo()` Obtains an array of information objects representing the set of all MIDI devices available on the system.
`static MidiFileFormat`	`getMidiFileFormat(File file)` Obtains the MIDI file format of the specified `File`.
`static MidiFileFormat`	`getMidiFileFormat(InputStream stream)` Obtains the MIDI file format of the data in the specified input stream.
`static MidiFileFormat`	`getMidiFileFormat(URL url)` Obtains the MIDI file format of the data in the specified URL.
`static int[]`	`getMidiFileTypes()` Obtains the set of MIDI file types for which file writing support is provided by the system.
`static int[]`	`getMidiFileTypes(Sequence sequence)` Obtains the set of MIDI file types that the system can write from the sequence specified.
`static Receiver`	`getReceiver()` Obtains a MIDI receiver from an external MIDI port or other default device.
`static Sequence`	`getSequence(File file)` Obtains a MIDI sequence from the specified `File`.
`static Sequence`	`getSequence(InputStream stream)` Obtains a MIDI sequence from the specified input stream.
`static Sequence`	`getSequence(URL url)` Obtains a MIDI sequence from the specified URL.
`static Sequencer`	`getSequencer()` Obtains the default `Sequencer`, connected to a default device.
`static Sequencer`	`getSequencer(boolean connected)` Obtains the default `Sequencer`, optionally connected to a default device.
`static Soundbank`	`getSoundbank(File file)` Constructs a `Soundbank` by reading it from the specified `File`.
`static Soundbank`	`getSoundbank(InputStream stream)` Constructs a MIDI sound bank by reading it from the specified stream.
`static Soundbank`	`getSoundbank(URL url)` Constructs a `Soundbank` by reading it from the specified URL.
`static Synthesizer`	`getSynthesizer()` Obtains the default synthesizer.
`static Transmitter`	`getTransmitter()` Obtains a MIDI transmitter from an external MIDI port or other default source.
`static boolean`	`isFileTypeSupported(int fileType)` Indicates whether file writing support for the specified MIDI file type is provided by the system.
`static boolean`	`isFileTypeSupported(int fileType, Sequence sequence)` Indicates whether a MIDI file of the file type specified can be written from the sequence indicated.
`static int`	`write(Sequence in, int type, File out)` Writes a stream of bytes representing a file of the MIDI file type indicated to the external file provided.
`static int`	`write(Sequence in, int fileType, OutputStream out)` Writes a stream of bytes representing a file of the MIDI file type indicated to the output stream provided.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Method Detail

getMidiDeviceInfo

public static MidiDevice.Info[] getMidiDeviceInfo()

Obtains an array of information objects representing the set of all MIDI devices available on the system. A returned information object can then be used to obtain the corresponding device object, by invoking getMidiDevice.

Returns:: an array of MidiDevice.Info objects, one for each installed MIDI device. If no such devices are installed, an array of length 0 is returned.

getMidiDevice

public static MidiDevice getMidiDevice(MidiDevice.Info info)
                                throws MidiUnavailableException

Obtains the requested MIDI device.

Parameters:: info - a device information object representing the desired device.
Returns:: the requested device
Throws:: MidiUnavailableException - if the requested device is not available due to resource restrictions; IllegalArgumentException - if the info object does not represent a MIDI device installed on the system
See Also:: getMidiDeviceInfo()

getReceiver

public static Receiver getReceiver()
                            throws MidiUnavailableException

Obtains a MIDI receiver from an external MIDI port or other default device.

If the system property javax.sound.midi.Receiver is defined or it is defined in the file "sound.properties", it is used to identify the device that provides the default receiver. For details, refer to the class description. If a suitable MIDI port is not available, the Receiver is retrieved from an installed synthesizer.

If this method returns successfully, the MidiDevice the Receiver belongs to is opened implicitly, if it is not already open. It is possible to close an implicitly opened device by calling close on the returned Receiver. All open Receiver instances have to be closed in order to release system resources hold by the MidiDevice. For a detailed description of open/close behaviour see the class description of MidiDevice.

Returns:: the default MIDI receiver
Throws:: MidiUnavailableException - if the default receiver is not available due to resource restrictions, or no device providing receivers is installed in the system

getTransmitter

public static Transmitter getTransmitter()
                                  throws MidiUnavailableException

Obtains a MIDI transmitter from an external MIDI port or other default source.

If the system property javax.sound.midi.Transmitter is defined or it is defined in the file "sound.properties", it is used to identify the device that provides the default transmitter. For details, refer to the class description. If this method returns successfully, the MidiDevice the Transmitter belongs to is opened implicitly, if it is not already open. It is possible to close an implicitly opened device by calling close on the returned Transmitter. All open Transmitter instances have to be closed in order to release system resources hold by the MidiDevice. For a detailed description of open/close behaviour see the class description of MidiDevice.

Returns:: the default MIDI transmitter
Throws:: MidiUnavailableException - if the default transmitter is not available due to resource restrictions, or no device providing transmitters is installed in the system

getSynthesizer

public static Synthesizer getSynthesizer()
                                  throws MidiUnavailableException

Obtains the default synthesizer.

If the system property javax.sound.midi.Synthesizer is defined or it is defined in the file "sound.properties", it is used to identify the default synthesizer. For details, refer to the class description.

Returns:: the default synthesizer
Throws:: MidiUnavailableException - if the synthesizer is not available due to resource restrictions, or no synthesizer is installed in the system

getSequencer

public static Sequencer getSequencer()
                              throws MidiUnavailableException

Obtains the default Sequencer, connected to a default device. The returned Sequencer instance is connected to the default Synthesizer, as returned by getSynthesizer(). If there is no Synthesizer available, or the default Synthesizer cannot be opened, the sequencer is connected to the default Receiver, as returned by getReceiver(). The connection is made by retrieving a Transmitter instance from the Sequencer and setting its Receiver. Closing and re-opening the sequencer will restore the connection to the default device.

This method is equivalent to calling getSequencer(true).

If the system property javax.sound.midi.Sequencer is defined or it is defined in the file "sound.properties", it is used to identify the default sequencer. For details, refer to the class description.

Returns:: the default sequencer, connected to a default Receiver
Throws:: MidiUnavailableException - if the sequencer is not available due to resource restrictions, or there is no Receiver available by any installed MidiDevice, or no sequencer is installed in the system.
See Also:: getSequencer(boolean), getSynthesizer(), getReceiver()

getSequencer

public static Sequencer getSequencer(boolean connected)
                              throws MidiUnavailableException

Obtains the default Sequencer, optionally connected to a default device.

If connected is true, the returned Sequencer instance is connected to the default Synthesizer, as returned by getSynthesizer(). If there is no Synthesizer available, or the default Synthesizer cannot be opened, the sequencer is connected to the default Receiver, as returned by getReceiver(). The connection is made by retrieving a Transmitter instance from the Sequencer and setting its Receiver. Closing and re-opening the sequencer will restore the connection to the default device.

If connected is false, the returned Sequencer instance is not connected, it has no open Transmitters. In order to play the sequencer on a MIDI device, or a Synthesizer, it is necessary to get a Transmitter and set its Receiver.

Returns:: the default sequencer
Throws:: MidiUnavailableException - if the sequencer is not available due to resource restrictions, or no sequencer is installed in the system, or if connected is true, and there is no Receiver available by any installed MidiDevice
Since:: 1.5
See Also:: getSynthesizer(), getReceiver()

getSoundbank

public static Soundbank getSoundbank(InputStream stream)
                              throws InvalidMidiDataException,
                                     IOException

Constructs a MIDI sound bank by reading it from the specified stream. The stream must point to a valid MIDI soundbank file. In general, MIDI soundbank providers may need to read some data from the stream before determining whether they support it. These parsers must be able to mark the stream, read enough data to determine whether they support the stream, and, if not, reset the stream's read pointer to its original position. If the input stream does not support this, this method may fail with an IOException.

Parameters:: stream - the source of the sound bank data.
Returns:: the sound bank
Throws:: InvalidMidiDataException - if the stream does not point to valid MIDI soundbank data recognized by the system; IOException - if an I/O error occurred when loading the soundbank
See Also:: InputStream.markSupported(), InputStream.mark(int)

getSoundbank

public static Soundbank getSoundbank(URL url)
                              throws InvalidMidiDataException,
                                     IOException

Constructs a Soundbank by reading it from the specified URL. The URL must point to a valid MIDI soundbank file.

Parameters:: url - the source of the sound bank data
Returns:: the sound bank
Throws:: InvalidMidiDataException - if the URL does not point to valid MIDI soundbank data recognized by the system; IOException - if an I/O error occurred when loading the soundbank

getSoundbank

public static Soundbank getSoundbank(File file)
                              throws InvalidMidiDataException,
                                     IOException

Constructs a Soundbank by reading it from the specified File. The File must point to a valid MIDI soundbank file.

Parameters:: file - the source of the sound bank data
Returns:: the sound bank
Throws:: InvalidMidiDataException - if the File does not point to valid MIDI soundbank data recognized by the system; IOException - if an I/O error occurred when loading the soundbank

getMidiFileFormat

public static MidiFileFormat getMidiFileFormat(InputStream stream)
                                        throws InvalidMidiDataException,
                                               IOException

Obtains the MIDI file format of the data in the specified input stream. The stream must point to valid MIDI file data for a file type recognized by the system.

This method and/or the code it invokes may need to read some data from the stream to determine whether its data format is supported. The implementation may therefore need to mark the stream, read enough data to determine whether it is in a supported format, and reset the stream's read pointer to its original position. If the input stream does not permit this set of operations, this method may fail with an IOException.

This operation can only succeed for files of a type which can be parsed by an installed file reader. It may fail with an InvalidMidiDataException even for valid files if no compatible file reader is installed. It will also fail with an InvalidMidiDataException if a compatible file reader is installed, but encounters errors while determining the file format.

Parameters:: stream - the input stream from which file format information should be extracted
Returns:: an MidiFileFormat object describing the MIDI file format
Throws:: InvalidMidiDataException - if the stream does not point to valid MIDI file data recognized by the system; IOException - if an I/O exception occurs while accessing the stream
See Also:: getMidiFileFormat(URL), getMidiFileFormat(File), InputStream.markSupported(), InputStream.mark(int)

getMidiFileFormat

public static MidiFileFormat getMidiFileFormat(URL url)
                                        throws InvalidMidiDataException,
                                               IOException

Obtains the MIDI file format of the data in the specified URL. The URL must point to valid MIDI file data for a file type recognized by the system.

Parameters:: url - the URL from which file format information should be extracted
Returns:: a MidiFileFormat object describing the MIDI file format
Throws:: InvalidMidiDataException - if the URL does not point to valid MIDI file data recognized by the system; IOException - if an I/O exception occurs while accessing the URL
See Also:: getMidiFileFormat(InputStream), getMidiFileFormat(File)

getMidiFileFormat

public static MidiFileFormat getMidiFileFormat(File file)
                                        throws InvalidMidiDataException,
                                               IOException

Obtains the MIDI file format of the specified File. The File must point to valid MIDI file data for a file type recognized by the system.

Parameters:: file - the File from which file format information should be extracted
Returns:: a MidiFileFormat object describing the MIDI file format
Throws:: InvalidMidiDataException - if the File does not point to valid MIDI file data recognized by the system; IOException - if an I/O exception occurs while accessing the file
See Also:: getMidiFileFormat(InputStream), getMidiFileFormat(URL)

getSequence

public static Sequence getSequence(InputStream stream)
                            throws InvalidMidiDataException,
                                   IOException

Obtains a MIDI sequence from the specified input stream. The stream must point to valid MIDI file data for a file type recognized by the system.

Parameters:: stream - the input stream from which the Sequence should be constructed
Returns:: a Sequence object based on the MIDI file data contained in the input stream
Throws:: InvalidMidiDataException - if the stream does not point to valid MIDI file data recognized by the system; IOException - if an I/O exception occurs while accessing the stream
See Also:: InputStream.markSupported(), InputStream.mark(int)

getSequence

public static Sequence getSequence(URL url)
                            throws InvalidMidiDataException,
                                   IOException

Obtains a MIDI sequence from the specified URL. The URL must point to valid MIDI file data for a file type recognized by the system.

Parameters:: url - the URL from which the Sequence should be constructed
Returns:: a Sequence object based on the MIDI file data pointed to by the URL
Throws:: InvalidMidiDataException - if the URL does not point to valid MIDI file data recognized by the system; IOException - if an I/O exception occurs while accessing the URL

getSequence

public static Sequence getSequence(File file)
                            throws InvalidMidiDataException,
                                   IOException

Obtains a MIDI sequence from the specified File. The File must point to valid MIDI file data for a file type recognized by the system.

Parameters:: file - the File from which the Sequence should be constructed
Returns:: a Sequence object based on the MIDI file data pointed to by the File
Throws:: InvalidMidiDataException - if the File does not point to valid MIDI file data recognized by the system; IOException - if an I/O exception occurs

getMidiFileTypes

public static int[] getMidiFileTypes()

Obtains the set of MIDI file types for which file writing support is provided by the system.

Returns:: array of unique file types. If no file types are supported, an array of length 0 is returned.

isFileTypeSupported

public static boolean isFileTypeSupported(int fileType)

Indicates whether file writing support for the specified MIDI file type is provided by the system.

Parameters:: fileType - the file type for which write capabilities are queried
Returns:: true if the file type is supported, otherwise false

getMidiFileTypes

public static int[] getMidiFileTypes(Sequence sequence)

Obtains the set of MIDI file types that the system can write from the sequence specified.

Parameters:: sequence - the sequence for which MIDI file type support is queried
Returns:: the set of unique supported file types. If no file types are supported, returns an array of length 0.

isFileTypeSupported

public static boolean isFileTypeSupported(int fileType,
                                          Sequence sequence)

Indicates whether a MIDI file of the file type specified can be written from the sequence indicated.

Parameters:: fileType - the file type for which write capabilities are queried; sequence - the sequence for which file writing support is queried
Returns:: true if the file type is supported for this sequence, otherwise false

write

public static int write(Sequence in,
                        int fileType,
                        OutputStream out)
                 throws IOException

Writes a stream of bytes representing a file of the MIDI file type indicated to the output stream provided.

Parameters:: in - sequence containing MIDI data to be written to the file; fileType - the file type of the file to be written to the output stream; out - stream to which the file data should be written
Returns:: the number of bytes written to the output stream
Throws:: IOException - if an I/O exception occurs; IllegalArgumentException - if the file format is not supported by the system
See Also:: isFileTypeSupported(int, Sequence), getMidiFileTypes(Sequence)

write

public static int write(Sequence in,
                        int type,
                        File out)
                 throws IOException

Writes a stream of bytes representing a file of the MIDI file type indicated to the external file provided.

Parameters:: in - sequence containing MIDI data to be written to the file; type - the file type of the file to be written to the output stream; out - external file to which the file data should be written
Returns:: the number of bytes written to the file
Throws:: IOException - if an I/O exception occurs; IllegalArgumentException - if the file type is not supported by the system
See Also:: isFileTypeSupported(int, Sequence), getMidiFileTypes(Sequence)

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

MidiSystem (Java 2 Platform SE 5.0) - JDK 5 Documentation v1.5.0, Java 2 SDK 英文文档

javax.sound.midi Class MidiSystem

getMidiDeviceInfo

getMidiDevice

getReceiver

getTransmitter

getSynthesizer

getSequencer

getSequencer

getSoundbank

getSoundbank

getSoundbank

getMidiFileFormat

getMidiFileFormat

getMidiFileFormat

getSequence

getSequence

getSequence

getMidiFileTypes

isFileTypeSupported

getMidiFileTypes

isFileTypeSupported

write

write

javax.sound.midi
Class MidiSystem