jakarta.activation.DataHandler Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2019 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package jakarta.activation;
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.OutputStreamWriter;
import java.net.URL;
/**
* The DataHandler class provides a consistent interface to data
* available in many different sources and formats.
* It manages simple stream to string conversions and related operations
* using DataContentHandlers.
* It provides access to commands that can operate on the data.
* The commands are found using a CommandMap.
*
* DataHandler and CommandMaps
* The DataHandler keeps track of the current CommandMap that it uses to
* service requests for commands (getCommand,
* getAllCommands, getPreferredCommands).
* Each instance of a DataHandler may have a CommandMap associated with
* it using the setCommandMap method. If a CommandMap was
* not set, DataHandler calls the getDefaultCommandMap
* method in CommandMap and uses the value it returns. See
* CommandMap for more information.
*
* DataHandler and URLs
* The current DataHandler implementation creates a private
* instance of URLDataSource when it is constructed with a URL.
*
* @see jakarta.activation.CommandMap
* @see jakarta.activation.DataContentHandler
* @see jakarta.activation.DataSource
* @see jakarta.activation.URLDataSource
*/
public class DataHandler {
// Use the datasource to indicate whether we were started via the
// DataSource constructor or the object constructor.
private DataSource dataSource = null;
private DataSource objDataSource = null;
// The Object and mimetype from the constructor (if passed in).
// object remains null if it was instantiated with a
// DataSource.
private Object object = null;
private String objectMimeType = null;
// Keep track of the CommandMap
private CommandMap currentCommandMap = null;
// our transfer flavors
private static final ActivationDataFlavor emptyFlavors[] =
new ActivationDataFlavor[0];
private ActivationDataFlavor transferFlavors[] = emptyFlavors;
// our DataContentHandler
private DataContentHandler dataContentHandler = null;
private DataContentHandler factoryDCH = null;
// our DataContentHandlerFactory
private static DataContentHandlerFactory factory = null;
private DataContentHandlerFactory oldFactory = null;
// the short representation of the ContentType (sans params)
private String shortType = null;
/**
* Create a DataHandler instance referencing the
* specified DataSource. The data exists in a byte stream form.
* The DataSource will provide an InputStream to access the data.
*
* @param ds the DataSource
*/
public DataHandler(DataSource ds) {
// save a reference to the incoming DS
dataSource = ds;
oldFactory = factory; // keep track of the factory
}
/**
* Create a DataHandler instance representing an object
* of this MIME type. This constructor is
* used when the application already has an in-memory representation
* of the data in the form of a Java Object.
*
* @param obj the Java Object
* @param mimeType the MIME type of the object
*/
public DataHandler(Object obj, String mimeType) {
object = obj;
objectMimeType = mimeType;
oldFactory = factory; // keep track of the factory
}
/**
* Create a DataHandler instance referencing a URL.
* The DataHandler internally creates a URLDataSource
* instance to represent the URL.
*
* @param url a URL object
*/
public DataHandler(URL url) {
dataSource = new URLDataSource(url);
oldFactory = factory; // keep track of the factory
}
/**
* Return the CommandMap for this instance of DataHandler.
*/
private synchronized CommandMap getCommandMap() {
if (currentCommandMap != null)
return currentCommandMap;
else
return CommandMap.getDefaultCommandMap();
}
/**
* Return the DataSource associated with this instance
* of DataHandler.
*
* For DataHandlers that have been instantiated with a DataSource,
* this method returns the DataSource that was used to create the
* DataHandler object. In other cases the DataHandler
* constructs a DataSource from the data used to construct
* the DataHandler. DataSources created for DataHandlers not
* instantiated with a DataSource are cached for performance
* reasons.
*
* @return a valid DataSource object for this DataHandler
*/
public DataSource getDataSource() {
if (dataSource == null) {
// create one on the fly
if (objDataSource == null)
objDataSource = new DataHandlerDataSource(this);
return objDataSource;
}
return dataSource;
}
/**
* Return the name of the data object. If this DataHandler
* was created with a DataSource, this method calls through
* to the DataSource.getName method, otherwise it
* returns null.
*
* @return the name of the object
*/
public String getName() {
if (dataSource != null)
return dataSource.getName();
else
return null;
}
/**
* Return the MIME type of this object as retrieved from
* the source object. Note that this is the full
* type with parameters.
*
* @return the MIME type
*/
public String getContentType() {
if (dataSource != null) // data source case
return dataSource.getContentType();
else
return objectMimeType; // obj/type case
}
/**
* Get the InputStream for this object.
*
* For DataHandlers instantiated with a DataSource, the DataHandler
* calls the DataSource.getInputStream method and
* returns the result to the caller.
*
* For DataHandlers instantiated with an Object, the DataHandler
* first attempts to find a DataContentHandler for the Object. If
* the DataHandler can not find a DataContentHandler for this MIME
* type, it throws an UnsupportedDataTypeException. If it is
* successful, it creates a pipe and a thread. The thread uses the
* DataContentHandler's writeTo method to write the
* stream data into one end of the pipe. The other end of the pipe
* is returned to the caller. Because a thread is created to copy
* the data, IOExceptions that may occur during the copy can not be
* propagated back to the caller. The result is an empty stream.
*
* @return the InputStream representing this data
* @exception IOException if an I/O error occurs
*
* @see jakarta.activation.DataContentHandler#writeTo
* @see jakarta.activation.UnsupportedDataTypeException
*/
public InputStream getInputStream() throws IOException {
InputStream ins = null;
if (dataSource != null) {
ins = dataSource.getInputStream();
} else {
DataContentHandler dch = getDataContentHandler();
// we won't even try if we can't get a dch
if (dch == null)
throw new UnsupportedDataTypeException(
"no DCH for MIME type " + getBaseType());
if (dch instanceof ObjectDataContentHandler) {
if (((ObjectDataContentHandler)dch).getDCH() == null)
throw new UnsupportedDataTypeException(
"no object DCH for MIME type " + getBaseType());
}
// there is none but the default^^^^^^^^^^^^^^^^
final DataContentHandler fdch = dch;
// from bill s.
// ce n'est pas une pipe!
//
// NOTE: This block of code needs to throw exceptions, but
// can't because it is in another thread!!! ARG!
//
final PipedOutputStream pos = new PipedOutputStream();
PipedInputStream pin = new PipedInputStream(pos);
new Thread(
new Runnable() {
public void run() {
try {
fdch.writeTo(object, objectMimeType, pos);
} catch (IOException e) {
} finally {
try {
pos.close();
} catch (IOException ie) { }
}
}
},
"DataHandler.getInputStream").start();
ins = pin;
}
return ins;
}
/**
* Write the data to an OutputStream.
*
* If the DataHandler was created with a DataSource, writeTo
* retrieves the InputStream and copies the bytes from the
* InputStream to the OutputStream passed in.
*
* If the DataHandler was created with an object, writeTo
* retrieves the DataContentHandler for the object's type.
* If the DataContentHandler was found, it calls the
* writeTo method on the DataContentHandler.
*
* @param os the OutputStream to write to
* @exception IOException if an I/O error occurs
*/
public void writeTo(OutputStream os) throws IOException {
// for the DataSource case
if (dataSource != null) {
InputStream is = null;
byte data[] = new byte[8*1024];
int bytes_read;
is = dataSource.getInputStream();
try {
while ((bytes_read = is.read(data)) > 0) {
os.write(data, 0, bytes_read);
}
} finally {
is.close();
is = null;
}
} else { // for the Object case
DataContentHandler dch = getDataContentHandler();
dch.writeTo(object, objectMimeType, os);
}
}
/**
* Get an OutputStream for this DataHandler to allow overwriting
* the underlying data.
* If the DataHandler was created with a DataSource, the
* DataSource's getOutputStream method is called.
* Otherwise, null is returned.
*
* @return the OutputStream
* @exception IOException for failures creating the OutputStream
*
* @see jakarta.activation.DataSource#getOutputStream
* @see jakarta.activation.URLDataSource
*/
public OutputStream getOutputStream() throws IOException {
if (dataSource != null)
return dataSource.getOutputStream();
else
return null;
}
/**
* Return the ActivationDataFlavors in which this data is available.
*
* Returns an array of ActivationDataFlavor objects indicating the flavors
* the data can be provided in. The array is usually ordered
* according to preference for providing the data, from most
* richly descriptive to least richly descriptive.
*
* The DataHandler attempts to find a DataContentHandler that
* corresponds to the MIME type of the data. If one is located,
* the DataHandler calls the DataContentHandler's
* getTransferDataFlavors method.
*
* If a DataContentHandler can not be located, and if the
* DataHandler was created with a DataSource (or URL), one
* ActivationDataFlavor is returned that represents this object's MIME type
* and the java.io.InputStream class. If the
* DataHandler was created with an object and a MIME type,
* getTransferDataFlavors returns one ActivationDataFlavor that represents
* this object's MIME type and the object's class.
*
* @return an array of data flavors in which this data can be transferred
* @see jakarta.activation.DataContentHandler#getTransferDataFlavors
*/
public synchronized ActivationDataFlavor[] getTransferDataFlavors() {
if (factory != oldFactory) // if the factory has changed, clear cache
transferFlavors = emptyFlavors;
// if it's not set, set it...
if (transferFlavors == emptyFlavors)
transferFlavors = getDataContentHandler().getTransferDataFlavors();
if (transferFlavors == emptyFlavors)
return transferFlavors; // no need to clone an empty array
else
return transferFlavors.clone();
}
/**
* Returns whether the specified data flavor is supported
* for this object.
*
* This method iterates through the ActivationDataFlavors returned from
* getTransferDataFlavors, comparing each with
* the specified flavor.
*
* @param flavor the requested flavor for the data
* @return true if the data flavor is supported
* @see jakarta.activation.DataHandler#getTransferDataFlavors
*/
public boolean isDataFlavorSupported(ActivationDataFlavor flavor) {
ActivationDataFlavor[] lFlavors = getTransferDataFlavors();
for (int i = 0; i < lFlavors.length; i++) {
if (lFlavors[i].equals(flavor))
return true;
}
return false;
}
/**
* Returns an object that represents the data to be
* transferred. The class of the object returned is defined by the
* representation class of the data flavor.
*
* For DataHandler's created with DataSources or URLs:
*
* The DataHandler attempts to locate a DataContentHandler
* for this MIME type. If one is found, the passed in ActivationDataFlavor
* and the type of the data are passed to its getTransferData
* method. If the DataHandler fails to locate a DataContentHandler
* and the flavor specifies this object's MIME type and the
* java.io.InputStream class, this object's InputStream
* is returned.
* Otherwise it throws an IOException.
*
* For DataHandler's created with Objects:
*
* The DataHandler attempts to locate a DataContentHandler
* for this MIME type. If one is found, the passed in ActivationDataFlavor
* and the type of the data are passed to its getTransferData
* method. If the DataHandler fails to locate a DataContentHandler
* and the flavor specifies this object's MIME type and its class,
* this DataHandler's referenced object is returned.
* Otherwise it throws an IOException.
*
* @param flavor the requested flavor for the data
* @return the object
* @exception IOException if the data could not be
* converted to the requested flavor
* @exception IOException if an I/O error occurs
* @see jakarta.activation.ActivationDataFlavor
*/
public Object getTransferData(ActivationDataFlavor flavor)
throws IOException {
return getDataContentHandler().getTransferData(flavor, dataSource);
}
/**
* Set the CommandMap for use by this DataHandler.
* Setting it to null causes the CommandMap to revert
* to the CommandMap returned by the
* CommandMap.getDefaultCommandMap method.
* Changing the CommandMap, or setting it to null,
* clears out any data cached from the previous CommandMap.
*
* @param commandMap the CommandMap to use in this DataHandler
*
* @see jakarta.activation.CommandMap#setDefaultCommandMap
*/
public synchronized void setCommandMap(CommandMap commandMap) {
if (commandMap != currentCommandMap || commandMap == null) {
// clear cached values...
transferFlavors = emptyFlavors;
dataContentHandler = null;
currentCommandMap = commandMap;
}
}
/**
* Return the preferred commands for this type of data.
* This method calls the getPreferredCommands method
* in the CommandMap associated with this instance of DataHandler.
* This method returns an array that represents a subset of
* available commands. In cases where multiple commands for the
* MIME type represented by this DataHandler are present, the
* installed CommandMap chooses the appropriate commands.
*
* @return the CommandInfo objects representing the preferred commands
*
* @see jakarta.activation.CommandMap#getPreferredCommands
*/
public CommandInfo[] getPreferredCommands() {
if (dataSource != null)
return getCommandMap().getPreferredCommands(getBaseType(),
dataSource);
else
return getCommandMap().getPreferredCommands(getBaseType());
}
/**
* Return all the commands for this type of data.
* This method returns an array containing all commands
* for the type of data represented by this DataHandler. The
* MIME type for the underlying data represented by this DataHandler
* is used to call through to the getAllCommands method
* of the CommandMap associated with this DataHandler.
*
* @return the CommandInfo objects representing all the commands
*
* @see jakarta.activation.CommandMap#getAllCommands
*/
public CommandInfo[] getAllCommands() {
if (dataSource != null)
return getCommandMap().getAllCommands(getBaseType(), dataSource);
else
return getCommandMap().getAllCommands(getBaseType());
}
/**
* Get the command cmdName. Use the search semantics as
* defined by the CommandMap installed in this DataHandler. The
* MIME type for the underlying data represented by this DataHandler
* is used to call through to the getCommand method
* of the CommandMap associated with this DataHandler.
*
* @param cmdName the command name
* @return the CommandInfo corresponding to the command
*
* @see jakarta.activation.CommandMap#getCommand
*/
public CommandInfo getCommand(String cmdName) {
if (dataSource != null)
return getCommandMap().getCommand(getBaseType(), cmdName,
dataSource);
else
return getCommandMap().getCommand(getBaseType(), cmdName);
}
/**
* Return the data in its preferred Object form.
*
* If the DataHandler was instantiated with an object, return
* the object.
*
* If the DataHandler was instantiated with a DataSource,
* this method uses a DataContentHandler to return the content
* object for the data represented by this DataHandler. If no
* DataContentHandler can be found for the
* the type of this data, the DataHandler returns an
* InputStream for the data.
*
* @return the content.
* @exception IOException if an IOException occurs during
* this operation.
*/
public Object getContent() throws IOException {
if (object != null)
return object;
else
return getDataContentHandler().getContent(getDataSource());
}
/**
* A convenience method that takes a CommandInfo object
* and instantiates the corresponding command, usually
* a JavaBean component.
*
* This method calls the CommandInfo's getCommandObject
* method with the ClassLoader used to load
* the jakarta.activation.DataHandler class itself.
*
* @param cmdinfo the CommandInfo corresponding to a command
* @return the instantiated command object
*/
public Object getBean(CommandInfo cmdinfo) {
Object bean = null;
try {
// make the bean
ClassLoader cld = null;
// First try the "application's" class loader.
cld = SecuritySupport.getContextClassLoader();
if (cld == null)
cld = this.getClass().getClassLoader();
bean = cmdinfo.getCommandObject(this, cld);
} catch (IOException e) {
} catch (ClassNotFoundException e) { }
return bean;
}
/**
* Get the DataContentHandler for this DataHandler:
*
* If a DataContentHandlerFactory is set, use it.
* Otherwise look for an object to serve DCH in the
* following order:
*
* 1) if a factory is set, use it
* 2) if a CommandMap is set, use it
* 3) use the default CommandMap
*
* In any case, wrap the real DataContentHandler with one of our own
* to handle any missing cases, fill in defaults, and to ensure that
* we always have a non-null DataContentHandler.
*
* @return the requested DataContentHandler
*/
private synchronized DataContentHandler getDataContentHandler() {
// make sure the factory didn't change
if (factory != oldFactory) {
oldFactory = factory;
factoryDCH = null;
dataContentHandler = null;
transferFlavors = emptyFlavors;
}
if (dataContentHandler != null)
return dataContentHandler;
String simpleMT = getBaseType();
if (factoryDCH == null && factory != null)
factoryDCH = factory.createDataContentHandler(simpleMT);
if (factoryDCH != null)
dataContentHandler = factoryDCH;
if (dataContentHandler == null) {
if (dataSource != null)
dataContentHandler = getCommandMap().
createDataContentHandler(simpleMT, dataSource);
else
dataContentHandler = getCommandMap().
createDataContentHandler(simpleMT);
}
// getDataContentHandler always uses these 'wrapper' handlers
// to make sure it returns SOMETHING meaningful...
if (dataSource != null)
dataContentHandler = new DataSourceDataContentHandler(
dataContentHandler,
dataSource);
else
dataContentHandler = new ObjectDataContentHandler(
dataContentHandler,
object,
objectMimeType);
return dataContentHandler;
}
/**
* Use the MimeType class to extract the MIME type/subtype,
* ignoring the parameters. The type is cached.
*/
private synchronized String getBaseType() {
if (shortType == null) {
String ct = getContentType();
try {
MimeType mt = new MimeType(ct);
shortType = mt.getBaseType();
} catch (MimeTypeParseException e) {
shortType = ct;
}
}
return shortType;
}
/**
* Sets the DataContentHandlerFactory. The DataContentHandlerFactory
* is called first to find DataContentHandlers.
* The DataContentHandlerFactory can only be set once.
*
* If the DataContentHandlerFactory has already been set,
* this method throws an Error.
*
* @param newFactory the DataContentHandlerFactory
* @exception Error if the factory has already been defined.
*
* @see jakarta.activation.DataContentHandlerFactory
*/
public static synchronized void setDataContentHandlerFactory(
DataContentHandlerFactory newFactory) {
if (factory != null)
throw new Error("DataContentHandlerFactory already defined");
SecurityManager security = System.getSecurityManager();
if (security != null) {
try {
// if it's ok with the SecurityManager, it's ok with me...
security.checkSetFactory();
} catch (SecurityException ex) {
// otherwise, we also allow it if this code and the
// factory come from the same class loader (e.g.,
// the JAF classes were loaded with the applet classes).
if (DataHandler.class.getClassLoader() !=
newFactory.getClass().getClassLoader())
throw ex;
}
}
factory = newFactory;
}
}
/**
* The DataHanderDataSource class implements the
* DataSource interface when the DataHandler is constructed
* with an Object and a mimeType string.
*/
class DataHandlerDataSource implements DataSource {
DataHandler dataHandler = null;
/**
* The constructor.
*/
public DataHandlerDataSource(DataHandler dh) {
this.dataHandler = dh;
}
/**
* Returns an InputStream representing this object.
* @return the InputStream
*/
public InputStream getInputStream() throws IOException {
return dataHandler.getInputStream();
}
/**
* Returns the OutputStream for this object.
* @return the OutputStream
*/
public OutputStream getOutputStream() throws IOException {
return dataHandler.getOutputStream();
}
/**
* Returns the MIME type of the data represented by this object.
* @return the MIME type
*/
public String getContentType() {
return dataHandler.getContentType();
}
/**
* Returns the name of this object.
* @return the name of this object
*/
public String getName() {
return dataHandler.getName(); // what else would it be?
}
}
/*
* DataSourceDataContentHandler
*
* This is a private DataContentHandler that wraps the real
* DataContentHandler in the case where the DataHandler was instantiated
* with a DataSource.
*/
class DataSourceDataContentHandler implements DataContentHandler {
private DataSource ds = null;
private ActivationDataFlavor transferFlavors[] = null;
private DataContentHandler dch = null;
/**
* The constructor.
*/
public DataSourceDataContentHandler(DataContentHandler dch, DataSource ds) {
this.ds = ds;
this.dch = dch;
}
/**
* Return the ActivationDataFlavors for this
* DataContentHandler.
* @return the ActivationDataFlavors
*/
public ActivationDataFlavor[] getTransferDataFlavors() {
if (transferFlavors == null) {
if (dch != null) { // is there a dch?
transferFlavors = dch.getTransferDataFlavors();
} else {
transferFlavors = new ActivationDataFlavor[1];
transferFlavors[0] =
new ActivationDataFlavor(ds.getContentType(),
ds.getContentType());
}
}
return transferFlavors;
}
/**
* Return the Transfer Data of type ActivationDataFlavor from InputStream.
* @param df the ActivationDataFlavor
* @param ds the DataSource
* @return the constructed Object
*/
public Object getTransferData(ActivationDataFlavor df, DataSource ds)
throws IOException {
if (dch != null)
return dch.getTransferData(df, ds);
else if (df.equals(getTransferDataFlavors()[0])) // only have one now
return ds.getInputStream();
else
throw new IOException("Unsupported DataFlavor: " + df);
}
public Object getContent(DataSource ds) throws IOException {
if (dch != null)
return dch.getContent(ds);
else
return ds.getInputStream();
}
/**
* Write the object to the output stream.
*/
public void writeTo(Object obj, String mimeType, OutputStream os)
throws IOException {
if (dch != null)
dch.writeTo(obj, mimeType, os);
else
throw new UnsupportedDataTypeException(
"no DCH for content type " + ds.getContentType());
}
}
/*
* ObjectDataContentHandler
*
* This is a private DataContentHandler that wraps the real
* DataContentHandler in the case where the DataHandler was instantiated
* with an object.
*/
class ObjectDataContentHandler implements DataContentHandler {
private ActivationDataFlavor transferFlavors[] = null;
private Object obj;
private String mimeType;
private DataContentHandler dch = null;
/**
* The constructor.
*/
public ObjectDataContentHandler(DataContentHandler dch,
Object obj, String mimeType) {
this.obj = obj;
this.mimeType = mimeType;
this.dch = dch;
}
/**
* Return the DataContentHandler for this object.
* Used only by the DataHandler class.
*/
public DataContentHandler getDCH() {
return dch;
}
/**
* Return the ActivationDataFlavors for this
* DataContentHandler.
* @return the ActivationDataFlavors
*/
public synchronized ActivationDataFlavor[] getTransferDataFlavors() {
if (transferFlavors == null) {
if (dch != null) {
transferFlavors = dch.getTransferDataFlavors();
} else {
transferFlavors = new ActivationDataFlavor[1];
transferFlavors[0] = new ActivationDataFlavor(obj.getClass(),
mimeType, mimeType);
}
}
return transferFlavors;
}
/**
* Return the Transfer Data of type ActivationDataFlavor from InputStream.
* @param df the ActivationDataFlavor
* @param ds the DataSource
* @return the constructed Object
*/
public Object getTransferData(ActivationDataFlavor df, DataSource ds)
throws IOException {
if (dch != null)
return dch.getTransferData(df, ds);
else if (df.equals(getTransferDataFlavors()[0])) // only have one now
return obj;
else
throw new IOException("Unsupported DataFlavor: " + df);
}
public Object getContent(DataSource ds) {
return obj;
}
/**
* Write the object to the output stream.
*/
public void writeTo(Object obj, String mimeType, OutputStream os)
throws IOException {
if (dch != null)
dch.writeTo(obj, mimeType, os);
else if (obj instanceof byte[])
os.write((byte[])obj);
else if (obj instanceof String) {
OutputStreamWriter osw = new OutputStreamWriter(os);
osw.write((String)obj);
osw.flush();
} else
throw new UnsupportedDataTypeException(
"no object DCH for MIME type " + this.mimeType);
}
}