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package com.sun.net.httpserver;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.URI;
import java.util.Map;


This class encapsulates a HTTP request received and a
response to be generated in one exchange. It provides methods
for examining the request from the client, and for building and
sending the response.

 The typical life-cycle of a HttpExchange is shown in the sequence below: 
    
    
  1. getRequestMethod() to determine the command. 
  2. getRequestHeaders() to examine the request headers (if needed). 
  3. getRequestBody() returns an InputStream for reading the request body. After reading the request body, the stream should be closed. 
  4. getResponseHeaders() to set any response headers, except content-length. 
  5. sendResponseHeaders(int, long) to send the response headers. Must be called before next step. 
  6. getResponseBody() to get a OutputStream to send the response body. When the response body has been written, the stream must be closed to terminate the exchange. 

Terminating exchanges

Exchanges are terminated when both the request InputStream and response OutputStream are closed. Closing the OutputStream, implicitly closes the InputStream (if it is not already closed). However, it is recommended to consume all the data from the InputStream before closing it. The convenience method close() does all of these tasks. Closing an exchange without consuming all of the request body is not an error but may make the underlying TCP connection unusable for following exchanges. The effect of failing to terminate an exchange is undefined, but will typically result in resources failing to be freed/reused. 
Since:1.6
/**
 * This class encapsulates a HTTP request received and a
 * response to be generated in one exchange. It provides methods
 * for examining the request from the client, and for building and
 * sending the response.
 *
 * <p> The typical life-cycle of a {@code HttpExchange} is shown in the sequence
 * below:
 * <ol>
 *     <li>{@link #getRequestMethod()} to determine the command.
 *     <li>{@link #getRequestHeaders()} to examine the request headers (if
 *     needed).
 *     <li>{@link #getRequestBody()} returns an {@link InputStream} for
 *     reading the request body. After reading the request body, the stream
 *     should be closed.
 *     <li>{@link #getResponseHeaders()} to set any response headers, except
 *     content-length.
 *     <li>{@link #sendResponseHeaders(int,long)} to send the response headers.
 *     Must be called before next step.
 *     <li>{@link #getResponseBody()} to get a {@link OutputStream} to
 *     send the response body. When the response body has been written, the
 *     stream must be closed to terminate the exchange.
 * </ol>
 *
 * <b>Terminating exchanges</b>
 * <br>Exchanges are terminated when both the request {@code InputStream} and
 * response {@code OutputStream} are closed. Closing the {@code OutputStream},
 * implicitly closes the {@code InputStream} (if it is not already closed).
 * However, it is recommended to consume all the data from the {@code InputStream}
 * before closing it. The convenience method {@link #close()} does all of these
 * tasks. Closing an exchange without consuming all of the request body is not
 * an error but may make the underlying TCP connection unusable for following
 * exchanges. The effect of failing to terminate an exchange is undefined, but
 * will typically result in resources failing to be freed/reused.
 *
 * @since 1.6
 */

public abstract class HttpExchange implements AutoCloseable {

    
Constructor for subclasses to call.

/**
     * Constructor for subclasses to call.
     */
    protected HttpExchange() {
    }

    
Returns an immutable Map containing the HTTP headers that were included with this request. The keys in this Map will be the header names, while the values will be a List of Strings containing each value that was included (either for a header that was listed several times, or one that accepts a comma-delimited list of values on a single line). In either of these cases, the values for the header name will be presented in the order that they were included in the request. 
 The keys in Map are case-insensitive. 
Returns:a read-only Map which can be used to access request headers
/**
     * Returns an immutable {@link Map} containing the HTTP headers that were
     * included with this request. The keys in this {@code Map} will be the header
     * names, while the values will be a {@link java.util.List} of
     * {@linkplain java.lang.String Strings} containing each value that was
     * included (either for a header that was listed several times, or one that
     * accepts a comma-delimited list of values on a single line). In either of
     * these cases, the values for the header name will be presented in the
     * order that they were included in the request.
     *
     * <p> The keys in {@code Map} are case-insensitive.
     *
     * @return a read-only {@code Map} which can be used to access request headers
     */
    public abstract Headers getRequestHeaders();

    
Returns a mutable Map into which the HTTP response headers can be stored and which will be transmitted as part of this response. The keys in the Map will be the header names, while the values must be a List of Strings containing each value that should be included multiple times (in the order that they should be included). 
 The keys in Map are case-insensitive. 
Returns:a writable Map which can be used to set response headers.
/**
     * Returns a mutable {@link Map} into which the HTTP response headers can be
     * stored and which will be transmitted as part of this response. The keys in
     * the {@code Map} will be the header names, while the values must be a
     * {@link java.util.List} of {@linkplain java.lang.String Strings} containing
     * each value that should be included multiple times (in the order that they
     * should be included).
     *
     * <p> The keys in {@code Map} are case-insensitive.
     *
     * @return a writable {@code Map} which can be used to set response headers.
     */
    public abstract Headers getResponseHeaders();

    
Get the request URI. 
Returns:the request URI
/**
     * Get the request {@link URI}.
     *
     * @return the request {@code URI}
     */
    public abstract URI getRequestURI();

    
Get the request method.

Returns:the request method
/**
     * Get the request method.
     *
     * @return the request method
     */
    public abstract String getRequestMethod();

    
Get the HttpContext for this exchange. 
Returns:the HttpContext
/**
     * Get the {@link HttpContext} for this exchange.
     *
     * @return the {@code HttpContext}
     */
    public abstract HttpContext getHttpContext();

    
Ends this exchange by doing the following in sequence:

    
     
  1.  close the request InputStream, if not already closed. 
  2.  close the response OutputStream, if not already closed. 


/**
     * Ends this exchange by doing the following in sequence:
     * <ol>
     *      <li> close the request {@link InputStream}, if not already closed.
     *      <li> close the response {@link OutputStream}, if not already closed.
     * </ol>
     */
    public abstract void close();

    
Returns a stream from which the request body can be read. Multiple calls to this method will return the same stream. It is recommended that applications should consume (read) all of the data from this stream before closing it. If a stream is closed before all data has been read, then the InputStream.close() call will read and discard remaining data (up to an implementation specific number of bytes). 
Returns:the stream from which the request body can be read
/**
     * Returns a stream from which the request body can be read.
     * Multiple calls to this method will return the same stream.
     * It is recommended that applications should consume (read) all of the data
     * from this stream before closing it. If a stream is closed before all data
     * has been read, then the {@link InputStream#close()} call will read
     * and discard remaining data (up to an implementation specific number of
     * bytes).
     *
     * @return the stream from which the request body can be read
     */
    public abstract InputStream getRequestBody();

    
Returns a stream to which the response body must be written. sendResponseHeaders(int, long)) must be called prior to calling this method. Multiple calls to this method (for the same exchange) will return the same stream. In order to correctly terminate each exchange, the output stream must be closed, even if no response body is being sent. 
 Closing this stream implicitly closes the InputStream returned from getRequestBody() (if it is not already closed). 
 If the call to sendResponseHeaders(int, long) specified a fixed response body length, then the exact number of bytes specified in that call must be written to this stream. If too many bytes are written, then the write method of OutputStream will throw an IOException. If too few bytes are written then the stream OutputStream.close() will throw an IOException. In both cases, the exchange is aborted and the underlying TCP connection closed. 
Returns:the stream to which the response body is written
/**
     * Returns a stream to which the response body must be
     * written. {@link #sendResponseHeaders(int,long)}) must be called prior to
     * calling this method. Multiple calls to this method (for the same exchange)
     * will return the same stream. In order to correctly terminate each exchange,
     * the output stream must be closed, even if no response body is being sent.
     *
     * <p> Closing this stream implicitly closes the {@link InputStream}
     * returned from {@link #getRequestBody()} (if it is not already closed).
     *
     * <p> If the call to {@link #sendResponseHeaders(int, long)} specified a
     * fixed response body length, then the exact number of bytes specified in
     * that call must be written to this stream. If too many bytes are written,
     * then the write method of {@link OutputStream} will throw an {@code IOException}.
     * If too few bytes are written then the stream
     * {@link OutputStream#close()} will throw an {@code IOException}.
     * In both cases, the exchange is aborted and the underlying TCP connection
     * closed.
     *
     * @return the stream to which the response body is written
     */
    public abstract OutputStream getResponseBody();


    
Starts sending the response back to the client using the current set of response headers and the numeric response code as specified in this method. The response body length is also specified as follows. If the response length parameter is greater than zero, this specifies an exact number of bytes to send and the application must send that exact amount of data. If the response length parameter is zero, then chunked transfer encoding is used and an arbitrary amount of data may be sent. The application terminates the response body by closing the OutputStream. If response length has the value -1 then no response body is being sent. 
 If the content-length response header has not already been set then
this is set to the appropriate value depending on the response length
parameter.

 This method must be called prior to calling getResponseBody(). 
Params:
  • rCode –          the response code to send
  • responseLength – if > 0, specifies a fixed response body length and that exact number of bytes must be written to the stream acquired from getResponseCode() If == 0, then chunked encoding is used, and an arbitrary number of bytes may be written. If <= -1, then no response body length is specified and no response body may be written.
Throws:
  • IOException –   if the response headers have already been sent or an I/O error occurs
See Also:
Implementation Note:This implementation allows the caller to instruct the server to force a connection close after the exchange terminates, by supplying a Connection: close header to the response headers before sendResponseHeaders is called.
/**
     * Starts sending the response back to the client using the current set of
     * response headers and the numeric response code as specified in this
     * method. The response body length is also specified as follows. If the
     * response length parameter is greater than {@code zero}, this specifies an
     * exact number of bytes to send and the application must send that exact
     * amount of data. If the response length parameter is {@code zero}, then
     * chunked transfer encoding is used and an arbitrary amount of data may be
     * sent. The application terminates the response body by closing the
     * {@link OutputStream}.
     * If response length has the value {@code -1} then no response body is
     * being sent.
     *
     * <p> If the content-length response header has not already been set then
     * this is set to the appropriate value depending on the response length
     * parameter.
     *
     * <p> This method must be called prior to calling {@link #getResponseBody()}.
     *
     * @implNote This implementation allows the caller to instruct the
     * server to force a connection close after the exchange terminates, by
     * supplying a {@code Connection: close} header to the {@linkplain
     * #getResponseHeaders() response headers} before {@code sendResponseHeaders}
     * is called.
     *
     * @param rCode          the response code to send
     * @param responseLength if {@literal > 0}, specifies a fixed response body
     *                       length and that exact number of bytes must be written
     *                       to the stream acquired from {@link #getResponseCode()}
     *                       If {@literal == 0}, then chunked encoding is used,
     *                       and an arbitrary number of bytes may be written.
     *                       If {@literal <= -1}, then no response body length is
     *                       specified and no response body may be written.
     * @throws IOException   if the response headers have already been sent or an I/O error occurs
     * @see   HttpExchange#getResponseBody()
     */
    public abstract void sendResponseHeaders(int rCode, long responseLength) throws IOException;

    
Returns the address of the remote entity invoking this request.

Returns:the InetSocketAddress of the caller
/**
     * Returns the address of the remote entity invoking this request.
     *
     * @return the {@link InetSocketAddress} of the caller
     */
    public abstract InetSocketAddress getRemoteAddress();

    
Returns the response code, if it has already been set.

Returns:the response code, if available. -1 if not available yet.
/**
     * Returns the response code, if it has already been set.
     *
     * @return the response code, if available. {@code -1} if not available yet.
     */
    public abstract int getResponseCode();

    
Returns the local address on which the request was received.

Returns:the InetSocketAddress of the local interface
/**
     * Returns the local address on which the request was received.
     *
     * @return the {@link InetSocketAddress} of the local interface
     */
    public abstract InetSocketAddress getLocalAddress();

    
Returns the protocol string from the request in the form
protocol/majorVersion.minorVersion. For example, "HTTP/1.1". 
Returns:the protocol string from the request
/**
     * Returns the protocol string from the request in the form
     * <i>protocol/majorVersion.minorVersion</i>. For example,
     * "{@code HTTP/1.1}".
     *
     * @return the protocol string from the request
     */
    public abstract String getProtocol();

    
Filter modules may store arbitrary objects with HttpExchange instances as an out-of-band communication mechanism. Other filters or the exchange handler may then access these objects. 
 Each Filter class will document the attributes which they make available. 
Params:
  • name – the name of the attribute to retrieve
Throws:
Returns:the attribute object, or null if it does not exist
/**
     * {@link Filter} modules may store arbitrary objects with {@code HttpExchange}
     * instances as an out-of-band communication mechanism. Other filters
     * or the exchange handler may then access these objects.
     *
     * <p> Each {@code Filter} class will document the attributes which they make
     * available.
     *
     * @param name the name of the attribute to retrieve
     * @return the attribute object, or {@code null} if it does not exist
     * @throws NullPointerException if name is {@code null}
     */
    public abstract Object getAttribute(String name);

    
Filter modules may store arbitrary objects with HttpExchange instances as an out-of-band communication mechanism. Other filters or the exchange handler may then access these objects. 
 Each Filter class will document the attributes which they make available. 
Params:
  • name –  the name to associate with the attribute value
  • value – the object to store as the attribute value. null value is permitted.
Throws:
/**
     * {@link Filter} modules may store arbitrary objects with {@code HttpExchange}
     * instances as an out-of-band communication mechanism. Other filters
     * or the exchange handler may then access these objects.
     *
     * <p> Each {@code Filter} class will document the attributes which they make
     * available.
     *
     * @param name  the name to associate with the attribute value
     * @param value the object to store as the attribute value. {@code null}
     *              value is permitted.
     * @throws NullPointerException if name is {@code null}
     */
    public abstract void setAttribute(String name, Object value);

    
Used by Filters to wrap either (or both) of this exchange's InputStream and OutputStream, with the given filtered streams so that subsequent calls to getRequestBody() will return the given InputStream, and calls to getResponseBody() will return the given OutputStream. The streams provided to this call must wrap the original streams, and may be (but are not required to be) sub-classes of FilterInputStream and FilterOutputStream. 
Params:
  • i – the filtered input stream to set as this object's Inputstream, or null if no change
  • o – the filtered output stream to set as this object's Outputstream, or null if no change
/**
     * Used by {@linkplain com.sun.net.httpserver.Filter Filters} to wrap either
     * (or both) of this exchange's {@link InputStream} and
     * {@link OutputStream}, with the given filtered streams so that
     * subsequent calls to {@link #getRequestBody()} will return the given
     * {@code InputStream}, and calls to {@link #getResponseBody()} will return
     * the given {@code OutputStream}. The streams provided to this call must wrap
     * the original streams, and may be (but are not required to be) sub-classes
     * of {@link java.io.FilterInputStream} and {@link java.io.FilterOutputStream}.
     *
     * @param i the filtered input stream to set as this object's
     *          {@code Inputstream}, or {@code null} if no change
     * @param o the filtered output stream to set as this object's
     *          {@code Outputstream}, or {@code null} if no change
     */
    public abstract void setStreams(InputStream i, OutputStream o);


    
If an authenticator is set on the HttpContext that owns this exchange, then this method will return the HttpPrincipal that represents the authenticated user for this HttpExchange. 
Returns:the HttpPrincipal, or null if no authenticator is set
/**
     * If an authenticator is set on the {@link HttpContext} that owns this exchange,
     * then this method will return the {@link HttpPrincipal} that represents
     * the authenticated user for this {@code HttpExchange}.
     *
     * @return the {@code HttpPrincipal}, or {@code null} if no authenticator is set
     */
    public abstract HttpPrincipal getPrincipal();
}