34 * between a debugger and a target VM. A Connection is created when
35 * {@link com.sun.jdi.connect.spi.TransportService TransportService}
36 * establishes a connection and successfully handshakes with a target
37 * VM. A TransportService implementation provides a reliable
38 * JDWP packet transportation service and consequently a Connection
39 * provides a reliable flow of JDWP packets between the debugger
40 * and the target VM. A Connection is stream oriented, that is, the
41 * JDWP packets written to a connection are read by the target VM
42 * in the order in which they were written. Similiarly packets written
43 * to a Connection by the target VM are read by the debugger in the
44 * order in which they were written.
45 *
46 * <p> A connection is either open or closed. It is open upon creation,
47 * and remains open until it is closed. Once closed, it remains closed,
48 * and any attempt to invoke an I/O operation upon it will cause a
49 * {@link ClosedConnectionException} to be thrown. A connection can
50 * be tested by invoking the {@link #isOpen isOpen} method.
51 *
52 * <p> A Connection is safe for access by multiple concurrent threads,
53 * although at most one thread may be reading and at most one thread may
54 * be writing at any given time. </p>
55 *
56 * @since 1.5
57 */
58
59 @jdk.Exported
60 public abstract class Connection {
61
62 /**
63 * Reads a packet from the target VM.
64 *
65 * <p> Attempts to read a JDWP packet from the target VM.
66 * A read operation may block indefinitely and only returns
67 * when it reads all bytes of a packet, or in the case of a
68 * transport service that is based on a stream-oriented
69 * communication protocol, the end of stream is encountered.
70 *
71 * <p> Reading a packet does not do any integrity checking on
72 * the packet aside from a check that the length of the packet
73 * (as indicated by the value of the <tt>length</tt> field, the
74 * first four bytes of the packet) is 11 or more bytes.
75 * If the value of the <tt>length</tt> value is less then 11
76 * then an <tt>IOException</tt> is thrown.
77 *
78 * <p> Returns a byte array of a length equal to the length
79 * of the received packet, or a byte array of length 0 when an
80 * end of stream is encountered. If end of stream is encountered
81 * after some, but not all bytes of a packet, are read then it
82 * is considered an I/O error and an <tt>IOException</tt> is
83 * thrown. The first byte of the packet is stored in element
84 * <tt>0</tt> of the byte array, the second in element <tt>1</tt>,
85 * and so on. The bytes in the byte array are laid out as per the
86 * <a href="../../../../../../../../../technotes/guides/jpda/jdwp-spec.html">
87 * JDWP specification</a>. That is, all fields in the packet
88 * are in big endian order as per the JDWP specification.
89 *
90 * <p> This method may be invoked at any time. If another thread has
91 * already initiated a {@link #readPacket readPacket} on this
92 * connection then the invocation of this method will block until the
93 * first operation is complete. </p>
94 *
95 * @return the packet read from the target VM
96 *
97 * @throws ClosedConnectionException
98 * If the connection is closed, or another thread closes
99 * the connection while the readPacket is in progress.
100 *
101 * @throws java.io.IOException
102 * If the length of the packet (as indictaed by the first
103 * 4 bytes) is less than 11 bytes, or an I/O error occurs.
104 *
105 *
106 */
107 public abstract byte[] readPacket() throws IOException;
108
109 /**
110 * Writes a packet to the target VM.
111 *
112 * <p> Attempts to write, or send, a JDWP packet to the target VM.
113 * A write operation only returns after writing the entire packet
114 * to the target VM. Writing the entire packet does not mean
115 * the entire packet has been transmitted to the target VM
116 * but rather that all bytes have been written to the
117 * transport service. A transport service based on a TCP/IP connection
118 * may, for example, buffer some or all of the packet before
119 * transmission on the network.
120 *
121 * <p> The byte array provided to this method should be laid out
122 * as per the <a
123 * href="../../../../../../../../../technotes/guides/jpda/jdwp-spec.html">
124 * JDWP specification</a>. That is, all fields in the packet
125 * are in big endian order. The first byte, that is element
126 * <tt>pkt[0]</tt>, is the first byte of the <tt>length</tt> field.
127 * <tt>pkt[1]</tt> is the second byte of the <tt>length</tt> field,
128 * and so on.
129 *
130 * <p> Writing a packet does not do any integrity checking on
131 * the packet aside from checking the packet length. Checking
132 * the packet length requires checking that the value of the
133 * <tt>length</tt> field (as indicated by the first four bytes
134 * of the packet) is 11 or greater. Consequently the length of
135 * the byte array provided to this method, that is
136 * <tt>pkt.length</tt>, must be 11 or more, and must be equal
137 * or greater than the value of the <tt>length</tt> field. If the
138 * length of the byte array is greater than the value of
139 * the <tt>length</tt> field then all bytes from element
140 * <tt>pkt[length]</tt> onwards are ignored. In other words,
141 * any additional bytes that follow the packet in the byte
142 * array are ignored and will not be transmitted to the target
143 * VM.
144 *
145 * <p> A write operation may block or may complete immediately.
146 * The exact circumstances when an operation blocks depends on
147 * the transport service. In the case of a TCP/IP connection to
148 * the target VM, the writePacket method may block if there is
149 * network congestion or there is insufficient space to buffer
150 * the packet in the underlying network system.
151 *
152 * <p> This method may be invoked at any time. If another thread has
153 * already initiated a write operation upon this Connection then
154 * a subsequent invocation of this method will block until the first
155 * operation is complete. </p>
156 *
157 * @param pkt
158 * The packet to write to the target VM.
159 *
160 * @throws ClosedConnectionException
161 * If the connection is closed, or another thread closes
162 * the connection while the write operation is in progress.
163 *
164 * @throws java.io.IOException
165 * If an I/O error occurs.
166 *
167 * @throws IllegalArgumentException
168 * If the value of the <tt>length</tt> field is invalid,
169 * or the byte array is of insufficient length.
170 */
171 public abstract void writePacket(byte pkt[]) throws IOException;
172
173 /**
174 * Closes this connection.
175 *
176 * <p> If the connection is already closed then invoking this method
177 * has no effect. After a connection is closed, any further attempt
178 * calls to {@link #readPacket readPacket} or {@link #writePacket
179 * writePacket} will throw a {@link ClosedConnectionException}.
180 *
181 * <p> Any thread currently blocked in an I/O operation ({@link
182 * #readPacket readPacket} or {@link #writePacket writePacket})
183 * will throw a {@link ClosedConnectionException}).
184 *
185 * <p> This method may be invoked at any time. If some other thread has
186 * already invoked it, however, then another invocation will block until
187 * the first invocation is complete, after which it will return without
188 * effect. </p>
189 *
190 * @throws java.io.IOException
191 * If an I/O error occurs
192 */
193 public abstract void close() throws IOException;
194
195 /**
196 * Tells whether or not this connection is open. </p>
197 *
198 * @return <tt>true</tt> if, and only if, this connection is open
199 */
200 public abstract boolean isOpen();
201 }
|
34 * between a debugger and a target VM. A Connection is created when
35 * {@link com.sun.jdi.connect.spi.TransportService TransportService}
36 * establishes a connection and successfully handshakes with a target
37 * VM. A TransportService implementation provides a reliable
38 * JDWP packet transportation service and consequently a Connection
39 * provides a reliable flow of JDWP packets between the debugger
40 * and the target VM. A Connection is stream oriented, that is, the
41 * JDWP packets written to a connection are read by the target VM
42 * in the order in which they were written. Similiarly packets written
43 * to a Connection by the target VM are read by the debugger in the
44 * order in which they were written.
45 *
46 * <p> A connection is either open or closed. It is open upon creation,
47 * and remains open until it is closed. Once closed, it remains closed,
48 * and any attempt to invoke an I/O operation upon it will cause a
49 * {@link ClosedConnectionException} to be thrown. A connection can
50 * be tested by invoking the {@link #isOpen isOpen} method.
51 *
52 * <p> A Connection is safe for access by multiple concurrent threads,
53 * although at most one thread may be reading and at most one thread may
54 * be writing at any given time.
55 *
56 * @since 1.5
57 */
58
59 @jdk.Exported
60 public abstract class Connection {
61
62 /**
63 * Reads a packet from the target VM.
64 *
65 * <p> Attempts to read a JDWP packet from the target VM.
66 * A read operation may block indefinitely and only returns
67 * when it reads all bytes of a packet, or in the case of a
68 * transport service that is based on a stream-oriented
69 * communication protocol, the end of stream is encountered.
70 *
71 * <p> Reading a packet does not do any integrity checking on
72 * the packet aside from a check that the length of the packet
73 * (as indicated by the value of the {@code length} field, the
74 * first four bytes of the packet) is 11 or more bytes.
75 * If the value of the {@code length} value is less then 11
76 * then an {@code IOException} is thrown.
77 *
78 * <p> Returns a byte array of a length equal to the length
79 * of the received packet, or a byte array of length 0 when an
80 * end of stream is encountered. If end of stream is encountered
81 * after some, but not all bytes of a packet, are read then it
82 * is considered an I/O error and an {@code IOException} is
83 * thrown. The first byte of the packet is stored in element
84 * {@code 0} of the byte array, the second in element {@code 1},
85 * and so on. The bytes in the byte array are laid out as per the
86 * <a href="../../../../../../../../../technotes/guides/jpda/jdwp-spec.html">
87 * JDWP specification</a>. That is, all fields in the packet
88 * are in big endian order as per the JDWP specification.
89 *
90 * <p> This method may be invoked at any time. If another thread has
91 * already initiated a {@link #readPacket readPacket} on this
92 * connection then the invocation of this method will block until the
93 * first operation is complete.
94 *
95 * @return the packet read from the target VM
96 *
97 * @throws ClosedConnectionException
98 * If the connection is closed, or another thread closes
99 * the connection while the readPacket is in progress.
100 *
101 * @throws java.io.IOException
102 * If the length of the packet (as indictaed by the first
103 * 4 bytes) is less than 11 bytes, or an I/O error occurs.
104 *
105 *
106 */
107 public abstract byte[] readPacket() throws IOException;
108
109 /**
110 * Writes a packet to the target VM.
111 *
112 * <p> Attempts to write, or send, a JDWP packet to the target VM.
113 * A write operation only returns after writing the entire packet
114 * to the target VM. Writing the entire packet does not mean
115 * the entire packet has been transmitted to the target VM
116 * but rather that all bytes have been written to the
117 * transport service. A transport service based on a TCP/IP connection
118 * may, for example, buffer some or all of the packet before
119 * transmission on the network.
120 *
121 * <p> The byte array provided to this method should be laid out
122 * as per the <a
123 * href="../../../../../../../../../technotes/guides/jpda/jdwp-spec.html">
124 * JDWP specification</a>. That is, all fields in the packet
125 * are in big endian order. The first byte, that is element
126 * {@code pkt[0]}, is the first byte of the {@code length} field.
127 * {@code pkt[1]} is the second byte of the {@code length} field,
128 * and so on.
129 *
130 * <p> Writing a packet does not do any integrity checking on
131 * the packet aside from checking the packet length. Checking
132 * the packet length requires checking that the value of the
133 * {@code length} field (as indicated by the first four bytes
134 * of the packet) is 11 or greater. Consequently the length of
135 * the byte array provided to this method, that is
136 * {@code pkt.length}, must be 11 or more, and must be equal
137 * or greater than the value of the {@code length} field. If the
138 * length of the byte array is greater than the value of
139 * the {@code length} field then all bytes from element
140 * {@code pkt[length]} onwards are ignored. In other words,
141 * any additional bytes that follow the packet in the byte
142 * array are ignored and will not be transmitted to the target
143 * VM.
144 *
145 * <p> A write operation may block or may complete immediately.
146 * The exact circumstances when an operation blocks depends on
147 * the transport service. In the case of a TCP/IP connection to
148 * the target VM, the writePacket method may block if there is
149 * network congestion or there is insufficient space to buffer
150 * the packet in the underlying network system.
151 *
152 * <p> This method may be invoked at any time. If another thread has
153 * already initiated a write operation upon this Connection then
154 * a subsequent invocation of this method will block until the first
155 * operation is complete.
156 *
157 * @param pkt
158 * The packet to write to the target VM.
159 *
160 * @throws ClosedConnectionException
161 * If the connection is closed, or another thread closes
162 * the connection while the write operation is in progress.
163 *
164 * @throws java.io.IOException
165 * If an I/O error occurs.
166 *
167 * @throws IllegalArgumentException
168 * If the value of the {@code length} field is invalid,
169 * or the byte array is of insufficient length.
170 */
171 public abstract void writePacket(byte pkt[]) throws IOException;
172
173 /**
174 * Closes this connection.
175 *
176 * <p> If the connection is already closed then invoking this method
177 * has no effect. After a connection is closed, any further attempt
178 * calls to {@link #readPacket readPacket} or {@link #writePacket
179 * writePacket} will throw a {@link ClosedConnectionException}.
180 *
181 * <p> Any thread currently blocked in an I/O operation ({@link
182 * #readPacket readPacket} or {@link #writePacket writePacket})
183 * will throw a {@link ClosedConnectionException}).
184 *
185 * <p> This method may be invoked at any time. If some other thread has
186 * already invoked it, however, then another invocation will block until
187 * the first invocation is complete, after which it will return without
188 * effect.
189 *
190 * @throws java.io.IOException
191 * If an I/O error occurs
192 */
193 public abstract void close() throws IOException;
194
195 /**
196 * Tells whether or not this connection is open.
197 *
198 * @return {@code true} if and only if this connection is open
199 */
200 public abstract boolean isOpen();
201 }
|