Netty-----初探

　　今天看gateway 实现的时候看到个哥们基于的netty实现的gateway。so，解析一下Netty。

废话少说，maven pom 引入，down 下jar包。看了下netty的包结构，还是挺明确的，不像spring包那么多。

 

buffer,channel，是包装的JDK 的nio Buffer,Channel等类。

在io.netty.buffer.ByteBuf找到了如下的注释，解释了 limit ,flip等原生JDK api 的含义。

  1 /**
  2  * A random and sequential accessible sequence of zero or more bytes (octets).
  3  * This interface provides an abstract view for one or more primitive byte
  4  * arrays ({@code byte[]}) and {@linkplain ByteBuffer NIO buffers}.
  5  *
  6  * 
Creation of a buffer
  7  *
  8  * It is recommended to create a new buffer using the helper methods in
  9  * {@link Unpooled} rather than calling an individual implementation's
 10  * constructor.
 11  *
 12  * 
Random Access Indexing
 13  *
 14  * Just like an ordinary primitive byte array, {@link ByteBuf} uses
 15  * http://en.wikipedia.org/wiki/Zero-based_numbering">zero-based indexing.
 16  * It means the index of the first byte is always {@code 0} and the index of the last byte is
 17  * always {@link #capacity() capacity - 1}.  For example, to iterate all bytes of a buffer, you
 18  * can do the following, regardless of its internal implementation:
 19  *
 20  * 
 21  * {@link ByteBuf} buffer = ...;
 22  * for (int i = 0; i < buffer.capacity(); i ++) {
 23  *     byte b = buffer.getByte(i);
 24  *     System.out.println((char) b);
 25  * }
 26  * 
 27  *
 28  * 
Sequential Access Indexing
 29  *
 30  * {@link ByteBuf} provides two pointer variables to support sequential
 31  * read and write operations - {@link #readerIndex() readerIndex} for a read
 32  * operation and {@link #writerIndex() writerIndex} for a write operation
 33  * respectively. The following diagram shows how a buffer is segmented into
 34  * three areas by the two pointers:
 35  *
 36  * 
 37  * +-------------------+------------------+------------------+
 38  * | discardable bytes | readable bytes | writable bytes |
 39  * | | (CONTENT) | |
 40  * +-------------------+------------------+------------------+
 41  * | | | |
 42  * 0 <= readerIndex <= writerIndex <= capacity
 43  * 
 44  *
 45  * 
Readable bytes (the actual content)
 46  *
 47  * This segment is where the actual data is stored. Any operation whose name
 48  * starts with {@code read} or {@code skip} will get or skip the data at the
 49  * current {@link #readerIndex() readerIndex} and increase it by the number of
 50  * read bytes. If the argument of the read operation is also a
 51  * {@link ByteBuf} and no destination index is specified, the specified
 52  * buffer's {@link #writerIndex() writerIndex} is increased together.
 53  * 

 54  * If there's not enough content left, {@link IndexOutOfBoundsException} is
 55  * raised. The default value of newly allocated, wrapped or copied buffer's
 56  * {@link #readerIndex() readerIndex} is {@code 0}.
 57  *
 58  * 
 59  * // Iterates the readable bytes of a buffer.
 60  * {@link ByteBuf} buffer = ...;
 61  * while (buffer.readable()) {
 62  * System.out.println(buffer.readByte());
 63  * }
 64  * 
 65  *
 66  * 
Writable bytes
 67  *
 68  * This segment is a undefined space which needs to be filled. Any operation
 69  * whose name ends with {@code write} will write the data at the current
 70  * {@link #writerIndex() writerIndex} and increase it by the number of written
 71  * bytes. If the argument of the write operation is also a {@link ByteBuf},
 72  * and no source index is specified, the specified buffer's
 73  * {@link #readerIndex() readerIndex} is increased together.
 74  * 

 75  * If there's not enough writable bytes left, {@link IndexOutOfBoundsException}
 76  * is raised. The default value of newly allocated buffer's
 77  * {@link #writerIndex() writerIndex} is {@code 0}. The default value of
 78  * wrapped or copied buffer's {@link #writerIndex() writerIndex} is the
 79  * {@link #capacity() capacity} of the buffer.
 80  *
 81  * 
 82  * // Fills the writable bytes of a buffer with random integers.
 83  * {@link ByteBuf} buffer = ...;
 84  * while (buffer.maxWritableBytes() >= 4) {
 85  * buffer.writeInt(random.nextInt());
 86  * }
 87  * 
 88  *
 89  * 
Discardable bytes
 90  *
 91  * This segment contains the bytes which were read already by a read operation.
 92  * Initially, the size of this segment is {@code 0}, but its size increases up
 93  * to the {@link #writerIndex() writerIndex} as read operations are executed.
 94  * The read bytes can be discarded by calling {@link #discardReadBytes()} to
 95  * reclaim unused area as depicted by the following diagram:
 96  *
 97  * 
 98  * BEFORE discardReadBytes()
 99  *
100  * +-------------------+------------------+------------------+
101  * | discardable bytes | readable bytes | writable bytes |
102  * +-------------------+------------------+------------------+
103  * | | | |
104  * 0 <= readerIndex <= writerIndex <= capacity
105  *
106  *
107  * AFTER discardReadBytes()
108  *
109  * +------------------+--------------------------------------+
110  * | readable bytes | writable bytes (got more space) |
111  * +------------------+--------------------------------------+
112  * | | |
113  * readerIndex (0) <= writerIndex (decreased) <= capacity
114  * 
115  *
116  * Please note that there is no guarantee about the content of writable bytes
117  * after calling {@link #discardReadBytes()}. The writable bytes will not be
118  * moved in most cases and could even be filled with completely different data
119  * depending on the underlying buffer implementation.
120  *
121  * 
Clearing the buffer indexes
122  *
123  * You can set both {@link #readerIndex() readerIndex} and
124  * {@link #writerIndex() writerIndex} to {@code 0} by calling {@link #clear()}.
125  * It does not clear the buffer content (e.g. filling with {@code 0}) but just
126  * clears the two pointers. Please also note that the semantic of this
127  * operation is different from {@link ByteBuffer#clear()}.
128  *
129  * 
130  * BEFORE clear()
131  *
132  * +-------------------+------------------+------------------+
133  * | discardable bytes | readable bytes | writable bytes |
134  * +-------------------+------------------+------------------+
135  * | | | |
136  * 0 <= readerIndex <= writerIndex <= capacity
137  *
138  *
139  * AFTER clear()
140  *
141  * +---------------------------------------------------------+
142  * | writable bytes (got more space) |
143  * +---------------------------------------------------------+
144  * | |
145  * 0 = readerIndex = writerIndex <= capacity
146  * 
147  *
148  * 
Search operations
149  *
150  * For simple single-byte searches, use {@link #indexOf(int, int, byte)} and {@link #bytesBefore(int, int, byte)}.
151  * {@link #bytesBefore(byte)} is especially useful when you deal with a {@code NUL}-terminated string.
152  * For complicated searches, use {@link #forEachByte(int, int, ByteBufProcessor)} with a {@link ByteBufProcessor}
153  * implementation.
154  *
155  * 
Mark and reset
156  *
157  * There are two marker indexes in every buffer. One is for storing
158  * {@link #readerIndex() readerIndex} and the other is for storing
159  * {@link #writerIndex() writerIndex}. You can always reposition one of the
160  * two indexes by calling a reset method. It works in a similar fashion to
161  * the mark and reset methods in {@link InputStream} except that there's no
162  * {@code readlimit}.
163  *
164  * 
Derived buffers
165  *
166  * You can create a view of an existing buffer by calling either
167  * {@link #duplicate()}, {@link #slice()} or {@link #slice(int, int)}.
168  * A derived buffer will have an independent {@link #readerIndex() readerIndex},
169  * {@link #writerIndex() writerIndex} and marker indexes, while it shares
170  * other internal data representation, just like a NIO buffer does.
171  * 

172  * In case a completely fresh copy of an existing buffer is required, please
173  * call {@link #copy()} method instead.
174  *
175  * 
Conversion to existing JDK types
176  *
177  * 
Byte array
178  *
179  * If a {@link ByteBuf} is backed by a byte array (i.e. {@code byte[]}),
180  * you can access it directly via the {@link #array()} method. To determine
181  * if a buffer is backed by a byte array, {@link #hasArray()} should be used.
182  *
183  * 
NIO Buffers
184  *
185  * If a {@link ByteBuf} can be converted into an NIO {@link ByteBuffer} which shares its
186  * content (i.e. view buffer), you can get it via the {@link #nioBuffer()} method. To determine
187  * if a buffer can be converted into an NIO buffer, use {@link #nioBufferCount()}.
188  *
189  * 
Strings
190  *
191  * Various {@link #toString(Charset)} methods convert a {@link ByteBuf}
192  * into a {@link String}. Please note that {@link #toString()} is not a
193  * conversion method.
194  *
195  * 
I/O Streams
196  *
197  * Please refer to {@link ByteBufInputStream} and
198  * {@link ByteBufOutputStream}.
199 */

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转载于:https://www.cnblogs.com/anyehome/p/8478398.html