Netty——ByteBuffer的内部结构演示示例
Posted 小志的博客
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了Netty——ByteBuffer的内部结构演示示例相关的知识，希望对你有一定的参考价值。
目录
一、pom.xml文件引入依赖
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.39.Final</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.18</version>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.5</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>19.0</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
<dependency>
<groupId>com.google.protobuf</groupId>
<artifactId>protobuf-java</artifactId>
<version>3.11.3</version>
</dependency>
二、编写工具类（此工具类复制即可使用）
package com.example.nettytest.nio.day1;
import io.netty.util.internal.StringUtil;
import java.nio.ByteBuffer;
import static io.netty.util.internal.MathUtil.isOutOfBounds;
import static io.netty.util.internal.StringUtil.NEWLINE;
public class ByteBufferUtil
private static final char[] BYTE2CHAR = new char[256];
private static final char[] HEXDUMP_TABLE = new char[256 * 4];
private static final String[] HEXPADDING = new String[16];
private static final String[] HEXDUMP_ROWPREFIXES = new String[65536 >>> 4];
private static final String[] BYTE2HEX = new String[256];
private static final String[] BYTEPADDING = new String[16];
static
final char[] DIGITS = "0123456789abcdef".toCharArray();
for (int i = 0; i < 256; i++)
HEXDUMP_TABLE[i << 1] = DIGITS[i >>> 4 & 0x0F];
HEXDUMP_TABLE[(i << 1) + 1] = DIGITS[i & 0x0F];
int i;
// Generate the lookup table for hex dump paddings
for (i = 0; i < HEXPADDING.length; i++)
int padding = HEXPADDING.length - i;
StringBuilder buf = new StringBuilder(padding * 3);
for (int j = 0; j < padding; j++)
buf.append(" ");
HEXPADDING[i] = buf.toString();
// Generate the lookup table for the start-offset header in each row (up to 64KiB).
for (i = 0; i < HEXDUMP_ROWPREFIXES.length; i++)
StringBuilder buf = new StringBuilder(12);
buf.append(NEWLINE);
buf.append(Long.toHexString(i << 4 & 0xFFFFFFFFL | 0x100000000L));
buf.setCharAt(buf.length() - 9, '|');
buf.append('|');
HEXDUMP_ROWPREFIXES[i] = buf.toString();
// Generate the lookup table for byte-to-hex-dump conversion
for (i = 0; i < BYTE2HEX.length; i++)
BYTE2HEX[i] = ' ' + StringUtil.byteToHexStringPadded(i);
// Generate the lookup table for byte dump paddings
for (i = 0; i < BYTEPADDING.length; i++)
int padding = BYTEPADDING.length - i;
StringBuilder buf = new StringBuilder(padding);
for (int j = 0; j < padding; j++)
buf.append(' ');
BYTEPADDING[i] = buf.toString();
// Generate the lookup table for byte-to-char conversion
for (i = 0; i < BYTE2CHAR.length; i++)
if (i <= 0x1f || i >= 0x7f)
BYTE2CHAR[i] = '.';
else
BYTE2CHAR[i] = (char) i;
/**
* 打印所有内容
* @param buffer
*/
public static void debugAll(ByteBuffer buffer)
int oldlimit = buffer.limit();
buffer.limit(buffer.capacity());
StringBuilder origin = new StringBuilder(256);
appendPrettyHexDump(origin, buffer, 0, buffer.capacity());
System.out.println("+--------+-------------------- all ------------------------+----------------+");
System.out.printf("position: [%d], limit: [%d]\\n", buffer.position(), oldlimit);
System.out.println(origin);
buffer.limit(oldlimit);
/**
* 打印可读取内容
* @param buffer
*/
public static void debugRead(ByteBuffer buffer)
StringBuilder builder = new StringBuilder(256);
appendPrettyHexDump(builder, buffer, buffer.position(), buffer.limit() - buffer.position());
System.out.println("+--------+-------------------- read -----------------------+----------------+");
System.out.printf("position: [%d], limit: [%d]\\n", buffer.position(), buffer.limit());
System.out.println(builder);
public static void main(String[] args)
ByteBuffer buffer = ByteBuffer.allocate(10);
buffer.put(new byte[]97, 98, 99, 100);
debugAll(buffer);
private static void appendPrettyHexDump(StringBuilder dump, ByteBuffer buf, int offset, int length)
if (isOutOfBounds(offset, length, buf.capacity()))
throw new IndexOutOfBoundsException(
"expected: " + "0 <= offset(" + offset + ") <= offset + length(" + length
+ ") <= " + "buf.capacity(" + buf.capacity() + ')');
if (length == 0)
return;
dump.append(
" +-------------------------------------------------+" +
NEWLINE + " | 0 1 2 3 4 5 6 7 8 9 a b c d e f |" +
NEWLINE + "+--------+-------------------------------------------------+----------------+");
final int startIndex = offset;
final int fullRows = length >>> 4;
final int remainder = length & 0xF;
// Dump the rows which have 16 bytes.
for (int row = 0; row < fullRows; row++)
int rowStartIndex = (row << 4) + startIndex;
// Per-row prefix.
appendHexDumpRowPrefix(dump, row, rowStartIndex);
// Hex dump
int rowEndIndex = rowStartIndex + 16;
for (int j = rowStartIndex; j < rowEndIndex; j++)
dump.append(BYTE2HEX[getUnsignedByte(buf, j)]);
dump.append(" |");
// ASCII dump
for (int j = rowStartIndex; j < rowEndIndex; j++)
dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]);
dump.append('|');
// Dump the last row which has less than 16 bytes.
if (remainder != 0)
int rowStartIndex = (fullRows << 4) + startIndex;
appendHexDumpRowPrefix(dump, fullRows, rowStartIndex);
// Hex dump
int rowEndIndex = rowStartIndex + remainder;
for (int j = rowStartIndex; j < rowEndIndex; j++)
dump.append(BYTE2HEX[getUnsignedByte(buf, j)]);
dump.append(HEXPADDING[remainder]);
dump.append(" |");
// Ascii dump
for (int j = rowStartIndex; j < rowEndIndex; j++)
dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]);
dump.append(BYTEPADDING[remainder]);
dump.append('|');
dump.append(NEWLINE +
"+--------+-------------------------------------------------+----------------+");
private static void appendHexDumpRowPrefix(StringBuilder dump, int row, int rowStartIndex)
if (row < HEXDUMP_ROWPREFIXES.length)
dump.append(HEXDUMP_ROWPREFIXES[row]);
else
dump.append(NEWLINE);
dump.append(Long.toHexString(rowStartIndex & 0xFFFFFFFFL | 0x100000000L));
dump.setCharAt(dump.length() - 9, '|');
dump.append('|');
public static short getUnsignedByte(ByteBuffer buffer, int index)
return (short) (buffer.get(index) & 0xFF);
三、测试类示例演示（一）
-
测试类
package com.example.nettytest.nio.day1; import java.nio.ByteBuffer; import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll; public class TestByteBufferReadWrite public static void main(String[] args) ByteBuffer buffer = ByteBuffer.allocate(10); /** * 写入十六进制的一个字节 * */ buffer.put((byte) 0x61); // 'a' debugAll(buffer); -
输出结果
四、测试类示例演示（二）
-
测试类
package com.example.nettytest.nio.day1; import java.nio.ByteBuffer; import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll; public class TestByteBufferReadWrite public static void main(String[] args) ByteBuffer buffer = ByteBuffer.allocate(10); /** * 写入一个十六进制的字节数组 * */ buffer.put(new byte[]0x62, 0x63, 0x64); debugAll(buffer); -
输出结果
五、测试类示例演示（三）
-
测试类
package com.example.nettytest.nio.day1; import java.nio.ByteBuffer; import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll; public class TestByteBufferReadWrite public static void main(String[] args) ByteBuffer buffer = ByteBuffer.allocate(10); /** * 写入十六进制的一个字节 * */ buffer.put((byte) 0x61); // 'a' debugAll(buffer); /** * 写入一个十六进制的字节数组 * */ buffer.put(new byte[]0x62, 0x63, 0x64); // b c d debugAll(buffer); /** * 切换到读模式，读取一个字节（该十六进制字节读取后会转换成十进制并输出） * */ buffer.flip(); System.out.println(buffer.get()); debugAll(buffer); -
输出结果
