Java 异常处理之 BufferUnderflowException（BufferUnderflowException 概述、常见发生场景、避免策略）

一、BufferUnderflowException 概述

1. BufferUnderflowException 是 Java NIO 包中的一个运行时异常，是 RuntimeException 的子类

public class BufferUnderflowException extends RuntimeException {...
}

# 继承关系java.lang.Object-> java.lang.Throwable-> java.lang.Exception-> java.lang.RuntimeException-> java.nio.BufferUnderflowException

2. 它发生在尝试从缓冲区读取比实际剩余更多的数据时，即缓冲区位置（position）已经到达或超过限制（limit）

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二、常见发生场景

1. 读取数据

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());int i1 = byteBuffer.getInt();// 读取 4 字节没问题
System.out.println("第 1 次读取：" + i1);
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());int i2 = byteBuffer.getInt();// 再读取 4 字节没问题
System.out.println("第 2 次读取：" + i2);
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());int i3 = byteBuffer.getInt(); // 再读取 4 字节，会抛出 BufferUnderflowException 异常
System.out.println("第 3 次读取：" + i3);
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());

# 输出结果初始化
pos=0, remaining=10, limit=10
第 1 次读取：0
pos=4, remaining=6, limit=10
第 2 次读取：0
pos=8, remaining=2, limit=10
Exception in thread "main" java.nio.BufferUnderflowException

2. 批量读取数据

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byte[] bytes = new byte[15];
byteBuffer.get(bytes);
System.out.println("读取数据：" + new String(bytes));
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());

# 输出结果初始化
pos=0, remaining=10, limit=10
Exception in thread "main" java.nio.BufferUnderflowException

3. 调用 flip 方法后，（批量）读取数据

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());String data = "abc";
byteBuffer.put(data.getBytes());
System.out.println("添加数据：" + data);
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byteBuffer.flip();
System.out.println("调用 flip 方法");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byte[] bytes1 = new byte[2];
byteBuffer.get(bytes1);
System.out.println("第 1 次读取：" + new String(bytes1));
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byte[] bytes2 = new byte[2];
byteBuffer.get(bytes2);
System.out.println("第 2 次读取：" + new String(bytes2));
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());

# 输出结果初始化
pos=0, remaining=10, limit=10
添加数据：abc
pos=3, remaining=7, limit=10
调用 flip 方法
pos=0, remaining=3, limit=3
第 1 次读取：ab
pos=2, remaining=1, limit=3
Exception in thread "main" java.nio.BufferUnderflowException

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三、避免策略

1、基本介绍

1. 总是调用 remaining 方法检查剩余数据是否足够，不同的读取方法对读取长度有不同的要求

方法	读取长度（字节）
byte get()	1
char getChar()	2
short getShort()	2
int getInt()	4
long getLong()	8
float getFloat()	4
double getDouble()	8
ByteBuffer get(byte[] dst)	dst.length

2. 必要时，也可以通过 try catch 捕获异常

2、演示

1. 读取数据（调用 remaining 方法检查）

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());int num = 1;
while (true) {if (byteBuffer.remaining() >= 4) {int i1 = byteBuffer.getInt();System.out.println("第 " + num + " 次读取：" + i1);System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());num++;} else {System.out.println("第 " + num + " 次读取");System.out.println("数据不足，无法读取");break;}
}

# 输出结果初始化
pos=0, remaining=10, limit=10
第 1 次读取：0
pos=4, remaining=6, limit=10
第 2 次读取：0
pos=8, remaining=2, limit=10
第 3 次读取
数据不足，无法读取

2. 批量读取数据（调用 remaining 方法检查）

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byte[] bytes = new byte[15];
if (byteBuffer.remaining() < bytes.length) {System.out.println("数据不足，无法读取");
} else {byteBuffer.get(bytes);System.out.println("读取数据：" + new String(bytes));System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());
}

# 输出结果初始化
pos=0, remaining=10, limit=10
数据不足，无法读取

3. 调用 flip 方法后，（批量）读取数据（调用 remaining 方法检查）

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());String data = "abc";
byteBuffer.put(data.getBytes());
System.out.println("添加数据：" + data);
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byteBuffer.flip();
System.out.println("调用 flip 方法");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());byte[] bytes1 = new byte[2];
if (byteBuffer.remaining() < bytes1.length) {System.out.println("第 1 次读取");System.out.println("数据不足，无法读取");
} else {byteBuffer.get(bytes1);System.out.println("第 1 次读取：" + new String(bytes1));System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());
}byte[] bytes2 = new byte[2];
if (byteBuffer.remaining() < bytes2.length) {System.out.println("第 2 次读取");System.out.println("数据不足，无法读取");
} else {byteBuffer.get(bytes2);System.out.println("第 2 次读取：" + new String(bytes2));System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());
}

# 输出结果初始化
pos=0, remaining=10, limit=10
添加数据：abc
pos=3, remaining=7, limit=10
调用 flip 方法
pos=0, remaining=3, limit=3
第 1 次读取：ab
pos=2, remaining=1, limit=3
第 2 次读取
数据不足，无法读取

4. 通过 try catch 捕获异常

ByteBuffer byteBuffer = ByteBuffer.allocate(10);
System.out.println("初始化");
System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());try {byte[] bytes = new byte[15];byteBuffer.get(bytes);System.out.println("读取数据：" + new String(bytes));System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());
} catch (BufferUnderflowException e) {e.printStackTrace();System.out.println("读取数据失败");System.out.println("pos=" + byteBuffer.position() + ", remaining=" + byteBuffer.remaining() + ", limit=" + byteBuffer.limit());
}

# 输出结果初始化
pos=0, remaining=10, limit=10
java.nio.BufferUnderflowException
读取数据失败
pos=0, remaining=10, limit=10