nio | 易学教程

netty学习笔记

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1、在没有任何encoder、decoder的情况下，Netty发送接收数据都是按照ByteBuf的形式，其它形式都是不合法的。 ByteBuf result = (ByteBuf) msg; byte[] data = new byte[result.readableBytes()]; result.readBytes(data); String resultStr = new String(data); // 接收并打印客户端的信息 System.out.println("Client said:" + resultStr); // 释放资源，这行很关键 result.release(); // 向客户端发送消息 String response = "I am ok!"; // 在当前场景下，发送的数据必须转换成ByteBuf数组 ByteBuf encoded = ctx.alloc().buffer(4 * response.length()); encoded.writeBytes(response.getBytes()); ctx.write(encoded); ctx.flush(); 2、接收发送数据操作都是通过handler实现的，handler在netty中占据了非常重要的位置。 class HelloServerInHandler extends

java attach file from virtual filesystem to email

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来源： https://stackoverflow.com/questions/44392639/java-attach-file-from-virtual-filesystem-to-email

java.nio.Buffer not loading clear() method on runtime

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问题 So I am a developer for a project that uses a java agent to inject. It should be noted though that this error occurs after main is called. Everything is going fine for most users, but a few are having an issue where java.nio.IntBuffer isn't loading clear() (inherited from Buffer) Error: java.lang.NoSuchMethodError: java.nio.IntBuffer.clear()Ljava/nio/IntBuffer; Then the stacktrace, which simply gives the first time clear() is called in our code. What is the cause of this (besides the fact

How to read a huge CSV file from Google Cloud Storage line by line using Java?

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问题 I'm new to Google Cloud Platform. I'm trying to read a CSV file present in Google Cloud Storage (non-public bucket accessed via Service Account key) line by line which is around 1GB. I couldn't find any option to read the file present in the Google Cloud Storage (GCS) line by line. I only see the read by chunksize/byte size options. Since I'm trying to read a CSV, I don't want to use read by chunksize since it may split a record while reading. Solutions tried so far: Tried copying the

How to read a huge CSV file from Google Cloud Storage line by line using Java?

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Java AsyncHttpClient: broken file while writing from LazyResponseBodyPart to AsynchronousFileChannel

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问题 I use AsyncHttpClient library for async non blocking requests. My case: write data to a file as it is received over the network. For download file from remote host and save to file I used default ResponseBodyPartFactory.EAGER and AsynchronousFileChannel so as not to block the netty thread as data arrives. But as my measurements showed, in comparison with LAZY the memory consumption in the Java heap increases many times over. So I decided to go straight to LAZY , but did not consider the

Java AsynchronousFileChannel - thread usage

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问题 I understand Java's AsynchronousFileChannel to be an async api (does not block the calling thread) and can use a thread in a system thread pool. My question is: do AsynchronousFileChannel operations have a 1:1 thread ratio? In other words, if a loop use AsynchronousFileChannel to read 100 of files, will it use 100 threads to do that or will it use only a small number of threads (in standard NIO fashion)? 回答1: AsynchronousFileChannel implementation used in general (and actually used e.g. on

Sending message using non-blocking I/O in java(NIO API)

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问题 I'm writing a server/client program that clients send text message to server.I have used non-blocking I/O (NIO API) but messages on the server do not display correctly.this is my code on server: private JTextArea displayArea; private int numBytes; private ByteBuffer buffer; /*... some code is here ...*/ displayArea = new JTextArea(); add(new JScrollPane(displayArea), BorderLayout.CENTER); setSize(400, 500); setVisible(true); /*... some code is here ...*/ buffer = ByteBuffer.allocate(20);

Avoid extra new line, writing on .txt file

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问题 Currently I am using java.nio.file.File.write(Path, Iterable, Charset) to write txt file. Code is here... Path filePath = Paths.get("d:\\myFile.txt"); List<String> lineList =Arrays.asList("1. Hello", "2. I am Fine", "3. What about U ?"); Files.write(filePath, lineList, Charset.forName("UTF-8")); But one more (4th) empty line generated in the text file. How can I avoid 4th empty line ? 1 | 1. Hello 2 | 2. I am Fine 3 | 3. What about U ? 4 | 回答1: From javadoc for write: "Each line is a char

Avoid extra new line, writing on .txt file

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