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This article mainly explains "how to use java Netty to transfer files, send fragments, and continue biography at breakpoints". The content in the article is simple and clear, and it is easy to learn and understand. below, please follow the editor's way of thinking to study and learn "how to use java Netty to transfer files, send fragments, and resume biography at breakpoints."

Development environment

1. Jdk1.8 [netty can only be partially supported below jdk1.7]

2. Netty4.1.36.Final [netty3.x 4.x 5 changes greatly each time, and the interface class name also changes]

Code sample itstack-demo-netty-2-04

└── src

├── main

│ └── java

│ └── org.itstack.demo.netty

│ ├── client

│ │ ├── MyChannelInitializer.java

│ │ ├── MyClientHandler.java

│ │ └── NettyClient.java

│ ├── codec

│ │ ├── ObjDecoder.java

│ │ └── ObjEncoder.java

│ ├── domain

│ │ ├── Constants.java

│ │ ├── FileBurstData.java

│ │ ├── FileBurstInstruct.java

│ │ ├── FileDescInfo.java

│ │ └── FileTransferProtocol.java

│ ├── server

│ │ ├── MyChannelInitializer.java

│ │ ├── MyServerHandler.java

│ │ └── NettyServer.java

│ └── util

│ ├── CacheUtil.java

│ ├── FileUtil.java

│ ├── MsgUtil.java

│ └── SerializationUtil.java

│

└── test

└── java

└── org.itstack.demo.test

├── ApiTest.java

├── NettyClientTest.java

└── NettyServerTest.java

Demo part of the key code block, complete code download follow official account; bugstack wormhole stack

Client/MyClientHandler.java * file client; channelRead handles the file protocol, in which the simulation transfer process is interrupted and the scene test can be commented out

@ Override

Public void channelRead (ChannelHandlerContext ctx, Object msg) throws Exception {

/ / data format verification

If (! (msg instanceof FileTransferProtocol)) return

FileTransferProtocol fileTransferProtocol = (FileTransferProtocol) msg

/ / 0 transfer file 'request', 1 file transfer 'instruction', 2 file transfer 'data'

Switch (fileTransferProtocol.getTransferType ()) {

Case 1:

FileBurstInstruct fileBurstInstruct = (FileBurstInstruct) fileTransferProtocol.getTransferObj ()

/ / Constants.FileStatus {0 start, 1 middle, 2 end, 3 finish}

If (Constants.FileStatus.COMPLETE = = fileBurstInstruct.getStatus ()) {

Ctx.flush ()

Ctx.close ()

System.exit (- 1)

Return

}

FileBurstData fileBurstData = FileUtil.readFile (fileBurstInstruct.getClientFileUrl (), fileBurstInstruct.getReadPosition ())

Ctx.writeAndFlush (MsgUtil.buildTransferData (fileBurstData))

System.out.println (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss") .format (new Date ()) + "bugstack wormhole stack client transfers file information. FILE:" + fileBurstData.getFileName () + "SIZE (byte):" + (fileBurstData.getEndPos ()-fileBurstData.getBeginPos ()

Break

Default:

Break

}

/ * the simulation transmission process is interrupted, and the scenario test can be commented out.

*

, /

System.out.println (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss") .format (new Date ()) + "bugstack wormhole stack client transfers file information [actively disconnects links to simulate breakpoint continuation]")

Ctx.flush ()

Ctx.close ()

System.exit (- 1)

}

Domain/FileBurstData.java * File sharding data block

/ * *

* File sharding data

* wormhole stack: https://bugstack.cn

* official account: bugstack wormhole stack {get learning source code}

* wormhole group: ① group 5398358 ② group 5360692

* Create by fuzhengwei on 2019

, /

Public class FileBurstData {

Private String fileUrl; / / client file address

Private String fileName; / / File name

Private Integer beginPos; / / start position

Private Integer endPos; / / end position

Private byte [] bytes; / / file bytes; asymmetric encryption can be used in practical applications to ensure the security of transmitted information

Private Integer status; / / Constants.FileStatus {0 start, 1 middle, 2 end, 3 finish}

... Get/set

}

Domain/FileBurstInstruct.java * File fragmentation instruction

/ * *

* File fragmentation instruction

* wormhole stack: https://bugstack.cn

* official account: bugstack wormhole stack {get learning source code}

* wormhole group: ① group 5398358 ② group 5360692

* Create by fuzhengwei on @ 2019

, /

Public class FileBurstInstruct {

Private Integer status; / / Constants.FileStatus {0 start, 1 middle, 2 end, 3 finish}

Private String clientFileUrl; / / client file URL

Private Integer readPosition; / / read location

... Get/set

}

Domain/FileDescInfo.java * File transfer information

/ * *

* File description information

* wormhole stack: https://bugstack.cn

* official account: bugstack wormhole stack {get learning source code}

* wormhole group: ① group 5398358 ② group 5360692

* Create by fuzhengwei on @ 2019

, /

Public class FileDescInfo {

Private String fileUrl

Private String fileName

Private Long fileSize

... Get/set

}

Domain/FileTransferProtocol.java * File transfer Protocol

/ * *

* File transfer Protocol

* wormhole stack: https://bugstack.cn

* official account: bugstack wormhole stack {get learning source code}

* wormhole group: 5360692

* Create by fuzhengwei on @ 2019

, /

Public class FileTransferProtocol {

Private Integer transferType; / / 0 request transfer file, 1 file transfer instruction, 2 file transfer data

Private Object transferObj; / / data object; (0) FileDescInfo, (1) FileBurstInstruct, (2) FileBurstData

... Get/set

}

ServerMyServerHandler.java * file server; channelRead handles the file protocol and contains save resume information for resuming transmission at breakpoints

@ Override

Public void channelRead (ChannelHandlerContext ctx, Object msg) throws Exception {

/ / data format verification

If (! (msg instanceof FileTransferProtocol)) return

FileTransferProtocol fileTransferProtocol = (FileTransferProtocol) msg

/ / 0 transfer file 'request', 1 file transfer 'instruction', 2 file transfer 'data'

Switch (fileTransferProtocol.getTransferType ()) {

Case 0:

FileDescInfo fileDescInfo = (FileDescInfo) fileTransferProtocol.getTransferObj ()

/ / continue transmitting information from breakpoint. In practical application, it is necessary to save the information from breakpoint to database.

FileBurstInstruct fileBurstInstructOld = CacheUtil.burstDataMap.get (fileDescInfo.getFileName ())

If (null! = fileBurstInstructOld) {

If (fileBurstInstructOld.getStatus ()) = = Constants.FileStatus.COMPLETE) {

CacheUtil.burstDataMap.remove (fileDescInfo.getFileName ())

}

/ / transfer completed to delete breakpoint information

System.out.println (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss") .format (new Date ()) + "bugstack wormhole stack server to receive client request for file transfer [breakpoint resume]." + JSON.toJSONString (fileBurstInstructOld))

Ctx.writeAndFlush (MsgUtil.buildTransferInstruct (fileBurstInstructOld))

Return

}

/ / send a message

FileTransferProtocol sendFileTransferProtocol = MsgUtil.buildTransferInstruct (Constants.FileStatus.BEGIN, fileDescInfo.getFileUrl (), 0)

Ctx.writeAndFlush (sendFileTransferProtocol)

System.out.println (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss") .format (new Date ()) + "bugstack wormhole stack server that receives client requests to transfer files." + JSON.toJSONString (fileDescInfo))

Break

Case 2:

FileBurstData fileBurstData = (FileBurstData) fileTransferProtocol.getTransferObj ()

FileBurstInstruct fileBurstInstruct = FileUtil.writeFile ("egvax /", fileBurstData)

/ / Save breakpoint resume information

CacheUtil.burstDataMap.put (fileBurstData.getFileName (), fileBurstInstruct)

Ctx.writeAndFlush (MsgUtil.buildTransferInstruct (fileBurstInstruct))

System.out.println (new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss") .format (new Date ()) + "bugstack wormhole stack server that receives file data transferred by the client." + JSON.toJSONString (fileBurstData))

/ / transfer completed to delete breakpoint information

If (fileBurstInstruct.getStatus ()) = = Constants.FileStatus.COMPLETE) {

CacheUtil.burstDataMap.remove (fileBurstData.getFileName ())

}

Break

Default:

Break

}

}

Util/FileUtil.java * File read and write tool, sharding read and write processing class

/ * *

* File read and write tool

* wormhole stack: https://bugstack.cn

* official account: bugstack wormhole stack {get learning source code}

* wormhole group: 5360692

* Create by fuzhengwei on @ 2019

, /

Public class FileUtil {

Public static FileBurstData readFile (String fileUrl, Integer readPosition) throws IOException {

File file = new File (fileUrl)

RandomAccessFile randomAccessFile = new RandomAccessFile (file, "r"); / / r: read-only mode rw: read-write mode

RandomAccessFile.seek (readPosition)

Byte [] bytes = new byte [1024]

Int readSize = randomAccessFile.read (bytes)

If (readSize

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