-
Marshalling
鎖定
- 外文名
- Marshalling
- 領 域
- 計算機科學
Marshalling簡介
Marshalling用途
Marshalling被用於實現不同的遠程過程調用（RPC）機制，這必須用到進程間的數據傳輸。Microsoft的組件對象模型（COM）中，當跨COM的套間（apartment）傳遞接口指針時，接口指針必須被marshalled。在.NET Framework下，在非受管（unmanaged）類型與CLR類型間，例如P/Invoke過程，必須做marshalling。例如，C#程序調用C語言寫的DLL，其中函數參數使用字符串，就需要做marshalling。
使用Mozilla應用程序框架的XPCOM的腳本或應用程序，廣泛使用marshalling。
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Marshalling例子
Microsoft Windows系列操作系統，Direct3D設備驅動程序是內核態驅動程序。DirectX運行時處理用户態API。用户態執行系統調用來執行內核態操作，需要CPU切換為內核態，這將耗費微秒級的時間來完成。在此期間，CPU不能執行任何操作。為優化性能，必須極小化CPU這種模式切換。 LinuxOpenGL驅動程序分為兩部分：內核驅動與用户空間驅動。用户空間驅動把所有OpenGL命令翻譯為機器碼提交給GPU。為減少系統調用，用户空間驅動實現marshalling。當GPU的命令緩衝區（command buffer）裝滿了繪圖數據，API簡單地把請求繪製的調用存放在一個臨時緩衝區；當命令緩衝區接近為空，執行內核模式切換一次性增加被存儲的命令。
Marshalling與序列化的比較
術語“marshal”被Python標準庫認為與“序列化”同義。但與Java相關的RFC 2713不認為二者是同義：
"marshal"一個對象意味着記錄下它的狀態與codebase(s)在這種方式，以便當這個marshal對象在被"unmarshalled"時，可以獲得最初代碼的一個副本，可能會自動裝入這個對象的類定義。可以marshal任何能被序列化或遠程（即實現java.rmi.Remote接口）。Marshalling類似序列化，除了marshalling也記錄codebases。Marshalling不同於序列化是marshalling特別處理遠程對象。
Marshalling序列化框架
JBoss Marshalling是一個Java對象序列化包，對JDK默認的序列化框架進行了優化，但又保持跟java.io.Serializable接口的兼容，同時增加了一些可調的參數和附加的特性，這些參數和特性可通過工廠類進行配置。
import lombok.Data;
import java.io.Serializable;
@Data
public class SubscribeReq implements Serializable {
/**
* 默認的序列號ID
*/
private static final long serialVersionUID = 1L;
private int subReqID;
private String userName;
private String productName;
private String phoneNumber;
private String address;
@Override
public String toString() {
return "SubscribeReq [subReqID=" + subReqID + ", userName=" + userName
+ ", productName=" + productName + ", phoneNumber="
+ phoneNumber + ", address=" + address + "]";
}
}
import lombok.Data;
import java.io.Serializable;
@Data
public class SubscribeResp implements Serializable {
/**
* 默認序列ID
*/
private static final long serialVersionUID = 1L;
private int subReqID;
private int respCode;
private String desc;
@Override
public String toString() {
return "SubscribeResp [subReqID=" + subReqID + ", respCode=" + respCode
+ ", desc=" + desc + "]";
}
}
編解碼工廠類：
import io.netty.handler.codec.marshalling.*;
import org.jboss.marshalling.MarshallerFactory;
import org.jboss.marshalling.Marshalling;
import org.jboss.marshalling.MarshallingConfiguration;
public final class MarshallingCodeCFactory {
/**
* 創建Jboss Marshalling解碼器MarshallingDecoder
*/
public static MarshallingDecoder buildMarshallingDecoder() {
//首先通過Marshalling工具類的getProvidedMarshallerFactory靜態方法獲取MarshallerFactory實例
//參數“serial”表示創建的是Java序列化工廠對象，它由jboss-marshalling-serial-1.3.0.CR9.jar提供。
final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
//創建了MarshallingConfiguration對象
final MarshallingConfiguration configuration = new MarshallingConfiguration();
//將它的版本號設置為5
configuration.setVersion(5);
//然後根據MarshallerFactory和MarshallingConfiguration創建UnmarshallerProvider實例
UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
//最後通過構造函數創建Netty的MarshallingDecoder對象
//它有兩個參數，分別是UnmarshallerProvider和單個消息序列化後的最大長度。
MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024);
return decoder;
}
/**
* 創建Jboss Marshalling編碼器MarshallingEncoder
*/
public static MarshallingEncoder buildMarshallingEncoder() {
final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
final MarshallingConfiguration configuration = new MarshallingConfiguration();
configuration.setVersion(5);
//創建MarshallerProvider對象，它用於創建Netty提供的MarshallingEncoder實例
MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
//MarshallingEncoder用於將實現序列化接口的POJO對象序列化為二進制數組。
MarshallingEncoder encoder = new MarshallingEncoder(provider);
return encoder;
}
}
服務端代碼示例：
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
public class SubReqServer {
public void bind(int port) throws Exception {
// 配置服務端的NIO線程組
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 100)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer() {
@Override
public void initChannel(Channel ch) {
//通過工廠類創建MarshallingEncoder解碼器，並添加到ChannelPipeline.
ch.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
//通過工廠類創建MarshallingEncoder編碼器，並添加到ChannelPipeline中。
ch.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
ch.pipeline().addLast(new SubReqServerHandler());
}
});
// 綁定端口，同步等待成功
ChannelFuture f = b.bind(port).sync();
// 等待服務端監聽端口關閉
f.channel().closeFuture().sync();
} finally {
// 優雅退出，釋放線程池資源
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
int port = 8080;
if (args != null && args.length > 0) {
try {
port = Integer.valueOf(args[0]);
} catch (NumberFormatException e) {
// 採用默認值
}
}
new SubReqServer().bind(port);
}
}
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
@ChannelHandler.Sharable
public class SubReqServerHandler extends ChannelHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg)
throws Exception {
//經過解碼器handler ObjectDecoder的解碼，
//SubReqServerHandler接收到的請求消息已經被自動解碼為SubscribeReq對象，可以直接使用。
SubscribeReq req = (SubscribeReq) msg;
if ("Lilinfeng".equalsIgnoreCase(req.getUserName())) {
System.out.println("Service accept client subscribe req : ["
+ req.toString() + "]");
//對訂購者的用户名進行合法性校驗，校驗通過後打印訂購請求消息，構造訂購成功應答消息立即發送給客户端。
ctx.writeAndFlush(resp(req.getSubReqID()));
}
}
private SubscribeResp resp(int subReqID) {
SubscribeResp resp = new SubscribeResp();
resp.setSubReqID(subReqID);
resp.setRespCode(0);
resp.setDesc("Netty book order succeed, 3 days later, sent to the designated address");
return resp;
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();// 發生異常，關閉鏈路
}
}
客户端代碼示例：
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
public class SubReqClient {
public void connect(int port, String host) throws Exception {
// 配置客户端NIO線程組
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group).channel(NioSocketChannel.class)
.option(ChannelOption.TCP_NODELAY, true)
.handler(new ChannelInitializer() {
@Override
public void initChannel(Channel ch)
throws Exception {
ch.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
ch.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
ch.pipeline().addLast(new SubReqClientHandler());
}
});
// 發起異步連接操作
ChannelFuture f = b.connect(host, port).sync();
// 等待客户端鏈路關閉
f.channel().closeFuture().sync();
} finally {
// 優雅退出，釋放NIO線程組
group.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
int port = 8080;
if (args != null && args.length > 0) {
try {
port = Integer.valueOf(args[0]);
} catch (NumberFormatException e) {
// 採用默認值
}
}
new SubReqClient().connect(port, "127.0.0.1");
}
}
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
public class SubReqClientHandler extends ChannelHandlerAdapter {
public SubReqClientHandler() {
}
@Override
public void channelActive(ChannelHandlerContext ctx) {
//在鏈路激活的時候循環構造10條訂購請求消息，最後一次性地發送給服務端。
for (int i = 0; i < 10; i++) {
ctx.write(subReq(i));
}
ctx.flush();
}
private SubscribeReq subReq(int i) {
SubscribeReq req = new SubscribeReq();
req.setAddress("南京市江寧區方山國家地質公園");
req.setPhoneNumber("138xxxxxxxxx");
req.setProductName("Netty For Marshalling");
req.setSubReqID(i);
req.setUserName("Lilinfeng");
return req;
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg)
throws Exception {
//由於對象解碼器已經對訂購請求應答消息進行了自動解碼，
//因此，SubReqClientHandler接收到的消息已經是解碼成功後的訂購應答消息。
System.out.println("Receive server response : [" + msg + "]");
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
運行結果：
服務端結果：
14:48:45.475 [nioEventLoopGroup-2-1] INFO i.n.handler.logging.LoggingHandler - [id: 0x71ea5def, /0:0:0:0:0:0:0:0:8080] RECEIVED: [id: 0x876eb7b4, /127.0.0.1:57423 => /127.0.0.1:8080] 14:48:45.707 [nioEventLoopGroup-3-1] DEBUG io.netty.util.ResourceLeakDetector - -Dio.netty.leakDetectionLevel: simple Service accept client subscribe req : [SubscribeReq [subReqID=0, userName=Lilinfeng, productName=Netty For Marshalling, phoneNumber=138xxxxxxxxx, address=南京市江寧區方山國家地質公園]] Service accept client subscribe req : [SubscribeReq [subReqID=1, userName=Lilinfeng, productName=Netty For Marshalling, phoneNumber=138xxxxxxxxx, address=南京市江寧區方山國家地質公園]] .......................................................................... Service accept client subscribe req : [SubscribeReq [subReqID=9, userName=Lilinfeng, productName=Netty For Marshalling, phoneNumber=138xxxxxxxxx, address=南京市江寧區方山國家地質公園]]
客户端結果：
Receive server response : [SubscribeResp [subReqID=0, respCode=0, desc=Netty book order succeed, 3 days later, sent to the designated address]] .......................................................................... Receive server response : [SubscribeResp [subReqID=9, respCode=0, desc=Netty book order succeed, 3 days later, sent to the designated address]]
- 參考資料
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- 1. The train marshalling problem ．Elsevier[引用日期2018-06-28]
