使用 Java 类 实现Http协议

  • Z时代
  • 2024-01-10
  • 分类：IT

Java 实现Http协议

HTTP协议属于应用层协议，它构建于TCP和IP协议之上，处于TCP/IP协议架构层的顶端，所以，它不用处理下层协议间诸如丢包补发、握手及数据的分段及重新组装等繁琐的细节，使开发人员可以专注于应用业务。

协议是通信的规范，为了更好的理解HTTP协议，我们可以基于Java的Socket API接口，通过设计一个简单的应用层通信协议，来简单分析下协议实现的过程和细节。

在我们今天的示例程序中，客户端会向服务端发送一条命令，服务端在接收到命令后，会判断命令是否是“HELLO”，如果是“HELLO”， 则服务端返回给客户端的响应为“hello”，否则，服务端返回给客户端的响应为“bye bye”。

我们接下来用Java实现这个简单的应用层通信协议，

一、协议请求的定义

协议的请求主要包括：编码、命令和命令长度三个字段。

package com.binghe.params;
/**
 * 协议请求的定义
 * @author binghe
 *
 */
public class Request {
 /**
  * 协议编码
  */
 private byte encode;
 /**
  * 命令
  */
 private String command;
 /**
  * 命令长度
  */
 private int commandLength;
 public Request() {
  super();
 }
 public Request(byte encode, String command, int commandLength) {
  super();
  this.encode = encode;
  this.command = command;
  this.commandLength = commandLength;
 }
 public byte getEncode() {
  return encode;
 }
 public void setEncode(byte encode) {
  this.encode = encode;
 }
 public String getCommand() {
  return command;
 }
 public void setCommand(String command) {
  this.command = command;
 }
 public int getCommandLength() {
  return commandLength;
 }
 public void setCommandLength(int commandLength) {
  this.commandLength = commandLength;
 }
 @Override
 public String toString() {
  return "Request [encode=" + encode + ", command=" + command
    + ", commandLength=" + commandLength + "]";
 }
}

二、响应协议的定义

协议的响应主要包括：编码、响应内容和响应长度三个字段。

package com.binghe.params;
/**
 * 协议响应的定义
 * @author binghe
 *
 */
public class Response {
 /**
  * 编码
  */
 private byte encode;
 /**
  * 响应内容
  */
 private String response;
 /**
  * 响应长度
  */
 private int responseLength;
 public Response() {
  super();
 }
 public Response(byte encode, String response, int responseLength) {
  super();
  this.encode = encode;
  this.response = response;
  this.responseLength = responseLength;
 }
 public byte getEncode() {
  return encode;
 }
 public void setEncode(byte encode) {
  this.encode = encode;
 }
 public String getResponse() {
  return response;
 }
 public void setResponse(String response) {
  this.response = response;
 }
 public int getResponseLength() {
  return responseLength;
 }
 public void setResponseLength(int responseLength) {
  this.responseLength = responseLength;
 }
 @Override
 public String toString() {
  return "Response [encode=" + encode + ", response=" + response
    + ", responseLength=" + responseLength + "]";
 }
}

三、编码常量定义

编码常量的定义主要包括UTF-8和GBK两种编码。

package com.binghe.constant;
/**
 * 常量类
 * @author binghe
 *
 */
public final class Encode {
 //UTF-8编码
 public static final byte UTF8 = 1;
 //GBK编码
 public static final byte GBK = 2;
}

四、客户端的实现

客户端先构造一个request请求，通过Socket接口将其发送到远端，并接收远端的响应信息，并构造成一个Response对象。

package com.binghe.protocol.client;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import com.binghe.constant.Encode;
import com.binghe.params.Request;
import com.binghe.params.Response;
import com.binghe.utils.ProtocolUtils;
/**
 * 客户端代码
 * @author binghe
 *
 */
public final class Client {
 public static void main(String[] args) throws IOException{
  //请求
  Request request = new Request();
  request.setCommand("HELLO");
  request.setCommandLength(request.getCommand().length());
  request.setEncode(Encode.UTF8);
  Socket client = new Socket("127.0.0.1", 4567);
  OutputStream out = client.getOutputStream();
  //发送请求
  ProtocolUtils.writeRequest(out, request);
  //读取响应数据
  InputStream in = client.getInputStream();
  Response response = ProtocolUtils.readResponse(in);
  System.out.println("获取的响应结果信息为: " + response.toString());
 }
}

五、服务端的实现

服务端接收客户端的请求，根据接收命令的不同，响应不同的消息信息，如果是“HELLO”命令，则响应“hello”信息，否则响应“bye bye”信息。

package com.binghe.protocol.server;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import com.binghe.constant.Encode;
import com.binghe.params.Request;
import com.binghe.params.Response;
import com.binghe.utils.ProtocolUtils;
/**
 * Server端代码
 * @author binghe
 *
 */
public final class Server {
 public static void main(String[] args) throws IOException{
  ServerSocket server = new ServerSocket(4567);
  while (true) {
   Socket client = server.accept();
   //读取请求数据
   InputStream input = client.getInputStream();
   Request request = ProtocolUtils.readRequest(input);
   System.out.println("收到的请求参数为: " + request.toString());
   OutputStream out = client.getOutputStream();
   //组装响应数据
   Response response = new Response();
   response.setEncode(Encode.UTF8);
   if("HELLO".equals(request.getCommand())){
    response.setResponse("hello");
   }else{
    response.setResponse("bye bye");
   }
   response.setResponseLength(response.getResponse().length());
   ProtocolUtils.writeResponse(out, response);
  }
 }
}

六、ProtocolUtils工具类的实现

ProtocolUtils的readRequest方法将从传递进来的输入流中读取请求的encode、command和commandLength三个参数，进行相应的编码转化，构造成Request对象返回。而writeResponse方法则是将response对象的字段根据对应的编码写入到响应的输出流中。

有一个细节需要重点注意：OutputStream中直接写入一个int类型，会截取其低8位，丢弃其高24位，所以，在传递和接收数据时，需要进行相应的转化操作。

package com.binghe.utils;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import com.binghe.constant.Encode;
import com.binghe.params.Request;
import com.binghe.params.Response;
/**
 * 协议工具类
 * @author binghe
 *
 */
public final class ProtocolUtils {
 /**
  * 从输入流中反序列化Request对象
  * @param input
  * @return
  * @throws IOException
  */
 public static Request readRequest(InputStream input) throws IOException{
  //读取编码
  byte[] encodeByte = new byte[1];
  input.read(encodeByte);
  byte encode = encodeByte[0];
  //读取命令长度
  byte[] commandLengthBytes = new byte[4];
  input.read(commandLengthBytes);
  int commandLength = ByteUtils.byte2Int(commandLengthBytes);
  //读取命令
  byte[] commandBytes = new byte[commandLength];
  input.read(commandBytes);
  String command = "";
  if(Encode.UTF8 == encode){
   command = new String(commandBytes, "UTF-8");
  }else if(Encode.GBK == encode){
   command = new String(commandBytes, "GBK");
  }
  //组装请求返回
  Request request = new Request(encode, command, commandLength);
  return request;
 }
 /**
  * 从输入流中反序列化Response对象
  * @param input
  * @return
  * @throws IOException
  */
 public static Response readResponse(InputStream input) throws IOException{
  //读取编码
  byte[] encodeByte = new byte[1];
  input.read(encodeByte);
  byte encode = encodeByte[0];
  //读取响应长度
  byte[] responseLengthBytes = new byte[4];
  input.read(responseLengthBytes);
  int responseLength = ByteUtils.byte2Int(responseLengthBytes);
  //读取命令
  byte[] responseBytes = new byte[responseLength];
  input.read(responseBytes);
  String response = "";
  if(Encode.UTF8 == encode){
   response = new String(responseBytes, "UTF-8");
  }else if(Encode.GBK == encode){
   response = new String(responseBytes, "GBK");
  }
  //组装请求返回
  Response resp = new Response(encode, response, responseLength);
  return resp;
 }
 /**
  * 序列化请求信息
  * @param output
  * @param response
  */
 public static void writeRequest(OutputStream output, Request request) throws IOException{
  //将response响应返回给客户端
  output.write(request.getEncode());
  //output.write(response.getResponseLength());直接write一个int类型会截取低8位传输丢弃高24位
  output.write(ByteUtils.int2ByteArray(request.getCommandLength()));
  if(Encode.UTF8 == request.getEncode()){
   output.write(request.getCommand().getBytes("UTF-8"));
  }else if(Encode.GBK == request.getEncode()){
   output.write(request.getCommand().getBytes("GBK"));
  }
  output.flush();
 }
 /**
  * 序列化响应信息
  * @param output
  * @param response
  */
 public static void writeResponse(OutputStream output, Response response) throws IOException{
  //将response响应返回给客户端
  output.write(response.getEncode());
  //output.write(response.getResponseLength());直接write一个int类型会截取低8位传输丢弃高24位
  output.write(ByteUtils.int2ByteArray(response.getResponseLength()));
  if(Encode.UTF8 == response.getEncode()){
   output.write(response.getResponse().getBytes("UTF-8"));
  }else if(Encode.GBK == response.getEncode()){
   output.write(response.getResponse().getBytes("GBK"));
  }
  output.flush();
 }
}

七、ByteUtils类的实现

package com.binghe.utils;
/**
 * 字节转化工具类
 * @author binghe
 *
 */
public final class ByteUtils {
 /**
  * 将byte数组转化为int数字
  * @param bytes
  * @return
  */
 public static int byte2Int(byte[] bytes){
  int num = bytes[3] & 0xFF;
  num |= ((bytes[2] << 8) & 0xFF00);
  num |= ((bytes[1] << 16) & 0xFF0000);
  num |= ((bytes[0] << 24) & 0xFF000000);
  return num;
 }
 /**
  * 将int类型数字转化为byte数组
  * @param num
  * @return
  */
 public static byte[] int2ByteArray(int i){
  byte[] result = new byte[4];
  result[0]  = (byte)(( i >> 24 ) & 0xFF);
  result[1]  = (byte)(( i >> 16 ) & 0xFF);
  result[2]  = (byte)(( i >> 8 ) & 0xFF);
  result[3]  = (byte)(i & 0xFF);
  return result;
 }
}

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