使用 Java 類 實現Http協議

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Java 實現Http協議

HTTP協議屬於應用層協議，它構建於TCP和IP協議之上，處於TCP/IP協議架構層的頂端，所以，它不用處理下層協議間諸如丟包補發、握手及數據的分段及重新組裝等繁瑣的細節，使開發人員可以專註於應用業務。

協議是通信的規范，為瞭更好的理解HTTP協議，我們可以基於Java的Socket API接口，通過設計一個簡單的應用層通信協議，來簡單分析下協議實現的過程和細節。

在我們今天的示例程序中，客戶端會向服務端發送一條命令，服務端在接收到命令後，會判斷命令是否是“HELLO”，如果是“HELLO”， 則服務端返回給客戶端的響應為“hello”，否則，服務端返回給客戶端的響應為“bye bye”。

我們接下來用Java實現這個簡單的應用層通信協議，

一、協議請求的定義

協議的請求主要包括：編碼、命令和命令長度三個字段。

package com.binghe.params;
/**
 * 協議請求的定義
 * @author binghe
 *
 */
public class Request {
 /**
  * 協議編碼
  */
 private byte encode;
 
 /**
  * 命令
  */
 private String command;
 
 /**
  * 命令長度
  */
 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、響應協議的定義

協議的響應主要包括：編碼、響應內容和響應長度三個字段。

package com.binghe.params;

/**
 * 協議響應的定義
 * @author binghe
 *
 */
public class Response {
 /**
  * 編碼
  */
 private byte encode;
 
 /**
  * 響應內容
  */
 private String response;
 
 /**
  * 響應長度
  */
 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、編碼常量定義

編碼常量的定義主要包括UTF-8和GBK兩種編碼。

package com.binghe.constant;

/**
 * 常量類
 * @author binghe
 *
 */
public final class Encode {
 //UTF-8編碼
 public static final byte UTF8 = 1;
 //GBK編碼
 public static final byte GBK = 2;
}

四、客戶端的實現

客戶端先構造一個request請求，通過Socket接口將其發送到遠端，並接收遠端的響應信息，並構造成一個Response對象。

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;

/**
 * 客戶端代碼
 * @author binghe
 *
 */
public final class Client {
 public static void main(String[] args) throws IOException{
  //請求
  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();
  
  //發送請求
  ProtocolUtils.writeRequest(out, request);
  
  //讀取響應數據
  InputStream in = client.getInputStream();
  Response response = ProtocolUtils.readResponse(in);
  System.out.println("獲取的響應結果信息為: " + response.toString());
 }
}

五、服務端的實現

服務端接收客戶端的請求，根據接收命令的不同，響應不同的消息信息，如果是“HELLO”命令，則響應“hello”信息，否則響應“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端代碼
 * @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();
   //讀取請求數據
   InputStream input = client.getInputStream();
   Request request = ProtocolUtils.readRequest(input);
   System.out.println("收到的請求參數為: " + request.toString());
   OutputStream out = client.getOutputStream();
   //組裝響應數據
   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工具類的實現

ProtocolUtils的readRequest方法將從傳遞進來的輸入流中讀取請求的encode、command和commandLength三個參數，進行相應的編碼轉化，構造成Request對象返回。而writeResponse方法則是將response對象的字段根據對應的編碼寫入到響應的輸出流中。

有一個細節需要重點註意：OutputStream中直接寫入一個int類型，會截取其低8位，丟棄其高24位，所以，在傳遞和接收數據時，需要進行相應的轉化操作。

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;

/**
 * 協議工具類
 * @author binghe
 *
 */
public final class ProtocolUtils {
 /**
  * 從輸入流中反序列化Request對象
  * @param input
  * @return
  * @throws IOException
  */
 public static Request readRequest(InputStream input) throws IOException{
  //讀取編碼
  byte[] encodeByte = new byte[1];
  input.read(encodeByte);
  byte encode = encodeByte[0];
  
  //讀取命令長度
  byte[] commandLengthBytes = new byte[4];
  input.read(commandLengthBytes);
  int commandLength = ByteUtils.byte2Int(commandLengthBytes);
  
  //讀取命令
  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");
  }
  //組裝請求返回
  Request request = new Request(encode, command, commandLength);
  return request;
 }
 /**
  * 從輸入流中反序列化Response對象
  * @param input
  * @return
  * @throws IOException
  */
 public static Response readResponse(InputStream input) throws IOException{
  //讀取編碼
  byte[] encodeByte = new byte[1];
  input.read(encodeByte);
  byte encode = encodeByte[0];
  
  //讀取響應長度
  byte[] responseLengthBytes = new byte[4];
  input.read(responseLengthBytes);
  int responseLength = ByteUtils.byte2Int(responseLengthBytes);
  
  //讀取命令
  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");
  }
  //組裝請求返回
  Response resp = new Response(encode, response, responseLength);
  return resp;
 }
 
 /**
  * 序列化請求信息
  * @param output
  * @param response
  */
 public static void writeRequest(OutputStream output, Request request) throws IOException{
  //將response響應返回給客戶端
  output.write(request.getEncode());
  //output.write(response.getResponseLength());直接write一個int類型會截取低8位傳輸丟棄高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();
 }
 /**
  * 序列化響應信息
  * @param output
  * @param response
  */
 public static void writeResponse(OutputStream output, Response response) throws IOException{
  //將response響應返回給客戶端
  output.write(response.getEncode());
  //output.write(response.getResponseLength());直接write一個int類型會截取低8位傳輸丟棄高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類的實現

package com.binghe.utils;

/**
 * 字節轉化工具類
 * @author binghe
 *
 */
public final class ByteUtils {
 /**
  * 將byte數組轉化為int數字
  * @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;
 }
 
 /**
  * 將int類型數字轉化為byte數組
  * @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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