Http些许己见

一，什么是Http协议：

超文本传输协议（Http-Hypertext-tranfer-protocal），定义了浏览器（即万维网客户端进程）怎样向万维网服务器请求万维网文档，以及服务器怎样

把文档传递给浏览器。从层次的角度来看，Http协议是应用层的协议，它是万维网上可靠的交换文件（文字，图片，音频等各种媒体文件）的基础。

二，http协议的工作流程：

1，客户端与服务端建立连接。

2，客户端向服务发送请求 ，请求格式：url(统一资源标示符，http(协议)://www.baidu.com（对应主机地址的域名）/search/error.html（接口）)。

3，服务器收到请求后，给予相应的响应。

4，客户端接收到服务响应信息后，断开连接。

（一句话概括就是：客户端请求数据，服务端响应数据。也是个无状态的协议）

三，http协议的特点：

1，支持客户端/服务端模式

2，简单快捷：客户端向服务端请求服务时，只需要传送请求方法和路径。同时由于Http协议的简单，使得服务端的程序规模小，因而通讯速度很快。

3，灵活：Http协议允许传输任意类型的数据对象，正在传输的数据类型由Content-type标记

4，无连接：限制每次连接只处理一个请求。

5，无状态：Http协议是无状态协议。意味着后续请求需要前面的信息，它需要重传。

四，http1.1与Http1.0的区别：

http1.0时，每次连接断开后Tcp/Ip连接也会断开，Tcp/Ip连接不能复用，Http1.1则可以复用Tcp/Ip连接，减少了三次握手，提高效率。

Http1.1在Request里面增加了一个Host域。

Android中HttpURLConnection的应用。

加载一张图片：

package com.wang.demo_android;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.os.Handler;
import android.util.Log;
import android.webkit.WebView;
import android.widget.ImageView;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;


public class HttpThread extends Thread{
    
    private WebView webView;
    private ImageView imageView;
    
    private Handler handler;
    private String url;
    
    public HttpThread(String url,WebView webView,Handler handler) {
        this.url = url;
        this.webView = webView;
        this.handler = handler;
    }
    
    public HttpThread(String url,ImageView imageView,Handler handler){
        this.url = url;
        this.imageView = imageView;
        this.handler = handler;
    }
    
    StringBuffer html =null;
    @Override
    public void run() {
        LoadImg();
    }
    
    private void loadHtml(){
        URL HttpUrl = null;
        try {
            HttpUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) HttpUrl.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            html = new StringBuffer();
            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String str;
            while( (str=reader.readLine())!=null){
                html.append(str);
            }
            handler.post(new Runnable() {
                
                @Override
                public void run() {
                   webView.loadData(html.toString(), "text/html;charset=utf-8", null);
                   Log.i("wangsongbin", "loadData");
                }
            });
        } catch (Exception e) {
            Log.i("wangsongbin", e.getMessage());
        }
        
    }
    
    private void LoadImg(){
        InputStream in = null;
        FileOutputStream fos = null;
        try {
            URL imgUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) imgUrl.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            in = conn.getInputStream();
            //判断SD卡是否挂载
            if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                //拿到sd卡的根目录
                File parent = new File(Environment.getExternalStorageDirectory().toString()+"/Alarms");
                String fileName = url.substring(url.lastIndexOf("/")+1);
                File file = new File(parent, fileName);
                Log.i("wangsongbin", file.getAbsolutePath());
                fos = new FileOutputStream(file);
                byte[] buf =new byte[2*1024];
                int len =0;
                while((len = in.read(buf))!= -1){
                    fos.write(buf, 0, len);
                };
                String customUrl = Environment.getExternalStorageDirectory().toString()+"/Alarms/"+fileName;
                final Bitmap bitmap = BitmapFactory.decodeFile(customUrl);
                handler.post(new Runnable() {
                    
                    @Override
                    public void run() {
                        imageView.setImageBitmap(bitmap);
                        
                    }
                });
                
            }
        } catch (Exception e) {
        }finally{
            try {
                in.close();
                fos.close();
            } catch (Exception e) {
                
            }
        }
        
    }

}

多线程下载图片：

package com.wang.demo_android.download;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.ImageView;

import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public class ImageLoader {
    
    private static String tag ="wangImgLoader";

    private Executor threadPool = Executors.newFixedThreadPool(3);

    private ImageView imageView;

    private static final int MSG_OK = 1;

    private String filePath;

    private Handler handler = new Handler() {
        int count = 0;

        public void handleMessage(android.os.Message msg) {

            switch (msg.what) {
                case MSG_OK:
                    count++;
                    Log.i(tag, "count:"+count);
                    if (count == 3) {
                        Bitmap bm = BitmapFactory.decodeFile(filePath);
                        imageView.setImageBitmap(bm);
                    }
                    break;
            }
        };
    };

    public ImageLoader(ImageView imageView) {
        this.imageView = imageView;
    }

    static class DownLoadImageRunnable implements Runnable {

        private String url;

        private long start;

        private long end;

        private String fileName;

        private Handler handler;

        public DownLoadImageRunnable(String url, long start, long end, String fileName,
                Handler handler) {
            this.url = url;
            this.start = start;
            this.end = end;
            this.fileName = fileName;
            this.handler = handler;
        }

        @Override
        public void run() {
            try {
                URL httpURL = new URL(url);
                HttpURLConnection conn = (HttpURLConnection) httpURL.openConnection();
                conn.setReadTimeout(5000);
                conn.setRequestProperty("Range", "bytes=" + start + "-" + end);// 这是分段请求的关键
                conn.setRequestMethod("GET");
                conn.setDoInput(true);
                InputStream in = conn.getInputStream();
                Log.i(tag, Environment.getExternalStorageState()+" ++ "+Environment.MEDIA_MOUNTED);
                Log.i(tag, "sdcard is useful");
                File file = new File(fileName);
                RandomAccessFile out = new RandomAccessFile(file, "rwd");// 可读，可写，可操作
                out.seek(start);
                int len = 0;
                byte[] buf = new byte[2 * 1024];
                while ((len = in.read(buf)) != -1) {
                    out.write(buf, 0, len);
                }
                if (in != null) {
                    in.close();
                }
                if (out != null) {
                    out.close();
                }
                Message msg = new Message();
                msg.what = MSG_OK;
                handler.sendMessage(msg);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }

    private static String getFileName(String url) {
        if (url != null) {
            return url.substring(url.lastIndexOf("/") + 1);
        }
        return null;
    }

    /**
     * 根据url加载一张图片
     * @param url
     */
    public void downLoadFile(String url) {
        try {
            URL httpURL = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) httpURL.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            long count = conn.getContentLength();
            long block = count / 3;
            long start = 0;
            long end = 0;
            String fileName = getFileName(url);
            File parent = Environment.getExternalStorageDirectory();
            File file = new File(parent, fileName);
            filePath = file.getAbsolutePath();
            Log.i(tag, "filePath"+filePath);
            for (int i = 0; i < 3; i++) {
                start = i * block;
                end = (i+1) * block;
                if (i == 2) {
                    end = count;
                }
                DownLoadImageRunnable runnalbe = new DownLoadImageRunnable(url, start, end,
                        filePath, handler);
                threadPool.execute(runnalbe);
            }

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

上传图片：

package com.wang.demo_android.download;

import cz.msebera.android.httpclient.HttpResponse;
import cz.msebera.android.httpclient.client.HttpClient;
import cz.msebera.android.httpclient.client.methods.HttpPost;
import cz.msebera.android.httpclient.impl.client.DefaultHttpClient;
import cz.msebera.android.httpclient.util.EntityUtils;

import android.os.Handler;
import android.util.Log;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class UploadThread extends Thread {

    private String url;

    private String fileName;
    
    private TextView tv_show;
    
    private Handler handler;
    
    public UploadThread(String url,String fileName,TextView tv_show,Handler handler) {
        this.url = url;
        this.fileName = fileName;
        this.tv_show = tv_show;
        this.handler = handler;
    }

    @Override
    public void run() {
        upLoad();
    }

    private void upLoad() {
        String boundary = "---------------------------7df2e821c0374";
        String prefix = "--";
        String end = "\r\n";
        // Content-Type
        // multipart/form-data;boundary=---------------------------7df2e821c0374
        // -----------------------------7df2e821c0374
        // ---------------------------7df2e821c0374--
        try {
            URL httpUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) httpUrl.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
            DataOutputStream out = new DataOutputStream(conn.getOutputStream());
            out.writeBytes(prefix + boundary + end);// 边界
            out.writeBytes("Content-Disposition: form-data; "+
            "name=\"file\"; filename=\""
                    + "shamo.jpg" + "\""+end);
            out.writeBytes("Content-Type: image/jpeg"+end+end);
            //编写实体数据
            FileInputStream fis =new FileInputStream(new File(fileName));
            byte[] buf = new byte[4*1024];
            int len = 0;
            while((len=fis.read(buf))!=-1){
                out.write(buf, 0, len);
            }
            out.writeBytes(end);
            out.writeBytes(prefix+boundary+prefix+end);//这个与iE上监听的不符
            out.flush();
            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            final StringBuffer sb = new StringBuffer();
            String str = "";
            while((str=in.readLine())!=null){
                sb.append(str);
            }
            handler.post(new Runnable() {
                
                @Override
                public void run() {
                    tv_show.setText(sb.toString());
                }
            });
            if(out!=null){
                out.close();
            }
            if(in!=null){
                in.close();
            }
            Log.i("wangFile", "has uploaded");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

Android中HttpClient的使用：

1，Google官方已经不再推荐使用HttpClient而推荐使用OkHttpClient,所以最新版本的SDK中已经删除了一些HttpClient的相关APi。

如果你仍然想要使用HttpClient，请下载jar（Http-4.3.6）：下载