三种读取网页上的图片方法，以及read() read(byte b)的使用

有人问这个问题，说实话我也就是从本地读读（难道和从网页尚读不一样吗？好像区别不大），就写了几个，中间也发现了不少问题。看代码把

package com;

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class TestInternet {
	Image image = null;
	public static void main(String args[]){
		TestInternet ti = new TestInternet();
		try {
			ti.getResource();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	public void getResource() throws IOException {
		String urlStr = "http://i3.itc.cn/20101008/394_06b5e5c1_d16a_48d2_9340_86b0c9292732_1.jpg";		
		URL url = new URL(urlStr);
		image = ImageIO.read(url);
		int width = image.getWidth(null);
		int height = image.getHeight(null);
		BufferedImage bi = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
		bi.getGraphics().drawImage(image, 0, 0, width , height, null); 
		FileOutputStream fos = new FileOutputStream(new File("myPic.jpg"));
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(fos);
		encoder.encode(bi); 
		fos.flush();
		fos.close();
		
	}

}

刚才又写了两种形式 上代码

package com;
import java.io.*;    
import java.net.MalformedURLException;    
import java.net.URL;    
   
   
public class DynamicGetURLImage {    
   
    /** 
      * @param args 
      */   
    public static void main(String[] args) {    
        // TODO Auto-generated method stub    
        try {    
            //图片的http全路径    
			String imgurl = "http://i3.itc.cn/20101008/394_06b5e5c1_d16a_48d2_9340_86b0c9292732_1.jpg"; 
			URL url = new URL(imgurl); 
			BufferedInputStream   in = new BufferedInputStream(url.openStream());    
			//保存的图片文件名    
			File img = new File("img.jpg");    
			BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(img));                   
            byte[] buf = new byte[2048];    
            int l = 0;
            int temp = 0;
            while( (l = in.read(buf)) != -1){  
            	temp =0;
            	temp += l;
                out.write(buf);
                 
             }
            System.out.println(temp);
             in.close();    
             out.close();    
         } catch (MalformedURLException e) {    
            // TODO Auto-generated catch block    
             e.printStackTrace();    
         } catch (IOException e) {    
            // TODO Auto-generated catch block    
             e.printStackTrace();    
         }    
            
     }    
   
}   

package com.yuanlai;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;


public class TestInternet {
	public static void main(String args[]){
		TestInternet ti = new TestInternet();
		try {
			ti.getResource();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	public void getResource() throws IOException {
		String urlStr = "http://i3.itc.cn/20101008/394_06b5e5c1_d16a_48d2_9340_86b0c9292732_1.jpg";
		int ResponseCode = 0;
		URL url = new URL(urlStr);
		HttpURLConnection connection = (HttpURLConnection) url.openConnection();
		connection.setRequestMethod("GET");
		connection.setConnectTimeout(2 * 1000);
		ResponseCode = connection.getResponseCode();
		System.out.println(ResponseCode);
		if (ResponseCode == 200) {
			InputStream inputStream = connection.getInputStream();
			byte[] b = readInputStream(inputStream);
			inputStream.close();
			System.out.println(b.length);
			FileOutputStream fos = new FileOutputStream(new File("myPic.jpg"));
			fos.write(b);
			fos.flush();
			fos.close();
		}
	}

	private byte[] readInputStream(InputStream inputStream) throws IOException {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		int l = -1;
		int temp = 0;
		byte [] by = new byte[1024];
		//int temp1 = inputStream.read(by);		
		/**
		while (temp1 != -1) {
			//baos.write(l);
			baos.write(by, 0, temp1);
			temp += l;
			temp1 = inputStream.read(by);
		}
		*/
		//read(byte[])是从输入流中读取一定数量的字节并将其存储在缓冲区数组 b 中
		//而read() 是读取下一个字节，
		while((l = inputStream.read(by)) >= 0){
			baos.write(by, 0, l);
		}
		return baos.toByteArray();
	}
}

看来得写个总结了，
第一种方式可以对图片进行操作，比如放大缩小什么的。
第二种比较简洁，适合做简单的应用的时候用，
第三种有点罗嗦，但你可以操作的东西比较多，比如connection对象等。


还有值得总结的地方就是关于read() 和read(byte[] b)
read() 指的是从输入流读取下一个数据字节。返回 0 到 255 范围内的 int 字节值。如果因已到达流末尾而没有可用的字节，则返回值 -1。
read(byte[]  b) 是开辟一块缓存区.“从输入流中读取一定数量的字节并将其存储在缓冲区数组 b 中。以整数形式返回实际读取的字节数”
read(b) 方法的效果等同于： read(b, 0, b.length)

注意判断的时候 要while((l = inputStream.read(by)) >= 0)  不能while((l = inputStream.read()) >= 0)