在线图片压缩后以ImageIO 流的形式 设置大小显示指定页面

1、Servlet 代码

public class ZoomImgServlet extends HttpServlet implements Servlet {

public void init(ServletConfig conf)throws ServletException {}
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
int width=352,height=233;//这是设置图片显示的宽和高
String srcImgPath=“http://pic.to8to.com/attch/day_160218/20160218_d968438a2434b62ba59dH7q5KEzTS6OH.png”;
resp.setDateHeader("Expires", 0L);
resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
resp.addHeader("Cache-Control", "post-check=0, pre-check=0");
resp.setHeader("Pragma", "no-cache");// 设置响应头信息，不缓存此内容
resp.setContentType("image/jpeg");
URL url = new URL(srcImgPath);
//打开链接
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
//设置请求方式为"GET"
conn.setRequestMethod("GET");
//超时响应时间为5秒
conn.setConnectTimeout(5 * 1000);
InputStream inStream = conn.getInputStream();
byte[] data = null;
ServletOutputStream out=null;
try {
data = readInputStream(inStream);
ByteArrayInputStream bin = new ByteArrayInputStream(data);
Image srcImg = ImageIO.read(bin);
BufferedImage buffImg = null;
buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
buffImg.getGraphics().drawImage(srcImg.getScaledInstance(width, height, Image.SCALE_SMOOTH), 0,0, null);
out = resp.getOutputStream();
ImageIO.write(buffImg, "PNG", out);
out.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
out.close();
}
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
super.doGet(req, resp);
}

private static byte[] readInputStream(InputStream inStream) throws Exception{
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
//创建一个Buffer字符串
byte[] buffer = new byte[1024];
//每次读取的字符串长度，如果为-1，代表全部读取完毕
int len = 0;
//使用一个输入流从buffer里把数据读取出来
while( (len=inStream.read(buffer)) != -1 ){
//用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度
outStream.write(buffer, 0, len);
}
//关闭输入流
inStream.close();
//把outStream里的数据写入内存
return outStream.toByteArray();
}
}

2、web.xml 配置

<servlet>
<servlet-name>zoomImgServlet</servlet-name>
<servlet-class>com.test.servlet.ZoomImgServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>zoomImgServlet</servlet-name>
<url-pattern>/zoomImg.jpg</url-pattern>
</servlet-mapping>

3、页面调用

<img src="${path}/zoomImg.jpg" />