webapi 接口传输图片数据流

java ,http协议接口，安卓客户端post请求服务端，服务端如何向客户端返回图片数据流（图形验证码）

package com.tz.controller;

import org.apache.commons.io.IOUtils;
import org.apache.struts2.ServletActionContext;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Random;

@Controller
@RequestMapping("/login")
public class loginController {

@RequestMapping(value = "/validation")
@ResponseBody
public String validation() throws IOException {

    String sRand = "";
    // 在内存中创建图象
    int width = 60, height = 20;
    BufferedImage image = new BufferedImage(width, height,
            BufferedImage.TYPE_INT_RGB);
    // 获取图形上下文
    Graphics g = image.getGraphics();
    // 生成随机类
    Random random = new Random();
    // 设定背景色
    g.setColor(getRandColor(200, 250));
    g.fillRect(0, 0, width, height);
    // 设定字体
    g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
    // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
    g.setColor(getRandColor(160, 200));
    for (int i = 0; i < 155; i++) {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(12);
        int yl = random.nextInt(12);
        g.drawLine(x, y, x + xl, y + yl);
    }
    // 取随机产生的认证码(4位数字)
    for (int i = 0; i < 4; i++) {
        String rand = String.valueOf(random.nextInt(10));
        sRand += rand;
        // 将认证码显示到图象中
        g.setColor(new Color(20 + random.nextInt(110), 20 + random
                .nextInt(110), 20 + random.nextInt(110)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
        g.drawString(rand, 13 * i + 6, 16);
    }
    // 图象生效
    g.dispose();
    //处理响应
    HttpServletResponse resp = ServletActionContext.getResponse();
    resp.setContentType("image/jpeg;charset=UTF-8");
    //获得输入流
    ByteArrayOutputStream bs =new ByteArrayOutputStream();
    ImageOutputStream imOut = ImageIO.createImageOutputStream(bs);
    ImageIO.write(image,"jpg",imOut); //scaledImage1为BufferedImage，jpg为图像的类型
    InputStream is =new ByteArrayInputStream(bs.toByteArray());
    IOUtils.copy(is, resp.getOutputStream());

    //将数字存入session...


    return null;
}

private Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色
    Random random = new Random();
    if (fc > 255)
        fc = 255;
    if (bc > 255)
        bc = 255;
    int r = fc + random.nextInt(bc - fc);
    int g = fc + random.nextInt(bc - fc);
    int b = fc + random.nextInt(bc - fc);
    return new Color(r, g, b);
}

}

在页面上用一个img标签,src指向后台的一个控制器,代码如上,可以生成一个简单的验证码

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