生成二维码

  在java中生成的二维码不存到磁盘里要直接输出到页面上，这就需要把生成的二维码直接以流的形式输出到页面上，我用的是myeclipse 和 tomcat

它的原理是：在加载页面时，根据img的src(code.jspx)找到对应的servlet(CodeServlet)，在servlet中编辑二维码中的内容，调用生成二维码的类EncoderHandler中的encoderQRcoder方法

1.首先要导入jar包（将jar包放到lib目录下）

      导入jar包的名称为：Qrcode_swetake 

     下载jar包的连接http://download.csdn.net/detail/huakaihualuo1223/4527504 

2.在java中生成二维码并以流的形式输出

package com.kaishengit.util;  
  
import java.awt.Color;  
import java.awt.Graphics2D;  
import java.awt.image.BufferedImage;  
  
import javax.imageio.ImageIO;  
import javax.servlet.http.HttpServletResponse;  
  
import com.swetake.util.Qrcode;  
  
  
public class EncoderHandler {  
      
    public void encoderQRCoder(String content, HttpServletResponse response) {  
        try {  
            Qrcode handler = new Qrcode();  
            handler.setQrcodeErrorCorrect('M');  
            handler.setQrcodeEncodeMode('B');  
            handler.setQrcodeVersion(7);  
              
            System.out.println(content);  
            byte[] contentBytes = content.getBytes("UTF-8");  
              
            BufferedImage bufImg = new BufferedImage(80, 80, BufferedImage.TYPE_INT_RGB);  
              
            Graphics2D gs = bufImg.createGraphics();  
              
            gs.setBackground(Color.WHITE);  
            gs.clearRect(0, 0, 140, 140);  
              
            //设定图像颜色：BLACK  
            gs.setColor(Color.BLACK);  
              
            //设置偏移量  不设置肯能导致解析出错  
            int pixoff = 2;  
            //输出内容：二维码  
            if(contentBytes.length > 0 && contentBytes.length < 124) {  
                boolean[][] codeOut = handler.calQrcode(contentBytes);  
                for(int i = 0; i < codeOut.length; i++) {  
                    for(int j = 0; j < codeOut.length; j++) {  
                        if(codeOut[j][i]) {  
                            gs.fillRect(j * 3 + pixoff, i * 3 + pixoff,3, 3);  
                        }  
                    }  
                }  
            } else {  
                System.err.println("QRCode content bytes length = " + contentBytes.length + " not in [ 0,120 ]. ");  
            }  
              
            gs.dispose();  
            bufImg.flush();  
              
              
              
            //生成二维码QRCode图片  
            ImageIO.write(bufImg, "jpg", response.getOutputStream());  
              
              
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
}  

3.建立一个servlet

package com.kaishengit.web;  
  
  
import java.io.IOException;  
  
import javax.servlet.ServletException;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
  
import com.kaishengit.util.EncoderHandler;  
  
public class CodeServlet extends HttpServlet {  
  
    private static final long serialVersionUID = 1L;  
      
    @Override  
    protected void service(HttpServletRequest requset, HttpServletResponse response)  
            throws ServletException, IOException {  
        String content = "姓名:maysnow 电话:123687495";  
        EncoderHandler encoder = new EncoderHandler();  
        encoder.encoderQRCoder(content, response);  
    }  
  
}  

4在web.xml中的配置

<servlet>  
    <servlet-name>CodeService</servlet-name>  
    <servlet-class>com.kaishengit.web.CodeServlet</servlet-class>  
  </servlet>  
  <servlet-mapping>  
    <servlet-name>CodeService</servlet-name>  
    <url-pattern>/code.jspx</url-pattern>  
  </servlet-mapping>

5.jsp中的img(其中img的src为对应的CodeServlet的url)

<img  style="height:80px;80px" src="code.jspx" />