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();
		}
	}
}

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);
	}

}

<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>

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

6.页面中生成的二维码