这个动态图片的实现原理是在servlet的response中写入一个ImageOutputStream，并由servlet容器将其转成图片，在非webwork的实现中，可以直接操作response，但是在webwork中，要想直接操作response的output则必须使用不需要对response操作的result类型
实现一个Result：
不可以用普通的dispatcherResult在response的outputStream中写入东西，否则将覆盖所有的dispatcher的jsp页面
上次的代码忘记加上response的设置不缓存了，这样即使使用IE的回退也会刷新图片
private HttpSession session;
/**
* @see com.opensymphony.webwork.dispatcher.WebWorkResultSupport#doExecute(java.lang.String,
* com.opensymphony.xwork.ActionInvocation)
*/
@Override
protected void doExecute(String finalLocation, ActionInvocation invocation) throws Exception
{
HttpServletRequest request = (HttpServletRequest) invocation.getInvocationContext().get(
ServletActionContext.HTTP_REQUEST);
HttpServletResponse response = (HttpServletResponse) invocation.getInvocationContext().get(
ServletActionContext.HTTP_RESPONSE);
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
VerifyImage verify = new VerifyImage();
OutputStream os = response.getOutputStream();
String str = verify.GetImage(os);
session = request.getSession(true);
session.setAttribute("rand", str);
}
在xwork.xml中配置result-type：
<result-types>
<result-type name="image"
class="com.bnt.afp.action.verify.ImageResult"/>
</result-types>
添加一个生成图片的action：
<action name="imageAction"
class="com.bnt.afp.action.verify.ImageAction">
<result name="success" type="image"/>
</action>
在需要生成验证图片的地方这样调用：
<img border=0 src="imageAction.action">
ImageAction里只要简单的返回SUCCESS就可以了
public String execute() throws IOException
{
return SUCCESS;
}
VerifyImage中生成图片的方法：（来自网上一个JSP生成动态验证图片的实例）
//获取生成的图片,返回生成的验证码，并将ImageOutputStream写入
public String GetImage(OutputStream outputStream){
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
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);
}
String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
g.dispose();
try {
ImageIO.write(image, "JPEG", outputStream);
outputStream.flush();
return sRand;
} catch (IOException e) {
e.printStackTrace();
return "fail";
}
}
public Color getRandColor(int fc,int bc){
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);
}
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