java web ----生成隨機驗證碼

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import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class RandImgResponse extends HttpServlet
{
private static final int WIDTH = 120;
private static final int HEIGHT = 35;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

//1.設置背景色
setBackGround(g);
//2.設置邊框
setBorder(g);
//3.換干擾線
drawNumLine(g);
//寫隨機數
drawRandomNum((Graphics2D)g);
//5.圖形寫給瀏覽器
response.setContentType("image/jpeg");
response.setDateHeader("expires", -1);
response.setHeader("Pragma", "no-cache");
response.setHeader("Cache-Control", "no-cache");
ImageIO.write(image, "jpg",response.getOutputStream());

}


private void drawNumLine(Graphics g)
{
g.setColor(Color.GREEN);
for (int i = 0; i < 5; i++)
{
int x1 = new Random().nextInt(WIDTH);
int y1 = new Random().nextInt(HEIGHT);

int x2 = new Random().nextInt(WIDTH);
int y2 = new Random().nextInt(HEIGHT);

g.drawLine(x1, y1, x2, y2);
}
}


private void drawRandomNum(Graphics2D g)
{
String st = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXY12345678790";
g.setColor(Color.RED);
g.setFont(new Font("宋體", Font.BOLD, 20));

int x = 10;
for (int i = 0; i < 4; i++)
{
int degree = new Random().nextInt()%30;//-30---30
String ch = st.charAt(new Random().nextInt(st.length()))+"";
g.rotate(degree*Math.PI/180, x, 20);
g.drawString(ch, x, 20);

g.rotate(-degree*Math.PI/180, x, 20);
x += 30;
}
}


private void setBorder(Graphics g)
{

g.setColor(Color.BLUE);
g.drawRect(1, 1, WIDTH-2, HEIGHT-2);

}
private void setBackGround(Graphics g)
{
g.setColor(Color.WHITE);
g.drawRect(0, 0, WIDTH, HEIGHT);
}


public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{


this.doGet(request, response);
}


}