jsp驗證碼代碼(1/4)

jsp教程驗證碼代碼

<%@ page contenttype="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
    <%!
    color getrandcolor(int fc,int bc){//給定範圍獲得隨機顏色
            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);
            }
    %>
    <%
    //設定頁面不緩衝
    response.setheader("pragma","no-cache");
    response.setheader("cache-control","no-cache");
    response.setdateheader("expires", 0);

    // 在記憶體中建立圖象
    int width=60, height=20;
    bufferedimage image = new bufferedimage(width, height, bufferedimage.type_int_rgb);

    // 擷取圖形上下文
    graphics g = image.getgraphics();

    //產生隨機類
    random random = new random();

    // 設定背景色
    g.setcolor(getrandcolor(200,250));
    g.fillrect(0, 0, width, height);

    //設定字型
    g.setfont(new font("times new roman",font.plain,18));

    //畫邊框
    //g.setcolor(new color());
    //g.drawrect(0,0,width-1,height-1);

    // 隨機產生155條幹擾線，使圖象中的認證碼不易被其它程式探測到
    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);
    }

    // 取隨機產生的認證碼(4位元字)
    string srand="";
    for (int i=0;i<4;i++){
        string rand=string.valueof(random.nextint(10));
        srand+=rand;
        // 將認證碼顯示到圖象中
        g.setcolor(new color(20+random.nextint(110),20+random.nextint(110),20+random.nextint(110)));//調用函數出來的顏色相同，可能是因為種子太接近，所以只能直接產生
        g.drawstring(rand,13*i+6,16);
    }

    // 將認證碼存入session
    session.setattribute("rand",srand);

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