triangleservlet.java

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// Fig. 5.02_02:  TriangleServlet.java
// 生成三角形的Servlet

package com.fatcat.webchart;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.awt.image.*;
import java.awt.*;
import com.sun.image.codec.jpeg.*;

public class TriangleServlet extends HttpServlet
{
  int[]TriangleXValues = new int[3];
  int[]TriangleYValues = new int[3];
  int alpha = 0; //等腰三角形的底角
  int baseLine = 0; //等腰三角形的底边长

  // 三角形的方向
  final int UP = 1, RIGHT = 2, DOWN = 3, LEFT = 4;

  // 三角形的绘制风格
  final int OUTLINE = 1, FILL = 2, MIXED = 3;

  Color fillColor = Color.BLACK; // 缺省的填充颜色
  Color outlineColor = Color.BLACK; //缺省的轮廓颜色

  public void drawTrigangle(int x, int y, int triangleDirection, int
                            triangleStryle, Graphics g)
  {
    // 计算偏移量
    int offset = (int)(baseLine / 2 * Math.tan(alpha * Math.PI / 180));

    // 计算三角形3个顶点的坐标
    switch (triangleDirection)
    {
      case 1:
        TriangleXValues[0] = x - baseLine / 2;
        TriangleYValues[0] = y;
        TriangleXValues[1] = x + baseLine / 2;
        TriangleYValues[1] = y;
        TriangleXValues[2] = x;
        TriangleYValues[2] = y - offset;
        break;

      case 2:
        TriangleXValues[0] = x;
        TriangleYValues[0] = y - baseLine / 2;
        TriangleXValues[1] = x;
        TriangleYValues[1] = y + baseLine / 2;
        TriangleXValues[2] = x + offset;
        TriangleYValues[2] = y;
        break;

      case 3:
        TriangleXValues[0] = x - baseLine / 2;
        TriangleYValues[0] = y;
        TriangleXValues[1] = x + baseLine / 2;
        TriangleYValues[1] = y;
        TriangleXValues[2] = x;
        TriangleYValues[2] = y + offset;
        break;

      case 4:
        TriangleXValues[0] = x;
        TriangleYValues[0] = y - baseLine / 2;
        TriangleXValues[1] = x;
        TriangleYValues[1] = y + baseLine / 2;
        TriangleXValues[2] = x - offset;
        TriangleYValues[2] = y;
        break;
    }

    // 根据三角形的坐标及风格进行绘制
    switch (triangleStryle)
    {
      case 1:
        g.setColor(outlineColor);
        g.drawPolygon(TriangleXValues, TriangleYValues, 3);
        break;

      case 2:
        g.setColor(fillColor);
        g.fillPolygon(TriangleXValues, TriangleYValues, 3);
        break;

      case 3:
        g.setColor(fillColor);
        g.fillPolygon(TriangleXValues, TriangleYValues, 3);
        g.setColor(outlineColor);
        g.drawPolygon(TriangleXValues, TriangleYValues, 3);
        break;
    }

  }

  public void setBaseLine(int baseLine)
  {
    this.baseLine = baseLine;
  }

  public void setAlpha(int alpha)
  {
    this.alpha = alpha;
  }

  public void setFillColor(Color fillColor)
  {
    this.fillColor = fillColor;
  }

  public void setOutlineColor(Color outlineColor)
  {
    this.outlineColor = outlineColor;
  }

  // 处理 HTTP get 请求
  public void doGet(HttpServletRequest request, HttpServletResponse response)
                    throws ServletException, IOException
  {

    // 清空缓冲区
    response.reset();

    // 注意这里的MIME类型
    response.setContentType("image/jpeg");

    // 创建一个 400X300 的图像
    int width = 400, height = 300;
    BufferedImage image = new BufferedImage(width, height,
      BufferedImage.TYPE_INT_RGB);

    // 得到图形环境对象 g
    Graphics g = image.getGraphics();

    Color oColor[] = new Color[5];
    oColor[0] = new Color(99, 99, 0);
    oColor[1] = new Color(255, 169, 66);
    oColor[2] = new Color(33, 255, 66);
    oColor[3] = new Color(33, 0, 255);
    oColor[4] = new Color(255, 0, 66);

    Color fColor[] = new Color[5];
    fColor[0] = Color.RED;
    fColor[1] = Color.BLUE;
    fColor[2] = Color.GREEN;
    fColor[3] = Color.ORANGE;
    fColor[4] = Color.CYAN;

    // 填充背景
    g.setColor(Color.WHITE);
    g.fillRect(0, 0, width, height);

    g.setColor(Color.BLACK);
    g.setFont(new Font("方正粗宋简体", Font.PLAIN, 30));
    g.drawString("随机生成三角形-Servlet版", 10, 35);

    int tempBaseLine = 100+(int)(Math.random() * 50);
    setBaseLine(tempBaseLine);

    int tempAlpha = 30+(int)(Math.random() * 30);
    setAlpha(tempAlpha);

    int tempOutlineColorIndex = (int)(Math.random() * 5);
    setOutlineColor(oColor[tempOutlineColorIndex]);

    int tempfillColorIndex = (int)(Math.random() * 5);
    setFillColor(fColor[tempfillColorIndex]);

    int tempDirection = 1+(int)(Math.random() * 4);
    int tempStyle = 1+(int)(Math.random() * 3);

    // 绘制三角形		
    drawTrigangle(180, 150, tempDirection, tempStyle, g);


    ServletOutputStream out = response.getOutputStream();
    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
    encoder.encode(image);
    out.close();
  }

  // 处理 HTTP post 请求, 和doGet一样
  public void doPost(HttpServletRequest request, HttpServletResponse response)
                     throws ServletException, IOException
  {
    doGet(request, response);
  }
}


/**************************************************************************
 * (C) Copyright 2004-2005 by Jingkui Zhong(钟京馗) and Huan Tang(唐桓).  *
 * All Rights Reserved.                                                   *
 *                                                                        *
 * DISCLAIMER: The authors of this code have used their                   *
 * best efforts in preparing the code. These efforts include the          *
 * development, research, and testing of the theories and programs        *
 * to determine their effectiveness. The authors and publisher make       *
 * no warranty of any kind, expressed or implied, with regard to these    *
 * programs or to the documentation contained in these codes. The authors *
 * shall not be liable in any event for incidental or consequential       *
 * damages in connection with, or arising out of, the furnishing,         *
 * performance, or use of these programs.                                 *
 **************************************************************************/