这样的程序为什么不能得到输出?大家来看看(程序不长!!)在线......

jackal81 2003-10-08 11:07:50

bean程序:

package com.lingnan;

import java.awt.Insets;
import java.awt.Font;
import java.io.PrintWriter;
import javax.servlet.http.HttpSession;
import org.jfree.data.*;
import org.jfree.chart.*;
import org.jfree.chart.plot.*;
import org.jfree.chart.entity.*;
import org.jfree.chart.urls.*;
import org.jfree.chart.servlet.*;
import org.jfree.chart.labels.StandardPieToolTipGenerator;

public class W {
private DefaultPieDataset data = new DefaultPieDataset();

public void setValue(){
data.setValue("联想", 27.3);
data.setValue("长城", 12.2);
data.setValue("海尔", 5.5);
data.setValue("美的", 17.1);
data.setValue("松下", 9.0);
data.setValue("科龙", 19.0);
}

public String generatePieChart(String title, HttpSession session, PrintWriter pw) {
String filename = null;
try {
//创建chart对象
PiePlot plot = new PiePlot(data);
plot.setInsets(new Insets(0, 5, 5, 5));
//在统计图片上建连结
plot.setURLGenerator(new StandardPieURLGenerator("link.jsp","section"));
plot.setToolTipGenerator(new StandardPieToolTipGenerator());
JFreeChart chart = new JFreeChart("", JFreeChart.DEFAULT_TITLE_FONT, plot, true);

chart.setBackgroundPaint(java.awt.Color.white);//设置图片的背景色

Font font = new Font("黑体",Font.CENTER_BASELINE,20);//设置图片标题的字体大小

TextTitle title = new TextTitle(title);
title.setFont(font);
chart.setTitle(title);

//把生成的图片放到临时目录
ChartRenderingInfo info = new ChartRenderingInfo(new StandardEntityCollection());
//500是图片长度，300是图片高度
filename = ServletUtilities.saveChartAsPNG(chart, 500, 300, info, session);

ChartUtilities.writeImageMap(pw, filename, info);
pw.flush();

} catch (Exception e) {
System.out.println("Exception - " + e.toString());
e.printStackTrace(System.out);
filename = "public_error_500x300.png";
}
return filename;
}
}

jsp程序:

<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import = "java.io.PrintWriter" %>
<%@ page import="com.lingnan.W"%>
<%

W chart = new W();
chart.setValue();
;

String filename = chart.generatePieChart("www.SenTom.net 网站访问统计表", session, new

PrintWriter(out));
String graphURL = request.getContextPath() + "/servlet/DisplayChart?filename=" + filename;

%>
<HTML>
<HEAD>
<TITLE>www.sentom.net</TITLE>
</HEAD>
<BODY>
<P ALIGN="CENTER">
<img src="<%= graphURL %>" width=500 height=300 border=0 usemap="#<%=filename%>">
</P>
</BODY>
</HTML>

这是一个例子程序,改动也不大,为什么在网页上输出一个大白框而不见图片,是servlet问题吗?大家给点意见..

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jackal81 2003-10-08

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牛X
你做过jfreechart吧留个联系方式,可以吗?

mtou 2003-10-08

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web.xml文件的配置

<web-app>
<servlet>
<servlet-name>DisplayChart</servlet-name>
<servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DisplayChart</servlet-name>
<url-pattern>/servlet/DisplayChart</url-pattern>
</servlet-mapping>
</web-app>

mtou 2003-10-08