简单的jfreechart的例子，没显示出来

Question

saveChartAsPNG?用writeChartAsJPEG试试。查一下指定目录下有没有生成相应图片文件。如果生成直接用浏览器的缩略图看有没有图象。如果有图象，则说明生成图片成功。

Answer 1

<img src="/servlet/DisplayChart?filename=jfreechart-48978.png" width=500 height=300 border=0 usemap="#jfreechart-48978.png"> 这是网页执行后的代码request.getContextPath()怎么会什么都没取到呢？src="/servlet/DisplayChart?filename=jfreechart-48978.png"  这个文件是生成在哪呢？

Answer 2

writeChartAsJPEG这个方法的参数和saveChartAsPNG是一样的吗？也是这个类的方法吗？

Answer 3

你要在web.xml文件中做配置
  <servlet>
    <servlet-name>DisplayChart</servlet-name>
    <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
  </servlet>
  <servlet>
  <servlet-mapping>
    <servlet-name>DisplayChart</servlet-name>
    <url-pattern>/servlet/DisplayChart</url-pattern>
  </servlet-mapping>
这样才可以，我记得在配置时还要注意servlet的顺序

Answer 4

saveChartAsJPEG
public static java.lang.String saveChartAsJPEG(JFreeChart chart,
                                               int width,
                                               int height,
                                               ChartRenderingInfo info,
                                               javax.servlet.http.HttpSession session)
                                        throws java.io.IOExceptionSaves the chart as a JPEG format file in the temporary directory and populates the ChartRenderingInfo object which can be used to generate an HTML image map. Parameters:
chart - the chart to be saved (null not permitted).
width - the width of the chart
height - the height of the chart
info - the ChartRenderingInfo object to be populated
session - the HttpSession of the client 
Returns:
the filename of the chart saved in the temporary directory 
Throws: 
java.io.IOException - if there is a problem saving the file.

Answer 5

在web.xml文件中加入以下内容后重启tomcat就可以了
  <servlet>
    <servlet-name>DisplayChart</servlet-name>
    <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
  </servlet>
  <servlet>
  <servlet-mapping>
    <servlet-name>DisplayChart</servlet-name>
    <url-pattern>/servlet/DisplayChart</url-pattern>
  </servlet-mapping>

Answer 6

不好意思，打错了，因该市
 <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>

Answer 7

我的一个web.xml:<?xml version="1.0"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd"><web-app>
<display-name>QM</display-name>
<servlet>
<servlet-name>webwork</servlet-name>
<servlet-class>com.opensymphony.webwork.dispatcher.ServletDispatcher</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>webwork</servlet-name>
<url-pattern>*.action</url-pattern>
</servlet-mapping>       <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>
<taglib>
<taglib-uri>webwork</taglib-uri>
<taglib-location>/WEB-INF/lib/webwork-2.1.jar</taglib-location>
</taglib>        <taglib>
<taglib-uri>http://displaytag.sourceforge.net/</taglib-uri>
<taglib-location>/WEB-INF/displaytag-11.tld</taglib-location>
</taglib>
       <welcome-file-list>
              <welcome-file>index.jsp</welcome-file>
              <welcome-file>default.jsp</welcome-file>
              <welcome-file>index.html</welcome-file>
      </welcome-file-list>        <resource-ref>
          <description>Oracle Datasource example</description>
          <res-ref-name>DS_SOP</res-ref-name>
          <res-type>javax.sql.DataSource</res-type>
          <res-auth>Container</res-auth>
       </resource-ref>
 
</web-app>