使用JSTL在Java bean的服务器上保存PNG文件 [英] Saving a PNG file on a server in a Java bean, using JSTL

问题描述

我在JSTL中写入一个更新页面，用户输入一些数字。然后我调用一个java bean - 将数字作为参数传递 - 使用JFreeChart创建一个PNG图像。所有这些都可以正常使用

ImageIO.write（myBufferedImage，png，新文件（C：/testChart.png））;

我也可以将图像保存到我的tomcat目录，并在我在本地主机上运行网站。但是，一旦这个代码在不是我的本地主机的服务器上，保存到tomcat目录将不起作用。我如何将这个文件直接写入服务器...到我的Eclipse项目的WebContent文件夹（其中的java bean在src文件夹中）？感谢您提前获得任何帮助。

解决方案

我建议您使用 ServletUtilities 类。它保存在java tempdir中，并在会话无效时进行清理。 :)然后显示文件的另一个提示是使用DisplayChart servlet来获取图像。
这在web.xml中

 < 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> 
  

然后，您如何使用jstl显示图像：

 < img src =< c：url value ='/ servlet / DisplayChart？'>< c：param name ='filename'value ='$ {yourFileNameHERE}'/>< / c：url> ALT = /> 
  

I am writing an update page in JSTL where the user inputs some numbers. I then call a java bean - passing the numbers as parameters - which, using JFreeChart, creates a PNG image. All of this works fine when I save the file directly on my hard drive using

ImageIO.write(myBufferedImage, "png", new File("C:/testChart.png"));

I can also save the image to my tomcat directory and view it when I am running the website on my localhost. However, once this code is up on a server that is not my local host, saving to the tomcat directory won't work. How do I write this file directly to the server..say to the WebContent folder of my Eclipse project (where the java bean is in the src folder)? Thanks in advance for any help.

解决方案

I would suggest that you use the ServletUtilities class. It saves in the java tempdir AND cleans up when the session is invalidated. :) Another hint for then displaying the file is to use the DisplayChart servlet to get your images. This goes in web.xml

      <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>

This is then how you display the image using jstl:

<img src="<c:url value='/servlet/DisplayChart?'><c:param name='filename' value='${yourFileNameHERE}' /></c:url>" alt=""/>

这篇关于使用JSTL在Java bean的服务器上保存PNG文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！