jfreechart生成图片后如何保存在指定路径？？

[jxzsdlh]

jfreechart生成图片后

//======================开始输出图片
response.setContentType("image/jpeg");
OutputStream webOutput = response.getOutputStream();
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

//首先将图片转换为byte数组
byte[] imageContexts;
ByteArrayOutputStream imageContextsOutput = new ByteArrayOutputStream();
ImageIO.write(bufferImage,"JPEG",imageContextsOutput);
imageContexts = imageContextsOutput.toByteArray();
如何保存在指定路径？？？
求救！！！！！！

[hlandxy]

使用
ServletUtilities.saveChartAsPNG(JFreeChart chart, int width, int height,
ChartRenderingInfo info, HttpSession session) throws IOException {

if (chart == null) {
throw new IllegalArgumentException("Null 'chart' argument.");
}
ServletUtilities.createTempDir();
String prefix = ServletUtilities.tempFilePrefix;
if (session == null) {
prefix = ServletUtilities.tempOneTimeFilePrefix;
}
File tempFile = File.createTempFile(prefix, ".png",
new File(System.getProperty("java.io.tmpdir")));
ChartUtilities.saveChartAsPNG(tempFile, chart, width, height, info);
if (session != null) {
ServletUtilities.registerChartForDeletion(tempFile, session);
}
return tempFile.getName();
}
ServletUtilities.saveChartAsJPEG(JFreeChart chart, int width, int height, javax.servlet.http.HttpSession session)

方法生成图片.图片默认地址是tomcat/temp目录下，如要自定义路径 。请将红色部分该为自己的路径。

[hlandxy]

继承ServletUtilities类，重载或重写saveChartAsPNG或saveChartAsJPEG方法

[咬一口幸福7855]

这个方法返回值类型是String 吗，我的报错啊！