原因：首先,JFreeChart和中文驗證碼的亂碼問題和jsp的編碼無關,是由于Java虛擬機找不到字體文件造成的,所以同類的Swing或者AWT的中文亂碼問題也適用

環境:
JDK1.5(JDK版本很重要,如果是1.4.2版本的話,JRE目錄下的字體配置文件不大一樣)
RedHat4.0
Tomcat5.0

解決方法:
1.確認%JavaHome%/jre/lib/fonts目錄下存在zysong.ttf
2.在%JavaHome%/jre/lib/fonts目錄下執行"ttmkfdir -o fonts.dir"命令,重新生成fonts.dir文件
3.確認/usr/share/fonts/zh_CN/TrueType目錄存在,如果不存在則mkdir創建
4.確認/usr/share/fonts/zh_CN/TrueType目錄下存在zysong.ttf
5.在%JavaHome%/jre/lib目錄下,執行 cp fontconfig.RedHat.3.properties.src fontconfig.properties
6.重新啟動tomcat,大功告成!

下面提供下載字體

http://www.javaeye.com/topics/download/0cc6d142-fc8a-466a-921c-158c6732e635

在windows下開發的web項目，移植到linux或unix系統下，常導致一些亂碼問題，主要是jdk1.5的漢字字體linux和unix支持得不夠充分。
     解決方案：拷貝windows的simsun.ttc 到java安裝目錄的字體目錄下，改名為simsun.ttf
服務器上的目錄為/opt/jdk1.5.0_02/jre/lib/fonts
然后修改fonts.dir為這樣,實際上就是設置為不管什么字體都用簡宋體,包括英文
48
simsun.ttf -b&h-lucidabright-medium-r-normal--0-0-0-0-p-0-iso8859-1
simsun.ttf -b&h-lucidabright-medium-i-normal--0-0-0-0-p-0-iso8859-1
simsun.ttf -b&h-lucidabright-demibold-r-normal--0-0-0-0-p-0-iso8859-1
simsun.ttf -b&h-lucidabright-demibold-i-normal--0-0-0-0-p-0-iso8859-1
simsun.ttf -b&h-lucidasans-medium-r-normal-sans-0-0-0-0-p-0-iso8859-1
simsun.ttf -b&h-lucidasans-bold-r-normal-sans-0-0-0-0-p-0-iso8859-1
simsun.ttf -b&h-lucidatypewriter-medium-r-normal-sans-0-0-0-0-m-0-iso8859-1
simsun.ttf -b&h-lucidatypewriter-bold-r-normal-sans-0-0-0-0-m-0-iso8859-1
simsun.ttf -b&h-lucidabright-medium-r-normal--0-0-0-0-p-0-iso8859-2
simsun.ttf -b&h-lucidabright-medium-i-normal--0-0-0-0-p-0-iso8859-2
simsun.ttf -b&h-lucidabright-demibold-r-normal--0-0-0-0-p-0-iso8859-2
simsun.ttf -b&h-lucidabright-demibold-i-normal--0-0-0-0-p-0-iso8859-2
simsun.ttf -b&h-lucidasans-medium-r-normal-sans-0-0-0-0-p-0-iso8859-2
simsun.ttf -b&h-lucidasans-bold-r-normal-sans-0-0-0-0-p-0-iso8859-2
simsun.ttf -b&h-lucidatypewriter-medium-r-normal-sans-0-0-0-0-m-0-iso8859-2
simsun.ttf -b&h-lucidatypewriter-bold-r-normal-sans-0-0-0-0-m-0-iso8859-2
simsun.ttf -b&h-lucidabright-medium-r-normal--0-0-0-0-p-0-iso8859-4
simsun.ttf -b&h-lucidabright-medium-i-normal--0-0-0-0-p-0-iso8859-4
simsun.ttf -b&h-lucidabright-demibold-r-normal--0-0-0-0-p-0-iso8859-4
simsun.ttf -b&h-lucidabright-demibold-i-normal--0-0-0-0-p-0-iso8859-4
simsun.ttf -b&h-lucidasans-medium-r-normal-sans-0-0-0-0-p-0-iso8859-4
simsun.ttf -b&h-lucidasans-bold-r-normal-sans-0-0-0-0-p-0-iso8859-4
simsun.ttf -b&h-lucidatypewriter-medium-r-normal-sans-0-0-0-0-m-0-iso8859-4
simsun.ttf -b&h-lucidatypewriter-bold-r-normal-sans-0-0-0-0-m-0-iso8859-4
simsun.ttf -b&h-lucidabright-medium-r-normal--0-0-0-0-p-0-iso8859-5
simsun.ttf -b&h-lucidabright-medium-i-normal--0-0-0-0-p-0-iso8859-5
simsun.ttf -b&h-lucidabright-demibold-r-normal--0-0-0-0-p-0-iso8859-5
simsun.ttf -b&h-lucidabright-demibold-i-normal--0-0-0-0-p-0-iso8859-5
simsun.ttf -b&h-lucidasans-medium-r-normal-sans-0-0-0-0-p-0-iso8859-5
simsun.ttf -b&h-lucidasans-bold-r-normal-sans-0-0-0-0-p-0-iso8859-5
simsun.ttf -b&h-lucidatypewriter-medium-r-normal-sans-0-0-0-0-m-0-iso8859-5
simsun.ttf -b&h-lucidatypewriter-bold-r-normal-sans-0-0-0-0-m-0-iso8859-5
simsun.ttf -b&h-lucidabright-medium-r-normal--0-0-0-0-p-0-iso8859-7
simsun.ttf -b&h-lucidabright-medium-i-normal--0-0-0-0-p-0-iso8859-7
simsun.ttf -b&h-lucidabright-demibold-r-normal--0-0-0-0-p-0-iso8859-7
simsun.ttf -b&h-lucidabright-demibold-i-normal--0-0-0-0-p-0-iso8859-7
simsun.ttf -b&h-lucidasans-medium-r-normal-sans-0-0-0-0-p-0-iso8859-7
simsun.ttf -b&h-lucidasans-bold-r-normal-sans-0-0-0-0-p-0-iso8859-7
simsun.ttf -b&h-lucidatypewriter-medium-r-normal-sans-0-0-0-0-m-0-iso8859-7
simsun.ttf -b&h-lucidatypewriter-bold-r-normal-sans-0-0-0-0-m-0-iso8859-7
simsun.ttf -b&h-lucidabright-medium-r-normal--0-0-0-0-p-0-iso8859-9
simsun.ttf -b&h-lucidabright-medium-i-normal--0-0-0-0-p-0-iso8859-9
simsun.ttf -b&h-lucidabright-demibold-r-normal--0-0-0-0-p-0-iso8859-9
simsun.ttf -b&h-lucidabright-demibold-i-normal--0-0-0-0-p-0-iso8859-9
simsun.ttf -b&h-lucidasans-medium-r-normal-sans-0-0-0-0-p-0-iso8859-9
simsun.ttf -b&h-lucidasans-bold-r-normal-sans-0-0-0-0-p-0-iso8859-9
simsun.ttf -b&h-lucidatypewriter-medium-r-normal-sans-0-0-0-0-m-0-iso8859-9

最后重起服務。