Jfreechart cannot automatically delete the generated image

In many cases, jfreechart cannot automatically delete the generated image as expected when the httpsession fails.

Analyze the original chartdeleter code

Public void valueunbound (httpsessionbindingevent event ){

Iterator iter = This. chartnames. listiterator ();
While (ITER. hasnext ()){
String filename = (string) ITER. Next ();
File file = new file (system. getproperty ("Java. Io. tmpdir"), filename );
If (file. exists ()){
File. Delete ();
}
}
Return;

}

The reason is that the path of the normally generated image is not always system. getproperty ("Java. Io. tmpdir ").

Solution:

Modify the original chartdeleter. Java file as follows:

...

Public chartdeleter (httpsession ){
Super ();
This. httpsession = httpsession;
}

Public void valueunbound (httpsessionbindingevent event ){

Iterator iter = This. chartnames. listiterator ();
While (ITER. hasnext ()){
String filename = (string) ITER. Next ();
File file = new file (this. httpsession. getservletcontext (). getrealpath ("/"), filename );
If (file. exists ()){
File. Delete ();
}
}
Return;

}

...

 

Modify servletutilities. Java as follows:

...

Public static string 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. gettempfileprefix ();
If (session = NULL ){
Prefix = servletutilities. gettemponetimefileprefix ();
}
File tempfile = file. createtempfile (prefix, ". PNG ",
New file (session. getservletcontext (). getrealpath ("/")));
Chartutilities. savechartaspng (tempfile, chart, width, height, Info );
If (session! = NULL ){
Servletutilities. registerchartfordeletion (tempfile, session );
}
Return tempfile. getname ();

}

...

The image is stored in the root directory of the project.

In fact, the more appropriate way is not to modify the source file, through inheritance, override method is a better choice.