In Tomcat's 4.1.18, Excel is displayed in the client page. However, Excel displayed in Tomcat's 5.0.19 is garbled. I solved like this.
Open Web.xml
In these, the following code is added, and the Tomcat is restarted.
XLS extension> application / msexcel mime-type> mime-mapping>
It turns out that Tomcat does not recognize .XLS format :-)