请教ActionForm里面定义FormFile出现OutOfMemoryErro

因为要做Upload功能，我在ActionForm里面定义了FormFile的属性。 这个Form里面有一个SELECT,是multiple, 我选了300多笔 ,点确认后没有进入Action里面,而是直接报错,报错的内容为:
java.lang.OutOfMemoryError: Java heap space
java.io.ByteArrayOutputStream.<init>(ByteArrayOutputStream.java:59)
org.apache.commons.fileupload.DeferredFileOutputStream.<init>(DeferredFileOutputStream.java:131)
org.apache.commons.fileupload.DefaultFileItem.getOutputStream(DefaultFileItem.java:558)
org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:406)
org.apache.struts.upload.CommonsMultipartRequestHandler.handleRequest(CommonsMultipartRequestHandler.java:193)
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:443)
org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:804)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:203)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
请问有哪位遇到过这种情况,怎样么解决,谢谢!另外我用的是TOMCAT.