java上传文件时tomcat崩溃

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在项目中，我用到的tomcat是5.5的，在linux上跑。最近发现在上传文件时，如果连续上传10个左右，就会出现tomcat崩溃的情况。JVM的内存我已经设置成为512M的了。现将代码分别贴出，请各位看一看：(是SSH架构的)

jsp:

<form action="tArenamessage.do" name="tArenamemessageForm" id="tArenamemessageForm" method="POST"  enctype="multipart/form-data" >
...
<input type="file" name="file1" />
<input type="file" name="file2" />
<input type="file" name="file3" />
....
/form>

===============================

struts.xml:

<form-bean name="TArenamemessageForm" type="org.apache.struts.validator.DynaValidatorForm">
  <form-property name="name"  type="java.lang.String" />
  ...
  <form-property name="file1"  type="org.apache.struts.upload.FormFile" />
  <form-property name="file2"  type="org.apache.struts.upload.FormFile" />
  <form-property name="file3"  type="org.apache.struts.upload.FormFile" />
</form>
<!-- 场馆管理模块 -->
<action path="/tArenamessage"  scope="request" type="org.springframework.web.struts.DelegatingActionProxy" validate="false" name="TArenamemessageForm"  >
  <forward name="service" path="/../WEB-INF/jsp/admin/jsp/tArenamessage.jsp"> </forward>  
</action>

====================================

aciton:

//保存
public boolean setBeanValueByDynaActionForm(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response){
this.myExecute(mapping, form, request, response);
DynaActionForm hzForm = (DynaActionForm) form;
...
FormFile localfile = null;
//外景照片
localfile = (FormFile)hzForm.get("file1");
if(localfile!=null) {this.upload(localfile, request, 6L);}

localfile = (FormFile)hzForm.get("file2");
if(localfile!=null) {this.upload(localfile, request, 6L);}

localfile = (FormFile)hzForm.get("file3");
if(localfile!=null) {this.upload(localfile, request, 6L);}

...
}
//上传文件
private void upload(FormFile localfile,HttpServletRequest request,long flag){
String finalFileName="";
if(localfile!=null) {
    finalFileName = Upload.uploadAttachment( localfile , request);//上传文件
}
if(finalFileName != null && !finalFileName.equals("")){
uploadFile(localfile,request,finalFileName,flag);//保存到附件表
}
}

上传文件的类:
public class Upload {
public static String uploadAttachment( FormFile file , HttpServletRequest request){
    if( SystemGlobal.uploadAccess[0].toString().indexOf(file.getContentType())>=0 && file.getFileSize() <= ( 2048 * (Integer.parseInt( SystemGlobal.uploadAccess[1].toString()) ))){ //是图片并且小于?k
      String path = SystemGlobal.webDir(request) + SystemGlobal.uploadAccess[2] +  System.getProperty("file.separator") + StringUtil.date2String() +  System.getProperty("file.separator");
      File dir = new File(path);
      if(!dir.exists()){dir.mkdir();}
      String filename = "";
      if(!file.getFileName().equals("")){
      try{
filename = StringUtil.time2String() + StringUtil.ramdom(4)+ "." + file.getFileName().substring(file.getFileName().length()-3) ;
InputStream stream = file.getInputStream();
FileOutputStream output = new FileOutputStream( path + filename );
int len = -1;
byte[] buf = new byte[102400];
while((len = stream.read(buf)) != -1){
        output.write(buf,0,len);
}
output.close();
stream.close();
}catch(IOException e){Log.error( Upload.class , "upload write stream ha error:" + e);}
}
return filename;
}
return "";
}

==============================
tareamanage.hbm.xml  一对多，一个场馆可以有多个图片

<set name="TUploadfiles" inverse="false" cascade="save-update" fetch="subselect" lazy="false">
<cache usage="read-write"/>
    <key>
        <column name="OBJID" length="50" />
    </key>
    <one-to-many class="com.webaorta.comm.pojo.TUploadfile" />
</set>
         
====================================
大致上就是这些了，代码里是否存在不合理的地方而导致什么原因从而令到tomcat死掉了呢？tomcat里的logs也没有一点报错的信息可以看的。


后来我直接将其转换为open session in view模式，奇怪的是我在windows下可以运行(开发机),但在linux下就报session已经关闭这个错误的了。这又是为什么呢？（服务器是linux系统）.

请各位看一看吧，如果搞不好这个可能会丢饭碗的。谢谢大家了。