线程安全java servlet
我需要知道以下代码在线程方面是否存在任何问题。我一直认为,只要不使用类级变量,线程就不是问题
public class UploadReferralImage extends HttpServlet
{
String CLASS_NAME = "UploadReferralImage";
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// Not handling Get, service must be invoked via Post.
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String METHOD_NAME = "doPost";
LogHelper.debug(PACKAGE_NAME, CLASS_NAME, METHOD_NAME, "Made it to the servlet");
String reply = upload(request);
response.setHeader("Content-Type", "text/xml");
response.getWriter().write(reply);
response.getWriter().flush();
response.getWriter().close();
}
public String upload(HttpServletRequest request)
{
String METHOD_NAME = "upload";
LogHelper.debug(PACKAGE_NAME, CLASS_NAME, METHOD_NAME, "Inside upload");
String replyMsg = "Unable to call ImageUpload";
try
{
ObjectInputStream inputFromApplet = new ObjectInputStream(request.getInputStream());
FileBean fBean = (FileBean) inputFromApplet.readObject();
inputFromApplet.close();
LogHelper.debug(PACKAGE_NAME, CLASS_NAME, METHOD_NAME, fBean.getFileName());
replyMsg = doImageUpload(fBean);
}
catch (IOException e)
{
e.printStackTrace();
replyMsg = "Exception :" + e.toString();
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
replyMsg = "Exception :" + e.toString();
}
return replyMsg;
}
private String doImageUpload(FileBean fBean)
{
//Save the file and return the response
SaveCaseClientAgent saveCaseClientAgent = new SaveCaseClientAgent();
saveCaseClientAgent.save(fBean);
}
# 1 楼答案
通常,servlet容器中只有一个servlet实例一次可重入地服务多个请求。因此,由于竞争条件,使用实例变量将事物从一个方法传递到另一个方法是baad的想法
最好(也是最简单)的解决方法是编写自己的“处理程序”类,每个请求实例化一次,然后将所有内容传递给它。在代码中,它看起来是这样的:
现在在
MyHandler
中,重用实例变量是非常安全的# 2 楼答案
你说得对
只要你不使用类级变量,你的
Servlet
就会是线程安全的为了安全起见,不妨让您的类级别
String
final
: