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[英]Servlet filters - passing an attribute not working with RequestDispatcher#forward
[英]Tomcat infinte loop on requestDispatcher#forward(). StackOverflowError
Tomcat在不斷重復這些行之后給了我StackOverflowError,其中DiceBoardDispatcher
是我的HttpServlet,在第34行我調用requestDispatcher#forward()
。
nl.rickhurkens.rollDice.web.diceBoard.DiceBoardDispatcher.doGet(DiceBoardDispatcher.java:34)
javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
nl.rickhurkens.rollDice.web.diceBoard.DiceBoardDispatcher.doGet(DiceBoardDispatcher.java:34)
javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
我想這與我的部署有關,這是我的web.xml的相關部分:
<servlet-mapping>
<servlet-name>DiceBoard</servlet-name>
<url-pattern>/dices/*</url-pattern>
</servlet-mapping>
<filter-mapping>
<filter-name>RollDiceFilter</filter-name>
<url-pattern>/dices/roll</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>SetSettingsFilter</filter-name>
<url-pattern>/dices/setup</url-pattern>
</filter-mapping>
我要做的是讓兩個動作都登陸同一頁面。 我以為我會這樣設置它。 每個操作都通過自己的Filter
,它們都以發送給JSP
的Servlet
結束。
我的url- /diceBoard/*
映射曾經是/diceBoard/*
,它是web-app中的某個文件夾。 從那里改為/dices/*
修復了去url/dices
。 現在我可以正常訪問該頁面,但是當進入url/dices/roll
我會得到無限循環(無論是POST還是GET)。
編輯:我的servlet代碼:
public class DiceBoardDispatcher extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
RequestDispatcher view = request.getRequestDispatcher("diceBoardPage.jsp");
view.forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
RequestDispatcher view = request.getRequestDispatcher("diceBoardPage.jsp");
view.forward(request, response);
}
}
和RollDiceFilter:
public class RollDiceFilter implements Filter {
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse res = (HttpServletResponse)response;
HttpSession session = req.getSession();
DiceBoard diceBoard = (DiceBoard)session.getAttribute("diceBoard");
String[] lockedValues = req.getParameterValues("lock");
diceBoard.unlockAllDice();
if (lockedValues != null) {
for (String value : lockedValues) {
if (value != null) {
try {
diceBoard.lockDice(Integer.parseInt(value));
} catch (DiceNotInCollectionException e) {
// TODO: redirect to error page.
e.printStackTrace();
}
}
}
}
diceBoard.getCup().roll();
chain.doFilter(req, res);
}
public void init(FilterConfig fConfig) throws ServletException { }
public void destroy() { }
}
這是您的錯誤所在的行:
RequestDispatcher view = request.getRequestDispatcher("diceBoardPage.jsp");
根據getRequestDispatcher API ,輸入uri是相對於當前servlet上下文的,所以當你在執行servlet時
/dices/roll
...它執行“diceBoardPage.jsp”的調度,實際上是調度到
/dices/diceBoardPage.jsp
什么servlet映射到這個模式? 根據您的部署描述符,以“/ dices / *”開頭的每個URL都映射到DiceBoard
。 IE是同一個servlet。 這是導致StackOverflowError的無限循環。
如果JSP必須停留在內部dices
URI,您必須限制其映射的URL模式DiceBoard
的servlet。 如果需要,請不要猶豫,添加幾個值:
<servlet-mapping>
<servlet-name>DiceBoard</servlet-name>
<url-pattern>/dices/one</url-pattern>
<url-pattern>/dices/two</url-pattern>
<url-pattern>/dices/three</url-pattern>
</servlet-mapping>
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