怎么解决

Question

else if("delete".equals(method)){
System.out.println("&&&&&&&&&&&&&");
int id=Integer.parseInt(request.getParameter("id")==null? "":request.getParameter("id").trim());
System.out.println(id);
int i=UserDao22.deleteUserById(id);
if(i==1){
request.setAttribute("result", "0000");
request.getRequestDispatcher("/qq/delete_user.jsp").forward(request, response);
}else{
request.setAttribute("result", "1111");
request.getRequestDispatcher("/qq/delete_user.jsp").forward(request, response);
}
}
严重: Servlet.service() for servlet UserServlet22 threw exception
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at action.UserServlet22.doPost(UserServlet22.java:141)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at action.MyFilter.doFilter(MyFilter.java:25)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)

Answer 1

int i=UserDao22.deleteUserById(id)
这个返回是int么？

Answer 2

java.lang.NumberFormatException: For input string: ""
应该是第三行request.getParameter("id")==null为true，导致Integer.parseInt("")参数错误我觉得可以这么改int id=Integer.parseInt(request.getParameter("id")==null? "-1":request.getParameter("id").trim());

Answer 3

int id=Integer.parseInt(request.getParameter("id")==null? "":request.getParameter("id").trim());
这句错了

Answer 4

先打印看 request.getParameter("id")值是否为null。int id =Integer.parseInt("");这句编译会有错误。所以，问题应该是你的id为空了