过滤器

Question

过滤器过滤后出现空白页！
可是我没有让它转向空白页，
是什么原因啊？

Answer 1

没有错误信息吗？
把你过滤器中的代码以及web.xml配置过滤器的地方贴出来

Answer 2

package filters;import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;import domain.User;
public class UserValidateFilter implements Filter
{
private FilterConfig filterConfig=null;

public void init(FilterConfig filterConfig)
{
this.filterConfig=filterConfig;
} public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain)
throws IOException,ServletException
{
User user=(User)((HttpServletRequest)request).getSession().getAttribute("user");
if(user==null)
{
request.getRequestDispatcher("../MainPage.jsp").forward(request,response);
}
}

public void destroy()
{
filterConfig=null;
}}
  <filter>
<filter-name>userValidate</filter-name>
<filter-class>filters.UserValidateFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>userValidate</filter-name>
<url-pattern>/jsp/*</url-pattern>
<dispather>request</dispather>
<dispather>forward</dispather>
</filter-mapping>

Answer 3

java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:604)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:197)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:191)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:119)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:79)
at org.apache.jsp.image_jsp._jspService(image_jsp.java:146)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:390)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:212)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:818)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:624)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)
at java.lang.Thread.run(Unknown Source)

Answer 4

    public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain)
    throws IOException,ServletException
    {
         request.setCharacterEncoding("utf-8");
         chain.doFilter(request, response);
    }

Answer 5

   <filter>
<filter-name>过虑器的别名</filter-name>
<filter-class>过虑器的包名.类名</filter-class>
</filter> <filter-mapping>
<filter-name>过虑器的别名</filter-name>
<servlet-name>页面1 的别名</servlet-name>
</filter-mapping>
<servlet>
<servlet-name>页面1 的别名</servlet-name>
<servlet-class>
页面1 的包名.类名
</servlet-class> </servlet>
<servlet-mapping>
<servlet-name>页面1 的别名</servlet-name>
<url-pattern>页面1 </url-pattern>
</servlet-mapping>
 
     ＜！－－ 在页面1的前面设置过虑器   －－＞

Answer 6

将<filter-mapping>
中的
<dispather>request</dispather>
<dispather>forward</dispather>
这两句代码去掉试试~~