字符集过滤类的 doFilter 方法的空值异常

[chengkunxf]

我的tomcat服务器运行后，日志信息里记录着程序一直在抛出这个异常：
2007-03-09 00:54:11 StandardWrapperValve[action]: Servlet.service() for servlet action threw exception
java.lang.NullPointerException
at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:372)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:229)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:28)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:595)

根据堆栈看，好象是说我的 字符集过滤类的 doFilter 方法的空值异常
但是这个类我实在是找不的参数传递的都是 容器对象，涉及到tomcat更底层支持类，我找不出解决错误的方法，请大家帮帮忙。小弟不胜感激!
SetCharacterEncodingFilter.java

package filters;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class SetCharacterEncodingFilter implements Filter{
protected String encoding = null ;
protected FilterConfig filterConfig = null ;
protected boolean ignore = true ;

public void destroy(){
this.encoding = null ;
this.filterConfig = null ;
}

public void doFilter( ServletRequest request , ServletResponse response , FilterChain chain)
throws IOException , ServletException{
if (ignore || (request.getCharacterEncoding() == null)){
String encoding = selectEncoding(request);
if (encoding != null)
request.setCharacterEncoding(encoding);
}
chain.doFilter(request , response);
}

public void init(FilterConfig filterConfig) throws ServletException{
this.filterConfig = filterConfig ;
this.encoding = filterConfig.getInitParameter("encoding");
String value = filterConfig.getInitParameter("ignore");
if (value == null)
this.ignore = true ;
else if (value.equalsIgnoreCase("true"))
this.ignore = true ;
else if (value.equalsIgnoreCase("yes"))
this.ignore = true ;
else
this.ignore = false ;
}

protected String selectEncoding( ServletRequest request){
return this.encoding;
}

}

java类的第28行：
chain.doFilter(request , response);
感觉应该是说chain 这个对象是空的。但不知道怎么解决。请大家给点意见。

[chengkunxf]

里面传进来的编码 是 gbk .

[hero_qx]

protected String selectEncoding( ServletRequest request){
return this.encoding;
}

你这个写得有点诡异了
。

[tigerleq]

//假设request.getCharacterEncoding() == null成立　执行以下代码
看还是不是你想要的结果
public void doFilter( ServletRequest request , ServletResponse response , FilterChain chain)
throws IOException , ServletException{
if (ignore || (request.getCharacterEncoding() == null)){
String encoding = selectEncoding(request);
if (encoding != null)
request.setCharacterEncoding(encoding);
}
chain.doFilter(request , response);
}

[tigerleq]

encoding 为null

[hero_qx]

if (encoding != null)
request.setCharacterEncoding(encoding);
}



你这里面传进来的是什么编码啊？
filterConfig.getInitParameter("encoding");