做了一个Struts2的例子结果报错严重: Servlet.service() for servlet jsp threw exception

Question

严重: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:610)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
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:188)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)
at org.apache.jsp.yanzhengma_jsp._jspService(yanzhengma_jsp.java:128)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
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 org.apache.struts2.dispatcher.ActionContextCleanUp.doFilter(ActionContextCleanUp.java:99)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:413)
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:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
at java.lang.Thread.run(Unknown Source)
运行Tomcat就抱错，能进入第一个页面但不能进入第二个页面，报错页面的错误提示
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception javax.servlet.ServletException: java.lang.NullPointerException
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)
root cause java.lang.NullPointerException
wyf.cgq.LoginDB.login(LoginDB.java:20)
wyf.cgq.LoginAction.execute(LoginAction.java:57)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:267)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:229)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept

Answer 1

java.lang.NullPointerException
wyf.cgq.LoginDB.login(LoginDB.java:20)空指针，看看哪个值没取到，这个20行

Answer 2

照着书上写的，我估计这里是不是有错rs=pstmt.executeQuery();

Answer 3

你是不是用来操作流了？
在servlet中我没有查到好的方法；
直接用jsp吧 
在使用完输出流以后调用以下两行代码即可:
out.clear();
out = pageContext.pushBody();

Answer 4

这有个相关的文章：
http://club.tech.sina.com.cn/thread-673833-1-1.html

Answer 5

用Struts2写的系统
public class LoginDB
{
public static String[] login(String uid,String pwd)
{
String[] impinfo=new String[2];//impinfo[0]:0表示没有这个用户，1表示是人事部的人，2表示不是人事部的人
impinfo[0]="0";
String impId=null;
Connection conn=null;
PreparedStatement pstmt=null;
ResultSet rs=null;
try
{
conn=getConnection();
String sql="select impRight,impId from userinfo where impId=? and pwd=?";
pstmt=conn.prepareStatement(sql);
pstmt.setString(1,uid);
pstmt.setString(2,pwd);
rs=pstmt.executeQuery();
if(rs.next())
{
impinfo[0]=rs.getInt("impRight")+"";
impinfo[1]=rs.getString("impId");
}
else
{
impinfo[0]="0";
}
}
catch(SQLException e)
{
e.printStackTrace();
}
finally
{
try
{
if(conn!=null){conn.close();}
if(pstmt!=null){pstmt.close();}
if(rs!=null){rs.close();}
}
catch(SQLException e)
{
e.printStackTrace();
}
}
return impinfo;
}

Answer 6

LoginAction.java:57行附近的reponse对象设置的对象重复了，你仔细对照下

Answer 7

if(rs.next())
if->while
还有关闭顺序也有问题

Answer 8

解决了，用的
out.clear();
out = pageContext.pushBody();方法解决的，谢谢大家帮助