【发布时间】：2020-03-17 05:18:32
【问题描述】：
我有一个返回 JSON 响应的 servlet。如果我执行response.getWriter 然后执行response.reset() 然后设置标题并打印输出，一切都很好。删除 response.reset() 后，在 Jetty 服务器上运行时出现异常，尽管我在浏览器中正确显示了输出。
SEVERE: Error while closing the output stream in order to commit response.
java.lang.IllegalStateException: WRITER
at org.eclipse.jetty.server.Response.getOutputStream(Response.java:917)
at org.glassfish.jersey.servlet.internal.ResponseWriter.writeResponseStatusAndHeaders(ResponseWriter.java:176)
at org.glassfish.jersey.server.ServerRuntime$Responder$1.getOutputStream(ServerRuntime.java:667)
at org.glassfish.jersey.message.internal.CommittingOutputStream.commitStream(CommittingOutputStream.java:200)
at org.glassfish.jersey.message.internal.CommittingOutputStream.flushBuffer(CommittingOutputStream.java:305)
at org.glassfish.jersey.message.internal.CommittingOutputStream.commit(CommittingOutputStream.java:261)
at org.glassfish.jersey.message.internal.CommittingOutputStream.close(CommittingOutputStream.java:276)
at org.glassfish.jersey.message.internal.OutboundMessageContext.close(OutboundMessageContext.java:839)
at org.glassfish.jersey.server.ContainerResponse.close(ContainerResponse.java:412)
at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:750)
at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:424)
at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:414)
at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:311)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:291)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1140)
at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:403)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:386)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:334)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:221)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:860)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1650)
at org.eclipse.jetty.servlets.GzipFilter.doFilter(GzipFilter.java:51)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1629)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:533)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:190)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1595)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:188)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1253)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:168)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:473)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1564)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:166)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1155)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.Server.handle(Server.java:530)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:347)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:256)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:102)
at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:247)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.produce(EatWhatYouKill.java:140)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:131)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:382)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:708)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:626)
at java.lang.Thread.run(Thread.java:748)
我检查了API Docs，但它根本没有帮助。
工作代码（使用 response.reset()）
public Response getData (
@Context HttpServletRequest request,
@Context HttpServletResponse response) throws IOException, SQLException, ServletException {
Writer out = null;
try {
request.setCharacterEncoding("UTF-8");
out = response.getWriter();
response.reset();
response.setCharacterEncoding("UTF-8");
response.setContentType("application/json");
response.addHeader("content-type", "gzip");
//Print the output in json format using out.write()
} catch (Exception e) {
return Response.status(400).entity("{\n\"Error Message\":\"" + StringEscapeUtils.escapeJson(e.getMessage().trim()) + "\"\n}").build();
}
out.flush();
return Response.ok().entity("").build();
}
我之前也尝试过设置标题，然后执行 getWriter，但这没有帮助。请建议 response.reset 到底在做什么，有什么办法可以摆脱它。
使用 Jetty 版本 9.4.8.v20180619
【问题讨论】：