标签：
最初实现的方式如下：
<service verb="get" noun="ProductCategoryContentFile"> <in-parameters> <parameter name="productCategoryContentId" required="true"/> </in-parameters> <actions> <entity-find-one entity-name="mantle.product.category.ProductCategoryContent" value-field="productCategoryContent"/> <if condition="productCategoryContent?.contentLocation"> <script>ec.web.sendResourceResponse(productCategoryContent.contentLocation, true)</script> </if> </actions> </service>
执行结果中图片可以展示出来，如果使用tomcat服务器的话是没有问题的，但是如果是在jetty中的话查看console的时候会出现如下的log
日志内容如下：
1 14:06:12.151 WARN 48402763-759 o.moqui.i.c.TransactionFacadeImpl Transaction rollback for [Error running transition in [http://localhost:8080/rest/s1/slp/products/categories/contents/100001/file]]. Here is the current location: 2 org.moqui.BaseException: Rollback location 3 at org.moqui.impl.context.TransactionFacadeImpl.rollback(TransactionFacadeImpl.groovy:415) [moqui-framework-2.0.0.jar:2.0.0] 4 at org.moqui.impl.context.TransactionFacadeImpl.rollback(TransactionFacadeImpl.groovy:398) [moqui-framework-2.0.0.jar:2.0.0] 5 at org.moqui.impl.screen.ScreenRenderImpl.internalRender(ScreenRenderImpl.groovy:349) [moqui-framework-2.0.0.jar:2.0.0] 6 at org.moqui.impl.screen.ScreenRenderImpl.render(ScreenRenderImpl.groovy:176) [moqui-framework-2.0.0.jar:2.0.0] 7 at org.moqui.impl.webapp.MoquiServlet.doScreenRequest(MoquiServlet.groovy:79) [moqui-framework-2.0.0.jar:2.0.0] 8 at org.moqui.impl.webapp.MoquiServlet.service(MoquiServlet.groovy:54) [moqui-framework-2.0.0.jar:2.0.0] 9 at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [moqui-2.0.0.war:3.1.0] 10 at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:837) [moqui-2.0.0.war:9.3.10.v20160621] 11 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1689) [moqui-2.0.0.war:9.3.10.v20160621] 12 at org.eclipse.jetty.websocket.server.WebSocketUpgradeFilter.d(WebSocketUpgradeFilter.java:225) [moqui-2.0.0.war:9.3.10.v20160621] 13 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1676) [moqui-2.0.0.war:9.3.10.v20160621] 14 at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:581) [moqui-2.0.0.war:9.3.10.v20160621] 15 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) [moqui-2.0.0.war:9.3.10.v20160621] 16 at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) [moqui-2.0.0.war:9.3.10.v20160621] 17 at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226) [moqui-2.0.0.war:9.3.10.v20160621] 18 at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180) [moqui-2.0.0.war:9.3.10.v20160621] 19 at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:511) [moqui-2.0.0.war:9.3.10.v20160621] 20 at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185) [moqui-2.0.0.war:9.3.10.v20160621] 21 at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112) [moqui-2.0.0.war:9.3.10.v20160621] 22 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) [moqui-2.0.0.war:9.3.10.v20160621] 23 at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134) [moqui-2.0.0.war:9.3.10.v20160621] 24 at org.eclipse.jetty.server.Server.handle(Server.java:524) [moqui-2.0.0.war:9.3.10.v20160621] 25 at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:319) [moqui-2.0.0.war:9.3.10.v20160621] 26 at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:253) [moqui-2.0.0.war:9.3.10.v20160621] 27 at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:273) [moqui-2.0.0.war:9.3.10.v20160621] 28 at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95) [moqui-2.0.0.war:9.3.10.v20160621] 29 at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93) [moqui-2.0.0.war:9.3.10.v20160621] 30 org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303) [moqui-2.0.0.war:9.3.10.v20160621] 31 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148) [moqui-2.0.0.war:9.3.10.v20160621] 32 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136) [moqui-2.0.0.war:9.3.10.v20160621] 33 at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671) [moqui-2.0.0.war:9.3.10.v20160621] 34 at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589) [moqui-2.0.0.war:9.3.10.v20160621] 35 at java.lang.Thread.run(Thread.java:745) [?:1.8.0_77] 36 14:06:12.153 ERROR 48402763-759 o.m.i.w.MoquiServlet Internal error processing request: STREAM 37 java.lang.IllegalStateException: STREAM 38 at org.eclipse.jetty.server.Response.getWriter(Response.java:891) ~[?:?] 39 at org.moqui.impl.context.WebFacadeImpl.sendJsonError(WebFacadeImpl.groovy:647) ~[moqui-framework-2.0.0.jar:2.0.0] 40 at org.moqui.impl.context.WebFacadeImpl.handleServiceRestCall(WebFacadeImpl.groovy:1184) ~[moqui-framework-2.0.0.jar:2.0.0] 41 at org.moqui.context.WebFacade$handleServiceRestCall.call(Unknown Source) ~[?:?] 42 at rest_xml_transition_s1_actions.run(rest_xml_transition_s1_actions:6) ~[script:?] 43 at org.moqui.impl.actions.XmlAction.run(XmlAction.groovy:66) ~[moqui-framework-2.0.0.jar:2.0.0] 44 at org.moqui.impl.screen.ScreenDefinition$TransitionItem.run(ScreenDefinition.groovy:701) ~[moqui-framework-2.0.0.jar:2.0.0] 45 at org.moqui.impl.screen.ScreenRenderImpl.recursiveRunTransition(ScreenRenderImpl.groovy:239) ~[moqui-framework-2.0.0.jar:2.0.0] 46 at org.moqui.impl.screen.ScreenRenderImpl.recursiveRunTransition(ScreenRenderImpl.groovy:233) ~[moqui-framework-2.0.0.jar:2.0.0] 47 at org.moqui.impl.screen.ScreenRenderImpl.internalRender(ScreenRenderImpl.groovy:347) ~[moqui-framework-2.0.0.jar:2.0.0] 48 at org.moqui.impl.screen.ScreenRenderImpl.render(ScreenRenderImvy:176) ~[moqui-framework-2.0.0.jar:2.0.0] 49 at org.moqui.impl.webapp.MoquiServlet.doScreenRequest(MoquiServlet.groovy:79) [moqui-framework-2.0.0.jar:2.0.0] 50 at org.moqui.impl.webapp.MoquiServlet.service(MoquiServlet.groovy:54) [moqui-framework-2.0.0.jar:2.0.0] 51 at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [moqui-2.0.0.war:3.1.0] 52 at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:837) [moqui-2.0.0.war:9.3.10.v20160621] 53 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1689) [moqui-2.0.0.war:9.3.10.v20160621] 54 at org.eclipse.jetty.websocket.server.WebSocketUpgradeFilter.doFilter(WebSocketUpgradeFilter.java:225) [moqui-2.0.0.war:9.3.10.v20160621] 55 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1676) [moqui-2.0.0.war:9.3.10.v20160621] 56 at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:581) [moqui-2.0.0.war:9.3.10.v20160621] 57 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) [moqui-2.0.0.war:9.3.10.v20160621] 58 at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) [moqui-2.0.0.war:9.3.10.v20160621] 59 at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226) [moqui-2.0.0.war:9.3.10.v20160621] 60 at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180) [moqui-2.0.0.war:9.3.10.v20160621] 61 at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:511) [moqui-2.0.0.war:9.3.10.v20160621] 62 at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185) [moqui-2.0.0.war:9.3.10.v20160621] 63 at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112) [moqui-2.0.0.war:9.3.10.v20160621] 64 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) [moqui-2.0.0.war:9.3.10.v20160621] 65 at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134) [moqui-2.0.0.war:9.3.10.v20160621] 66 at org.ejetty.server.Server.handle(Server.java:524) [moqui-2.0.0.war:9.3.10.v20160621] 67 at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:319) [moqui-2.0.0.war:9.3.10.v20160621] 68 at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:253) [moqui-2.0.0.war:9.3.10.v20160621] 69 at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:273) [moqui-2.0.0.war:9.3.10.v20160621] 70 at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95) [moqui-2.0.0.war:9.3.10.v20160621] 71 at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93) [moqui-2.0.0.war:9.3.10.v20160621] 72 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303) [moqui-2.0.0.war:9.3.10.v20160621] 73 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148) [moqui-2.0.0.war:9.3.10.v20160621] 74 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136) [moqui-2.0.0.war:9.3.10.v20160621] 75 at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671) [moqui-2.0.0.war:9.3.10.v20160621] 76 at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589) [moqui-2.0.0.war:9.3.10.v20160621] 77 at java.lang.Thread.run(Thread.java:745) [?:1.8.0_77] 78 14:06:12.165 WARN 48402763-759 o.moqui.i.c.TransactionFacadeImpl Rollback only not set on current transaction, status is STATUS_NO_TRANSACTION 79 14:06:12.165 ERROR 48402763-759 o.m.i.w.MoquiServlet Error rendering internal-error error screen, sending code 500 with message: STREAM 80 java.lang.RuntimeException: Error rendering screen [component://webroot/screen/webroot.xml] 81 at org.moqui.impl.screen.ScreenRenderImpl.doActualRender(ScreenRenderImpl.groovy:737) ~[moqui-framework-2.0.0.jar:2.0.0] 82 at org.moqui.impl.screen.ScreenRenderImpl.internalRender(ScreenRenderImpl.groovy:594) ~[moqui-framework-2.0.0.jar:2.0.0] 83 .moqui.impl.screen.ScreenRenderImpl.render(ScreenRenderImpl.groovy:176) ~[moqui-framework-2.0.0.jar:2.0.0] 84 at org.moqui.impl.webapp.MoquiServlet.sendErrorResponse(MoquiServlet.groovy:142) [moqui-framework-2.0.0.jar:2.0.0] 85 at org.moqui.impl.webapp.MoquiServlet.doScreenRequest(MoquiServlet.groovy:103) [moqui-framework-2.0.0.jar:2.0.0] 86 at org.moqui.impl.webapp.MoquiServlet.service(MoquiServlet.groovy:54) [moqui-framework-2.0.0.jar:2.0.0] 87 at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [moqui-2.0.0.war:3.1.0] 88 at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:837) [moqui-2.0.0.war:9.3.10.v20160621] 89 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1689) [moqui-2.0.0.war:9.3.10.v20160621] 90 at org.eclipse.jetty.websocket.server.WebSocketUpgradeFilter.doFilter(WebSocketUpgradeFilter.java:225) [moqui-2.0.0.war:9.3.10.v20160621] 91 at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1676) [moqui-2.0.0.war:9.3.10.v20160621] 92 at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:581) [moqui-2.0.0.war:9.3.10.v20160621] 93 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) [moqui-2.0.0.war:9.3.10.v20160621] 94 at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548) [moqui-2.0.0.war:9.3.10.v20160621] 95 at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226) [moqui-2.0.0.war:9.3.10.v20160621] 96 at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180) [moqui-2.0.0.war:9.3.10.v20160621] 97 at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:511) [moqui-2.0.0.war:9.3.10.v20160621] 98 at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185) [moqui-2.0.0.war:9.3.10.v20160621] 99 at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112) [moqui-2.0.0.war:9.3.10.v20160621] 100 at org.eclipse.jetty.server.handler.ScopedHandler.handle(Scoped.java:141) [moqui-2.0.0.war:9.3.10.v20160621] 101 at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134) [moqui-2.0.0.war:9.3.10.v20160621] 102 at org.eclipse.jetty.server.Server.handle(Server.java:524) [moqui-2.0.0.war:9.3.10.v20160621] 103 at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:319) [moqui-2.0.0.war:9.3.10.v20160621] 104 at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:253) [moqui-2.0.0.war:9.3.10.v20160621] 105 at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:273) [moqui-2.0.0.war:9.3.10.v20160621] 106 at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95) [moqui-2.0.0.war:9.3.10.v20160621] 107 at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93) [moqui-2.0.0.war:9.3.10.v20160621] 108 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303) [moqui-2.0.0.war:9.3.10.v20160621] 109 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148) [moqui-2.0.0.war:9.3.10.v20160621] 110 at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136) [moqui-2.0.0.war:9.3.10.v20160621] 111 at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671) [moqui-2.0.0.war:9.3.10.v20160621] 112 at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589) [moqui-2.0.0.war:9.3.10.v20160621] 113 at java.lang.Thread.run(Thread.java:745) [?:1.8.0_77] 114 Caused by: java.lang.IllegalStateException: STREAM 115 at org.eclipse.jetty.server.Response.getWriter(Response.java:891) ~[?:?] 116 at org.moqui.impl.screen.ScreenRenderImpl.getWriter(ScreenRenderImpl.groovy:107) ~[moqui-framework-2.0.0.jar:2.0.0] 117 at org.moqui.impl.screen.ScreenWidgets.render(ScreenWidgets.groovy:43) ~[moqui-framework-2.0.0.jar:2.0.0] 118 at org.moqui.impl.screen.ScreenSection.renderSingle(ScreenSection.groovy:140) ~[moqui-framework-2.0.0.jar:2.0.0] 119 at org.moquicreen.ScreenSection.render(ScreenSection.groovy:113) ~[moqui-framework-2.0.0.jar:2.0.0] 120 at org.moqui.impl.screen.ScreenDefinition.render(ScreenDefinition.groovy:459) ~[moqui-framework-2.0.0.jar:2.0.0] 121 at org.moqui.impl.screen.ScreenRenderImpl.doActualRender(ScreenRenderImpl.groovy:719) ~[moqui-framework-2.0.0.jar:2.0.0] 122 ... 32 more
关于这个问题主要是和jetty处理getWriter和getOutputStream的方式有关：
在jetty中的处理方式如下：
1 这两个方法在jetty容易中是这么处理： 2 org.eclipse.jetty.server.Response继承自j2ee里面的HttpServletResponse.java类 3 org.eclipse.jetty.server.Response.java类里面 4 5 public ServletOutputStream getOutputStream() throws IOException 6 { 7 if (_outputState!=NONE && _outputState!=STREAM) 如果状态为WRITER状态，则抛出异常 8 throw new IllegalStateException("WRITER"); 9 10 _outputState=STREAM; 把response状态改为STREAM流状态 11 return _connection.getOutputStream(); 12 } 13 14 public PrintWriter getWriter() throws IOException 15 { 16 if (_outputState!=NONE && _outputState!=WRITER) 如果状态为STREAM，则抛出异常 17 throw new IllegalStateException("STREAM"); 18 19 /* if there is no writer yet */ 20 if (_writer==null) 21 { 22 /* get encoding from Content-Type header */ 23 String encoding = _characterEncoding; 24 25 if (encoding==null) 26 { 27 /* implementation of educated defaults */ 28 if(_mimeType!=null) 29 encoding = null; // TODO getHttpContext().getEncodingByMimeType(_mimeType); 30 31 if (encoding==null) 32 encoding = StringUtil.__ISO_8859_1; 33 34 setCharacterEncoding(encoding); 35 } 36 37 /* construct Writer using correct encoding */ 38 _writer = _connection.getPrintWriter(encoding); 39 } 40 _outputState=WRITER; 把response状态改为WRITER状态， 41 return _writer; 42 } 43 44 也就是说在j2ee，web应用里面不能同时打开PrintWriter和OutputStream，否则就是抛出上面那个异常。 45 46 jetty的response里面有三种状态： 47 public static final int 48 NONE=0, 未调用getPrintWriter和getOutputStream之前的默认状态 49 STREAM=1, 二进制流状态 调用getOutputStream之后的状态 50 WRITER=2; 字符流状态 51 52 53 解决方法： 54 1.在应用中只使用一个，要么都用getPrintWriter,要么都用getOutputStream。 55 2.在webx 中的com.alibaba.citrus.service.requestcontext.buffered.impl.BufferedResponseImpl.java类中有下面这么解决方案： 56 57 /** 58 * 取得输出流。 59 * 60 * @return response的输出流 61 * @throws IOException 输入输出失败 62 */ 63 @Override 64 public ServletOutputStream getOutputStream() throws IOException { 65 if (stream != null) { 66 return stream; 67 } 68 69 if (writer != null) { 70 // 如果getWriter方法已经被调用，则将writer转换成OutputStream 71 // 这样做会增加少量额外的内存开销，但标准的servlet engine不会遇到这种情形， 72 // 只有少数servlet engine需要这种做法（resin）。 73 if (writerAdapter != null) { 74 return writerAdapter; 75 } else { 76 log.debug("Attampt to getOutputStream after calling getWriter. This may cause unnecessary system cost."); 77 writerAdapter = new WriterOutputStream(writer, getCharacterEncoding()); 78 return writerAdapter; 79 } 80 } 81 82 if (buffering) { 83 // 注意，servletStream一旦创建，就不改变， 84 // 如果需要改变，只需要改变其下面的bytes流即可。 85 if (bytesStack == null) { 86 bytesStack = new Stack<ByteArrayOutputStream>(); 87 } 88 89 ByteArrayOutputStream bytes = new ByteArrayOutputStream(); 90 91 bytesStack.push(bytes); 92 stream = new BufferedServletOutputStream(bytes); 93 94 log.debug("Created new byte buffer"); 95 } else { 96 stream = super.getOutputStream(); 97 } 98 99 return stream; 100 } 101 102 /** 103 * 取得输出字符流。 104 * 105 * @return response的输出字符流 106 * @throws IOException 输入输出失败 107 */ 108 @Override 109 public PrintWriter getWriter() throws IOException { 110 if (writer != null) { 111 return writer; 112 } 113 114 if (stream != null) { 115 // 如果getOutputStream方法已经被调用，则将stream转换成PrintWriter。 116 // 这样做会增加少量额外的内存开销，但标准的servlet engine不会遇到这种情形， 117 // 只有少数servlet engine需要这种做法（resin）。 118 if (streamAdapter != null) { 119 return streamAdapter; 120 } else { 121 log.debug("Attampt to getWriter after calling getOutputStream. This may cause unnecessary system cost."); 122 streamAdapter = new PrintWriter(new OutputStreamWriter(stream, getCharacterEncoding()), true); 123 return streamAdapter; 124 } 125 } 126 127 if (buffering) { 128 // 注意，servletWriter一旦创建，就不改变， 129 // 如果需要改变，只需要改变其下面的chars流即可。 130 if (charsStack == null) { 131 charsStack = new Stack<StringWriter>(); 132 } 133 134 StringWriter chars = new StringWriter(); 135 136 charsStack.push(chars); 137 writer = new BufferedServletWriter(chars); 138 139 log.debug("Created new character buffer"); 140 } else { 141 writer = super.getWriter(); 142 } 143 144 return writer; 145 } 146 147 148 所以在我们自己的应用中就不要再调用完j2ee的原生response的getPrintWriter之后再调用原生的getOutputStream()，或者调用原生的response的getOutputStream之后再调用getPrintWriter。
下面就IllegalStateException宜昌做分析：
web容器生成的servlet代码中有out.write("")，这和response.getOutputStream()产生冲突。
servlet规范中有说明，不能既使用response.getOutputStream()又调用response.getWriter(),无论先调用哪一个，在调用第二个的时候就抛出IllegalStateException
基于此，我们可以通过增加out.clear()和outpageContext.pushBody来解决，在写入图片的使用需要加入flush()
OutputStream output = response.getOutputStream();
output.flush();
工作框架各种使用整理 -- 访问图片的时候访问成功但是会有错误日志
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原文地址：http://www.cnblogs.com/dream-to-pku/p/5714732.html
