FreeMarker template error: The following has evaluated to null or missing: ==> [in template "component://snj2/template/catalog/ProductDetail.ftl" at line 389, column 19] ---- Tip: It's the step after the last dot that caused this error, not those before it. ---- Tip: If the failing expression is known to be legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)?? ---- ---- FTL stack trace ("~" means nesting-related): - Failed at: #if (product.originalImageUrl?string?... [in template "component://snj2/template/catalog/ProductDetail.ftl" at line 389, column 13] ---- Java stack trace (for programmers): ---- freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...] at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134) at freemarker.core.UnexpectedTypeException.newDesciptionBuilder(UnexpectedTypeException.java:80) at freemarker.core.UnexpectedTypeException.<init>(UnexpectedTypeException.java:43) at freemarker.core.BuiltInsForMultipleTypes$stringBI._eval(BuiltInsForMultipleTypes.java:709) at freemarker.core.Expression.eval(Expression.java:81) at freemarker.core.ExistenceBuiltins$ExistenceBuiltIn.evalMaybeNonexistentTarget(ExistenceBuiltins.java:52) at freemarker.core.ExistenceBuiltins$has_contentBI._eval(ExistenceBuiltins.java:112) at freemarker.core.ExistenceBuiltins$has_contentBI.evalToBoolean(ExistenceBuiltins.java:119) at freemarker.core.AndExpression.evalToBoolean(AndExpression.java:36) at freemarker.core.ParentheticalExpression.evalToBoolean(ParentheticalExpression.java:35) at freemarker.core.IfBlock.accept(IfBlock.java:49) at freemarker.core.Environment.visit(Environment.java:326) at freemarker.core.Environment.visit(Environment.java:332) at freemarker.core.Environment.visit(Environment.java:332) at freemarker.core.Environment.process(Environment.java:305) at org.apache.ofbiz.base.util.template.FreeMarkerWorker.renderTemplate(FreeMarkerWorker.java:263) at org.apache.ofbiz.widget.model.HtmlWidget.renderHtmlTemplate(HtmlWidget.java:167) at org.apache.ofbiz.widget.model.HtmlWidget$HtmlTemplate.renderWidgetString(HtmlWidget.java:216) at org.apache.ofbiz.widget.model.HtmlWidget.renderWidgetString(HtmlWidget.java:140) at org.apache.ofbiz.widget.model.ModelScreenWidget$PlatformSpecific.renderWidgetString(ModelScreenWidget.java:1321) at org.apache.ofbiz.widget.model.ModelScreenWidget.renderSubWidgetsString(ModelScreenWidget.java:98) at org.apache.ofbiz.widget.model.ModelScreenWidget$Section.renderWidgetString(ModelScreenWidget.java:280) at org.apache.ofbiz.widget.model.ModelScreen.renderScreenString(ModelScreen.java:164) at org.apache.ofbiz.widget.model.ScreenFactory.renderReferencedScreen(ScreenFactory.java:214) at org.apache.ofbiz.widget.model.ModelScreenWidget$IncludeScreen.renderWidgetString(ModelScreenWidget.java:780) at org.apache.ofbiz.widget.model.ModelScreenWidget.renderSubWidgetsString(ModelScreenWidget.java:98) at org.apache.ofbiz.widget.model.ModelScreenWidget$Section.renderWidgetString(ModelScreenWidget.java:280) at org.apache.ofbiz.widget.model.ModelScreenWidget.renderSubWidgetsString(ModelScreenWidget.java:98) at org.apache.ofbiz.widget.model.ModelScreenWidget$DecoratorSection.renderWidgetString(ModelScreenWidget.java:906) at org.apache.ofbiz.widget.model.ModelScreenWidget$SectionsRenderer.render(ModelScreenWidget.java:127) at org.apache.ofbiz.widget.model.ModelScreenWidget$DecoratorSectionInclude.renderWidgetString(ModelScreenWidget.java:943) at org.apache.ofbiz.widget.model.ModelScreenWidget.renderSubWidgetsString(ModelScreenWidget.java:98) at org.apache.ofbiz.widget.model.ModelScreenWidget$Section.renderWidgetString(ModelScreenWidget.java:280) at org.apache.ofbiz.widget.model.ModelScreenWidget.renderSubWidgetsString(ModelScreenWidget.java:98) at org.apache.ofbiz.widget.model.ModelScreenWidget$Section.renderWidgetString(ModelScreenWidget.java:280) at org.apache.ofbiz.widget.model.ModelScreen.renderScreenString(ModelScreen.java:164) at org.apache.ofbiz.widget.model.ScreenFactory.renderReferencedScreen(ScreenFactory.java:214) at org.apache.ofbiz.widget.model.ModelScreenWidget$DecoratorScreen.renderWidgetString(ModelScreenWidget.java:860) at org.apache.ofbiz.widget.model.ModelScreenWidget.renderSubWidgetsString(ModelScreenWidget.java:98) at org.apache.ofbiz.widget.model.ModelScreenWidget$Section.renderWidgetString(ModelScreenWidget.java:280) at org.apache.ofbiz.widget.model.ModelScreen.renderScreenString(ModelScreen.java:164) at org.apache.ofbiz.widget.renderer.ScreenRenderer.render(ScreenRenderer.java:136) at org.apache.ofbiz.widget.renderer.ScreenRenderer.render(ScreenRenderer.java:98) at org.apache.ofbiz.widget.renderer.macro.MacroScreenViewHandler.render(MacroScreenViewHandler.java:157) at org.apache.ofbiz.webapp.control.RequestHandler.renderView(RequestHandler.java:1001) at org.apache.ofbiz.webapp.control.RequestHandler.doRequest(RequestHandler.java:653) at org.apache.ofbiz.webapp.control.ControlServlet.doGet(ControlServlet.java:213) at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:720) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318) at org.apache.ofbiz.product.category.CatalogUrlServlet.doGet(CatalogUrlServlet.java:153) at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.ofbiz.webapp.control.ContextFilter.doFilter(ContextFilter.java:324) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.ofbiz.content.content.ContentUrlFilter.doFilter(ContentUrlFilter.java:99) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.ofbiz.product.category.CatalogUrlFilter.doFilter(CatalogUrlFilter.java:338) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528) at org.apache.coyote.ajp.AbstractAjpProcessor.process(AbstractAjpProcessor.java:873) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:748)
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Principles of planar near-field antenna measurements

by Stuart Gregson, John McCormick and Clive Parini

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Description

This single volume provides a comprehensive introduction and explanation of both the theory and practice of 'Planar Near-Field Antenna Measurements' from its basic postulates and assumptions, to the intricacies of its deployment in complex and demanding measurement scenarios. To do this the book initially examines the properties of antennas that allow them to enhance the free space interaction of electronic systems and this leads into a full description of the theory of 'Planar Near-Field Scanning'.The utility of the planar methodology is illustrated with example measurement campaigns that include discussion of the characterisation of a wide range of antennas. Advanced techniques, including back transforms and poly-planar scan techniques, plus error assessment and correction, are examined and explained along with an extensive review of data assessment methodologies.

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Product Details

  • Institution of Engineerin Brand
  • 9780863417368 ISBN-13:
  • 0863417361 ISBN-10:
  • 0863417361 ISBN-10
  • 9780863417368 ISBN-13
  • New Condition
  • Hardback Media
  • 5 business days Generally Ships in
  • 0 in * 6.26 in * 9.25 in Dimensions:
  • 1 lb Weight: