无法编译 JasperReports 的 webapp 示例

Question

这是我第一次在官方发行版中运行 JasperReports 的 webapp 示例。 我将 \dist 和 \lib 中的 jar 放入 webapp 示例中，并将 webapp-sample 的整个目录部署到 tomcat 中。 但是当我尝试使用默认页面编译 WebappReport.jrxml 时，我看到一个 error.jsp，它显示以下提示：

JasperReports 遇到此错误：

net.sf.jasperreports.engine.JRException: Errors were encountered when compiling report expressions class file:
1. scriptlets.WebappScriptlet cannot be resolved to a type
                value = ((scriptlets.WebappScriptlet)((scriptlets.WebappScriptlet)parameter_REPORT_SCRIPTLET.getValue())).hello(); //$JR_EXPR_ID=23$
                          <------------------------>
2. scriptlets.WebappScriptlet cannot be resolved to a type
                value = ((scriptlets.WebappScriptlet)((scriptlets.WebappScriptlet)parameter_REPORT_SCRIPTLET.getValue())).hello(); //$JR_EXPR_ID=23$
                                                       <------------------------>
3. scriptlets.WebappScriptlet cannot be resolved to a type
                value = ((scriptlets.WebappScriptlet)((scriptlets.WebappScriptlet)parameter_REPORT_SCRIPTLET.getValue())).hello(); //$JR_EXPR_ID=23$
                          <------------------------>
4. scriptlets.WebappScriptlet cannot be resolved to a type
                value = ((scriptlets.WebappScriptlet)((scriptlets.WebappScriptlet)parameter_REPORT_SCRIPTLET.getValue())).hello(); //$JR_EXPR_ID=23$
                                                       <------------------------>
5. scriptlets.WebappScriptlet cannot be resolved to a type
                value = ((scriptlets.WebappScriptlet)((scriptlets.WebappScriptlet)parameter_REPORT_SCRIPTLET.getValue())).hello(); //$JR_EXPR_ID=23$
                          <------------------------>
6. scriptlets.WebappScriptlet cannot be resolved to a type
                value = ((scriptlets.WebappScriptlet)((scriptlets.WebappScriptlet)parameter_REPORT_SCRIPTLET.getValue())).hello(); //$JR_EXPR_ID=23$
                                                       <------------------------>
6 errors

at net.sf.jasperreports.engine.design.JRAbstractCompiler.compileReport(JRAbstractCompiler.java:191)
at net.sf.jasperreports.engine.JasperCompileManager.compileReport(JasperCompileManager.java:212)
at net.sf.jasperreports.engine.JasperCompileManager.compileReportToFile(JasperCompileManager.java:128)
at net.sf.jasperreports.engine.JasperCompileManager.compileReportToFile(JasperCompileManager.java:87)
at org.apache.jsp.jsp.compile_jsp._jspService(compile_jsp.java:61)
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:388)
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.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:291)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:877)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:594)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1675)
at java.lang.Thread.run(Thread.java:619)

Answer 1

这是由于一个 bug（在我们的 JasperServer 中），JDT 编译器编译从缓存加载的报告缺少类路径上的 scriptlet。最初运行报告时不会发生这种情况，因为在这种情况下，JDT 求值器（而不是编译器）与类路径上的 scriptlet 一起使用。换句话说：

1. 使用 JDT 评估器运行报表，将 scriptlet 添加到类路径
2. 报表从缓存加载并使用 JDT 编译器进行编译，类路径上没有 scriptlet（因为 JDT 编译器与包含的应用程序共享其类路径，相反到有自己的类路径的评估器）。

快速解决方法是将 scriptlet 添加到包含应用程序的类路径中。