Freemarker error 4

1. Error description

May 28 9:56:48 freemarker. log. JDK14LoggerFactory $ JDK14Logger error: Template processing error: "Expression student. course is undefined on line 15, column 24 in course. ftl. "Expression student. course is undefined on line 15, column 24 in course. ftl. the problematic instruction: ---------- ==>$ {student. course} [on line 15, column 22 in course. ftl] ---------- Java backtrace for programmers: ---------- freemarker. core. invalidReferenceException: Expression student. course is undefined on line 15, column 24 in course. ftl. at freemarker. core. templateObject. assertNonNull (TemplateObject. java: 125) at freemarker. core. expression. getStringValue (Expression. java: 118) at freemarker. core. expression. getStringValue (Expression. java: 93) at freemarker. core. dollarVariable. accept (DollarVariable. java: 76) at freemarker. core. environment. visit (Environment. java: 221) at freemarker. core. mixedContent. accept (MixedContent. java: 92) at freemarker. core. environment. visit (Environment. java: 221) at freemarker. core. environment. process (Environment. java: 199) at freemarker. template. template. process (Template. java: 259) at com. you. freemarker. freemarkerTemplate. printFtl (FreemarkerTemplate. java: 77) at com. you. test. freemarker. freemarkerTest. studentPrint (FreemarkerTest. java: 141) at com. you. test. freemarker. freemarkerTest. testCourse (FreemarkerTest. java: 128) at sun. reflect. nativeMethodAccessorImpl. invoke0 (Native Method) at sun. reflect. nativeMethodAccessorImpl. invoke (Unknown Source) at sun. reflect. delegatingMethodAccessorImpl. invoke (Unknown Source) at java. lang. reflect. method. invoke (Unknown Source) at org. junit. runners. model. frameworkMethod $1. runReflectiveCall (FrameworkMethod. java: 45) at org. junit. internal. runners. model. reflectiveCallable. run (ReflectiveCallable. java: 15) at org. junit. runners. model. frameworkMethod. invokeExplosively (FrameworkMethod. java: 42) at org. junit. internal. runners. statements. invokeMethod. evaluate (InvokeMethod. java: 20) at org. junit. internal. runners. statements. runBefores. evaluate (RunBefores. java: 28) at org. junit. runners. parentRunner. runLeaf (ParentRunner. java: 263) at org. junit. runners. blockJUnit4ClassRunner. runChild (BlockJUnit4ClassRunner. java: 68) at org. junit. runners. blockJUnit4ClassRunner. runChild (BlockJUnit4ClassRunner. java: 47) at org. junit. runners. parentRunner $ 3.run( ParentRunner. java: 231) at org. junit. runners. parentRunner $1. schedule (ParentRunner. java: 60) at org. junit. runners. parentRunner. runChildren (ParentRunner. java: 229) at org. junit. runners. parentRunner. access $000 (ParentRunner. java: 50) at org. junit. runners. parentRunner $2. evaluate (ParentRunner. java: 222) at org. junit. runners. parentRunner. run (ParentRunner. java: 300) at org. eclipse. jdt. internal. junit4.runner. JUnit4TestReference. run (JUnit4TestReference. java: 50) at org. eclipse. jdt. internal. junit. runner. testExecution. run (TestExecution. java: 38) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. runTests (RemoteTestRunner. java: 467) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. runTests (RemoteTestRunner. java: 683) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. run (RemoteTestRunner. java: 390) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. main (RemoteTestRunner. java: 197) Expression student. course is undefined on line 15, column 24 in course. ftl. the problematic instruction: ---------- ==>$ {student. course} [on line 15, column 22 in course. ftl] ---------- Java backtrace for programmers: ---------- freemarker. core. invalidReferenceException: Expression student. course is undefined on line 15, column 24 in course. ftl. at freemarker. core. templateObject. assertNonNull (TemplateObject. java: 125) at freemarker. core. expression. getStringValue (Expression. java: 118) at freemarker. core. expression. getStringValue (Expression. java: 93) at freemarker. core. dollarVariable. accept (DollarVariable. java: 76) at freemarker. core. environment. visit (Environment. java: 221) at freemarker. core. mixedContent. accept (MixedContent. java: 92) at freemarker. core. environment. visit (Environment. java: 221) at freemarker. core. environment. process (Environment. java: 199) at freemarker. template. template. process (Template. java: 259) at com. you. freemarker. freemarkerTemplate. printFtl (FreemarkerTemplate. java: 77) at com. you. test. freemarker. freemarkerTest. studentPrint (FreemarkerTest. java: 141) at com. you. test. freemarker. freemarkerTest. testCourse (FreemarkerTest. java: 128) at sun. reflect. nativeMethodAccessorImpl. invoke0 (Native Method) at sun. reflect. nativeMethodAccessorImpl. invoke (Unknown Source) at sun. reflect. delegatingMethodAccessorImpl. invoke (Unknown Source) at java. lang. reflect. method. invoke (Unknown Source) at org. junit. runners. model. frameworkMethod $1. runReflectiveCall (FrameworkMethod. java: 45) at org. junit. internal. runners. model. reflectiveCallable. run (ReflectiveCallable. java: 15) at org. junit. runners. model. frameworkMethod. invokeExplosively (FrameworkMethod. java: 42) at org. junit. internal. runners. statements. invokeMethod. evaluate (InvokeMethod. java: 20) at org. junit. internal. runners. statements. runBefores. evaluate (RunBefores. java: 28) at org. junit. runners. parentRunner. runLeaf (ParentRunner. java: 263) at org. junit. runners. blockJUnit4ClassRunner. runChild (BlockJUnit4ClassRunner. java: 68) at org. junit. runners. blockJUnit4ClassRunner. runChild (BlockJUnit4ClassRunner. java: 47) at org. junit. runners. parentRunner $ 3.run( ParentRunner. java: 231) at org. junit. runners. parentRunner $1. schedule (ParentRunner. java: 60) at org. junit. runners. parentRunner. runChildren (ParentRunner. java: 229) at org. junit. runners. parentRunner. access $000 (ParentRunner. java: 50) at org. junit. runners. parentRunner $2. evaluate (ParentRunner. java: 222) at org. junit. runners. parentRunner. run (ParentRunner. java: 300) at org. eclipse. jdt. internal. junit4.runner. JUnit4TestReference. run (JUnit4TestReference. java: 50) at org. eclipse. jdt. internal. junit. runner. testExecution. run (TestExecution. java: 38) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. runTests (RemoteTestRunner. java: 467) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. runTests (RemoteTestRunner. java: 683) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. run (RemoteTestRunner. java: 390) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. main (RemoteTestRunner. java: 197)      
     Student Information      Name: Zhang Sanfeng Gender: male age: 16 birthdays: Address: QQ: 78,451,214 Course: Expression student, Hongshan district, Wuchang City, Hubei Province. course is undefined on line 15, column 24 in course. ftl. the problematic instruction: ---------- ==>$ {student. course} [on line 15, column 22 in course. ftl] ---------- Java backtrace for programmers: ---------- freemarker. core. invalidReferenceException: Expression student. course is undefined on line 15, column 24 in course. ftl. at freemarker. core. templateObject. assertNonNull (TemplateObject. java: 125) at freemarker. core. expression. getStringValue (Expression. java: 118) at freemarker. core. expression. getStringValue (Expression. java: 93) at freemarker. core. dollarVariable. accept (DollarVariable. java: 76) at freemarker. core. environment. visit (Environment. java: 221) at freemarker. core. mixedContent. accept (MixedContent. java: 92) at freemarker. core. environment. visit (Environment. java: 221) at freemarker. core. environment. process (Environment. java: 199) at freemarker. template. template. process (Template. java: 259) at com. you. freemarker. freemarkerTemplate. printFtl (FreemarkerTemplate. java: 77) at com. you. test. freemarker. freemarkerTest. studentPrint (FreemarkerTest. java: 141) at com. you. test. freemarker. freemarkerTest. testCourse (FreemarkerTest. java: 128) at sun. reflect. nativeMethodAccessorImpl. invoke0 (Native Method) at sun. reflect. nativeMethodAccessorImpl. invoke (Unknown Source) at sun. reflect. delegatingMethodAccessorImpl. invoke (Unknown Source) at java. lang. reflect. method. invoke (Unknown Source) at org. junit. runners. model. frameworkMethod $1. runReflectiveCall (FrameworkMethod. java: 45) at org. junit. internal. runners. model. reflectiveCallable. run (ReflectiveCallable. java: 15) at org. junit. runners. model. frameworkMethod. invokeExplosively (FrameworkMethod. java: 42) at org. junit. internal. runners. statements. invokeMethod. evaluate (InvokeMethod. java: 20) at org. junit. internal. runners. statements. runBefores. evaluate (RunBefores. java: 28) at org. junit. runners. parentRunner. runLeaf (ParentRunner. java: 263) at org. junit. runners. blockJUnit4ClassRunner. runChild (BlockJUnit4ClassRunner. java: 68) at org. junit. runners. blockJUnit4ClassRunner. runChild (BlockJUnit4ClassRunner. java: 47) at org. junit. runners. parentRunner $ 3.run( ParentRunner. java: 231) at org. junit. runners. parentRunner $1. schedule (ParentRunner. java: 60) at org. junit. runners. parentRunner. runChildren (ParentRunner. java: 229) at org. junit. runners. parentRunner. access $000 (ParentRunner. java: 50) at org. junit. runners. parentRunner $2. evaluate (ParentRunner. java: 222) at org. junit. runners. parentRunner. run (ParentRunner. java: 300) at org. eclipse. jdt. internal. junit4.runner. JUnit4TestReference. run (JUnit4TestReference. java: 50) at org. eclipse. jdt. internal. junit. runner. testExecution. run (TestExecution. java: 38) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. runTests (RemoteTestRunner. java: 467) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. runTests (RemoteTestRunner. java: 683) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. run (RemoteTestRunner. java: 390) at org. eclipse. jdt. internal. junit. runner. remoteTestRunner. main (RemoteTestRunner. java: 197)

2. Error cause

The course attribute in the Student class is not assigned a value, and the freemarker returns an error for the attribute that is null.

Course: $ {student. course}

3. Solution

Add "!" after the property value

Course: $ {student. course !}