异常-----Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.\u003Cformat> or ?string(format) built-

1、错误描述

 五月 27, 2014 12:07:05 上午 freemarker.log.JDK14LoggerFactory$JDK14Logger error
 严重: Template processing error: "Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.\u003Cformat> or ?string(format) built-in with this date."

 Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
 The problematic instruction:
 ----------
 ==> ${student.studentBirthday} [on line 17, column 12 in student.ftl]
 ----------

 Java backtrace for programmers:
 ----------
 freemarker.template.TemplateModelException: Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
     at freemarker.core.Environment.formatDate(Environment.java:776)
     at freemarker.core.Expression.getStringValue(Expression.java:105)
     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.student(FreemarkerTest.java:125)
     at com.you.test.freemarker.FreemarkerTest.testStudent(FreemarkerTest.java:111)
     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)

 Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
 The problematic instruction:
 ----------
 ==> ${student.studentBirthday} [on line 17, column 12 in student.ftl]
 ----------

 Java backtrace for programmers:
 ----------
 freemarker.template.TemplateModelException: Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
     at freemarker.core.Environment.formatDate(Environment.java:776)
     at freemarker.core.Expression.getStringValue(Expression.java:105)
     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)
 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 <html>
   <head>
     <title>学生信息</title>

     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
     <meta http-equiv="description" content="this is my page">
     <meta http-equiv="content-type" content="text/html; charset=UTF-8">

   </head>

   <body>
         姓名：张三丰
          性别：男
          年龄：34
          生日：
 Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
 The problematic instruction:
 ----------
 ==> ${student.studentBirthday} [on line 17, column 12 in student.ftl]
 ----------

 Java backtrace for programmers:
 ----------
 freemarker.template.TemplateModelException: Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
     at freemarker.core.Environment.formatDate(Environment.java:776)
     at freemarker.core.Expression.getStringValue(Expression.java:105)
     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.student(FreemarkerTest.java:125)
     at com.you.test.freemarker.FreemarkerTest.testStudent(FreemarkerTest.java:111)
     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)
     at com.you.test.freemarker.FreemarkerTest.student(FreemarkerTest.java:125)
     at com.you.test.freemarker.FreemarkerTest.testStudent(FreemarkerTest.java:111)
     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$2.evaluate(ParentRunner.java:222)
     at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
     at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
     at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
     at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
     at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
     at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
     at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
 五月 27, 2014 12:07:05 上午 freemarker.log.JDK14LoggerFactory$JDK14Logger error
 严重: Template processing error: "Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.\u003Cformat> or ?string(format) built-in with this date."

 Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
 The problematic instruction:
 ----------
 ==> ${student.studentBirthday} [on line 17, column 12 in student.ftl]
 ----------

 Java backtrace for programmers:
 ----------
 freemarker.template.TemplateModelException: Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
     at freemarker.core.Environment.formatDate(Environment.java:776)
     at freemarker.core.Expression.getStringValue(Expression.java:105)
     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.printFile(FreemarkerTemplate.java:109)
     at com.you.test.freemarker.FreemarkerTest.studentFile(FreemarkerTest.java:139)
     at com.you.test.freemarker.FreemarkerTest.testStudent(FreemarkerTest.java:112)
     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)

 Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
 The problematic instruction:
 ----------
 ==> ${student.studentBirthday} [on line 17, column 12 in student.ftl]
 ----------

 Java backtrace for programmers:
 ----------
 freemarker.template.TemplateModelException: Can't convert the date to string, because it is not known which parts of the date variable are in use. Use ?date, ?time or ?datetime built-in, or ?string.<format> or ?string(format) built-in with this date.
     at freemarker.core.Environment.formatDate(Environment.java:776)
     at freemarker.core.Expression.getStringValue(Expression.java:105)
     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.printFile(FreemarkerTemplate.java:109)
     at com.you.test.freemarker.FreemarkerTest.studentFile(FreemarkerTest.java:139)
     at com.you.test.freemarker.FreemarkerTest.testStudent(FreemarkerTest.java:112)
     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、错误原因

不能将Date类型直接转化为String类型

3、解决办法

将日期类型后面添加如下：

原来：生日：${student.studentBirthday}

修改后：生日：${(student.studentBirthday)?string("yyyy-MM-dd")}