SpringとThymeleafを使用してオブジェクトを表示できません

Question

SpringとThymeleafを使用してスーパー単純なアプリケーションを作成しようとしていましたが、転送オブジェクトに問題があります。

クラスPerson.java：

<table 
        class="col-md-12 table-bordered table-striped table-condensed cf"> 
        <thead class="cf"> 
         <tr> 
          <th>First name</th> 
          <th>Last name</th> 
          <th>Age</th> 
         </tr> 
        </thead> 
        <tbody> 
         <div th:each="person : ${people}"> 
         <tr> 
          <td th:text="${person.firstName}"></td> 
          <td th:text="${person.lastName}"></td> 
          <td th:text="${person.age}"></td> 
         </tr> 
         </div> 
        </tbody> 
       </table> 

：私のhtmlファイルのフラグメントがどのように見える

@Controller 
@RequestMapping({"/people", "/people/"}) 
public class PeoplePageController { 

    @RequestMapping(method = RequestMethod.GET) 
    public String initPeoplePage(Model model) { 

     ArrayList<Person> people = createRandomPeople(5); 

     model.addAttribute("people", people); 
     return "peoplePage"; 
    } 

    private ArrayList<Person> createRandomPeople(int numberOfPeople) { 
     ArrayList<Person> people = new ArrayList<Person>(); 
     for (int i = 0; i < numberOfPeople; i++) { 
      Person person = new Person("FirstName" + i, "LastName" + i, i + 20); 
      people.add(person); 
     } 
     return people; 
    } 
} 

：

public class Person { 

private String firstName; 

private String lastName; 

private int age; 

public Person(String firstName, String lastName, int age) { 
    super(); 
    this.firstName = firstName; 
    this.lastName = lastName; 
    this.age = age; 
} 

public String getFirstName() { 
    return firstName; 
} 

public void setFirstName(String firstName) { 
    this.firstName = firstName; 
} 

public String getLastName() { 
    return lastName; 
} 

public void setLastName(String lastName) { 
    this.lastName = lastName; 
} 

public int getAge() { 
    return age; 
} 

public void setAge(int age) { 
    this.age = age; 
} 

}

私のコントローラクラスPeoplePageCotroller.javaは次のようになります

は、結果では、私は例外「SpelEvaluationException」を取得し、私はそれを修正する方法が分からない：

org.springframework.expression.spel.SpelEvaluationException: EL1007E:(pos 0): Property or field 'firstName' cannot be found on null 
at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:220) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:94) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:46) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:374) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:88) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:120) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:267) ~[spring-expression-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.thymeleaf.spring4.expression.SpelVariableExpressionEvaluator.evaluate(SpelVariableExpressionEvaluator.java:139) ~[thymeleaf-spring4-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.standard.expression.VariableExpression.executeVariable(VariableExpression.java:154) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.standard.expression.SimpleExpression.executeSimple(SimpleExpression.java:59) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.standard.expression.Expression.execute(Expression.java:103) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.standard.expression.Expression.execute(Expression.java:133) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.standard.expression.Expression.execute(Expression.java:120) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.standard.processor.attr.AbstractStandardTextChildModifierAttrProcessor.getText(AbstractStandardTextChildModifierAttrProcessor.java:68) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.processor.attr.AbstractTextChildModifierAttrProcessor.getModifiedChildren(AbstractTextChildModifierAttrProcessor.java:59) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.processor.attr.AbstractChildrenModifierAttrProcessor.processAttribute(AbstractChildrenModifierAttrProcessor.java:59) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.processor.attr.AbstractAttrProcessor.doProcess(AbstractAttrProcessor.java:87) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.processor.AbstractProcessor.process(AbstractProcessor.java:212) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.applyNextProcessor(Node.java:1017) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:972) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.computeNextChild(NestableNode.java:695) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.NestableNode.doAdditionalProcess(NestableNode.java:668) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Node.processNode(Node.java:990) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.dom.Document.process(Document.java:93) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1155) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1060) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1011) ~[thymeleaf-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.spring4.view.ThymeleafView.renderFragment(ThymeleafView.java:335) ~[thymeleaf-spring4-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.thymeleaf.spring4.view.ThymeleafView.render(ThymeleafView.java:190) ~[thymeleaf-spring4-2.1.4.RELEASE.jar:2.1.4.RELEASE] 
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1246) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1029) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:973) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:858) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) ~[tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1502) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1458) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_40] 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_40] 
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.0.33.jar:8.0.33] 
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_40] 

Answer 1

たぶん、問題は、HTMLテーブルを構築するために反復を使用しているどのように関係しています。 divを追加して各行を反復する必要はありませんが、代わりにtrタグを使用してください。反復についてThymeleafドキュメントの

<table class="col-md-12 table-bordered table-striped table-condensed cf"> 
    <thead class="cf"> 
    <tr> 
     <th>First name</th> 
     <th>Last name</th> 
     <th>Age</th> 
    </tr> 
    </thead> 
    <tbody> 
    <tr th:each="person : ${people}"> 
     <td th:text="${person.firstName}"></td> 
     <td th:text="${person.lastName}"></td> 
     <td th:text="${person.age}"></td> 
    </tr> 
    </tbody> 
</table> 

詳細情報：あなたの例ではhttp://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#using-theach

Answer 2

私は自分でこのコードを試してみましたが、それがnullオブジェクトが人々に追加されたときにのみ起こるあらゆるerrors.Itせずに動作しますリスト。

例：

ArrayList<Person> people = createRandomPeople(5); 
people.add(null);