java - 无法使用 Spring 和 Thymeleaf 传输 View 上的对象

Question

我试图使用 Spring 和 Thymeleaf 创建 super 简单的应用程序，但在 View 上传输对象时遇到一些问题。

类 Person.java :

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;
}

}

我的 Controller 类 PeoplePageCotroller.java 看起来像:

@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;
    }
}

我的 html 文件的片段如下所示:

<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>

结果我得到异常“SpelEvaluationException”，我不知道如何修复它:

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

也许问题与您如何使用迭代来构建 HTML 表有关。您不需要添加 div 来迭代每一行，而是使用 tr 标记。在您的示例中:

<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>

Thymeleaf 文档中有关迭代的更多信息:http://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#using-theach