java Thymeleaf下拉菜单故障

2 周，1 日 Questions & Answers 49

有一段时间以来，我一直在围绕这个问题，试图让一个简单的下拉菜单工作。它由测试对象填充。这些测试对象存储在一个列表中，该列表包含在TestController对象中。TestController还有一个“activeTest”字段，我们希望在该字段中存储下拉菜单中提交的测试。它应该是这样工作的：

1*从下拉菜单中选择测试对象 2*新闻稿提交 3*表单的POST方法应采用所选的测试对象，并通过将其添加为activeTest的当前值。setActiveTest（测试）

我有几个反复出现的错误，但现在我有一个主要的错误阻碍了我的进步：

“bean名称“test”的BindingResult或普通目标对象都不能作为请求属性使用”

我知道这与HTML视图中的第15行有关（选择th:field=“*{test}”），但我不知道如何解决它，也不知道它希望我修复什么

控制器：

@ComponentScan
@Controller
public class TeacherController {

    TestController testcont = TestController.getInstance();


    @RequestMapping(value = {"/sendTest"}, method = RequestMethod.GET)
    public String currentTestOptions(Model model) {

        model.addAttribute("test", new Test());
        model.addAttribute("tests", testcont.showAllTests());
        model.addAttribute("currentTest", testcont.getActiveTest());


        return "sendTest";
    }

    @RequestMapping(value = {"/sendTest"}, method = RequestMethod.POST)
    public String sendTest(@ModelAttribute("test") @Valid @RequestBody Test test){

        testcont.SetActiveTest(test);


        return "sendTest";
    }
}

HTML:

<body>
    <p>
        <a href='/Teacher/NewTest'>New Test upload</a> <a href='/Teacher/TestResults'>See Test Results</a>
    </p>

    <form id="dropdown" th:action="@{/sendTest}" th:object="${test}" method='post'>

        <label>Select test</label> 
        <select th:field="*{test}">
            <option th:each="test : ${tests}" 
                value="${test}"
                th:text="${test.name}"></option>
        <input type='submit' value='Submit'>

    </form>

    <a> Current test for students: </a>
    <p th:text="${activeTest}" ></p>
    <div>
    <a>Available tests for students:</a>
    <th:block th:each="Test : ${tests}">
        <tr>
            <td th:text="${Test.getName()}">...</td>
            <td th:text="${Test.getFile().getName()}">...</td>
        </tr>
    </div>
</body>

测试等级：

public class Test implements Serializable{
    /**
     * 
     */
    private static final long serialVersionUID = -8729209678450935222L;
    private File file;
    private String name;
    private String question;
    private String answer1;
    private String answer2;
    private double studentAnswer;
    private List<Double> answers;
    private List<Student> students;

    public Test(File file, String name, String question, String answer1, String answer2) {
        this.file = file;
        this.name = name;
        this.question = question;
        this.answer1 = answer1;
        this.answer2 = answer2;
        answers= new ArrayList<>();
        students = new ArrayList<>();
    }
// Getters and setters for above fields.
}

TestController类，其中包含存储所有测试对象的列表：

public class TestController {

    private static TestController instance = null;
    private List<Test> tests;
    private List<Student> students;
    private Test active = null;

    private TestController() {
        tests = new ArrayList<>();
        students = new ArrayList<>();
        loadTests();
    }

    public static TestController getInstance() {
        if (instance == null) {
            instance = new TestController();
        }
        return instance;

    }

    public void SetActiveTest(Test test) {
        active = test;
    }

    public Test getActiveTest() {
        System.out.println(active);
        return active;
    }

    public List<Test> showAllTests() {
        return tests;
    }
    // Other methods
}

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java Thymeleaf下拉菜单故障

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