Question

我试图在其中显示一个带有复选框列表的表单。有两个Java类来保存我需要的数据：

public class CategoryAndSelection {

    private Category category;
    private boolean selection;

    public Category getCategory() {
        return category;
    }

    public void setCategory(Category category) {
        this.category = category;
    }

    public boolean getSelection() {
        return selection;
    }

    public void setSelection(boolean selection) {
        this.selection = selection;
    }

    public CategoryAndSelection() {
    }

    public CategoryAndSelection(Category category, boolean selection) {

        super();

        this.category = category;
        this.selection = selection;
    }
}

和

public class GroupAndCategoriesAndSelections {

    private Group group;
    private List<CategoryAndSelection> categoriesAndSelections;

    public Group getGroup() {
        return group;
    }

    public void setGroup(Group group) {
        this.group = group;
    }

    public List<CategoryAndSelection> getCategoriesAndSelections() {
        return categoriesAndSelections;
    }

    public void setCategoriesAndSelections(List<CategoryAndSelection> categoriesAndSelections) {
        this.categoriesAndSelections = categoriesAndSelections;
    }

    public GroupAndCategoriesAndSelections() {
    }

    public GroupAndCategoriesAndSelections(List<Category> categories) {

        this.group = new Group();
        this.categoriesAndSelections = new ArrayList<CategoryAndSelection>();

        for (Category category : categories) {

            CategoryAndSelection categoryAndSelection = new CategoryAndSelection(category, false);
            this.categoriesAndSelections.add(categoryAndSelection);
        }
    }
}

在我的控制器中，我确保初始化数据并将其作为属性添加到模型中：

CategoryRepository cr = new CategoryRepository(pm);
List<Category> catList = cr.getAllForProject(project, "title asc");
GroupAndCategoriesAndSelections groupAndCategoriesAndSelections = new GroupAndCategoriesAndSelections(catList);
model.addAttribute("groupAndCategoriesAndSelections", groupAndCategoriesAndSelections);

JSP文件的相应位如下所示：

<form:form method="POST" modelAttribute="groupAndCategoriesAndSelections">
    <%-- ... --%>
    <c:forEach items="${groupAndCategoriesAndSelections.categoriesAndSelections}" varStatus="status" >
        <form:checkbox path="categoriesAndSelections[${status.index}].selection" value="categoriesAndSelections[${status.index}].selection" />
        <br />
    </c:forEach>
</form:form>

这可行，但出于某种原因，这并不是：

<form:form method="POST" modelAttribute="groupAndCategoriesAndSelections">
    <%-- ... --%>
    <form:checkboxes items="${categoriesAndSelections}" path="selection" />
</form:form>

由于某种原因，它会产生IllegalArgumentException: 'items' must not be null。这是为什么？关于这个标签，我不明白什么？

<form：checkboxes>＆＃39; items＆＃39;不能为空

0 个答案: