Spring Boot:如何在 thymleaf 中绑定 POST 上的对象列表 [英] Spring Boot : How to bind list of objects on POST in thymleaf

问题描述

我有一个关于 GET 请求的记录列表，它显示在带有复选框的 UI 上.

@GetMapping("/list")公共字符串列表(模型模型){model.addAttribute("记录", createRecords());返回列表"；}

这是我的记录 POJO:

class Record {选择了私有布尔值；私有整数 ID；私人字符串名称；私人字符串电话；//....

我在 UI 中显示如下:

<tr><td><input type="checkbox" th:field="*{selected}" th:checked="${record.selected}"/></td><td th:field="*{id}" th:text="${record.id}"/><td th:field="${name}" th:text="${record.name}"/><td th:field="${phone}" th:text="${record.phone}"/></tr></th:block>

我很难从 UI 获取 POST 上所选记录的 List.我只是从 POST 中取回一个对象.

我想要在 POST 映射中这样的东西:

@PostMapping("/list")公共字符串选择(@ModelAttribute ArrayList记录){//... 至少选定记录的 id//... 或所有记录返回选定的

请帮忙.

解决方案

导致您的问题的潜在原因有很多.下面列出的三项应该可以帮助您正确映射表单:

1. 您应该正确构建表单，包括使用 * 符号来减少重复，例如:

   <tr><td><input type="checkbox" th:field="*{selected}"/></td><td><input type="text" th:field="*{id}"/></td><td><input type="text" th:field="*{name}"/></td><td><input type="text" th:field="*{phone}"/></td></tr></th:block>

   如Spring + Thymeleaf 教程中所示

2. 在循环 ${records} 时，您可能需要使用双下划线表示法，以便在表单中正确填写每个 Record.根据 Thymeleaf + Spring 教程:<块引用>

   ..__${...}__ 语法是一个预处理表达式，它是在实际计算整个表达式之前计算的内部表达式.

   参见例如这个问题.

3. 通过接受用 @ 注释的 List，仔细检查您是否在 Spring @Controller 中正确处理了结果列表ModelAttribute 或 @RequestParam.(您似乎已经在这样做了.)

   参见例如这个问题.

I have a list of records on GET request which is shown on UI with a checkbox.

@GetMapping("/list")
public String list(Model model) {
    model.addAttribute("records", createRecords());
    return "list";
}

This is my Record POJO:

class Record {
    private boolean selected;   
    private Integer id; 
    private String name;    
    private String phone;
    //....

I am showing in UI as below:

<th:block th:each = "record : ${records}">
<tr>
    <td><input type="checkbox" th:field="*{selected}" th:checked="${record.selected}" /></td>
    <td th:field="*{id}" th:text="${record.id}" />
    <td th:field="${name}" th:text="${record.name}" />
    <td th:field="${phone}" th:text="${record.phone}" />
</tr>
</th:block>

I am having hard time to get the List of selected records on POST from UI. I just gets one object back from POST.

I want something like this in POST mapping:

@PostMapping("/list")
public String select(@ModelAttribute ArrayList<Record> records) {
    //... at least ids of selected records
    //... or all the records back with selected

Please help.

解决方案

There are a number of potential causes of your problem. The three items listed below should help you get the form mapped correctly:

1. You should build the form correctly, including using the * notation to reduce repetition, for example:

   <th:block th:each = "record : ${records}">
     <tr>
       <td><input type="checkbox" th:field="*{selected}"/></td>
       <td><input type="text" th:field="*{id}"/></td>
       <td><input type="text" th:field="*{name}"/></td>
       <td><input type="text" th:field="*{phone}"/></td>
     </tr>
   </th:block>
   

   As shown in the Spring + Thymeleaf tutorial

2. You may need to use the double-underscore notation when looping over ${records} to get each Record filled correctly in your form. As per the Thymeleaf + Spring tutorial:

   ..__${...}__ syntax is a preprocessing expression, which is an inner expression that is evaluated before actually evaluating the whole expression.

   See for example this question.

3. Double-check that you're handling the resulting list correctly in your Spring @Controller by accepting a List<Record> annotated with @ModelAttribute or @RequestParam. (It looks like you're doing this already.)

   See for example this question.

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