How to post a list to controller in Thymeleaf - spring-boot

Question

I am new to Thymeleaf,Maybe this is a simple question.Please help me.Thanks.
Controller code:
#Controller
public class TestController {
#GetMapping(value = "/")
public String testget(Map<String, Object> model) {
TestBean bean = new TestBean();
List<Person> list = new ArrayList<>();
for (int index = 1; index < 5; index++) {
Person p = new Person();
p.setId(index);
p.setName("name" + index);
list.add(p);
}
model.put("allList", "nothing");
bean.setList(list);
model.put("testbean", bean);
return "NewFile";
}
#PostMapping(value = "/")
public String testpost(Map<String, Object> model//
, #ModelAttribute(name = "testbean") TestBean bean) {
List<Person> list = bean.getList();
model.put("bean", bean);
model.put("allList", list.toString());
return "NewFile";
}}
simple mapper and a Person bean:
#Data
public class TestBean {
private List<Person> list;
}
#Data
public class Person {
private int id;
private String name;
}
HTML code :
<form action="#" th:action="#{/}" th:object="${testbean}" method="post">
<p th:text="'ALL : ' + ${allList}"></p>
<table>
<tr th:each="person : ${testbean.list}">
<td>Id:<input type="text" th:value="${person.id}"
/></td>
<td>name: <input type="text" th:value="${person.name}" /></td>
</tr>
</table>
<input type="submit" value="submit" />
</form>
I want put list to page and change properties to refresh.
but i don't know how to add th:field tag, I try to add
**th:field="*{testbean.list[__${index}__].id}"**
but it failed with :
Invalid property 'testbean' of bean class [com.TestBean]
UPDATE1
And i tried
th:field="*{list[__${index}__].id}"
I got a error Where I added th:field
Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Error during execution of processor 'org.thymeleaf.spring4.processor.attr.SpringInputGeneralFieldAttrProcessor' (NewFile:14)] with root cause
java.lang.NumberFormatException: For input string: "null"
My questions is what i can do something that i can get a List in controller.

Answer 1

Invalid property 'testbean' of bean class [com.TestBean]
Use th:field="*{list[__${index}__].id} pattern without testbean definition. If you use * notation then it will reference to parent object.
java.lang.NumberFormatException: For input string: "null"
Add any variable like "rowStat" to the loop for keeping status index:
th:each="person,rowStat : ${testbean.list}"
and access it like th:field="*{list[__${rowStat.index}__].id}. So index will not be null and no problem converting the string to int.

Answer 2

This is how I do it on page that lists some search results - table with checkboxes. Code itself is stripped only to relevant lines. places.content is a collection of Place objects.
<form th:action="#{selected-places}" method="POST" >
<tr th:each="place,i : ${places.content}">
<td><input name="places" th:value="${place.id}" type="checkbox"></td>
</tr>
</form>
And the controller side
#PostMapping(value = "/selected-places", params = "action=delete")
public String deletePlaces(#RequestParam Place[] places, RedirectAttributesModelMap model) {
....
}
As you can see, despite fact that form is sending only list of IDs, spring will autohydrate model entities. You can always Place[] places to collection of integers and it still will work.