Like/Dislike function with Spring Boot and Thymeleaf - java

I have a table in my Thymeleaf template which shows database data. I have additional two columns which contain Like and Dislike buttons for each row. I want to enable liking/disliking "posts". My idea was to simply increment Like/Dislike count in a database by updating database entity. So, in my template I got this:
<table id="css-serial" class="table table-striped table-inverse">
<tbody>
<tr>
<th>#</th>
<th>Kategorija</th>
<th>Vic</th>
<th>Likes</th>
<th>Dislikes</th>
<th>Razlika</th>
<th>Like</th>
<th>Dislike</th>
</tr>
<tr th:each="joke : ${jokes}">
<form method="POST" th:object="${updateJoke}" th:action="#{/}">
<td></td>
<td> <pre th:text="${joke.getCatName()}"></pre> </td>
<td> <div class="preforma" th:text="${joke.getContent()}" th:field="*{content}"></div> </td>
<td th:text="${joke.getLikes()}" th:field="*{likes}"></td>
<td th:text="${joke.getDislikes()}" th:field="*{dislikes}"></td>
<td th:text="${joke.likesDislikesSubtraction()}"></td>
<td><input type="submit" value="Svidja mi se" name="like"/></td>
<td><input type="submit" value="Ne svidja mi se" name="dislike"/></td>
</form>
</tr>
</tbody>
</table>
Controller GET and POST methods:
#RequestMapping(value="", method=RequestMethod.GET)
public String showJokes(Model model){
model.addAttribute("jokes", jokeService.listAllJokes());
return "jokestable";
}
#RequestMapping(params="like", method=RequestMethod.POST)
public String likeJoke(Joke joke, Model model){
model.addAttribute("updateJoke", joke);
jokeService.likeJoke(joke);
return showJokes(model);
}
#RequestMapping(params="dislike", method=RequestMethod.POST)
public String dislikeJoke(Joke joke, Model model){
model.addAttribute("updateJoke", joke);
jokeService.dislikeJoke(joke);
return showJokes(model);
}
Relevant methods in service layer:
public void likeJoke(Joke joke){
jokeRepository.likeJoke(joke.getContent());
}
public void dislikeJoke(Joke joke){
jokeRepository.dislikeJoke(joke.getContent());
}
Repository:
public interface JokeRepository extends CrudRepository<Joke, Long> {
Joke findByContent(String content);
#Modifying
#Query("UPDATE Joke j SET j.likes = j.likes+1 WHERE j.content=:content")
void likeJoke(#Param("content") String content);
#Modifying
#Query("UPDATE Joke j SET j.dislikes=j.dislikes+1 WHERE j.content=:content")
void dislikeJoke(#Param("content") String content);
}
This obviously doesn't work, and every time I hit the Like button, nothing happens, but when I go to IntelliJ, I see "Request method 'GET' not supported" (first time after refresh it shows this two times for each button, then every next time, only once). Is this solution even possible, or I have to change my approach? Any ideas?
P.S. Service class is annotated with #Transactional
If anyone wonders why do I
return showJokes(model);
it's because if I return template name, it doesn't show database data anymore when I hit the buttons, there's just empty table then (only th elements).
I suppose that possible problem could be that every Like button for every row is named the same, as well as Dislike buttons. But I don't know how to solve this.

Related

Get URL parameter using Spring

I have Spring application,I want to set parameter in URL and forward to URL.
For example,I click "Show detail" in index.html.Then go to /employees/show/1111.
ShowController.java get 1111.Now I click "show detail",result is white page error.
And I set break point ShowController.java,break point cannot was not working.
Where I should fix it?
Controller
#Controller
#RequestMapping("/employees/show/{employee.empId}/")
public class ShowController {
#Autowired
EmployeeService empService;
#GetMapping
public String details(#RequestParam("empId") String empId, Model model) {
Employee employee = empService.getEmployeeInfo(Long.parseLong(empId)); // break point at this row
model.addAttribute("employee", employee);
return "view/show";
}
index.html
<body>
<table>
<tr>
<th>Id</th>
<th>Name</th>
<th></th>
</tr>
<tr th:each="employee : ${employees}">
<td th:text="${employee.empId}"></td>
<td th:text="${employee.empName}"></td>
<td><a th:href="#{'/employees/show/' + ${employee.empId}}">Show detail</a></td>
</tr>
</table>
<br>
</body>
show.html
<body>
<div th:text="${employee.empId}"></div>
<div th:text="${employee.empName}"></div>
</body>
This folder structure.
The problem is the url. You are using /employees/show/{employee.empId}/ as a base url. And #GetMappingis not mapped to any url, so it takes the exact url from #RequestMapping("/employees/show/{employee.empId}/").
#RequestParam is to extract query parameters, form parameters, and even files from the request, while #PathVariable is used to tell Spring that part of the URI path is a value you want passed to your method.
So, in your case it seems mixed, you are using #RequestParam instead of #PathVariable.
#Controller
#RequestMapping("/employees/show/{employee:.*}/") //since spring will skip anything after a dot(.)
....
#GetMapping
public String details(#PathVariable("empId") String empId, Model model) {....}

How to extract JSP forEach index to Controller on POST/DELETE?

I have a jsp table with dynamically created rows - each row is binded to DAO. Each row also has a button that is supposed to provide availability to delete that DAO from DB and of course from the table itself.
My question is, how can I inform controller which exactly DAO was called to be deleted?
My idea was to extract varStatus index to controller and find it with #ModelAttribute ("games") somehow, but honestly I don't know how to pass this index up to controller. I know model is generated by controller and passed to JSP which extracts the data from the model and renders it, but what I'm doing here is obviously a POST/DELETE method.
My Controller mapping for that jsp:
#RequestMapping(value="/deleteGame", method=RequestMethod.GET)
public String getDeleteGame (ModelMap model) {
List<Game> myGames = gamesService.fetchById();
model.addAttribute("games", myGames);
return "deleteGame";
}
#RequestMapping(value="/deleteGame", method=RequestMethod.POST)
public String postDeleteGame (ModelMap model) {
return "deleteGame";
}
And here is my ref JSP table:
<div class="table-responsive" id="tableWithBg">
<table class = "table-hover">
<thead>
<tr>
<th class="col-md-2">TITLE</th>
<th class="col-md-2">TYPE</th>
<th class="col-md-2">MODE</th>
<th class="col-md-2">PRODUCER</th>
<th class="col-md-3">OPINION</th>
<th class="col-md-1">DELETE</th>
</tr>
</thead>
<tbody>
<c:forEach items="${games}" var="game" varStatus="loopIndex">
<tr>
<td>${game.title}</td>
<td>${game.type}</td>
<td>${game.mode}</td>
<td>${game.producent}</td>
<td>${game.opinion}</td>
<td>
<button type="button" action="delete" onclick="getCategoryIndex(${loopIndex.index})" class="btn btn-danger">
<strong>X</strong>
</button>
</td>
</tr>
</c:forEach>
</tbody>
</table>
</div>
Firstly, add common class(like class="js-delete-game") to all your delete button to check which button is triggered.
data-game-id="${game.id}" is game's unique id (supposing that your unique id is id) to remove appropriate game.
<button data-game-id="${game.id}" type="button" class="js-delete-game" id="js-delete-game${game.id}">
<strong>X</strong>
</button>
An event handler to check which button is clicked and ajax method to remove your game.
//<table id="game-list">
$("#game-list").on('click','.js-delete-game',function(event){
var id = $(event.target).data('gameId'); //data-game-id Get your unique game ID from the clicked button.
var data = JSON.stringify({"id":id});
var rowId= "#"+event.target.id; //get button id from clicked button and create selector
$.ajax({
type : "DELETE",
url : "${pageContext.request.contextPath}/deleteGame",
contentType: "application/json",
data : data,
success: function(data){
//remove row deleted on page without refreshing.
$(rowId).closest('tr').remove();
}
});
});
Finally change your mapping method as follows:
#RequestMapping(value = "/deleteGame" , method = RequestMethod.DELETE)
#ResponseBody
public void deleteGameById(#RequestBody Map<String, String> id) {
//your logic maybe different
gamesService.remove(id.get("id"));
}
Briefly, if you click the delete button, the game's unique id will send to server. Now you can get the id on server-side and delete the game by id.

How to map input value from form to URL of findById()

/welcome/employees
I have a input area where user enters `"empNo"` and clicks on "Find Employee", mapping to be done to /welcome/employees/find/{id}.
[`it should insted be move to url appended with empNo`][2]
Here I have everything fine while I directly enter the url, it gives up the result.
but the Find Employee button isn't mapped to entered /welcome/employees/find/{id} instead to /welcome/employees/find/.
and how to map the entered emp No to Find Employee button.Please shed some light.
Controller get employee method working fine only when I manually enter the URL.
list.jsp form page
<input type="text" path="empNo" value="${employee.empNo}" placeholder="Employee No."/>${employee.empNo}
<a href="/welcome/employees/find/${employee.empNo}" class="btn btn-primary">
<span class="glyphicon glyphicon-search"></span> Find Employee
</a>
find.jsp
<h2>Employee information</h2>
<form action="/welcome/employees/find/${employee.empNo}">
<table class="table table-bordered">
<tr>
<th>Employee No.</th>
<th>First Name</th>
<th>Last Name</th>
<th>Gender</th>
<th>Birth Date</th>
<th>Hire Date</th>
</tr>
<tr>
<td>"${employee.empNo}"</td>
<td>"${employee.firstName}"</td>
<td>"${employee.lastName}"</td>
<td>"${employee.gender}"</td>
<td>"${employee.birthDate}"</td>
<td>"${employee.hireDate}"</td>
</tr>
</table>
</form>
Back
#RequestMapping(value = "/employees/find/{empNo}", method = RequestMethod.GET)
public String getEmployee(#PathVariable("empNo") long empNo, Model model){
Employee employee1=this.employeeService.findEmployeeById(empNo);
model.addAttribute(employee1);
return "employees/find";
}
and when I click on find employee it directs to
http://localhost:8080/welcome/employees/find/
Here is the simple approach without any javascript.
listing.jsp
<form action="/welcome/employees/find" method="get">
<input name="empNo" placeholder="Employee No."/>
<button type="submit">Find Employee</button>
</form>
Explaination: when you do ${employee.empNo}, you're getting the value out of the empNo variable inside employee object. But you don't want to use this value to find. You want to use the value in the textbox to find.
controller
#RequestMapping(value = "/employees/find", method = RequestMethod.GET)
public String getEmployee(#RequestParam("empNo") long empNo, Model model){
Employee employee1=this.employeeService.findEmployeeById(empNo);
model.addAttribute(employee1);
return "employees/find";
}
You don't need <form> in find.jsp unless you want to do something.

How to bind an object list with thymeleaf?

I am having a lot of difficulty with POSTing back a form to the controller, which should contain simply an arraylist of objects that the user may edit.
The form loads up correctly, but when it's posted, it never seems to actually post anything.
Here is my form:
<form action="#" th:action="#{/query/submitQuery}" th:object="${clientList}" method="post">
<table class="table table-bordered table-hover table-striped">
<thead>
<tr>
<th>Select</th>
<th>Client ID</th>
<th>IP Addresss</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr th:each="currentClient, stat : ${clientList}">
<td><input type="checkbox" th:checked="${currentClient.selected}" /></td>
<td th:text="${currentClient.getClientID()}" ></td>
<td th:text="${currentClient.getIpAddress()}"></td>
<td th:text="${currentClient.getDescription()}" ></td>
</tr>
</tbody>
</table>
<button type="submit" value="submit" class="btn btn-success">Submit</button>
</form>
Above works fine, it loads up the list correctly. However, when I POST, it returns a empty object (of size 0). I believe this is due to the lack of th:field, but anyway here is controller POST method:
...
private List<ClientWithSelection> allClientsWithSelection = new ArrayList<ClientWithSelection>();
//GET method
...
model.addAttribute("clientList", allClientsWithSelection)
....
//POST method
#RequestMapping(value="/submitQuery", method = RequestMethod.POST)
public String processQuery(#ModelAttribute(value="clientList") ArrayList clientList, Model model){
//clientList== 0 in size
...
}
I have tried adding a th:field but regardless of what I do, it causes an exception.
I've tried:
...
<tr th:each="currentClient, stat : ${clientList}">
<td><input type="checkbox" th:checked="${currentClient.selected}" th:field="*{}" /></td>
<td th th:field="*{currentClient.selected}" ></td>
...
I cannot access currentClient (compile error), I can't even select clientList, it gives me options like get(), add(), clearAll() etc, so it things it should have an array, however, I cannot pass in an array.
I've also tried using something like th:field=${}, this causes runtime exception
I've tried
th:field = "*{clientList[__currentClient.clientID__]}"
but also compile error.
Any ideas?
UPDATE 1:
Tobias suggested that I need to wrap my list in a wraapper. So that's what I did:
ClientWithSelectionWrapper:
public class ClientWithSelectionListWrapper {
private ArrayList<ClientWithSelection> clientList;
public List<ClientWithSelection> getClientList(){
return clientList;
}
public void setClientList(ArrayList<ClientWithSelection> clients){
this.clientList = clients;
}
}
My page:
<form action="#" th:action="#{/query/submitQuery}" th:object="${wrapper}" method="post">
....
<tr th:each="currentClient, stat : ${wrapper.clientList}">
<td th:text="${stat}"></td>
<td>
<input type="checkbox"
th:name="|clientList[${stat.index}]|"
th:value="${currentClient.getClientID()}"
th:checked="${currentClient.selected}" />
</td>
<td th:text="${currentClient.getClientID()}" ></td>
<td th:text="${currentClient.getIpAddress()}"></td>
<td th:text="${currentClient.getDescription()}" ></td>
</tr>
Above loads fine:
Then my controller:
#RequestMapping(value="/submitQuery", method = RequestMethod.POST)
public String processQuery(#ModelAttribute ClientWithSelectionListWrapper wrapper, Model model){
...
}
The page loads correctly, the data is displayed as expected. If I post the form without any selection I get this:
org.springframework.expression.spel.SpelEvaluationException: EL1007E:(pos 0): Property or field 'clientList' cannot be found on null
Not sure why it's complaining
(In the GET Method it has: model.addAttribute("wrapper", wrapper);)
If I then make a selection, i.e. tick the first entry:
There was an unexpected error (type=Bad Request, status=400).
Validation failed for object='clientWithSelectionListWrapper'. Error count: 1
I'm guessing my POST controller is not getting the clientWithSelectionListWrapper. Not sure why, since I have set the wrapper object to be posted back via the th:object="wrapper" in the FORM header.
UPDATE 2:
I've made some progress! Finally the submitted form is being picked up by the POST method in controller. However, all the properties appear to be null, except for whether the item has been ticked or not. I've made various changes, this is how it is looking:
<form action="#" th:action="#{/query/submitQuery}" th:object="${wrapper}" method="post">
....
<tr th:each="currentClient, stat : ${clientList}">
<td th:text="${stat}"></td>
<td>
<input type="checkbox"
th:name="|clientList[${stat.index}]|"
th:value="${currentClient.getClientID()}"
th:checked="${currentClient.selected}"
th:field="*{clientList[__${stat.index}__].selected}">
</td>
<td th:text="${currentClient.getClientID()}"
th:field="*{clientList[__${stat.index}__].clientID}"
th:value="${currentClient.getClientID()}"
></td>
<td th:text="${currentClient.getIpAddress()}"
th:field="*{clientList[__${stat.index}__].ipAddress}"
th:value="${currentClient.getIpAddress()}"
></td>
<td th:text="${currentClient.getDescription()}"
th:field="*{clientList[__${stat.index}__].description}"
th:value="${currentClient.getDescription()}"
></td>
</tr>
I also added a default param-less constructor to my wrapper class and added a bindingResult param to POST method (not sure if needed).
public String processQuery(#ModelAttribute ClientWithSelectionListWrapper wrapper, BindingResult bindingResult, Model model)
So when an object is being posted, this is how it is looking:
Of course, the systemInfo is supposed to be null (at this stage), but the clientID is always 0, and ipAddress/Description always null. The selected boolean is correct though for all properties. I'm sure I've made a mistake on one of the properties somewhere. Back to investigation.
UPDATE 3:
Ok I've managed to fill up all the values correctly! But I had to change my td to include an <input /> which is not what I wanted... Nonetheless, the values are populating correctly, suggesting spring looks for an input tag perhaps for data mapping?
Here is an example of how I changed the clientID table data:
<td>
<input type="text" readonly="readonly"
th:name="|clientList[${stat.index}]|"
th:value="${currentClient.getClientID()}"
th:field="*{clientList[__${stat.index}__].clientID}"
/>
</td>
Now I need to figure out how to display it as plain data, ideally without any presence of an input box...
You need a wrapper object to hold the submited data, like this one:
public class ClientForm {
private ArrayList<String> clientList;
public ArrayList<String> getClientList() {
return clientList;
}
public void setClientList(ArrayList<String> clientList) {
this.clientList = clientList;
}
}
and use it as the #ModelAttribute in your processQuery method:
#RequestMapping(value="/submitQuery", method = RequestMethod.POST)
public String processQuery(#ModelAttribute ClientForm form, Model model){
System.out.println(form.getClientList());
}
Moreover, the input element needs a name and a value. If you directly build the html, then take into account that the name must be clientList[i], where i is the position of the item in the list:
<tr th:each="currentClient, stat : ${clientList}">
<td><input type="checkbox"
th:name="|clientList[${stat.index}]|"
th:value="${currentClient.getClientID()}"
th:checked="${currentClient.selected}" />
</td>
<td th:text="${currentClient.getClientID()}" ></td>
<td th:text="${currentClient.getIpAddress()}"></td>
<td th:text="${currentClient.getDescription()}" ></td>
</tr>
Note that clientList can contain null at
intermediate positions. Per example, if posted data is:
clientList[1] = 'B'
clientList[3] = 'D'
the resulting ArrayList will be: [null, B, null, D]
UPDATE 1:
In my exmple above, ClientForm is a wrapper for List<String>. But in your case ClientWithSelectionListWrapper contains ArrayList<ClientWithSelection>. Therefor clientList[1] should be clientList[1].clientID and so on with the other properties you want to sent back:
<tr th:each="currentClient, stat : ${wrapper.clientList}">
<td><input type="checkbox" th:name="|clientList[${stat.index}].clientID|"
th:value="${currentClient.getClientID()}" th:checked="${currentClient.selected}" /></td>
<td th:text="${currentClient.getClientID()}"></td>
<td th:text="${currentClient.getIpAddress()}"></td>
<td th:text="${currentClient.getDescription()}"></td>
</tr>
I've built a little demo, so you can test it:
Application.java
#SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
ClientWithSelection.java
public class ClientWithSelection {
private Boolean selected;
private String clientID;
private String ipAddress;
private String description;
public ClientWithSelection() {
}
public ClientWithSelection(Boolean selected, String clientID, String ipAddress, String description) {
super();
this.selected = selected;
this.clientID = clientID;
this.ipAddress = ipAddress;
this.description = description;
}
/* Getters and setters ... */
}
ClientWithSelectionListWrapper.java
public class ClientWithSelectionListWrapper {
private ArrayList<ClientWithSelection> clientList;
public ArrayList<ClientWithSelection> getClientList() {
return clientList;
}
public void setClientList(ArrayList<ClientWithSelection> clients) {
this.clientList = clients;
}
}
TestController.java
#Controller
class TestController {
private ArrayList<ClientWithSelection> allClientsWithSelection = new ArrayList<ClientWithSelection>();
public TestController() {
/* Dummy data */
allClientsWithSelection.add(new ClientWithSelection(false, "1", "192.168.0.10", "Client A"));
allClientsWithSelection.add(new ClientWithSelection(false, "2", "192.168.0.11", "Client B"));
allClientsWithSelection.add(new ClientWithSelection(false, "3", "192.168.0.12", "Client C"));
allClientsWithSelection.add(new ClientWithSelection(false, "4", "192.168.0.13", "Client D"));
}
#RequestMapping("/")
String index(Model model) {
ClientWithSelectionListWrapper wrapper = new ClientWithSelectionListWrapper();
wrapper.setClientList(allClientsWithSelection);
model.addAttribute("wrapper", wrapper);
return "test";
}
#RequestMapping(value = "/query/submitQuery", method = RequestMethod.POST)
public String processQuery(#ModelAttribute ClientWithSelectionListWrapper wrapper, Model model) {
System.out.println(wrapper.getClientList() != null ? wrapper.getClientList().size() : "null list");
System.out.println("--");
model.addAttribute("wrapper", wrapper);
return "test";
}
}
test.html
<!DOCTYPE html>
<html>
<head></head>
<body>
<form action="#" th:action="#{/query/submitQuery}" th:object="${wrapper}" method="post">
<table class="table table-bordered table-hover table-striped">
<thead>
<tr>
<th>Select</th>
<th>Client ID</th>
<th>IP Addresss</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr th:each="currentClient, stat : ${wrapper.clientList}">
<td><input type="checkbox" th:name="|clientList[${stat.index}].clientID|"
th:value="${currentClient.getClientID()}" th:checked="${currentClient.selected}" /></td>
<td th:text="${currentClient.getClientID()}"></td>
<td th:text="${currentClient.getIpAddress()}"></td>
<td th:text="${currentClient.getDescription()}"></td>
</tr>
</tbody>
</table>
<button type="submit" value="submit" class="btn btn-success">Submit</button>
</form>
</body>
</html>
UPDATE 1.B:
Below is the same example using th:field and sending back all other attributes as hidden values.
<tbody>
<tr th:each="currentClient, stat : *{clientList}">
<td>
<input type="checkbox" th:field="*{clientList[__${stat.index}__].selected}" />
<input type="hidden" th:field="*{clientList[__${stat.index}__].clientID}" />
<input type="hidden" th:field="*{clientList[__${stat.index}__].ipAddress}" />
<input type="hidden" th:field="*{clientList[__${stat.index}__].description}" />
</td>
<td th:text="${currentClient.getClientID()}"></td>
<td th:text="${currentClient.getIpAddress()}"></td>
<td th:text="${currentClient.getDescription()}"></td>
</tr>
</tbody>
When you want to select objects in thymeleaf, you dont actually need to create a wrapper for the purpose of storing a boolean select field. Using dynamic fields as per the thymeleaf guide with syntax th:field="*{rows[__${rowStat.index}__].variety}" is good for when you want to access an already existing set of objects in a collection. Its not really designed for doing selections by using wrapper objects IMO as it creates unnecessary boilerplate code and is sort of a hack.
Consider this simple example, a Person can select Drinks they like. Note: Constructors, Getters and setters are omitted for clarity. Also, these objects are normally stored in a database but I am using in memory arrays to explain the concept.
public class Person {
private Long id;
private List<Drink> drinks;
}
public class Drink {
private Long id;
private String name;
}
Spring controllers
The main thing here is that we are storing the Person in the Model so we can bind it to the form within th:object.
Secondly, the selectableDrinks are the drinks a person can select on the UI.
#GetMapping("/drinks")
public String getDrinks(Model model) {
Person person = new Person(30L);
// ud normally get these from the database.
List<Drink> selectableDrinks = Arrays.asList(
new Drink(1L, "coke"),
new Drink(2L, "fanta"),
new Drink(3L, "sprite")
);
model.addAttribute("person", person);
model.addAttribute("selectableDrinks", selectableDrinks);
return "templates/drinks";
}
#PostMapping("/drinks")
public String postDrinks(#ModelAttribute("person") Person person) {
// person.drinks will contain only the selected drinks
System.out.println(person);
return "templates/drinks";
}
Template code
Pay close attention to the li loop and how selectableDrinks is used to get all possible drinks that can be selected.
The checkbox th:field really expands to person.drinks since th:object is bound to Person and *{drinks} simply is the shortcut to referring to a property on the Person object. You can think of this as just telling spring/thymeleaf that any selected Drinks are going to be put into the ArrayList at location person.drinks.
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml"
xmlns:th="http://www.thymeleaf.org"
xmlns:layout="http://www.ultraq.net.nz/thymeleaf/layout" >
<body>
<div class="ui top attached segment">
<div class="ui top attached label">Drink demo</div>
<form class="ui form" th:action="#{/drinks}" method="post" th:object="${person}">
<ul>
<li th:each="drink : ${selectableDrinks}">
<div class="ui checkbox">
<input type="checkbox" th:field="*{drinks}" th:value="${drink.id}">
<label th:text="${drink.name}"></label>
</div>
</li>
</ul>
<div class="field">
<button class="ui button" type="submit">Submit</button>
</div>
</form>
</div>
</body>
</html>
Any way...the secret sauce is using th:value=${drinks.id}. This relies on spring converters. When the form is posted, spring will try recreate a Person and to do this it needs to know how to convert any selected drink.id strings into the actual Drink type. Note: If you did th:value${drinks} the value key in the checkbox html would be the toString() representation of a Drink which is not what you want, hence need to use the id!. If you are following along, all you need to do is create your own converter if one isn't already created.
Without a converter you will receive an error like
Failed to convert property value of type 'java.lang.String' to required type 'java.util.List' for property 'drinks'
You can turn on logging in application.properties to see the errors in detail.
logging.level.org.springframework.web=TRACE
This just means spring doesn't know how to convert a string id representing a drink.id into a Drink. The below is an example of a Converter that fixes this issue. Normally you would inject a repository in get access the database.
#Component
public class DrinkConverter implements Converter<String, Drink> {
#Override
public Drink convert(String id) {
System.out.println("Trying to convert id=" + id + " into a drink");
int parsedId = Integer.parseInt(id);
List<Drink> selectableDrinks = Arrays.asList(
new Drink(1L, "coke"),
new Drink(2L, "fanta"),
new Drink(3L, "sprite")
);
int index = parsedId - 1;
return selectableDrinks.get(index);
}
}
If an entity has a corresponding spring data repository, spring automatically creates the converters and will handle fetching the entity when an id is provided (string id seems to be fine too so spring does some additional conversions there by the looks). This is really cool but can be confusing to understand at first.

Spring POST a large list of objects to controller

I followed the code from http://viralpatel.net/blogs/spring-mvc-multi-row-submit-java-list/ to post a list of objects to my Spring Controller. Soon, I ran into IndexOutOfBoundsException when the list size reached 256.
I found an answer which said setting the setAutoGrowCollectionLimit in WebDataBinder would solve this issue. So in my controller I did:
#InitBinder
public void initBinder(WebDataBinder binder) {
binder.setAutoGrowCollectionLimit(2048);
}
#RequestMapping(value="/upload", method=RequestMethod.POST)
public String postData(Model model){
List<Products> products = //Some processing to get products list
ProductList productList = new ProductList();
productList.setProducts(products);
System.out.println(“Total records loaded: "+products.size());
model.addAttribute("productform", productList);
return “upload”;
}
#RequestMapping(value=“/process”, method=RequestMethod.POST)
public String uploadProcessedData(#ModelAttribute("productform") ProductList productList){
System.out.println(“Total records received: “+productList.getProducts().size());
return "upload";
}
My JSP code:
<form:form method="post" action="${pageContext.request.contextPath}/process” modelAttribute="productform">
<table>
<tr>
<th>Record</th>
<th>name</th>
</tr>
<c:forEach var="product" items="${productform.products}" varStatus="status">
<tr>
<td><c:out value="${status.index + 1}" /></td>
<td><input name="products[${status.index}].name” value="${product.name}”/></td>
</tr>
</c:forEach>
</table>
<input type="submit" value="Save" />
</form:form>
However, my form has 1000+ records and the controller only receives 556 records. Why this number? Is this because of any size limit? How can I get Spring to load all the 1000+ records.
You might want to add the enctype=multipart/form-data in the form tag for huge data, especially if you have non-ASCII characters in the payload. That might enable sending huge data in chunks.

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