Binding list to checkbox in spring

Question

I have Offer entity class :

@Entity
public class Offer {

    public Offer(){}
    private int offerId;
    private String offerBanner;
    private String offerLongDesc; 
    private int offerLikeCount ;

    List<Category> categoryList ;

    @DateTimeFormat(pattern= "dd/MM/yyyy")
    private Date offerStartDate; 
    <----all getters and setters---->    
}

And a Category entity class @Entity public class Category{

    public Category() {}

    private int categoryId;
    private int categoryParentId;
    private String categoryName;
    private Date categoryCreationDate;
    <--getters n setters--->

}

In my offerDetails form i am trying to bind the categoryList (attribute Offer entity) to checkbox

offerEntry.jsp

<form:form class="form-horizontal" action="/addOffer" commandName="offerDetails" method="post" enctype="multipart/form-data" style=" margin-top:20px; padding-right:50px; padding-left:10px; ">

    <div class="checkbox-list">
        <c:forEach var="category" varStatus="categoryStatus" items="${categoriesList}">
            <form:checkbox path="categoryList"  value="${category.categoryId}"/> <c:out                                                 value="${category.categoryName}" /><br>
        </c:forEach>
    </div>
    <-----Other div elements------>

</form:form>

I have Offer entity class :

@Entity
public class Offer {

    public Offer(){}
    private int offerId;
    private String offerBanner;
    private String offerLongDesc; 
    private int offerLikeCount ;

    List<Category> categoryList ;

    @DateTimeFormat(pattern= "dd/MM/yyyy")
    private Date offerStartDate; 
    <----all getters and setters---->    
}

And a Category entity class @Entity public class Category{

    public Category() {}

    private int categoryId;
    private int categoryParentId;
    private String categoryName;
    private Date categoryCreationDate;
    <--getters n setters--->

}

In my offerDetails form i am trying to bind the categoryList (attribute Offer entity) to checkbox

offerEntry.jsp

<form:form class="form-horizontal" action="/addOffer" commandName="offerDetails" method="post" enctype="multipart/form-data" style=" margin-top:20px; padding-right:50px; padding-left:10px; ">

    <div class="checkbox-list">
        <c:forEach var="category" varStatus="categoryStatus" items="${categoriesList}">
            <form:checkbox path="categoryList"  value="${category.categoryId}"/> <c:out                                                 value="${category.categoryName}" /><br>
        </c:forEach>
    </div>
    <-----Other div elements------>

</form:form>

and here is my controller :

@RequestMapping(value = {"/addOffer"}, method = RequestMethod.GET)
public ModelAndView offerForm() {

    ModelAndView mv = new ModelAndView("offerEntry");
    Offer offer = new Offer();
    try{
        List<Category> categoryList=categoryRepository.getAllCategories();
        mv.addObject("categoriesList",categoryList);
    }catch(Exception e)
    {
    }
    mv.addObject("offerDetails",offer);
    return mv;
}

Converter class :

public class CategoryIdtoCategory implements Converter<String, Category>
{
    @Inject
    private CategoryRepository categoryRepo;
    @Override
    public Category convert(String  categoryId)
    {
    try{
        int categoryIdI = Integer.parseInt(categoryId);
        return categoryRepo.findCategoryById(categoryIdI);
    }catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

On Submit i want selected checkbox values to populate offerDetails.categoryList collection.

I have registered converter as well (for converting those category Ids to categoryObjects)

Bean registration:

<beans:bean id="conversionService"  class="org.springframework.format.support.FormattingConversionServiceFactoryBean" >
    <beans:property name="converters">
        <beans:list>
            <beans:bean class="com.service.util.CategoryIdtoCategory"/>
        </beans:list>
    </beans:property>
</beans:bean>

I am still getting following error :

[Failed to convert property value of type 'java.lang.String' to required type 'java.util.List' for property 'categoryList'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [com.domain.Category] for property 'categoryList[0]': no matching editors or conversion strategy found]

I am new to Spring . Please Excuse me if its a silly question. Your help would be appreciated . :)

Answer 1

1. In the JSP change path to reference the category
2. In category entity override equal and hash methods
3. In converter convert result of toString method in the Category entity to a Category object.

Answer 2

You can solve with @InitBinder in your controller like :

@InitBinder
protected void initBinder(WebDataBinder binder) throws Exception{
    binder.registerCustomEditor(Set.class,"categoryList", new CustomCollectionEditor(Set.class){
        protected Object convertElement(Object element){
            if (element instanceof String) {
                Category category = categoryCache.get(Integer.parseInt(element.toString()));
                return role;
            }
            return null;
        }
    });
}