FAQ: howto display checkboxes/multiselect

[Colin Yates]

The question of how to support checkboxes keeps appearing over and over again. This is how I deal with it:

Assume:

  class MyClass {
    private String id;
    private String name;
    // accessors
  }

  class MyBackingObject {
    private MyClass[] myClasses;
    // accessors
  }

In my simpleFormController I register a MyClassPropertyEditor in initBinder:

  public initBinder(HttpServletRequest request, ServletRequestDataBinder binder) {
    binder.registerCustomEditor(MyClass.class, new MyClassPropertyEditor());
  }

then in reference data I construct a map of *all* possible instances of MyClass:

public Map referenceData(HttpServletRequest request, Object command, Errors errors) throws Exception {
  MyBackingObject form = (MyBackingObject) command;
  Set selectedMyClasses = new HashSet().addAll(Arrays.asList(form.getMyClasses()));

  Map allMyClasses = new HashMap();
  for (Iterator i = myDAO.getAllMyClasses(); i.hasNext(); ) {
    MyClass myClass = (MyClass) i.next();
    allMyClasses.put(myClass, new Boolean(selectedMyClasses.contains(myClass));
  }
 
  Map model = new HashMap();
  model.put("allMyClasses", allMyClasses);
  return model;
}

then in my jsp:

  <c&#58;forEach items="$&#123;allMyClasses&#125;" var="allMyClassesEntry">
    <input type="checkbox" name="command.myClasses" value="$&#123;allMyClassesEntry.key.name&#125;" <c&#58;if test="$&#123;allMyClassesEntry.value&#125;">selected</c&#58;if>></input>
  </c&#58;forEach>

I typed this in, so it probably doesn't compile, but you get the idea

HTH.

[martinl]

You forgot to show the code of MyClassPropertyEditor.

[ypj]

Then how to bind the items?

[ypj]

And another questioin: Dose c:forEach support Map? Can a Map be iteratored by the froEach tag?

[Cowboy Bob]

And another questioin: Dose c:forEach support Map? Can a Map be iteratored by the froEach tag?

Yes, you get an Entry object in your var with "key" and "value" values.

<spring&#58;bind path="searchCommand.areaCode">
    <select name="areaCode">
        <option value="">--</option>
        <c&#58;forEach var="county" items="$&#123;countyMap&#125;">
            <option value='<c&#58;out value="$&#123;county.key&#125;"/>' <c&#58;if test="$&#123;status.value == county.key&#125;">selected</c&#58;if>><c&#58;out value="$&#123;county.value&#125;"/></option>
        </c&#58;forEach>
    </select>
</spring&#58;bind>

Bob

[ypj]

Thanks Bob.

[kermie5000]

also would like to see myclasspropertyeditor...

[Colin Yates]

The source code for myClassPropertyEditor is absolutely pointless It entirely depends on what the class is an how to retrieve it.

For example, if I myClass was a persisted class, i.e. a User and I was entering the user name, then my propertyEditor might look like:

  public final UserPropertyEditor extends PropertyEditorSupport {
    private final UserDAO dao;

    public UserPropertyEditor (final UserDAO theDAO) {
        this.dao = theDAO;
    }

    public String getAsText() {
        User user = (User) getValue();
        return user.getUserName();
    }

    public void setAsText(final String value) {
        try {
            User user = dao.findUser(value);
            super.setValue(user);
        } catch (final ObjectRetrievalFailureException e) {
            LOGGER.debug("Cannot find user with username: " + value);
            super.setValue(null);
        }
    }
  }

HTH.

[Trickle]

Ytesco, I have tried what you have said above and I still can not get my valuies to bind. I have a class that only contains a list, and that list gets populated with my value class that holds all the data. Everything works fine except that the variables on my value class are not getting set with the values from the page when I submit. I have a feeling that it has something to do with the Propert Editor, but I can not figure out how to set that up.

Do you have any ideas or need more information?

[Colin Yates]

Can you post your code please.