I've made a converter:
public class BooleanToDateConverter implements Converter<Boolean, Date> {
private static final long serialVersionUID = 1L;
#Override
public Date convertToModel(Boolean value, Class<? extends Date> targetType, Locale locale)
throws com.vaadin.data.util.converter.Converter.ConversionException {
if (value == true) {
return new Date();
} else {
return null;
}
}
#Override
public Boolean convertToPresentation(Date value, Class<? extends Boolean> targetType, Locale locale)
throws com.vaadin.data.util.converter.Converter.ConversionException {
if (value == null) {
return false;
} else {
return true;
}
}
#Override
public Class<Date> getModelType() {
return Date.class;
}
#Override
public Class<Boolean> getPresentationType() {
return Boolean.class;
}
}
Then I have a Vaadin ComboBox myComboBox
I try to set my converter to it:
myComboBox.setConverter(new BooleanToDateConverter());
Then I get an error in Eclipse saying:
The method setConverter(Class<?>) in the type AbstractField<Object> is not applicable for the arguments (BooleanToDateConverter)
However, I've seen other converters being used similarly and they don't get errors. Why?
Your code cannot be compiled because there is no setConverter() method available on class ComboBox that fits your custom converter. Let me explain how converters are used on select components and what is the idea behind the specific method signatures you find for setting converters on a ComboBox.
ComboBox provides two overloaded versions of setConverter():
setConverter(Class<?> datamodelType): set a pre-registered converter for the given data model type
setConverter(Converter<Object, ?> converter): set a concrete converter instance
Both of these methods are actually inherited from class AbstractField<T> where T is the data type managed by the field (e.g. Strings for text fields, Date for a DateField, Object for ComboBoxes). A converter is typically used to convert between a presentation type (such as the textual representation of a value on the UI) and its internal model type (such as a date, a monetary value or a custom JavaBean). So, for instance, if you have a Label you can use a StringToDateConverter to correctly display a Date object, which has been set as the value of the Label, in a properly localized way.
How is that with select components such as ComboBox? Here the type T is Object. The data type of a select component actually represents the item ID of the selected item from the underlying container data source. So, if you use a BeanItemContainer as the data source of a ComboBox, the container's item IDs (and hence the selected value of the ComboBox) are the contained JavaBean objects themselves. The concrete type of the item IDs depends on the container implementation used. Therefore, select components are Field components with value type Object. In other words, select components use Object as presentation type.
That is why you can only set a converter instance on a select component whose generic PRESENTATION type is Object. The model type can be chosen freely. And this also explain why you can't set a converter with presentation type Boolean and model type Date on a ComboBox -- ComboBox doesn't use Boolean as presentation type.
I wrote a blog post about Vaadin FieldGroups which also provides a good example for a use case when to use a Converter<Object, ?> on a ComboBox. You can find this article at http://blog.oio.de/2014/04/25/select-nested-javabeans-vaadin-fieldgroup/.
I don't know what you want to achieve with your code, because a converter between a presentation type of Boolean and a model type of Date doesn't make much sense. I can only guess that you want to implementat some sort of decision logic, maybe to decide whether or not a date has been set? In that case you need to take a different approach.
For reference, have a look at the Book of Vaadin on Converters.
I have a problem with <h:inputText>. In particular I have a series of inputtext, combobox, calendar on an xhtml page.
Each of them has the value attribute like follow value="#{myBean.first}", value="#{myBean.second}", and so on.
In this manner myBean must have an enormous number of setter and getter.
I need to use only one setter and only one getter like the following:
public void setValue(String theId, String theValue){}
public String getValue(String theId){}
So in these only two methods I use a Map with key=theId and value=theValue inserted by user.
My question is how can do this in xhtml page?
That's how value-tag would be? Is there a special notice for passing a parameter to setter/getter?
Note that the "parameter" added to the inputText could be an object.
How can I do?
If you want to store the key/value pairs in a Map, you can reference the map directly in your UI components. Say your backing bean has this:
public Map<String, Object> getDataMap() { return dataMap; }
public void setDataMap(Map<String,Object> dataMap) { this.dataMap = dataMap; }
Your xhtml could look like this:
<h:inputText value="#{myBean.dataMap['first']}" />
<h:inputText value="#{myBean.dataMap['second']}" />
I'm using app engine datastore so I have entity like this.
#PersistenceCapable
public class Author {
#PrimaryKey
#Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
#JsonProperty("id")
#JsonSerialize(using = JsonKeySerializer.class)
#JsonDeserialize(using = JsonKeyDeserializer.class)
private Key key;
....
}
When the model is sent to view, it will serialize the Key object as an Id value. Then, if I send data back from view I want to deserialize the Id back to Key object by using JsonKeyDeserializer class.
public class JsonKeyDeserializer extends JsonDeserializer<Key> {
#Override
public Key deserialize(JsonParser jsonParser, DeserializationContext deserializeContext)
throws IOException, JsonProcessingException {
String id = jsonParser.getText();
if (id.isEmpty()) {
return null;
}
// Here is the problem because I have several entities and I can't fix the Author class in this deserializer like this.
// I want to know what class is being deserialized at runtime.
// return KeyFactory.createKey(Author.class.getSimpleName(), Integer.parseInt(id))
}
}
I tried to debug the value in deserialize's parameters but I can't find the way to get the target deserialized class. How can I solve this?
You may have misunderstood the role of KeySerializer/KeyDeserializer: they are used for Java Map keys, and not as generic identifiers in database sense of term "key".
So you probably would need to use regular JsonSerializer/JsonDeserializer instead.
As to type: it is assumed that handlers are constructed for specific types, and no extra type information is passed during serialization or deserialization process: expected type (if handlers are used for different types) must be passed during construction.
When registering general serializers or deserializers, you can do this when implementing Module, as one of the arguments is type for which (de)serializer is requested.
When defining handlers directly for properties (like when using annotations), this information is available on createContextual() callback of interface ContextualSerializer (and -Deserializer), if your handler implements it: BeanProperty is passed to specify property (in this case field with annotation), and you can access its type. This information needs to be stored to be used during (de)serialization.
EDIT: as author pointed out, I actually misread the question: KeySerializer is the class name, not annotation.
I am creating a web application, where you have to read a list of objects / entities from a DB and populate it in a JSF <h:selectOneMenu>. I am unable to code this. Can someone show me how to do it?
I know how to get a List<User> from the DB. What I need to know is, how to populate this list in a <h:selectOneMenu>.
<h:selectOneMenu value="#{bean.name}">
...?
</h:selectOneMenu>
Based on your question history, you're using JSF 2.x. So, here's a JSF 2.x targeted answer. In JSF 1.x you would be forced to wrap item values/labels in ugly SelectItem instances. This is fortunately not needed anymore in JSF 2.x.
Basic example
To answer your question directly, just use <f:selectItems> whose value points to a List<T> property which you preserve from the DB during bean's (post)construction. Here's a basic kickoff example assuming that T actually represents a String.
<h:selectOneMenu value="#{bean.name}">
<f:selectItems value="#{bean.names}" />
</h:selectOneMenu>
with
#ManagedBean
#RequestScoped
public class Bean {
private String name;
private List<String> names;
#EJB
private NameService nameService;
#PostConstruct
public void init() {
names = nameService.list();
}
// ... (getters, setters, etc)
}
Simple as that. Actually, the T's toString() will be used to represent both the dropdown item label and value. So, when you're instead of List<String> using a list of complex objects like List<SomeEntity> and you haven't overridden the class' toString() method, then you would see com.example.SomeEntity#hashcode as item values. See next section how to solve it properly.
Also note that the bean for <f:selectItems> value does not necessarily need to be the same bean as the bean for <h:selectOneMenu> value. This is useful whenever the values are actually applicationwide constants which you just have to load only once during application's startup. You could then just make it a property of an application scoped bean.
<h:selectOneMenu value="#{bean.name}">
<f:selectItems value="#{data.names}" />
</h:selectOneMenu>
Complex objects as available items
Whenever T concerns a complex object (a javabean), such as User which has a String property of name, then you could use the var attribute to get hold of the iteration variable which you in turn can use in itemValue and/or itemLabel attribtues (if you omit the itemLabel, then the label becomes the same as the value).
Example #1:
<h:selectOneMenu value="#{bean.userName}">
<f:selectItems value="#{bean.users}" var="user" itemValue="#{user.name}" />
</h:selectOneMenu>
with
private String userName;
private List<User> users;
#EJB
private UserService userService;
#PostConstruct
public void init() {
users = userService.list();
}
// ... (getters, setters, etc)
Or when it has a Long property id which you would rather like to set as item value:
Example #2:
<h:selectOneMenu value="#{bean.userId}">
<f:selectItems value="#{bean.users}" var="user" itemValue="#{user.id}" itemLabel="#{user.name}" />
</h:selectOneMenu>
with
private Long userId;
private List<User> users;
// ... (the same as in previous bean example)
Complex object as selected item
Whenever you would like to set it to a T property in the bean as well and T represents an User, then you would need to bake a custom Converter which converts between User and an unique string representation (which can be the id property). Do note that the itemValue must represent the complex object itself, exactly the type which needs to be set as selection component's value.
<h:selectOneMenu value="#{bean.user}" converter="#{userConverter}">
<f:selectItems value="#{bean.users}" var="user" itemValue="#{user}" itemLabel="#{user.name}" />
</h:selectOneMenu>
with
private User user;
private List<User> users;
// ... (the same as in previous bean example)
and
#ManagedBean
#RequestScoped
public class UserConverter implements Converter {
#EJB
private UserService userService;
#Override
public Object getAsObject(FacesContext context, UIComponent component, String submittedValue) {
if (submittedValue == null || submittedValue.isEmpty()) {
return null;
}
try {
return userService.find(Long.valueOf(submittedValue));
} catch (NumberFormatException e) {
throw new ConverterException(new FacesMessage(String.format("%s is not a valid User ID", submittedValue)), e);
}
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object modelValue) {
if (modelValue == null) {
return "";
}
if (modelValue instanceof User) {
return String.valueOf(((User) modelValue).getId());
} else {
throw new ConverterException(new FacesMessage(String.format("%s is not a valid User", modelValue)), e);
}
}
}
(please note that the Converter is a bit hacky in order to be able to inject an #EJB in a JSF converter; normally one would have annotated it as #FacesConverter(forClass=User.class), but that unfortunately doesn't allow #EJB injections)
Don't forget to make sure that the complex object class has equals() and hashCode() properly implemented, otherwise JSF will during render fail to show preselected item(s), and you'll on submit face Validation Error: Value is not valid.
public class User {
private Long id;
#Override
public boolean equals(Object other) {
return (other != null && getClass() == other.getClass() && id != null)
? id.equals(((User) other).id)
: (other == this);
}
#Override
public int hashCode() {
return (id != null)
? (getClass().hashCode() + id.hashCode())
: super.hashCode();
}
}
Complex objects with a generic converter
Head to this answer: Implement converters for entities with Java Generics.
Complex objects without a custom converter
The JSF utility library OmniFaces offers a special converter out the box which allows you to use complex objects in <h:selectOneMenu> without the need to create a custom converter. The SelectItemsConverter will simply do the conversion based on readily available items in <f:selectItem(s)>.
<h:selectOneMenu value="#{bean.user}" converter="omnifaces.SelectItemsConverter">
<f:selectItems value="#{bean.users}" var="user" itemValue="#{user}" itemLabel="#{user.name}" />
</h:selectOneMenu>
See also:
Our <h:selectOneMenu> wiki page
View-Page
<h:selectOneMenu id="selectOneCB" value="#{page.selectedName}">
<f:selectItems value="#{page.names}"/>
</h:selectOneMenu>
Backing-Bean
List<SelectItem> names = new ArrayList<SelectItem>();
//-- Populate list from database
names.add(new SelectItem(valueObject,"label"));
//-- setter/getter accessor methods for list
To display particular selected record, it must be one of the values in the list.
Roll-your-own generic converter for complex objects as selected item
The Balusc gives a very useful overview answer on this subject. But there is one alternative he does not present: The Roll-your-own generic converter that handles complex objects as the selected item. This is very complex to do if you want to handle all cases, but pretty simple for simple cases.
The code below contains an example of such a converter. It works in the same spirit as the OmniFaces SelectItemsConverter as it looks through the children of a component for UISelectItem(s) containing objects. The difference is that it only handles bindings to either simple collections of entity objects, or to strings. It does not handle item groups, collections of SelectItems, arrays and probably a lot of other things.
The entities that the component binds to must implement the IdObject interface. (This could be solved in other way, such as using toString.)
Note that the entities must implement equals in such a way that two entities with the same ID compares equal.
The only thing that you need to do to use it is to specify it as converter on the select component, bind to an entity property and a list of possible entities:
<h:selectOneMenu value="#{bean.user}" converter="selectListConverter">
<f:selectItem itemValue="unselected" itemLabel="Select user..."/>
<f:selectItem itemValue="empty" itemLabel="No user"/>
<f:selectItems value="#{bean.users}" var="user" itemValue="#{user}" itemLabel="#{user.name}" />
</h:selectOneMenu>
Converter:
/**
* A converter for select components (those that have select items as children).
*
* It convertes the selected value string into one of its element entities, thus allowing
* binding to complex objects.
*
* It only handles simple uses of select components, in which the value is a simple list of
* entities. No ItemGroups, arrays or other kinds of values.
*
* Items it binds to can be strings or implementations of the {#link IdObject} interface.
*/
#FacesConverter("selectListConverter")
public class SelectListConverter implements Converter {
public static interface IdObject {
public String getDisplayId();
}
#Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
if (value == null || value.isEmpty()) {
return null;
}
return component.getChildren().stream()
.flatMap(child -> getEntriesOfItem(child))
.filter(o -> value.equals(o instanceof IdObject ? ((IdObject) o).getDisplayId() : o))
.findAny().orElse(null);
}
/**
* Gets the values stored in a {#link UISelectItem} or a {#link UISelectItems}.
* For other components returns an empty stream.
*/
private Stream<?> getEntriesOfItem(UIComponent child) {
if (child instanceof UISelectItem) {
UISelectItem item = (UISelectItem) child;
if (!item.isNoSelectionOption()) {
return Stream.of(item.getValue());
}
} else if (child instanceof UISelectItems) {
Object value = ((UISelectItems) child).getValue();
if (value instanceof Collection) {
return ((Collection<?>) value).stream();
} else {
throw new IllegalStateException("Unsupported value of UISelectItems: " + value);
}
}
return Stream.empty();
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
if (value == null) return null;
if (value instanceof String) return (String) value;
if (value instanceof IdObject) return ((IdObject) value).getDisplayId();
throw new IllegalArgumentException("Unexpected value type");
}
}
I'm doing it like this:
Models are ViewScoped
converter:
#Named
#ViewScoped
public class ViewScopedFacesConverter implements Converter, Serializable
{
private static final long serialVersionUID = 1L;
private Map<String, Object> converterMap;
#PostConstruct
void postConstruct(){
converterMap = new HashMap<>();
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object object) {
String selectItemValue = String.valueOf( object.hashCode() );
converterMap.put( selectItemValue, object );
return selectItemValue;
}
#Override
public Object getAsObject(FacesContext context, UIComponent component, String selectItemValue){
return converterMap.get(selectItemValue);
}
}
and bind to component with:
<f:converter binding="#{viewScopedFacesConverter}" />
If you will use entity id rather than hashCode you can hit a collision- if you have few lists on one page for different entities (classes) with the same id
Call me lazy but coding a Converter seems like a lot of unnecessary work. I'm using Primefaces and, not having used a plain vanilla JSF2 listbox or dropdown menu before, I just assumed (being lazy) that the widget could handle complex objects, i.e. pass the selected object as is to its corresponding getter/setter like so many other widgets do. I was disappointed to find (after hours of head scratching) that this capability does not exist for this widget type without a Converter. In fact if you supply a setter for the complex object rather than for a String, it fails silently (simply doesn't call the setter, no Exception, no JS error), and I spent a ton of time going through BalusC's excellent troubleshooting tool to find the cause, to no avail since none of those suggestions applied. My conclusion: listbox/menu widget needs adapting that other JSF2 widgets do not. This seems misleading and prone to leading the uninformed developer like myself down a rabbit hole.
In the end I resisted coding a Converter and found through trial and error that if you set the widget value to a complex object, e.g.:
<p:selectOneListbox id="adminEvents" value="#{testBean.selectedEvent}">
... when the user selects an item, the widget can call a String setter for that object, e.g. setSelectedThing(String thingString) {...}, and the String passed is a JSON String representing the Thing object. I can parse it to determine which object was selected. This feels a little like a hack, but less of a hack than a Converter.
I am building a tree structure which an object references itself in like so:
public class ProjectObjectOL extends JavaScriptObject {
protected ProjectObjectOL() { }
public final native boolean getStatus() /*-{ return this.status; }-*/;
public final native String getError() /*-{ return this.error_message; }-*/;
public final native JsArray<ProjectObjectOL> getChildren() /*-{ this.children; }-*/;
}
My problem is that I can't seem to get the children of the object. I've tested it out, and I'm quite sure the JSON structure being passed back consists of an object that contains an array of children of that type which can contain children, etc.
...but when trying to access even the simplest information about the children, the length of the array, it returns 0 every time. I've tried with no success to figure out what it's doing wrong, all the other data returns fine, but this one piece will NOT retrieve the children. Here is an example of how I might (directly) access the length for testing:
JSONObject oResults = (JSONObject) JSONParser.parse(response.getText());
ProjectListOL testoutputOL = oResults.isObject().getJavaScriptObject().cast();
ProjectObjectOL testObject = testoutputOL.getProjectList().get(1);
Window.alert(testObject.getChildren().length()+"");
A ProjectListOL contains an array of ProjectObjectOLs. In the example above I simply grabbed the one I KNOW has children. I'm using ColdFusion for the backend that returns the JSON object. Once again, I have output this object multiple times, both in GWT and outside (directly dumping the JSON object from the file) verifying that the object is indeed set up how I expect it to be set up.
I missed an obvious mistake:
public final native JsArray<ProjectObjectOL> getChildren() /*-{ this.children; }-*/;
OOPS:
public final native JsArray<ProjectObjectOL> getChildren() /*-{ **return** this.children; }-*/;