I cannot see why the question is duplicate. If I debug the code then - when the button is clicked - no new value of projectSelected is being detected. Even the hashCode is the same. The equals method of the ProjectEntity only contains the id which is the same since it comes from the database and is not changed anywhere. Null values don't exist in the selection.
There was, however, too much code to reproduce the problem. I removed unnecessary code and the problem still persists.
Original question: In the following form with 3 <p:selectOneMenu> -fields if the submit button is clicked a valueChangeEvent is fired for the projectSelector field although it hasn't changed. Why is that? Like that the actual action behind the button is never called. I would expect a valueChangeEvent to be fired only in case the project changes.
Update: Trying to find the cause I replaced the ProjectEntity with String and then it worked. So I thought it must be the equals method of ProjectEntity but that only compares the id. I debugged further and found out that the selected value is being compared with a ProjectEntity with all fields set to null which gives a false and hence a valueChangeEvent. So the question is why is there a ProjectEntity with all fields set to null? I debugged into UIInput.compareValues which has that "null"-ProjectEntity being the previous value. That is being returned by UIOuput.getLocalValue. Where does it come from?
Update2: Even when using the equals and hashCode from selectOneMenu shows after submit always the last item in the list as selected item the behaviour does not change. I created an ear file readily to be deployed to e.g. a wildfly and would appreciate any help since I am stuck on this question.
<h:form>
<p:outputLabel value="#{msgs.timeProject}"/>
<p:selectOneMenu value="#{timeBean.model.projectSelected}"
converter="projectConverter"
onchange="submit()"
valueChangeListener="#{timeBean.projectChanged}"
immediate="true"
required="true">
<f:selectItems value="#{timeBean.model.allProjects}"
var="singleProject"
itemValue="#{singleProject}"
itemLabel="#{singleProject.name}"/>
</p:selectOneMenu>
<p:commandButton value="#{msgs.send}"
action="#{timeBean.myAction}"
ajax="false"/>
<p:outputLabel value="#{timeBean.model.resultValue}"
rendered="#{not empty timeBean.model.resultValue}"/>
</h:form>
The converter
#FacesConverter(value = "projectConverter")
public class ProjectConverter implements Converter {
#Inject
private ProjectService projectService;
#Override
public Object getAsObject(final FacesContext facesContext, final UIComponent uiComponent, final String projectName) {
if (StringUtils.isEmpty(projectName)) {
return null;
}
final List<ProjectEntity> projects = projectService.findAll();
for (ProjectEntity project : projects) {
if (StringUtils.equals(projectName, project.getName())) {
return project;
}
}
return null;
}
#Override
public String getAsString(final FacesContext facesContext, final UIComponent uiComponent, final Object value) {
if (value == null) {
return null;
}
if (value instanceof ProjectEntity) {
return ((ProjectEntity) value).getName();
}
return "???projectName???";
}
}
The equals-method of the ProjectEntity
#Override
public boolean equals(final Object o) {
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
final ProjectEntity that = (ProjectEntity) o;
return id != null ? id.equals(that.id) : that.id == null;
}
And the change listener inside the timeBean
public void projectChanged(final ValueChangeEvent event) {
final ProjectEntity projectSelected = (ProjectEntity) event.getNewValue();
model.setProjectSelected(projectSelected);
final FacesContext context = FacesContext.getCurrentInstance();
context.renderResponse();
}
The TimeModel
public class TimeModel {
private ProjectEntity projectSelected;
private List<ProjectEntity> allProjects;
private String resultValue;
... getters and setters ...
I'll guess, that the problem resides inside the ProjectConverter class, cause it may run into troubles to assign a valid projectService instance. Maybe you remove the injection and try to compute the value programatically in the getAsObject, getAsString methods by explicit cdi-finders.
I remember to run in a similar situation, when i was injecting in a ServletFilter.
Related
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 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.
We now started to use JSF 2.3 on our existing JSF 2.2 project. On our custom converters we got warning Converter is a raw type. References to generic type Converter<T> should be parameterized.
Problem that we experiencing is when we tried to fix that warning using generics:
#FacesConverter(value = "myConverter", managed = true)
public class MyConverter implements Converter<MyCustomObject>{
#Override
public MyCustomObject getAsObject(FacesContext context, UIComponent component, String submittedValue){}
#Override
public String getAsString(FacesContext context, UIComponent component, MyCustomObject modelValue) {}
}
and when converter is used for example in
<!DOCTYPE html>
<ui:composition xmlns="http://www.w3.org/1999/xhtml"
xmlns:c="http://xmlns.jcp.org/jsp/jstl/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:ui="http://java.sun.com/jsf/facelets">
<h:selectOneMenu id="#{componentId}" value="#{componentValue}">
<f:converter converterId="myConverter" />
<f:selectItem itemLabel="label"
itemValue="" />
<f:selectItems value="listOfValues"
var="singleValue"
itemValue="singleValue.value"
itemLabel="singleValue.label" />
</h:selectOneMenu>
then ClassCastException with message java.lang.String cannot be cast to MyCustomObjectis thrown. There is also one line in stacktrace that maybe can help com.sun.faces.cdi.CdiConverter.getAsString(CdiConverter.java:109).
But when converter generics definition changed from MyCustomObject to Object :
#FacesConverter(value = "myConverter", managed = true)
public class MyConverter implements Converter<Object>{
#Override
public Object getAsObject(FacesContext context, UIComponent component, String submittedValue){}
#Override
public String getAsString(FacesContext context, UIComponent component, Object modelValue) {}
}
then everything works as expected, but that obviously beats the purpose of Converter<T> interface.
I had same issue here and came up with following solution that actually not just compiles but also runs well:
some_page.xhtml (relevant excerpt):
<h:selectOneMenu styleClass="select" id="companyUserOwner" value="#{adminCompanyDataController.companyUserOwner}">
<f:converter converterId="UserConverter" />
<f:selectItem itemValue="#{null}" itemLabel="#{msg.NONE_SELECTED}" />
<f:selectItems value="#{userController.allUsers()}" var="companyUserOwner" itemValue="#{companyUserOwner}" itemLabel="#{companyUserOwner.userContact.contactFirstName} #{companyUserOwner.userContact.contactFamilyName} (#{companyUserOwner.userName})" />
</h:selectOneMenu>
Please note that the above JSF code is full of custom stuff and may not work on your end. And that my converter compiles without rawtype warning (JSF 2.3+, not 2.2!):
SomeUserConverter.java:
#FacesConverter (value = "UserConverter")
public class SomeUserConverter implements Converter<User> {
/**
* User EJB
*/
private static UserSessionBeanRemote USER_BEAN;
/**
* Default constructor
*/
public SomeUserConverter () {
}
#Override
public User getAsObject (final FacesContext context, final UIComponent component, final String submittedValue) {
// Is the value null or empty?
if ((null == submittedValue) || (submittedValue.trim().isEmpty())) {
// Return null
return null;
}
// Init instance
User user = null;
try {
// Try to parse the value as long
final Long userId = Long.valueOf(submittedValue);
// Try to get user instance from it
user = USER_BEAN.findUserById(userId);
} catch (final NumberFormatException ex) {
// Throw again
throw new ConverterException(ex);
} catch (final UserNotFoundException ex) {
// User was not found, return null
}
// Return it
return user;
}
#Override
public String getAsString (final FacesContext context, final UIComponent component, final User value) {
// Is the object null?
if ((null == value) || (String.valueOf(value).isEmpty())) {
// Is null
return ""; //NOI18N
}
// Return id number
return String.valueOf(value.getUserId());
}
}
This converter class has the JNDI lookup removed (I will rewrite that part later anyway) but it should be enough for demonstrating the important parts:
Converter<User> (by User is a custom POJI) preventing raw-type warning
value="UserConverter" that is the actual name you use in your JSF page
And most important, which actually fixed the ClassCastException:
<f:selectItem itemValue="#{null}" itemLabel="#{msg.NONE_SELECTED}" />
By omitting #{null} an empty string instead of null is being handled over to your getAsString method!
This last one actually fixed the said exception and my application is working again with much lesser warnings and much better type-hinting.
Need to remove forClass as value is there: FacesConverter is using both value andforClass, only value will be applied.
The raw-type warning will come (since Java SE 5) because you use an interface which has a generic (mostly stated as <T> after the interface name) which you need to satisfy so the compiler stop throwing that warning at you.
I had two issues with the FacesConverter.
First one, when I didn't use forClass = MyCustomObject.class I got the exact same error message as you had. Putting the forClass attribute in the #FacesConverter annotation solved the issue. It should solve it also for you...
Secondly, I suppose this is happening in the getAsString method? I had another issue with String casting and I had to do: return myCustomObject.getId().toString() where id is of type Long. After that I adapted my getAsObject to fetch the MyCustomObject based on the id. Maybe it is not directly related to your problem, but I thought it was important to mention as it is something I often bump into when writing converters.
I have used the HashMap method for binding a list of checkboxes to a Map<String, Boolean> with success. This is nice since it allows you to have a dynamic number of checkboxes.
I'm trying to extend that to a variable length list of selectManyMenu. Being that they are selectMany, I'd like to be able to bind to a Map<String, List<MyObject>>. I have a single example working where I can bind a single selectManyMenu to a List<MyObject> and everything works fine, but whey I put a dynamic number of selectManyMenus inside a ui:repeat and attempt to bind to the map, I end up with weird results. The values are stored correctly in the map, as verified by the debugger, and calling toString(), but the runtime thinks the map's values are of type Object and not List<MyObject> and throws ClassCastExceptions when I try to access the map's keys.
I'm guessing it has something to do with how JSF determines the runtime type of the target of your binding, and since I am binding to a value in a Map, it doesn't know to get the type from the value type parameter of the map. Is there any workaround to this, other than probably patching Mojarra?
In general, how can I have a page with a dynamic number of selectManyMenus? Without, of course using Primefaces' <p:solveThisProblemForMe> component. (In all seriousness, Primefaces is not an option here, due to factors outside of my control.)
The question UISelectMany on a List<T> causes java.lang.ClassCastException: java.lang.String cannot be cast to T had some good information that I wasn't aware of, but I'm still having issues with this SSCE:
JSF:
<ui:define name="content">
<h:form>
<ui:repeat value="#{testBean.itemCategories}" var="category">
<h:selectManyMenu value="#{testBean.selectedItemMap[category]}">
<f:selectItems value="#{testBean.availableItems}" var="item" itemValue="#{item}" itemLabel="#{item.name}"></f:selectItems>
<f:converter binding="#{itemConverter}"></f:converter>
<f:validator validatorId="test.itemValidator"></f:validator>
</h:selectManyMenu>
</ui:repeat>
<h:commandButton value="Submit">
<f:ajax listener="#{testBean.submitSelections}" execute="#form"></f:ajax>
</h:commandButton>
</h:form>
</ui:define>
Converter:
#Named
public class ItemConverter implements Converter {
#Inject
ItemStore itemStore;
#Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
return itemStore.getById(value);
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
return Optional.of(value)
.filter(v -> Item.class.isInstance(v))
.map(v -> ((Item) v).getId())
.orElse(null);
}
}
Backing Bean:
#Data
#Slf4j
#Named
#ViewScoped
public class TestBean implements Serializable {
private static final long serialVersionUID = 1L;
#Inject
ItemStore itemStore;
List<Item> availableItems;
List<String> itemCategories;
Map<String, List<Item>> selectedItemMap = new HashMap<>();
public void initialize() {
log.debug("Initialized TestBean");
availableItems = itemStore.getAllItems();
itemCategories = new ArrayList<>();
itemCategories.add("First Category");
itemCategories.add("Second Category");
itemCategories.add("Third Category");
}
public void submitSelections(AjaxBehaviorEvent event) {
log.debug("Submitted Selections");
selectedItemMap.entrySet().forEach(entry -> {
String key = entry.getKey();
List<Item> items = entry.getValue();
log.debug("Key: {}", key);
items.forEach(item -> {
log.debug(" Value: {}", item);
});
});
}
}
ItemStore just contains a HashMap and delegate methods to access Items by their ID field.
Item:
#Data
#Builder
public class Item {
private String id;
private String name;
private String value;
}
ItemListValidator:
#FacesValidator("test.itemValidator")
public class ItemListValidator implements Validator {
#Override
public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
if (List.class.isInstance(value)) {
if (((List) value).size() < 1) {
throw new ValidatorException(new FacesMessage(FacesMessage.SEVERITY_FATAL, "You must select at least 1 Admin Area", "You must select at least 1 Admin Area"));
}
}
}
}
Error:
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to java.util.List
Stacktrace snipped but occurs on this line:
List<Item> items = entry.getValue();
What am I missing here?
As hinted in the related question UISelectMany on a List<T> causes java.lang.ClassCastException: java.lang.String cannot be cast to T, generic type arguments are unavailable during runtime. In other words, EL doesn't know you have a Map<String, List<Item>>. All EL knows is that you have a Map, so unless you explicitly specify a converter for the selected values, and a collection type for the collection, JSF will default to String for selected values and an object array Object[] for the collection. Do note that the [ in [Ljava.lang.Object indicates an array.
Given that you want the collection type to be an instance of java.util.List, you need to specify the collectionType attribute with the FQN of the desired concrete implementation.
<h:selectManyMenu ... collectionType="java.util.ArrayList">
JSF will then make sure that the right collection type is being instantiated in order to fill the selected items and put in the model. Here's a related question where such a solution is being used but then for a different reason: org.hibernate.LazyInitializationException at com.sun.faces.renderkit.html_basic.MenuRenderer.convertSelectManyValuesForModel.
Update: I should have tested the above theory. This doesn't work in Mojarra when the collection behind collectionType is in turn wrapped in another generic collection/map. Mojarra only checks the collectionType if the UISelectMany value itself already represents an instance of java.util.Collection. However, due to it being wrapped in a Map, its (raw) type becomes java.lang.Object and then Mojarra will skip the check for any collectionType.
MyFaces did a better job in this in its UISelectMany renderer, it works over there.
As far as I inspected Mojarra's source code, there's no way to work around this other way than replacing Map<String, List<Long>> by a List<Category> where Category is a custom object having String name and List<MyObject> selectedItems properties. True, this really kills the advantage of Map of having dynamic keys in EL, but it is what it is.
Here's a MCVE using Long as item type (just substitute it with your MyObject):
private List<Category> categories;
private List<Long> availableItems;
#PostConstruct
public void init() {
categories = Arrays.asList(new Category("one"), new Category("two"), new Category("three"));
availableItems = Arrays.asList(1L, 2L, 3L, 4L, 5L);
}
public void submit() {
categories.forEach(c -> {
System.out.println("Name: " + c.getName());
for (Long selectedItem : c.getSelectedItems()) {
System.out.println("Selected item: " + selectedItem);
}
});
// ...
}
public class Category {
private String name;
private List<Long> selectedItems;
public Category(String name) {
this.name = name;
}
// ...
}
<h:form>
<ui:repeat value="#{bean.categories}" var="category">
<h:selectManyMenu value="#{category.selectedItems}" converter="javax.faces.Long">
<f:selectItems value="#{bean.availableItems}" />
</h:selectManyMenu>
</ui:repeat>
<h:commandButton value="submit" action="#{bean.submit}">
<f:ajax execute="#form" />
</h:commandButton>
</h:form>
Do note that collectionType is unnecessary here. Only the converter is still necessary.
Unrelated to the concrete problem, I'd like to point out that selectedItemMap.entrySet().forEach(entry -> { String key ...; List<Item> items ...;}) can be simplified to selectedItemMap.forEach((key, items) -> {}) and that ItemListValidator is unnecessary if you just use required="true" on the input component.
Converter :
#FacesConverter("bigDecimalConverter")
public class BigDecimalConverter implements Converter {
private static final int SCALE = 2;
#Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
if (value == null || value.isEmpty()) {
return null;
}
try {
return new BigDecimal(value);
} catch (NumberFormatException e) {
throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_ERROR, null, "Message"), e);
}
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
if (value == null) {
return "";
}
BigDecimal newValue;
if (value instanceof Long) {
newValue = BigDecimal.valueOf((Long) value);
} else if (value instanceof Double) {
newValue = BigDecimal.valueOf((Double) value);
} else if (!(value instanceof BigDecimal)) {
throw new ConverterException("Message");
} else {
newValue = (BigDecimal) value;
}
DecimalFormat formatter = (DecimalFormat) NumberFormat.getNumberInstance();
formatter.setGroupingUsed(false);
formatter.setMinimumFractionDigits(SCALE);
formatter.setMaximumFractionDigits(SCALE);
return formatter.format(newValue);
}
}
List :
<p:selectOneMenu id="list" value="#{bean.value}">
<f:selectItems var="row" value="#{bean.list}" itemLabel="#{row}" itemValue="#{row}"/>
<f:converter converterId="bigDecimalConverter"/>
</p:selectOneMenu>
<p:message id="msg" for="list"/>
<p:commandButton value="Submit" update="list msg" actionListener="#{bean.action}"/>
The managed bean backed by the above <p:selectOneMenu> :
#ManagedBean
#ViewScoped
public class Bean implements Serializable {
private List<BigDecimal> list; // Getter only.
private BigDecimal value; // Getter & setter.
private static final long serialVersionUID = 1L;
public Bean() {}
#PostConstruct
private void init() {
list = new ArrayList<BigDecimal>(){{
add(BigDecimal.valueOf(10));
add(BigDecimal.valueOf(20.11));
add(BigDecimal.valueOf(30));
add(BigDecimal.valueOf(40));
add(BigDecimal.valueOf(50));
}};
}
public void action() {
System.out.println("action() called : " + value);
}
}
A validation message, "Validation Error: Value is not valid" appears upon submission of the form. The getAsObject() method throws no exception upon form submission.
If a value with a scale like 20.11 is selected in the list, then the validation passes. It appears that the equals() method in the java.math.BigDecimal class goes fishy which for example, considers two BigDecimal objects equal, only if both of them are equal in value and scale thus 10.0 != 10.00 which requires compareTo() for them to be equal.
Any suggestion?
You lose information when converting to String. The default JSF BigDecimalConverter does this right, it uses BigDecimal#toString in its getAsString. The BigDecimal#toString's javadoc says:
There is a one-to-one mapping between the distinguishable BigDecimal values and the result of this conversion. That is, every distinguishable BigDecimal value (unscaled value and scale) has a unique string representation as a result of using toString. If that string representation is converted back to a BigDecimal using the BigDecimal(String) constructor, then the original value will be recovered.
This is exactly what you need. Don't treat converters like they must produce user readable-writable results when converting to String. They mustn't and often don't. They produce a String representation of an object, or an object reference. That's it. The selectItems' itemLabel defines a user readable representation in this case. I'm assuming that you don't want user writable values here, that you really have a fixed list of values for user to choose from.
If you really mean that this data must always have a scale of 2, and you need a user writable value, then that would be better checked in a validator, and user input could be helped out with p:inputMask.
Finally, let's set aside the fact, that your converter is not the best. It says "data must have a scale of 2". Then your should provide conforming data in your selectItems. More generally, server defined values must conform to relevant converters and validators. E.g. you could have problems in the same vein, when using the DateTimeConverter with the pattern "dd.MM.yyyy", but setting the default value to be new Date() without getting rid of the time part.
See also (more general notions about converters): https://stackoverflow.com/a/30529976/1341535