org.omnifaces.cdi

Annotation Type Param

@Qualifier
 @Retention(value=RUNTIME)
 @Target(value={METHOD,FIELD,PARAMETER})
public @interface Param

The CDI annotation @Param allows you to inject, convert and validate a HTTP request or path parameter in a CDI managed bean.

For HTTP request parameters it's basically like <f:viewParam>, but with the major difference that the injected parameter is directly available during PostConstruct, allowing a much easier way of processing without the need for a <f:event type="preRenderView"> or <f:viewAction> in the view.

Usage

Request parameters

The example below injects the request parameter with name foo.

 @Param
 private String foo;
 

By default the name of the request parameter is taken from the name of the variable into which injection takes place. The name can be optionally specified via the name attribute. The example below injects the request parameter with name foo into a variable named bar.

 @Param(name="foo")
 private String bar;
 

The name attribute is only mandatory when using constructor injection in OmniFaces 3.5 or older as there is no information about constructor parameter names. The example below injects the request parameter with name foo as a constructor parameter.

 @Inject
 public Bean(@Param(name="foo") String foo) {
     // ...
 }
 

Since OmniFaces 3.6 it is not necessary anymore if the parameter has a name according to the class file as per Parameter#isNamePresent().

 @Inject
 public Bean(@Param String foo) {
     // ...
 }
 

Multi-valued request parameters

Multi-valued parameters are also supported by specifying a List or array type. The support was added in OmniFaces 2.4.

 @Param(name="foo")
 private List<String> foos;

 @Param(name="bar")
 private String[] bars;
 

Path parameters

Path parameters can be injected by specifying the pathIndex attribute representing the zero-based index of the path parameter. The support was added in OmniFaces 2.5. On an example request https://example.com/mypage/firstname.lastname, which is mapped to /mypage.xhtml, the below example injects the path parameter firstname.lastname.

 @Param(pathIndex=0)
 private String user;
 

This takes precedence over the name attribute.

Conversion and validation

Standard types for which JSF already has a build in converter like String, Long, Boolean, etc or for which there's already a converter registered via forClass, can be injected without explicitly specifying a converter.

 @Param
 private Long id;
 

Other types do need a converter. The following is an example of the injection of request parameter user following a request such as https://example.com/mypage?user=42:

 @Param(converter="userConverter", validator="priviledgedUser")
 private User user;
 

This also works on multi-valued parameters.

 @Param(name="user", converter="userConverter")
 private List<User> users;
 

This also works on path parameters. The following is an example of the injection of path parameter user following a request such as https://example.com/mypage/42:

 @Param(pathIndex=0, converter="userConverter", validator="priviledgedUser")
 private User user;
 

Note that the converter and validator attributes can be specified in 3 ways:

• A string value representing the converter/validator ID like so converter="userConverter".
• An EL expression returning the converter/validator ID string like so converter="#{bean.converterId}".
• An EL expression returning the concrete converter/validator instance like so converter="#{converterBean}".

Instead of converter or validator you can also use converterClass or validatorClass:

 @Param(converterClass=UserConverter.class, validatorClass=PriviledgedUser.class)
 private User user;
 

Note that this is ignored when converter or validator is also specified.

In case you want to specify converter or validator attributes, then you can use converterAttributes or validatorAttributes respectively. They accept an array of Attribute arguments whose value can be a string literal or an EL expression such as value = "#{bean.property}".

 @Param(
     converterClass = DateTimeConverter.class,
     converterAttributes = { @Attribute(name = "pattern", value = "yyyyMMdd") },
     converterMessage = "{1}: \"{0}\" is not the date format we had in mind! Please use the format yyyyMMdd.")
 private Date date;
 

Yes, you can use converterMessage and validatorMessage to customize the error message.

In case the converted parameter value is not serializable, while the managed bean is serializable, you could inject it into a field of type ParamValue, with V the actual type of the converted parameter. Deserialization in this case works by converting from the original parameter again.

 @Inject @Param(converter="someIdToInputStreamConverter")
 private ParamValue<InputStream> content; // Extreme example :) Be careful with resource leaking.
 

If conversion or validation fails, null is injected if the injection target is NOT ParamValue. Otherwise a ParamValue instance is injected, but it will contain a null value. In both cases, the conversion and validation messages (if any) will be set in the JSF context then, and FacesContext.isValidationFailed() will return true.

Historical note

Before OmniFaces 3.6, the @Param which is not of type ParamValue also required @Inject as in:

 @Inject @Param
 private String foo;
 

But this is not needed anymore since OmniFaces 3.6. This has the following advantages:

• Less code
• Not anymore confusing "No bean is eligible for injection to the injection point [JSR-365 §5.2.2]" warnings in IDEs like Eclipse (caused by the dynamic/generic type of the injection point).

These will not anymore use the DynamicParamValueProducer. Instead the injection is "manually" done while creating the bean.

Since:

1.6

Author:

Arjan Tijms, Bauke Scholtz

See Also:

ParamValue, Attribute, ParamExtension, ParamProducer, DynamicParamValueProducer

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
String	converter (Optional/Required) The converter to be used for converting the parameter to the type that is to be injected.
Attribute[]	converterAttributes (Optional) Attributes that will be set on the converter instance obtained from converter() or converterClass().
Class<? extends Converter>	converterClass (Optional) Class of the converter to be used for converting the parameter to the type that is to be injected.
String	converterMessage (Optional) A message that will be used if conversion fails instead of the message set by the converter.
boolean	disableBeanValidation (Optional) Flag that disables bean validation for this instance.
String	label (Optional) the label used to refer to the parameter.
String	name (Optional) The name of the request parameter.
boolean	overrideGlobalBeanValidationDisabled (Optional) Flag that overrides the global BeanValidator.DISABLE_DEFAULT_BEAN_VALIDATOR_PARAM_NAME setting.
int	pathIndex (Optional) The index of the path parameter.
boolean	required (Optional) Flag indicating if this parameter is required (must be present) or not.
String	requiredMessage (Optional) A message that will be used if a non-empty value is submitted instead of the default message associated with the RequiredValidator.
Attribute[]	validatorAttributes (Optional) Attributes that will be set on each of the validator instances obtained from validators() and validatorClasses().
Class<? extends Validator>[]	validatorClasses (Optional) Class of one ore more validators to be used for validating the (converted) parameter.
String	validatorMessage (Optional) A message that will be used if validation fails instead of the message set by the validator(s).
String[]	validators (Optional) The validators to be used for validating the (converted) parameter.

Element Detail

name

public abstract String name

(Optional) The name of the request parameter. If not specified the name of the injection target field will be used.

Returns:

The name of the request parameter.

Default:

""

pathIndex

public abstract int pathIndex

(Optional) The index of the path parameter. If specified the parameter will be extracted from the request path info on the given index instead of as request parameter. The first path parameter has an index of 0. This takes precedence over name attribute.

Returns:

The index of the path parameter.

Since:

2.5

Default:

-1

label

public abstract String label

(Optional) the label used to refer to the parameter.

Returns:

The label used to refer the parameter, defaults to the name attribute.

Default:

""

converter

public abstract String converter

(Optional/Required) The converter to be used for converting the parameter to the type that is to be injected. Optional if the target type is String, otherwise required.

A converter can be specified in 3 ways:

1. A string value representing the converter-id as used by Application.createConverter(String)
2. An EL expression that resolves to a String representing the converter-id
3. An EL expression that resolves to a Converter instance.

If this attribute is specified in addition to converterClass(), this attribute takes precedence.

Returns:

The converter used to convert the parameter to model value.

Default:

""

required

public abstract boolean required

(Optional) Flag indicating if this parameter is required (must be present) or not. The required check is done after conversion and before validation. A value is said to be not present if it turns out to be empty according to the semantics of Utils.isEmpty(Object).

Returns:

Whether the absence of the parameter should cause a validation error.

Default:

false

validators

public abstract String[] validators

(Optional) The validators to be used for validating the (converted) parameter.

A validator can be specified in 3 ways:

1. A string value representing the validator-id as used by Application.createValidator(String)
2. An EL expression that resolves to a String representing the validator-id
3. An EL expression that resolves to a Validator instance.

If this attribute is specified in addition to validatorClasses() then the validators from both attributes will be added to the final collection of validators. The validators from this attribute will however be called first.

Returns:

The validators used to validate the (converted) parameter.

Default:

{}

converterClass

public abstract Class<? extends Converter> converterClass

(Optional) Class of the converter to be used for converting the parameter to the type that is to be injected. This is ignored when converter() is specified.

Returns:

The converter class used to convert the parameter to model value.

Default:

javax.faces.convert.Converter.class

validatorClasses

public abstract Class<? extends Validator>[] validatorClasses

(Optional) Class of one ore more validators to be used for validating the (converted) parameter. These will run after the ones specified in validators().

Returns:

The validator classes used to validate the (converted) parameter.

Default:

{}

converterAttributes

public abstract Attribute[] converterAttributes

(Optional) Attributes that will be set on the converter instance obtained from converter() or converterClass().

For each attribute the converter instance should have a writable JavaBeans property with the same name. The value can be a string literal or an EL expression. String literals are coerced if necessary if there's a PropertyEditor available (the JDK provides these for the primitive types and their corresponding boxed types).

Attributes for which the converter doesn't have a property (setter) are silently ignored.

Returns:

The attributes which need to be set on the converter.

Default:

{}

validatorAttributes

public abstract Attribute[] validatorAttributes

(Optional) Attributes that will be set on each of the validator instances obtained from validators() and validatorClasses().

For each attribute the validator instances should have a writable JavaBeans property with the same name. The value can be a string literal or an EL expression. String literals are coerced if necessary if there's a PropertyEditor available (the JDK provides these for the primitive types and their corresponding boxed types).

Attributes for which any given validator doesn't have a property (setter) are silently ignored.

Returns:

The attributes which need to be set on the validators.

Default:

{}

converterMessage

public abstract String converterMessage

(Optional) A message that will be used if conversion fails instead of the message set by the converter.

The value for which conversion failed is available as {0}. The label associated with this parameter value (see the label() attribute) is available as {1}.

Returns:

The error message to be used when the converter() or converterClass() fail.

Default:

""

validatorMessage

public abstract String validatorMessage

(Optional) A message that will be used if validation fails instead of the message set by the validator(s).

The value for which validation failed is available as {0}. The label associated with this parameter value (see the label() attribute) is available as {1}.

Returns:

The error message to be used when any of the validators() or validatorClasses() fail.

Default:

""

requiredMessage

public abstract String requiredMessage

(Optional) A message that will be used if a non-empty value is submitted instead of the default message associated with the RequiredValidator.

The (empty) value for which the required check failed is available as {0}. (this will be either null or the empty string) The label associated with this parameter value (see the label() attribute) is available as {1}.

Returns:

The error message to be used on empty submit while required() is true.

Default:

""

disableBeanValidation

public abstract boolean disableBeanValidation

(Optional) Flag that disables bean validation for this instance.

NOTE: bean validation at the moment (OmniFaces 1.6) is done against the ParamValue that is injected. In many cases this will be of limited use. We hope to directly inject the converted type in OmniFaces 1.7 and then bean validation will make more sense.

If true no bean validation will be attempted. If false (the default) no specific action is taken, and it will depend on the availability of bean validation and the global BeanValidator.DISABLE_DEFAULT_BEAN_VALIDATOR_PARAM_NAME setting whether bean validation is attempted or not.

Returns:

Whether to disable bean validation or not.

Default:

false

overrideGlobalBeanValidationDisabled

public abstract boolean overrideGlobalBeanValidationDisabled

(Optional) Flag that overrides the global BeanValidator.DISABLE_DEFAULT_BEAN_VALIDATOR_PARAM_NAME setting.

If true bean validation will be performed for this instance (given that bean validation is available) despite it globally being disabled. If false (the default) no specific action is taken.

Returns:

Whether to override that JSF bean validation is globally disabled.

Default:

false