Param (OmniFaces 2.5 API)

```
@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.
```
 @Inject @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.
```
 @Inject @Param(name="foo")
 private String bar;
 
```
The name attribute is only mandatory when using constructor injection 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) {
     // ...
 }
 
```
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.
```
 @Inject @Param(name="foo")
 private List<String> foos;

 @Inject @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 http://example.com/mypage/firstname.lastname, which is mapped to /mypage.xhtml, the below example injects the path parameter firstname.lastname.
```
 @Inject @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.
```
 @Inject @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 http://example.com/mypage?user=42:
```
 @Inject @Param(converter="userConverter", validator="priviledgedUser")
 private User user;
 
```
This also works on multi-valued parameters.
```
 @Inject @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 http://example.com/mypage/42:
```
 @Inject @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}".
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.
Since:

1.6

Author:

Arjan Tijms

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

Annotation Type Param

Usage

Request parameters

Multi-valued request parameters

Path parameters

Conversion and validation

Optional Element Summary

Element Detail

name

pathIndex

label

converter

required

validators

converterClass

validatorClasses

converterAttributes

validatorAttributes

converterMessage

validatorMessage

requiredMessage

disableBeanValidation

overrideGlobalBeanValidationDisabled