EnumConverter (Java EE 5 SDK)

javax.faces.convert Class EnumConverter

java.lang.Object
  javax.faces.convert.EnumConverter

所有已实现的接口:

StateHolder, Converter

public class EnumConverter

extends Object

implements Converter, StateHolder

Converter implementation for java.lang.Enum (and enum primitive) values.

从以下版本开始:

1.2

CONVERTER_ID

public static final String CONVERTER_ID

The standard converter id for this converter.

另请参见:

常量字段

ENUM_ID

public static final String ENUM_ID

The message identifier of the FacesMessage to be created if the conversion to Enum fails. The message format string for this message may optionally include the following placeholders:

• {0} replaced by the unconverted value.
• {1} replaced by one of the enum constants or the empty string if none can be found.
• {2} replaced by a String whose value is the label of the input component that produced this message.

另请参见:

常量字段

ENUM_NO_CLASS_ID

public static final String ENUM_NO_CLASS_ID

The message identifier of the FacesMessage to be created if the conversion to Enum fails and no target class has been provided. The message format string for this message may optionally include the following placeholders:

• {0} replaced by the unconverted value.
• {1} replaced by a String whose value is the label of the input component that produced this message.

另请参见:

常量字段

EnumConverter

public EnumConverter()

EnumConverter

public EnumConverter(Class targetClass)

getAsObject

public Object getAsObject(FacesContext context,
                          UIComponent component,
                          String value)

Convert the value argument to one of the enum constants of the class provided in our constructor. If no target class argument has been provided to the constructor of this instance, throw a ConverterException containing the ENUM_NO_CLASS_ID message with proper parameters. If the value argument is null or it has a length of zero, return null. Otherwise, perform the equivalent of Enum.valueOf using target class and value and return the Object. If the conversion fails, throw a ConverterException containing the ENUM_ID message with proper parameters.

规范说明:

getAsObject in interface Converter

参数:

context - the FacesContext for this request.

component - the UIComponent to which this value will be applied.

value - the String value to be converted to Object.

返回:

null if the value to convert is null, otherwise the result of the conversion

抛出异常:

ConverterException - if conversion cannot be successfully performed

NullPointerException - if context or component is null

getAsString

public String getAsString(FacesContext context,
                          UIComponent component,
                          Object value)

Convert the enum constant given by the value argument into a String. If no target class argument has been provided to the constructor of this instance, throw a ConverterException containing the ENUM_NO_CLASS_ID message with proper parameters. If the value,/code> argument is null, return null. If the value is an instance of the provided target class, return its string value (value.toString()). Otherwise, throw a ConverterException containing the ENUM_ID message with proper parameters.

规范说明:

getAsString in interface Converter

参数:

context - FacesContext for the request being processed

component - UIComponent with which this model object value is associated

value - Model object value to be converted (may be null)

返回:

a zero-length String if value is null, otherwise the result of the conversion

抛出异常:

ConverterException - if conversion cannot be successfully performed

NullPointerException - if context or component is null

restoreState

public void restoreState(FacesContext facesContext,
                         Object object)

Description copied from interface: StateHolder

Perform any processing required to restore the state from the entries in the state Object.

If the class that implements this interface has references to instances that also implement StateHolder (such as a UIComponent with event handlers, validators, etc.) this method must call the StateHolder.restoreState(javax.faces.context.FacesContext, java.lang.Object) method on all those instances as well.

规范说明:

restoreState in interface StateHolder

saveState

public Object saveState(FacesContext facesContext)

Description copied from interface: StateHolder

Gets the state of the instance as a Serializable Object.

If the class that implements this interface has references to instances that implement StateHolder (such as a UIComponent with event handlers, validators, etc.) this method must call the StateHolder.saveState(javax.faces.context.FacesContext) method on all those instances as well. This method must not save the state of children and facets. That is done via the StateManager

This method must not alter the state of the implementing object. In other words, after executing this code:

 Object state = component.saveState(facesContext);
 

component should be the same as before executing it.

The return from this method must be Serializable

规范说明:

saveState in interface StateHolder

public void setTransient(boolean b)

public boolean isTransient()