StateHolder (Java EE 5)

Java EE API

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javax.faces.component Interface StateHolder

All Known Implementing Classes:
DateTimeConverter, DoubleRangeValidator, EnumConverter, HtmlColumn, HtmlCommandButton, HtmlCommandLink, HtmlDataTable, HtmlForm, HtmlGraphicImage, HtmlInputHidden, HtmlInputSecret, HtmlInputText, HtmlInputTextarea, HtmlMessage, HtmlMessages, HtmlOutputFormat, HtmlOutputLabel, HtmlOutputLink, HtmlOutputText, HtmlPanelGrid, HtmlPanelGroup, HtmlSelectBooleanCheckbox, HtmlSelectManyCheckbox, HtmlSelectManyListbox, HtmlSelectManyMenu, HtmlSelectOneListbox, HtmlSelectOneMenu, HtmlSelectOneRadio, LengthValidator, LongRangeValidator, MethodExpressionActionListener, MethodExpressionValidator, MethodExpressionValueChangeListener, NumberConverter, UIColumn, UICommand, UIComponent, UIComponentBase, UIData, UIForm, UIGraphic, UIInput, UIMessage, UIMessages, UINamingContainer, UIOutput, UIPanel, UIParameter, UISelectBoolean, UISelectItem, UISelectItems, UISelectMany, UISelectOne, UIViewRoot
public interface StateHolder

Implemented by: DateTimeConverter, DoubleRangeValidator, EnumConverter, LengthValidator, LongRangeValidator, MethodExpressionActionListener, MethodExpressionValidator, MethodExpressionValueChangeListener, NumberConverter, UIComponent

此接口由需要在请求之间保存其状态的类实现。

实现者必须实现此类中的 #saveState 和 #restoreState 方法，因为这两个方法之间有紧密耦合的协定。换句话说，如果有继承层次结构，则不允许使 #saveState 和 #restoreState 方法驻留在不同的层次结构级别。

实现者必须具有不带参数的公共构造方法。

英文文档：

This interface is implemented by classes that need to save their state between requests.

An implementor must implement both saveState(javax.faces.context.FacesContext) and restoreState(javax.faces.context.FacesContext, java.lang.Object) methods in this class, since these two methods have a tightly coupled contract between themselves. In other words, if there is an ineritance hierarchy, it is not permissable to have the saveState(javax.faces.context.FacesContext) and restoreState(javax.faces.context.FacesContext, java.lang.Object) methods reside at different levels of the hierarchy.

An implementor must have a public no-args constructor.

Method Summary
 boolean isTransient()
          If true, the Object implementing this interface must not participate in state saving or restoring.
 void restoreState(FacesContext context, Object state)
           Perform any processing required to restore the state from the entries in the state Object.
 Object saveState(FacesContext context)
           Gets the state of the instance as a Serializable Object.
 void setTransient(boolean newTransientValue)
          Denotes whether or not the Object implementing this interface must or must not participate in state saving or restoring.
 

Method Detail

public Object saveState(FacesContext context)

获取作为 Serializable 对象的实例状态。

如果实现此接口的类包含指向实现 StateHolder 的实例的引用（例如带有事件处理程序、验证器等的 UIComponent），则此方法还必须调用所有这些实例上的 #saveState 方法。此方法不能保存子组件和 facet 的状态。通过 javax.faces.application.StateManager 可做到这一点

此方法不能修改实现对象的状态。换句话说，在执行此代码后：

Object state = component.saveState(facesContext);

component 应与执行前相同。

此方法的返回值必须是 Serializable

ThrowsNullPointerException: 如果 context 为 null
英文文档：

saveState

Object saveState(FacesContext context)

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 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

Throws:
NullPointerException - if context is null

public void restoreState(FacesContext context, Object state)

执行从状态 Object 中的条目恢复状态所需的任何处理。

如果实现此接口的类包含指向也实现了 StateHolder 的实例的引用（例如带有事件处理程序、验证器等的 UIComponent），则此方法还必须调用所有这些实例上的 #restoreState 方法。

ThrowsNullPointerException: 如果 context 或 state 为 null
英文文档：

restoreState

void restoreState(FacesContext context,
                  Object state)

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 restoreState(javax.faces.context.FacesContext, java.lang.Object) method on all those instances as well.

Throws:
NullPointerException - if either context or state are null

public boolean isTransient()

如果为 true，则实现此接口的 Object 不得参与状态保存或恢复。

英文文档：

isTransient

boolean isTransient()

If true, the Object implementing this interface must not participate in state saving or restoring.

public void setTransient(boolean newTransientValue)

表示实现此接口的 Object 必须或不得参与状态保存或恢复。

newTransientValue 如果此 Object 将参与状态保存或恢复，则 boolean 传递 true，否则传递 false。
英文文档：

setTransient

void setTransient(boolean newTransientValue)

Denotes whether or not the Object implementing this interface must or must not participate in state saving or restoring.

Parameters:
newTransientValue - boolean pass true if this Object will participate in state saving or restoring, otherwise pass false.
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一看就知道只有菜鸟才干这么无知的事啦。

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