er.extensions.components

Class ERXDynamicElement.ContextData<T>

java.lang.Object

er.extensions.components.ERXDynamicElement.ContextData<T>

Type Parameters:

T - type of data to store

Enclosing class:

ERXDynamicElement

protected static class ERXDynamicElement.ContextData<T>
extends Object

This class is used to store values that cannot be stored in instance variables as dynamic elements have to be thread-safe. Internally the userInfo of the current context is used to store the values, so all information is only valid for one request-response cycle. A stack is used per key so multiple nested components of the same type can use the same key safely.

You have to use begin before first usage of the field and end at the end of the cycle to clean up the corresponding stack. Without balanced calls of begin and end very bad things will happen. Thus it is advisable to use a try-finally (see example below). As you have to make these calls during appendToResponse, taleValuesFromRequest and invokeAction you should put those calls into overridden methods of beforeProcessing and afterProcessing respectively to avoid code duplication.

It is advisable too to choose a unique key, as different component types will use the same userInfo. It is suggested to use a key composed by the component and field name (e.g. MyDynamicElement.myField). The ContextData field itself can and should be declared static as it doesn't store the value itself, it is only used as an accessor to the value stored within the context.

Example:

 public static final ContextData<String> myField = new ContextData<>("MyClass.myField");
 
 public void appendToResponse(WOResponse response, WOContext context) {
   beforeProcessing(context);
   try {
     response.appendContentString("Current value: " + myField.value(context));
   } finally {
     afterProcessing(context);
   }
 }
 
 public void takeValuesFromRequest(WORequest request, WOContext context) {
   beforeProcessing(context);
   try {
     …
   } finally {
     afterProcessing(context);
   }
 }
 
 public WOActionResults invokeAction(WORequest request, WOContext context) {
   beforeProcessing(context);
   try {
     …
   } finally {
     afterProcessing(context);
   }
 }
 
 protected void beforeProcessing(WOContext context) {
   myField.begin(context, "myValue");
 }
 
 protected void afterProcessing(WOContext context) {
   myField.end(context);
 }
 

Author:

sgaertner

Constructor Summary

Constructors

Constructor and Description
ContextData(String key)

Method Summary

Modifier and Type	Method and Description
void	begin(com.webobjects.appserver.WOContext context, ERXDynamicElement component, String name) Push a value from a specific binding onto the stack.
void	begin(com.webobjects.appserver.WOContext context, T value) Push a constant value onto the stack.
void	end(com.webobjects.appserver.WOContext context) Removes the current value from the stack.
String	key() The key this object uses to store values in the context's userInfo.
void	setValue(com.webobjects.appserver.WOContext context, T value) Replace the current value on the stack with a new value.
protected Stack<T>	stack(com.webobjects.appserver.WOContext context)
String	toString()
T	value(com.webobjects.appserver.WOContext context) Returns the current value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ContextData

public ContextData(String key)

Method Detail

key

public String key()

The key this object uses to store values in the context's userInfo.

Returns:

the key

stack

protected Stack<T> stack(com.webobjects.appserver.WOContext context)

begin

public void begin(com.webobjects.appserver.WOContext context,
                  T value)

Push a constant value onto the stack.

Parameters:

context - context of the transaction

value - constant value

begin

public void begin(com.webobjects.appserver.WOContext context,
                  ERXDynamicElement component,
                  String name)

Push a value from a specific binding onto the stack.

Parameters:

context - context of the transaction

component - the current dynamic element

name - binding name

setValue

public void setValue(com.webobjects.appserver.WOContext context,
                     T value)

Replace the current value on the stack with a new value.

Parameters:

context - context of the transaction

value - constant value

value

public T value(com.webobjects.appserver.WOContext context)

Returns the current value.

Parameters:

context - context of the transaction

Returns:

current value

end

public void end(com.webobjects.appserver.WOContext context)

Removes the current value from the stack. If you pushed multiple values onto the stack by calling begin() several times you have to call end() the same number of times.

Parameters:

context - context of the transaction

toString

public String toString()

Overrides:

toString in class Object