MutableData

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public class MutableData extends Object

Instances of this class encapsulate the data and priority at a location. It is used in transactions, and it is intended to be inspected and then updated to the desired data at that location.

Note that changes made to a child MutableData instance will be visible to the parent and vice versa.

Public Method Summary

MutableData	child(String path) Used to obtain a MutableData instance that encapsulates the data and priority at the given relative path.
boolean	equals(Object o)
Iterable<MutableData>	getChildren() Used to iterate over the immediate children at this location for (MutableData child : parent.getChildren()) {     ...
long	getChildrenCount()
String	getKey()
Object	getPriority() Gets the current priority at this location.
<T> T	getValue(GenericTypeIndicator<T> t) Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection.
Object	getValue() getValue() returns the data contained in this instance as native types.
<T> T	getValue(Class<T> valueType) This method is used to marshall the data contained in this instance into a class of your choosing.
boolean	hasChild(String path)
boolean	hasChildren()
void	setPriority(Object priority) Sets the priority at this location
void	setValue(Object value) Set the data at this location to the given value.
String	toString()

Inherited Method Summary

From class java.lang.Object

Object	clone()
boolean	equals(Object arg0)
void	finalize()
final Class<?>	getClass()
int	hashCode()
final void	notify()
final void	notifyAll()
String	toString()
final void	wait(long arg0, int arg1)
final void	wait(long arg0)
final void	wait()

Public Methods

public MutableData child (String path)

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Used to obtain a MutableData instance that encapsulates the data and priority at the given relative path.

Parameters

path	A relative path

Returns

• An instance encapsulating the data and priority at the given path

public boolean equals (Object o)

public Iterable<MutableData> getChildren ()

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Used to iterate over the immediate children at this location
for (MutableData child : parent.getChildren()) {
    ...
}

Returns

• The immediate children at this location

public long getChildrenCount ()

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Returns

• The number of immediate children at this location

public String getKey ()

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Returns

• The key name of this location, or null if it is the top-most location

public Object getPriority ()

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Gets the current priority at this location. The possible return types are:

• Double
• String

Note that null is allowed

Returns

• The priority at this location as a native type or null if no priority was set

public T getValue (GenericTypeIndicator<T> t)

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Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection. So, in the case where you want a List of Message instances, you will need to do something like the following:

     GenericTypeIndicator<List<Message>> t =
         new GenericTypeIndicator<List<Message>>() {};
     List<Message> messages = mutableData.getValue(t);
 

It is important to use a subclass of GenericTypeIndicator. See GenericTypeIndicator for more details

Parameters

t	A subclass of GenericTypeIndicator indicating the type of generic collection to be returned.

Returns

• A properly typed collection, populated with the data from this instance, or null if there is no data at this location.

public Object getValue ()

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getValue() returns the data contained in this instance as native types. The possible types returned are:

• Boolean
• String
• Long
• Double
• Map<String, Object>
• List<Object>

This list is recursive; the possible types for Object in the above list is given by the same list. These types correspond to the types available in JSON.

Returns

• The data contained in this instance as native types, or null if there is no data at this location.

public T getValue (Class<T> valueType)

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This method is used to marshall the data contained in this instance into a class of your choosing. The class must fit 2 simple constraints:

1. The class must have a default constructor that takes no arguments
2. The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

An example class might look like:

     class Message {
         private String author;
         private String text;

         private Message() {}

         public Message(String author, String text) {
             this.author = author;
             this.text = text;
         }

         public String getAuthor() {
             return author;
         }

         public String getText() {
             return text;
         }
     }


     // Later
     Message m = mutableData.getValue(Message.class);
 

Parameters

valueType	The class into which this data in this instance should be marshalled

Returns

• An instance of the class passed in, populated with the data from this instance, or null if there is no data at this location.

public boolean hasChild (String path)

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Parameters

path	A relative path

Returns

• True if data exists at the given path, otherwise false

public boolean hasChildren ()

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Returns

• True if the data at this location has children, false otherwise

public void setPriority (Object priority)

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Sets the priority at this location

Parameters

priority	The desired priority or null to clear the existing priority

public void setValue (Object value)

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Set the data at this location to the given value. The native types accepted by this method for the value correspond to the JSON types:

• Boolean
• Long
• Double
• Map<String, Object>
• List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

1. The class must have a default constructor that takes no arguments
2. The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e. Map<String, MyPOJO>, as well as null values.

Note that this overrides the priority, which must be set separately.

Parameters

value	The value to set at this location or null to delete the existing data

Throws

DatabaseException

public String toString ()