MutableData

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

Public Methods

public MutableData child (String path)

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 ()

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 ()

Returns
  • The number of immediate children at this location

public String getKey ()

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

public Object getPriority ()

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)

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 ()

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)

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)

Parameters
path A relative path
Returns
  • True if data exists at the given path, otherwise false

public boolean hasChildren ()

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

public void setPriority (Object priority)

Sets the priority at this location

Parameters
priority The desired priority or null to clear the existing priority

public void setValue (Object value)

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 ()