public class

MutableData

extends Object
java.lang.Object
   ↳ com.google.firebase.database.MutableData

Class Overview

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.

Summary

Public Methods
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()
[Expand]
Inherited Methods
From class java.lang.Object

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 String: A relative path
Returns
MutableData An instance encapsulating the data and priority at the given path

public boolean equals (Object o)

Parameters
o Object
Returns
boolean

public Iterable<MutableData> getChildren ()

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

Returns
Iterable<MutableData> The immediate children at this location

public long getChildrenCount ()

Returns
long The number of immediate children at this location

public String getKey ()

Returns
String 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
Object The priority at this location as a native type

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 GenericTypeIndicator: A subclass of GenericTypeIndicator indicating the type of generic collection to be returned.
Returns
T 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
Object 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 Class: The class into which this data in this instance should be marshalled
Returns
T 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 String: A relative path
Returns
boolean True if data exists at the given path, otherwise false

public boolean hasChildren ()

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

public void setPriority (Object priority)

Sets the priority at this location

Parameters
priority Object: The desired 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 Object: The value to set at this location
Throws
DatabaseException

public String toString ()

Returns
String