=Binding=
Binding is a mechanism for mapping a Java Class to a Datatype.
For example, take a java.lang.Double. The instance is a container (<code>private final double value;</code>) for the data and its Binding (DoubleBinding) is a way to access the data (<code>.valueOf()</code>, <code>.getDouble()</code>). 
    Java Object + Binding = Databoard Value

Bindings have the exact same composition tree structure as its respective <code>Datatype</code> - structural types have structural Bindings, and primitive types a single binding. To acquire a binding, the developer can use a utility that creates one using Java reflection functions.
<pre class="code">
    Binding binding = Binding.getBinding( Double.class );
</pre>

Sometimes classes cannot bound using automatic tool, for instance when using 3rd party classes which cannot be modified. The developer must then write binding self by sub-classing on of the 13 base binding classes (There is a base binding class for each Datatype). 
<pre class="code">
    Binding binding = new RecordBinding() { ... };
</pre>

'''[../javadoc/org/simantics/databoard/binding|org.simantics.databoard.binding]'''.
{| style="background-color: #f9f9f9; border: 1px solid #aaaaaa; "
|- style="background-color: #e9e9e9; " |
| '''Class''' || '''Description'''
|- 
| [../javadoc/org/simantics/databoard/binding/DataBinding.html|DataBinding]
| Base class for all data Bindings
|- 
| [../javadoc/org/simantics/databoard/binding/RecordBinding.html|RecordBinding]
| Record 
|- 
| [../javadoc/org/simantics/databoard/binding/ArrayBinding.html|ArrayBinding]
| Array - an ordered sequence of elements of one value.
|- 
| [../javadoc/org/simantics/databoard/binding/MapBinding.html|MapBinding]
| Map - an ''ordered'' map of keys to values. 
|- 
| [../javadoc/org/simantics/databoard/binding/UnionBinding.html|UnionBinding]
| Union
|- 
| [../javadoc/org/simantics/databoard/binding/BooleanBinding.html|BooleanBinding],[../javadoc/org/simantics/databoard/binding/IntBinding.html|IntBinding],[../javadoc/org/simantics/databoard/binding/LongBinding.html|LongBinding],[../javadoc/org/simantics/databoard/binding/FloatBinding.html|FloatBinding],[../javadoc/org/simantics/databoard/binding/DoubleBinding.html|DoubleBinding]
| Primitive and numeric Bindings
|- 
| [../javadoc/org/simantics/databoard/binding/StringBinding.html|StringBinding]
| String 
|- 
| [../javadoc/org/simantics/databoard/binding/OptionalBinding.html|OptionalBinding]
| Optional value
|- 
| [../javadoc/org/simantics/databoard/binding/VariantBinding.html|VariantBinding]
| Variant value
|}


Binding can be acquired or created using one of the following methods:
* Constructor 
* Constant
* Reflection-Read from a Class 
* Created using [../javadoc/org/simantics/databoard/bindingscheme/BindingScheme.html|BindingScheme]
<pre class="code">
    Binding binding = new DoubleBinding( doubleType );
    Binding binding = new RecordBinding() { ... };
    Binding binding = Bindings.DOUBLE;
    Binding binding = Binding.getBinding( Double.class );
    Binding binding = Binding.getBinding( Datatypes.DOUBLE );
</pre>

==Reflection==
'''Data Type and Binding can be read automatically from a Class by utility.'''
<pre class="code">
    Datatype type = Datatypes.getDatatype( Foo.class );
    Binding binding = Bindings.getBinding( Foo.class );
</pre>

Bindings for generics classes can be created by passing arguments.
<pre class="code">
    Binding e = Bindings.getBinding(List.class, String.class);
    List<String> list = (List<String>) e.createRandom(5);

    Binding binding = Bindings.getBinding( Map.class, Integer.class, Integer.class );
    Map<Integer, Integer> value = (Map<Integer, Integer>) binding.createDefault();
</pre>

Even cascading generics...
<pre class="code">
    Binding e = Bindings.getBinding(List.class, List.class, String.class);
    List<List<String>> listList = (List<List<String>>) e.createRandom(5);
</pre>

'''Classes are RecordTypes'''
<pre class="code">
    class Foo {
        public int x, y, z;
    }
</pre>
Is a binding to the following Datatype
<pre class="code">
    type Foo = { x : Integer, y : Integer, z : Integer }
</pre>

'''There are three types of classes supported, and therefore three ways how objects are constructed.'''
If you create binding for your class with Bindings#getBinding( clazz ), the class must adhere one of these format. You may have to add annotations such as @Recursive, @Optional, @Arguments. 

''Record-like classes:''
<pre class="code">
    class Foo {
        public String name;
        public Object value;
    }
</pre>

''Immutable classes:''
<pre class="code">
    class Foo {
        private String name;
        private Object value;
        
        public Foo(String name, Object value) {
            this.name = name;
            this.value = value;
        }
        
        public String getName() {
            return name;
        }
        
        public Object getValue() {
            return value;
        }
        
    }
</pre>

''Bean-like classes:''
<pre class="code">
    class Foo {
        private String name;
        private Object value;
        
        public void setName(String name) {
            this.name = name;
        }
        
        public void setValue(Object value) {
            this.value = value;
        }
        
        public String getName() {
            return name;
        }
        
        public Object getValue() {
            return value;
        }
        
    }
</pre<

'''Static and transient fields are omited:'''
<pre class="code">
    static final long serialVersionUID = -3387516993124229943L;
    transient int hashCode;
</pre>

'''Enumerations are Union Types'''
<pre class="code">
    enum Cars { Ferrari, Porche, Lamborghini, Jaguar }
</pre>    
is interpreted as union type
    type Cars = | Ferrari | Porche | Lamborghini | Jaguar

If you cannot modify the class, you have to create binding for it by subclassing base binding classes, eg. RecordBinding.

'''Other exceptions:'''
*<code>java.lang.Object</code> is <tt>Variant</tt>.
*<code>java.lang.Set<T></code> is <tt>Map(T, {})</tt>.
*<code>java.lang.TreeSet<T></code> is <tt>Map(T, {})</tt>.
*<code>java.lang.HashSet<T></code> is <tt>Map(T, {})</tt>. (Note HashSet binding has very low performance.)
*<code>java.lang.Map<K, V></code> is <tt>Map(K, V)</tt>.
*<code>java.lang.TreeMap<K, V></code> is <tt>Map(K, V)</tt>.
*<code>java.lang.HashMap<K, V></code> is <tt>Map(K, V)</tt>. (Note HashMap binding has very low performance.)
*<code>java.lang.List<T></code> is <tt>Array(T)</tt>.
*<code>java.lang.ArrayList<T></code> is <tt>Array(T)</tt>.
*<code>java.lang.LinkedList<T></code> is <tt>Array(T)</tt>.
*<code>void</code> is <tt>{}</tt>.
*The stacktrace of <code>Exception.class</code> is omited.

===Annotations===
Java Classes / Fields can be annotated with the following annotations ('''[../javadoc/org/simantics/databoard/annotations/|org.simantics.databoard.annotations]]''').


'''UnionTypes are abstract classes or interfaces with <code>@Union</code> annotation.'''
<pre class="code">
    @Union({A.class, B.class}) interface Union1 {		
    }
    
    class A implements Union1 {
        public int value;
    }
    
    class B implements Union1 {
        public String name;
    }
</pre>

'''<code>@Referable</code> denotes that the class has recursion and is a referable record.'''
<pre class="code">
    public @Referable class Node {
        public Node[] children;
    }
</pre>

'''Fields that can have <tt>null</tt> value have <code>@Optional</code> annotation.'''
<pre class="code">
    @Optional String name;
</pre>

'''String valid values are set with <code>@Pattern</code> as regular expression. ([http://en.wikipedia.org/wiki/Regular_expression])'''
<pre class="code">
    String @Pattern("(19|20)\\d\\d[- /.](0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])") date;
    
    type Date = String( Pattern = "(19|20)\d\d[- /.](0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])" )
</pre>

'''String content type is set with a <code>@MIMEType</code>. ([http://en.wikipedia.org/wiki/Mime_type MIME Type])'''
<pre class="code">
    @MIMEType("text/xml") String document;
</pre>

'''Array size restricted with @Length.'''
<pre class="code">
    @Length("[0..10]") int[] array;
    @Length({"[320]", "[240]"}) int[][] image;
</pre>

'''Valid numeric range is set with @Range.'''
<pre class="code">
    @Range("[0..100]") double alpha;
    @Range("[0..]" double length;
</pre>

'''<tt>Range</tt> and <tt>Length</tt> notation:'''
*Exact Value "0"
*Exclude all "()"
*Unlimited "[..]"
*Inclusive range "[0..100]"
*Exclusive range "(0..100)"
*Inclusive lower bound and exclusive upper bound "[0..100)"


'''Engineering unit type is given with @Unit.'''
<pre class="code">
    @Unit("km/h") double maxVelocity;
</pre>

'''The serializer generated with reflection can be overriden with @SpecializedSerializer'''
<pre class="code">
    @SpecializedSerializer(MySerializer.class) 
    public class MyRecord {
        ...
    }
</pre>

== Mapping Scheme ==
A ''binding scheme'' associates some data types with a unique binding. The mapping of types to bindings is bijective, there is one binding for each type and vice-versa.

<code>DefaultBindingScheme</code> is a scheme that converts any datatype to a binding. It prefers java.lang.X primitives.
The Class mapping for each type is listed below.
{| style="background-color: #f9f9f9; border: 1px solid #aaaaaa; "
|- style="background-color: #e9e9e9;
| '''Type''' || '''Class'''
|- 
| <code>BooleanType</code> || <code>Boolean.class</code>
|- 
| <code>ByteType</code> || <code>Byte.class</code>
|- 
| <code>FloatType</code> || <code>Float.class</code>
|- 
| <code>DoubleType</code> || <code>eDouble.class</code>
|- 
| <code>IntegerType</code> || <code>Integer.class</code>
|- 
| <code>LongType</code> || <code>Long.class</code>
|- 
| <code>StringType</code> || <code>String.class</code>
|- 
| <code>UnionType</code> || <code>TaggedObject.class</code>
|- 
| <code>OptionType</code> || <code>ValueContainer.class</code>
|- 
| <code>RecordType</code> || <code>Object[].class</code>
|- 
| <code>ArrayType</code> || <code>ArrayList.class</code>
|- 
| <code>Array(Byte)</code> || <code>byte[].class</code>
|- 
| <code>MapType</code> || <code>TreeMap.class</code>
|- 
| <code>VariantType</code> || <code>Variant.class</code>
|}

<code>MutableBindingScheme</code> is a scheme that provides a fully implementing mutable binding for all data types. 
The Class mapping for each type is listed below.

{| style="background-color: #f9f9f9; border: 1px solid #aaaaaa; "
|- style="background-color: #e9e9e9; " |
| '''Type''' || '''Class'''
|- 
| <code>BooleanType</code> || <code>MutableBoolean.class</code>
|- 
| <code>ByteType</code> || <code>MutableByte.class</code>
|- 
| <code>FloatType</code> || <code>MutableFloat.class</code>
|- 
| <code>DoubleType</code> || <code>MutableDouble.class</code>
|- 
| <code>IntegerType</code> || <code>MutableInt.class</code>
|- 
| <code>LongType</code> || <code>MutableLong.class</code>
|- 
| <code>StringType</code> || <code>MutableString.class</code>
|- 
| <code>UnionType</code> || <code>TaggedObject.class</code>
|- 
| <code>OptionType</code> || <code>ValueContainer.class</code>
|- 
| <code>RecordType</code> || <code>Object[].class</code>
|- 
| <code>ArrayType</code> || <code>ArrayList.class</code>
|- 
| <code>MapType</code> || <code>TreeMap.class</code>
|- 
| <code>VariantType</code> || <code>Variant.class</code>
|}


===Serialization===
[../javadoc/org/simantics/databoard/serialization/binary/Serializer.html|Serializer] is a class that serializes Values into and from binary serialization format. It follows the Databoard [Databoard_Specification#Binary_File_Format|Binary File Format].
<pre class="code">
    Binding binding = Bindings.DOUBLE;
    Serializer serializer = Bindings.getSerializer( binding );
    byte[] data = serializer.serialize( new Double( 100.0 ) );
    
    Double value = (Double) serializer.deserialize( data );
</pre>

Files can be partially accessed using BinaryAccessor, see [accessor|Accessors]. This is useful when handling larger than memory files.

===Validation===
'''Value''' can be ''well-formed'' or ''valid''. 
The domain of valid values are defined with restrictions in data types, and <code>@Length</code>, <code>@Range</code>, <code>@Pattern</code> and <code>@MIMEType</code> Annotations in Classes

Validation mechanism in Binding asserts that the instance is a valid value of the respective Data Type.
<pre class="code">
    try {
        Binding.assertInstaceIsValid( object );
    } catch( BindingException e ) {
        // In-valid object
    }
</pre>

===Other Notes===
*<tt>Binding</tt> is a <tt>Comparator</tt>, all data values are comparable, the order is defined in [[Databoard_Specification#Comparison|Specification]].
*<tt>Binding#createDefault()</tt> creates a valid instance of the Datatype.
*<tt>Binding#createRandom(int)</tt> creates a valid instance with random values. Useful for unit tests.
*<tt>Binding#clone(Object)</tt> creates a new instance with same content.
*<tt>Binding#readFrom(Object, Binding, Binding)</tt> copies contents from another object of same type.

===Parsing & Printing===

Data values are printed and parsed of the [[Databoard_Specification|Text notation]] with the following <code>Binding</code> methods:
<pre class="code">
    String text = binding.printValue( value, true );
    
    Object value = binding.parseValue( text );
</pre>
And also to value definitions <tt>''name : type = value''</tt>

<pre class="code">
    StringBuilder sb = new StringBuilder();
    DataValueRepository repo = new DataValueRepository();
    repo.put( "temp", binding, value );
    binding.printValue( value, sb, repo, true );
    String text = sb.toString();
    
    Object value = binding.parseValueDefinition( text );
</pre>