--- /dev/null
+=Accessors=\r
+Say, you have several gigabytes of data in a file. The whole object doesn't need to be serialized at once. You can read and write the value partially using [[svn:foundation/databoard/trunk/org.simantics.databoard/src/org/simantics/databoard/accessor/|Accessor]] interface. The actual container can be a file, memory byte[]/ByteBuffer or a Java Object. The content is structured as tree using Databoard's type system. All but referable records are supported (=no recursion in accessors). \r
+\r
+'''[../javadoc/org/simantics/databoard/accessor.html|org.simantics.databoard.accessor] interfaces'''.\r
+{| style="background-color: #e9e9e9; border: 1px solid #aaaaaa; "\r
+| '''Class'''\r
+| '''Description'''\r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/Accessor.html|Accessor]\r
+| Base class for all data Accessors\r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/RecordAccessor.html|RecordAccessor]\r
+| Record \r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/ArrayAccessor.html|ArrayAccessor]\r
+| Array - an ordered sequence of elements of one value.\r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/MapAccessor.html|MapAccessor]\r
+| Map - an ''ordered'' map of keys to values. \r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/UnionAccessor.html|UnionAccessor]\r
+| Union\r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/BooleanAccessor.html|BooleanAccessor],[../javadoc/org/simantics/databoard/accessor/IntAccessor.html|IntAccessor],[../javadoc/org/simantics/databoard/accessor/LongAccessor.html|LongAccessor],[../javadoc/org/simantics/databoard/accessor/FloatAccessor.html|FloatAccessor],[../javadoc/org/simantics/databoard/accessor/DoubleAccessor.html|DoubleAccessor]\r
+| Primitive and numeric Accessors\r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/StringAccessor.html|StringAccessor]\r
+| String \r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/OptionalAccessor.html|OptionalAccessor]\r
+| Optional value\r
+|- style="background-color: #f9f9f9; " |\r
+| [../javadoc/org/simantics/databoard/accessor/VariantAccessor.html|VariantAccessor]\r
+| Variant value\r
+|}\r
+\r
+[../javadoc/org/simantics/databoard/Accessors.html|Accessors] and [../javadoc/org/simantics/databoard/Files.html|Files] are facade classes that contains utilities for instantiating and handling Accessors.\r
+\r
+<code>[../javadoc/org/simantics/databoard/accessor/binary/index.html|Binary Accessor]</code> is an access to a value in binary format (<tt>byte[]</tt> or <tt>ByteBuffer</tt>).\r
+\r
+'''Example:''' Binary accessor\r
+<pre class="code">\r
+Datatype type = Datatypes.getDatatype( Rectangle2D.Double.class );\r
+Binding binding = Bindings.getBinding( Rectangle2D.Double.class );\r
+Serializer s = Binding.getSerializer( binding );\r
+\r
+// Serialize rectangle\r
+Rectangle2D rect = new Rectangle2D.Double(0,0, 10, 10);\r
+byte[] data = s.serialize(rect);\r
+\r
+// Open accessor to byte data and modify first field in the byte data\r
+RecordAccessor ra = Accessors.getAccessor(data, type);\r
+ra.setFieldValue(0, Bindings.DOUBLE, 5.0);\r
+\r
+// Deserialize values from the byte data back to the rectangle object\r
+s.deserialize(data, rect);\r
+System.out.println(rect.getX());\r
+</pre>\r
+\r
+'''Example:''' File accessor, create\r
+<pre class="code">\r
+RecordType type = Datatypes.getDatatype( Rectangle2D.Double.class );\r
+// Create a new file and initialize it with rectangle type, and open file accessor\r
+FileRecordAccessor fa = Accessors.createFile( file, type );\r
+\r
+// Write the first field (x)\r
+fa.setFieldValue(0, Bindings.DOUBLE, 5.0);\r
+fa.close();\r
+</pre>\r
+\r
+'''Example:''' File accessor, open\r
+<pre class="code">\r
+// Open an accessor to an existing binary file\r
+FileVariantAccessor fa = Accessors.openAccessor(file);\r
+RecordAccessor ra = fa.getContentAccessor();\r
+\r
+// Read the first field (x)\r
+Double x = (Double) ra.getFieldValue(0, Bindings.DOUBLE);\r
+fa.close();\r
+</pre>\r
+\r
+'''Example:''' Java Accessor\r
+<pre class="code">\r
+Binding binding = Bindings.getBinding(Rectangle2D.Double.class);\r
+Rectangle2D rect = new Rectangle2D.Double(0,0, 10, 10);\r
+\r
+// Open accessor to rectangle\r
+RecordAccessor ra = Accessors.getAccessor(binding, rect);\r
+\r
+// Set rectangle's first field (x) to 5.0\r
+ra.setFieldValue(0, Bindings.DOUBLE, 5.0);\r
+System.out.println( rect.getX() );\r
+</pre>\r
+\r
+\r
+==Accessor Reference==\r
+Accessors can be opened to a sub-nodes with AccessorReference or by calling getAccessor. AccessorReference is a string of instances, either accessor type specific of LabelReferences. \r
+<pre class="code">\r
+ ChildReference ref = ChildReference.compile(\r
+ new NameReference("node"),\r
+ new ComponentReference()\r
+ );\r
+ Accessor child = accessor.getComponent( ref );\r
+\r
+ ChildReference ref = ChildReference.compile(\r
+ new LabelReference("node"),\r
+ new LabelReference("v")\r
+ );\r
+ Accessor child = accessor.getComponent( ref );\r
+\r
+ ChildReference ref = ChildReference.create("n-node/v");\r
+ Accessor child = accessor.getComponent( ref );\r
+\r
+ ChildReference ref = ChildReference.create("node/v");\r
+ Accessor child = accessor.getComponent( ref );\r
+\r
+ VariantAccessor va = recordAccessor.getFieldAccessor("node");\r
+ Accessor child = va.getValueAccessor();\r
+</pre>\r
+\r
+==Listening mechanism==\r
+Accessor offers a monitoring mechanism for the data model. \r
+There is an <code>[../javadoc/org/simantics/databoard/accessor/interestset/InterestSet.html|InterestSet]</code> that is a description of a sub-tree that is to be monitored of the data model.\r
+<code>[../javadoc/org/simantics/databoard/accessor/event/Event.html|Events]</code> are objects that spawned on changes to the data model. Each event object is annotated with [../javadoc/org/simantics/databoard/accessor/reference/index.html|reference path] that is in relation to the node where the listener was placed.\r
+\r
+Accessor Listeners use [EventThread Pattern] pattern.\r
Code Review / simantics / platform.git / blobdiff