Work with XPath-Like Object Queries

Work with XPath-Like Object Queries

Using Aspose.3D for Java, you can select one or more objects under the current node using XPath-Like query syntax. The query syntax was inspired by XPath, so most concepts and syntax are similar, the query syntax is compatible with URL so it will be used in our cloud version in the future. Usually, a syntax is composed by Prefix Name Condition / Name Condition /.

Prefix	Description
//	Global selector, any descendant is treated as the root node to perform the selection
/	Root selector, only one ancestor is used to look up
Other	Assume it’s a name, and select the object by name in global selector mode

The name is a string that matches the object’s name, or wildcard * is used to match any name. The condition is an expression to decide whether to select the object, boolean operators (not) and or, comparison operators >/</>=/<=/=/!= are supported. To Access a property in the condition expression, ‘@’ prefix is used, e.g. @Name will read the Name property. A shortcut syntax for testing type is supported by <Mesh>, this is equivalent to [@Type = 'Mesh'], identifiers without a quote will be treated as a string.

Select all nodes using syntax global selector

 //<Node>

This is the short syntax of:

 //*[<Node>]

or

 //*[@Type = Node]

Select a second level node with a visible parent

 //<Node>[@Visible]/<Node>

Following is the sample code to query one or more objects:

// For complete examples and data files, please go to https://github.com/aspose-3d/Aspose.3D-for-Java
//Create a scene for testing
Scene s = new Scene();
// Create a child node
Node a = s.getRootNode().createChildNode("a");
// Create a sub-child node
a.createChildNode("a1");
// Create a sub-child node
a.createChildNode("a2");
// Create a child node
s.getRootNode().createChildNode("b");
// Create a child node
Node c = s.getRootNode().createChildNode("c");
// Create a sub-child node
c.createChildNode("c1").addEntity(new Camera("cam"));
// Create a sub-child node
c.createChildNode("c2").addEntity(new Light("light"));
/*
The hierarchy of the scene looks like:
 - Root
    - a
        - a1
        - a2
    - b
    - c
        - c1
            - cam
        - c2
            - light
             */
//select objects that has type Camera or name is 'light' whatever it's located.
List<A3DObject> objects = s.getRootNode().selectObjects("//*[(@Type = 'Camera') or (@Name = 'light')]");

//Select single camera object under the child nodes of node named 'c' under the root node
A3DObject c1 = s.getRootNode().selectSingleObject("/c/*/<Camera>");

// Select node named 'a1' under the root node, even if the 'a1' is not a directly child node of the
A3DObject obj = s.getRootNode().selectSingleObject("a1");

//Select the node itself, since the '/' is selected directly on the root node, so the root node is selected.
obj = s.getRootNode().selectSingleObject("/");