Absolute Location paths and descendant selection

Location Paths

Although there are many different kinds of XPath expressions, the one that’s of primary use in Java programs is the location path. A location path selects a set of nodes from an XML document. Each location path is composed of one or more location steps. Each location step has an axis, a node test and, optionally, one or more predicates. Furthermore, each location step is evaluated with respect to a particular context node. A double colon (::) separates the axis from the node test, and each predicate is enclosed in square brackets.

Example Location Path

Consider the following XML document:

Code

<albums>
<rock>
<title>Machine Head</title>
<artist>Deep Purple</artist>
</rock>
<blues>
<title>Greens From The Garden</title>
<artist>Cory Harris</artist>
</blues>
<country>
<title>The Ranch</title>
<artist>The Ranch</artist>
</country>
</albums>

If we wanted to select the “title” node of all albums, we could use the following (absolute) location paths:

Code

albums/rock/title
albums/blues/title
albums/country/title

The Result

Here are the nodes that are selected using the above location path.

Code

<title>Machine Head</title>
<title>Greens From The Garden</title>
<title>The Ranch</title>

The Root Node

If we wanted to select the root node, we could use either the node’s name or a forward slash. Both of these options are absolute location paths and select the root node.

Option 1 – use the root node’s name:

Code

albums

Option 2 – use a forward slash:

Code