Examples of org.apache.commons.configuration2.tree.xpath.XPathExpressionEngine

Package org.apache.commons.configuration2.tree.xpath

Examples of org.apache.commons.configuration2.tree.xpath.XPathExpressionEngine

org.apache.commons.configuration2.io.FileHandler
ns.apache.org/jxpath/"> Commons JXPath for handling XPath expressions and mapping them to the nodes of a hierarchical configuration. This makes the rich and powerful XPATH syntax available for accessing properties from a configuration object.

For selecting properties arbitrary XPATH expressions can be used, which select single or multiple configuration nodes. The associated {@code Configuration} instance will directly pass the specified property keysinto this engine. If a key is not syntactically correct, an exception will be thrown.

For adding new properties, this expression engine uses a specific syntax: the "key" of a new property must consist of two parts that are separated by whitespace:
1. An XPATH expression selecting a single node, to which the new element(s) are to be added. This can be an arbitrary complex expression, but it must select exactly one node, otherwise an exception will be thrown.
2. The name of the new element(s) to be added below this parent node. Here either a single node name or a complete path of nodes (separated by the "/" character or "@" for an attribute) can be specified.
Some examples for valid keys that can be passed into the configuration's {@code addProperty()} method follow:
```
 "/tables/table[1] type" 
```
This will add a new {@code type} node as a child of the first {@code table}element.
```
 "/tables/table[1] @type" 
```
Similar to the example above, but this time a new attribute named {@code type} will be added to the first {@code table} element.
```
 "/tables table/fields/field/name" 
```
This example shows how a complex path can be added. Parent node is the {@code tables} element. Here a new branch consisting of the nodes{@code table}, {@code fields}, {@code field}, and {@code name} will be added.
```
 "/tables table/fields/field@type" 
```
This is similar to the last example, but in this case a complex path ending with an attribute is defined.

Note: This extended syntax for adding properties only works with the {@code addProperty()} method. {@code setProperty()} does not supportcreating new nodes this way.

From version 1.7 on, it is possible to use regular keys in calls to {@code addProperty()} (i.e. keys that do not have to contain a whitespace asdelimiter). In this case the key is evaluated, and the biggest part pointing to an existing node is determined. The remaining part is then added as new path. As an example consider the key
```
 "tables/table[last()]/fields/field/name" 
```
If the key does not point to an existing node, the engine will check the paths {@code "tables/table[last()]/fields/field"}, {@code "tables/table[last()]/fields"}, {@code "tables/table[last()]"}, and so on, until a key is found which points to a node. Let's assume that the last key listed above can be resolved in this way. Then from this key the following key is derived: {@code "tables/table[last()] fields/field/name"} byappending the remaining part after a whitespace. This key can now be processed using the original algorithm. Keys of this form can also be used with the {@code setProperty()} method. However, it is still recommended touse the old format because it makes explicit at which position new nodes should be added. For keys without a whitespace delimiter there may be ambiguities.
@since 1.3 @version $Id: XPathExpressionEngine.java 1624601 2014-09-12 18:04:36Z oheger $

     * @param value the value to interpolate
     * @return the value with variables substituted
     */
    protected Object interpolate(Object value)
    {
        ConfigurationInterpolator ci = getInterpolator();
        return (ci != null) ? ci.interpolate(value) : value;
    }

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        boolean success;
        do
        {
            // do this in a loop because the ConfigurationInterpolator
            // instance may be changed by another thread
            ConfigurationInterpolator ciOld = getInterpolator();
            ConfigurationInterpolator ciNew =
                    (ciOld != null) ? ciOld : new ConfigurationInterpolator();
            ciNew.registerLookups(lookups);
            success = interpolator.compareAndSet(ciOld, ciNew);
        } while (!success);
    }

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    public void setDefaultLookups(Collection<? extends Lookup> lookups)
    {
        boolean success;
        do
        {
            ConfigurationInterpolator ciOld = getInterpolator();
            ConfigurationInterpolator ciNew =
                    (ciOld != null) ? ciOld : new ConfigurationInterpolator();
            Lookup confLookup = findConfigurationLookup(ciNew);
            if (confLookup == null)
            {
                confLookup = new ConfigurationLookup(this);
            }
            else
            {
                ciNew.removeDefaultLookup(confLookup);
            }
            ciNew.addDefaultLookups(lookups);
            ciNew.addDefaultLookup(confLookup);
            success = interpolator.compareAndSet(ciOld, ciNew);
        } while (!success);
    }

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    public void setParentInterpolator(ConfigurationInterpolator parent)
    {
        boolean success;
        do
        {
            ConfigurationInterpolator ciOld = getInterpolator();
            ConfigurationInterpolator ciNew =
                    (ciOld != null) ? ciOld : new ConfigurationInterpolator();
            ciNew.setParentInterpolator(parent);
            success = interpolator.compareAndSet(ciOld, ciNew);
        } while (!success);
    }

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     * @since 2.0
     */
    protected void cloneInterpolator(AbstractConfiguration orgConfig)
    {
        interpolator = new AtomicReference<ConfigurationInterpolator>();
        ConfigurationInterpolator orgInterpolator = orgConfig.getInterpolator();
        List<Lookup> defaultLookups = orgInterpolator.getDefaultLookups();
        Lookup lookup = findConfigurationLookup(orgInterpolator, orgConfig);
        if (lookup != null)
        {
            defaultLookups.remove(lookup);
        }


        installInterpolator(orgInterpolator.getLookups(), defaultLookups);
    }

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    @Override
    public final void installInterpolator(
            Map<String, ? extends Lookup> prefixLookups,
            Collection<? extends Lookup> defLookups)
    {
        InterpolatorSpecification spec =
                new InterpolatorSpecification.Builder()
                        .withPrefixLookups(prefixLookups)
                        .withDefaultLookups(defLookups)
                        .withDefaultLookup(new ConfigurationLookup(this))
                        .create();

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        parent.addProperty("tablespaces.tablespace.name", "default");
        parent.addProperty("tablespaces.tablespace(-1).name", "test");
        parent.addProperty("tables.table(0).var", "${brackets:x}");


        ConfigurationInterpolator interpolator = parent.getInterpolator();
        interpolator.registerLookup("brackets", new Lookup() {


            public String lookup(String key) {
                return "(" + key + ")";
            }

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        do
        {
            ConfigurationInterpolator ciOld = getInterpolator();
            ConfigurationInterpolator ciNew =
                    (ciOld != null) ? ciOld : new ConfigurationInterpolator();
            Lookup confLookup = findConfigurationLookup(ciNew);
            if (confLookup == null)
            {
                confLookup = new ConfigurationLookup(this);
            }
            else

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    protected void cloneInterpolator(AbstractConfiguration orgConfig)
    {
        interpolator = new AtomicReference<ConfigurationInterpolator>();
        ConfigurationInterpolator orgInterpolator = orgConfig.getInterpolator();
        List<Lookup> defaultLookups = orgInterpolator.getDefaultLookups();
        Lookup lookup = findConfigurationLookup(orgInterpolator, orgConfig);
        if (lookup != null)
        {
            defaultLookups.remove(lookup);
        }

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    @Before
    public void setUp() throws Exception
    {
        // any concrete class will do
        PropertiesConfiguration c = new PropertiesConfiguration();
        new FileHandler(c).load(ConfigurationAssert
                .getTestFile("test.properties"));
        sync = new SynchronizerTestImpl();
        c.setSynchronizer(sync);
        config = c;
    }

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