Module java.xml
Package javax.xml.xpath

# Class XPathFactory

java.lang.Object
javax.xml.xpath.XPathFactory

public abstract class XPathFactory extends Object

An `XPathFactory` instance can be used to create `XPath` objects.

See `newInstance(String uri)` for lookup mechanism.

The `XPathFactory` class is not thread-safe. In other words, it is the application's responsibility to ensure that at most one thread is using a `XPathFactory` object at any given moment. Implementations are encouraged to mark methods as `synchronized` to protect themselves from broken clients.

`XPathFactory` is not re-entrant. While one of the `newInstance` methods is being invoked, applications may not attempt to recursively invoke a `newInstance` method, even from the same thread.

Since:
  1.5

## Field Summary

Fields
Modifier and Type
Field
Description
`static final String`
`DEFAULT_OBJECT_MODEL_URI`
Default Object Model URI.
`static final String`
`DEFAULT_PROPERTY_NAME`
The default property name according to the JAXP spec.

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`XPathFactory()`
Protected constructor as `newInstance()` or `newInstance(String uri)` or `newInstance(String uri, String factoryClassName, ClassLoader classLoader)` should be used to create a new instance of an `XPathFactory`.

## Method Summary

Modifier and Type
Method
Description
`abstract boolean`
`getFeature(String name)`
Get the state of the named feature.
`abstract boolean`
`isObjectModelSupported(String objectModel)`
Is specified object model supported by this `XPathFactory`?
`static XPathFactory`
`newDefaultInstance()`
Creates a new instance of the `XPathFactory` builtin system-default implementation.
`static XPathFactory`
`newInstance()`
Get a new `XPathFactory` instance using the default object model, `DEFAULT_OBJECT_MODEL_URI`, the W3C DOM.
`static XPathFactory`
`newInstance(String uri)`
Obtains a new `XPathFactory` instance using the specified object model.
`static XPathFactory`
`newInstance(String uri, String factoryClassName, ClassLoader classLoader)`
Obtain a new instance of a `XPathFactory` from a factory class name.
`abstract XPath`
`newXPath()`
Return a new `XPath` using the underlying object model determined when the `XPathFactory` was instantiated.
`abstract void`
`setFeature(String name, boolean value)`
Set a feature for this `XPathFactory` and `XPath`s created by this factory.
`abstract void`
`setXPathFunctionResolver(XPathFunctionResolver resolver)`
Establish a default function resolver.
`abstract void`
`setXPathVariableResolver(XPathVariableResolver resolver)`
Establish a default variable resolver.

### Methods declared in class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Field Details

### DEFAULT_PROPERTY_NAME

public static final String DEFAULT_PROPERTY_NAME

The default property name according to the JAXP spec.

See Also:
  - Constant Field Values

### DEFAULT_OBJECT_MODEL_URI

public static final String DEFAULT_OBJECT_MODEL_URI

Default Object Model URI.

See Also:
  - Constant Field Values

## Constructor Details

### XPathFactory

protected XPathFactory()

Protected constructor as `newInstance()` or `newInstance(String uri)` or `newInstance(String uri, String factoryClassName, ClassLoader classLoader)` should be used to create a new instance of an `XPathFactory`.

## Method Details

### newDefaultInstance

public static XPathFactory newDefaultInstance()
Creates a new instance of the `XPathFactory` builtin system-default implementation.

Implementation Requirements:
  The `XPathFactory` builtin system-default implementation is only required to support the `default object model`, the W3C DOM, but may support additional object models.
Returns:
  A new instance of the `XPathFactory` builtin system-default implementation.
Since:
  9

### newInstance

public static XPathFactory newInstance()

Get a new `XPathFactory` instance using the default object model, `DEFAULT_OBJECT_MODEL_URI`, the W3C DOM.

This method is functionally equivalent to:

       newInstance(DEFAULT_OBJECT_MODEL_URI)

Since the implementation for the W3C DOM is always available, this method will never fail.

Returns:
  Instance of an `XPathFactory`.
Throws:
  `RuntimeException` - When there is a failure in creating an `XPathFactory` for the default object model.

### newInstance

public static XPathFactory newInstance(String uri) throws XPathFactoryConfigurationException
Obtains a new `XPathFactory` instance using the specified object model. This method uses the JAXP Lookup Mechanism to determine and load the `XPathFactory` implementation that supports the specified object model.

Tip for Trouble-shooting:

See `Properties.load(java.io.InputStream)` for exactly how a property file is parsed. In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it. For example:

       http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory

Parameters:
  `uri` - Identifies the underlying object model. The specification only defines the URI `DEFAULT_OBJECT_MODEL_URI`, `http://java.sun.com/jaxp/xpath/dom` for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
Returns:
  Instance of an `XPathFactory`.
Throws:
  `XPathFactoryConfigurationException` - If the specified object model is unavailable, or if there is a configuration error.
  `NullPointerException` - If `uri` is `null`.
  `IllegalArgumentException` - If `uri` is `null` or `uri.length() == 0`.

### newInstance

public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader) throws XPathFactoryConfigurationException

Obtain a new instance of a `XPathFactory` from a factory class name. `XPathFactory` is returned if specified factory class supports the specified object model. This function is useful when there are multiple providers in the classpath. It gives more control to the application as it can specify which provider should be loaded.

#### Tip for Trouble-shooting

Setting the `jaxp.debug` system property will cause this method to print a lot of debug messages to `System.err` about what it is doing and where it is looking at.

If you have problems try:

     java -Djaxp.debug=1 YourProgram ....

Parameters:
  `uri` - Identifies the underlying object model. The specification only defines the URI `DEFAULT_OBJECT_MODEL_URI`,`http://java.sun.com/jaxp/xpath/dom` for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
  `factoryClassName` - fully qualified factory class name that provides implementation of `javax.xml.xpath.XPathFactory`.
  `classLoader` - `ClassLoader` used to load the factory class. If `null` current `Thread`'s context classLoader is used to load the factory class.
Returns:
  New instance of a `XPathFactory`
Throws:
  `XPathFactoryConfigurationException` - if `factoryClassName` is `null`, or the factory class cannot be loaded, instantiated or the factory class does not support the object model specified in the `uri` parameter.
  `NullPointerException` - If `uri` is `null`.
  `IllegalArgumentException` - If `uri` is `null` or `uri.length() == 0`.
Since:
  1.6
See Also:
  - `newInstance()`
  - `newInstance(String uri)`

### isObjectModelSupported

public abstract boolean isObjectModelSupported(String objectModel)

Is specified object model supported by this `XPathFactory`?

Parameters:
  `objectModel` - Specifies the object model which the returned `XPathFactory` will understand.
Returns:
  `true` if `XPathFactory` supports `objectModel`, else `false`.
Throws:
  `NullPointerException` - If `objectModel` is `null`.
  `IllegalArgumentException` - If `objectModel.length() == 0`.

### setFeature

public abstract void setFeature(String name, boolean value) throws XPathFactoryConfigurationException

Set a feature for this `XPathFactory` and `XPath`s created by this factory.

Feature names are fully qualified `URI`s. Implementations may define their own features. An `XPathFactoryConfigurationException` is thrown if this `XPathFactory` or the `XPath`s it creates cannot support the feature. It is possible for an `XPathFactory` to expose a feature value but be unable to change its state.

All implementations are required to support the `XMLConstants.FEATURE_SECURE_PROCESSING` feature. When the feature is `true`, any reference to an external function is an error. Under these conditions, the implementation must not call the `XPathFunctionResolver` and must throw an `XPathFunctionException`.

Parameters:
  `name` - Feature name.
  `value` - Is feature state `true` or `false`.
Throws:
  `XPathFactoryConfigurationException` - if this `XPathFactory` or the `XPath`s it creates cannot support this feature.
  `NullPointerException` - if `name` is `null`.

### getFeature

public abstract boolean getFeature(String name) throws XPathFactoryConfigurationException

Get the state of the named feature.

Feature names are fully qualified `URI`s. Implementations may define their own features. An `XPathFactoryConfigurationException` is thrown if this `XPathFactory` or the `XPath`s it creates cannot support the feature. It is possible for an `XPathFactory` to expose a feature value but be unable to change its state.

Parameters:
  `name` - Feature name.
Returns:
  State of the named feature.
Throws:
  `XPathFactoryConfigurationException` - if this `XPathFactory` or the `XPath`s it creates cannot support this feature.
  `NullPointerException` - if `name` is `null`.

### setXPathVariableResolver

public abstract void setXPathVariableResolver(XPathVariableResolver resolver)

Establish a default variable resolver.

Any `XPath` objects constructed from this factory will use the specified resolver by default.

A `NullPointerException` is thrown if `resolver` is `null`.

Parameters:
  `resolver` - Variable resolver.
Throws:
  `NullPointerException` - If `resolver` is `null`.

### setXPathFunctionResolver

public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver)

Establish a default function resolver.

Any `XPath` objects constructed from this factory will use the specified resolver by default.

A `NullPointerException` is thrown if `resolver` is `null`.

Parameters:
  `resolver` - XPath function resolver.
Throws:
  `NullPointerException` - If `resolver` is `null`.

### newXPath

public abstract XPath newXPath()

Return a new `XPath` using the underlying object model determined when the `XPathFactory` was instantiated.

Returns:
  New instance of an `XPath`.