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
Modifier and Type | Field | Description |
---|---|---|
static String | DEFAULT_OBJECT_MODEL_URI | Default Object Model URI. |
static String | DEFAULT_PROPERTY_NAME | The default property name according to the JAXP spec. |
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | XPathFactory() | Protected constructor as |
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 |
static XPathFactory | newDefaultInstance() | Creates a new instance of the |
static XPathFactory | newInstance() | Get a new |
static XPathFactory | newInstance(String uri) | Get a new |
static XPathFactory | newInstance(String uri,
String factoryClassName,
ClassLoader classLoader) | Obtain a new instance of a |
abstract XPath | newXPath() | Return a new |
abstract void | setFeature(String name,
boolean value) | Set a feature for this |
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 Detail
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 Detail
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 Detail
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 thedefault 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 anXPathFactory
for the default object model.
newInstance
public static XPathFactory newInstance(String uri) throws XPathFactoryConfigurationException
Get a new XPathFactory
instance using the specified object model.
To find a XPathFactory
object, this method looks the following places in the following order where "the class loader" refers to the context class loader:
-
If the system property
DEFAULT_PROPERTY_NAME
+ ":uri" is present, where uri is the parameter to this method, then its value is read as a class name. The method will try to create a new instance of this class by using the class loader, and returns it if it is successfully created. -
Use the configuration file "jaxp.properties". The file is in standard
Properties
format and typically located in the conf directory of the Java installation. It contains the fully qualified name of the implementation class with the key being the system property defined above.The jaxp.properties file is read only once by the JAXP implementation and its values are then cached for future use. If the file does not exist when the first attempt is made to read from it, no further attempts are made to check for its existence. It is not possible to change the value of any property in jaxp.properties after it has been read for the first time.
-
Use the service-provider loading facility, defined by the
ServiceLoader
class, to attempt to locate and load an implementation of the service using the default loading mechanism: the service-provider loading facility will use the current thread's context class loader to attempt to load the service. If the context class loader is null, the system class loader will be used.
Each potential service provider is required to implement the methodisObjectModelSupported(String objectModel)
. The first service provider found that supports the specified object model is returned.
In case ofServiceConfigurationError
anXPathFactoryConfigurationException
will be thrown. -
Platform default
XPathFactory
is located in a platform specific way. There must be a platform defaultXPathFactory
for the W3C DOM, i.e.DEFAULT_OBJECT_MODEL_URI
.
If everything fails, an XPathFactoryConfigurationException
will be thrown.
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 URIDEFAULT_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
- Ifuri
isnull
. -
IllegalArgumentException
- Ifuri
isnull
oruri.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 URIDEFAULT_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 ofjavax.xml.xpath.XPathFactory
. -
classLoader
-ClassLoader
used to load the factory class. Ifnull
currentThread
's context classLoader is used to load the factory class. - Returns:
- New instance of a
XPathFactory
- Throws:
-
XPathFactoryConfigurationException
- iffactoryClassName
isnull
, or the factory class cannot be loaded, instantiated or the factory class does not support the object model specified in theuri
parameter. -
NullPointerException
- Ifuri
isnull
. -
IllegalArgumentException
- Ifuri
isnull
oruri.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 returnedXPathFactory
will understand. - Returns:
-
true
ifXPathFactory
supportsobjectModel
, elsefalse
. - Throws:
-
NullPointerException
- IfobjectModel
isnull
. -
IllegalArgumentException
- IfobjectModel.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 statetrue
orfalse
. - Throws:
-
XPathFactoryConfigurationException
- if thisXPathFactory
or theXPath
s it creates cannot support this feature. -
NullPointerException
- ifname
isnull
.
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 thisXPathFactory
or theXPath
s it creates cannot support this feature. -
NullPointerException
- ifname
isnull
.
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
- Ifresolver
isnull
.
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
- Ifresolver
isnull
.
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
.