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/**
 * Copyright (C) 2006-2015 phloc systems
 * http://www.phloc.com
 * office[at]phloc[dot]com
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.phloc.commons.xml.xpath;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
import javax.xml.namespace.NamespaceContext;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import javax.xml.xpath.XPathFunctionResolver;
import javax.xml.xpath.XPathVariableResolver;

import com.phloc.commons.ValueEnforcer;
import com.phloc.commons.annotations.Nonempty;
import com.phloc.commons.annotations.PresentForCodeCoverage;

/**
 * Utility class to create {@link XPath} and {@link XPathExpression} objects
 * more easily.
 * 
 * @author Philip Helger
 */
@NotThreadSafe
public final class XPathHelper
{
  private static final XPathFactory s_aXPathFactory = XPathFactory.newInstance ();

  @SuppressWarnings ("unused")
  @PresentForCodeCoverage
  private static final XPathHelper s_aInstance = new XPathHelper ();

  private XPathHelper ()
  {}

  /**
   * @return The default XPath factory. Be careful when manipulating this
   *         object! Never null.
   */
  @Nonnull
  public static XPathFactory getDefaultXPathFactory ()
  {
    return s_aXPathFactory;
  }

  /**
   * Create a new {@link XPath} without any special settings using the default
   * {@link XPathFactory}.
   * 
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath ()
  {
    return createNewXPath (s_aXPathFactory,
                           (XPathVariableResolver) null,
                           (XPathFunctionResolver) null,
                           (NamespaceContext) null);
  }

  /**
   * Create a new {@link XPath} without any special settings.
   * 
   * @param aXPathFactory
   *        The XPath factory object to use. May not be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nonnull final XPathFactory aXPathFactory)
  {
    return createNewXPath (aXPathFactory,
                           (XPathVariableResolver) null,
                           (XPathFunctionResolver) null,
                           (NamespaceContext) null);
  }

  /**
   * Create a new {@link XPath} with the passed variable resolver using the
   * default {@link XPathFactory}.
   * 
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nullable final XPathVariableResolver aVariableResolver)
  {
    return createNewXPath (s_aXPathFactory, aVariableResolver, (XPathFunctionResolver) null, (NamespaceContext) null);
  }

  /**
   * Create a new {@link XPath} with the passed variable resolver.
   * 
   * @param aXPathFactory
   *        The XPath factory object to use. May not be null.
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nonnull final XPathFactory aXPathFactory,
                                      @Nullable final XPathVariableResolver aVariableResolver)
  {
    return createNewXPath (aXPathFactory, aVariableResolver, (XPathFunctionResolver) null, (NamespaceContext) null);
  }

  /**
   * Create a new {@link XPath} with the passed function resolver using the
   * default {@link XPathFactory}.
   * 
   * @param aFunctionResolver
   *        Function resolver to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nullable final XPathFunctionResolver aFunctionResolver)
  {
    return createNewXPath (s_aXPathFactory, (XPathVariableResolver) null, aFunctionResolver, (NamespaceContext) null);
  }

  /**
   * Create a new {@link XPath} with the passed function resolver.
   * 
   * @param aXPathFactory
   *        The XPath factory object to use. May not be null.
   * @param aFunctionResolver
   *        Function resolver to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nonnull final XPathFactory aXPathFactory,
                                      @Nullable final XPathFunctionResolver aFunctionResolver)
  {
    return createNewXPath (aXPathFactory, (XPathVariableResolver) null, aFunctionResolver, (NamespaceContext) null);
  }

  /**
   * Create a new {@link XPath} with the passed namespace context using the
   * default {@link XPathFactory}.
   * 
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nullable final NamespaceContext aNamespaceContext)
  {
    return createNewXPath (s_aXPathFactory,
                           (XPathVariableResolver) null,
                           (XPathFunctionResolver) null,
                           aNamespaceContext);
  }

  /**
   * Create a new {@link XPath} with the passed namespace context.
   * 
   * @param aXPathFactory
   *        The XPath factory object to use. May not be null.
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nonnull final XPathFactory aXPathFactory,
                                      @Nullable final NamespaceContext aNamespaceContext)
  {
    return createNewXPath (aXPathFactory, (XPathVariableResolver) null, (XPathFunctionResolver) null, aNamespaceContext);
  }

  /**
   * Create a new {@link XPath} with the passed variable resolver and namespace
   * context using the default {@link XPathFactory}.
   * 
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nullable final XPathVariableResolver aVariableResolver,
                                      @Nullable final NamespaceContext aNamespaceContext)
  {
    return createNewXPath (s_aXPathFactory, aVariableResolver, (XPathFunctionResolver) null, aNamespaceContext);
  }

  /**
   * Create a new {@link XPath} with the passed variable resolver, function
   * resolver and namespace context using the default {@link XPathFactory}.
   * 
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @param aFunctionResolver
   *        Function resolver to be used. May be null.
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nullable final XPathVariableResolver aVariableResolver,
                                      @Nullable final XPathFunctionResolver aFunctionResolver,
                                      @Nullable final NamespaceContext aNamespaceContext)
  {
    return createNewXPath (s_aXPathFactory, aVariableResolver, aFunctionResolver, aNamespaceContext);
  }

  /**
   * Create a new {@link XPath} with the passed variable resolver, function
   * resolver and namespace context.
   * 
   * @param aXPathFactory
   *        The XPath factory object to use. May not be null.
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @param aFunctionResolver
   *        Function resolver to be used. May be null.
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @return The created non-null {@link XPath} object
   */
  @Nonnull
  public static XPath createNewXPath (@Nonnull final XPathFactory aXPathFactory,
                                      @Nullable final XPathVariableResolver aVariableResolver,
                                      @Nullable final XPathFunctionResolver aFunctionResolver,
                                      @Nullable final NamespaceContext aNamespaceContext)
  {
    ValueEnforcer.notNull (aXPathFactory, "XPathFactory");

    final XPath aXPath = aXPathFactory.newXPath ();
    if (aVariableResolver != null)
      aXPath.setXPathVariableResolver (aVariableResolver);
    if (aFunctionResolver != null)
      aXPath.setXPathFunctionResolver (aFunctionResolver);
    if (aNamespaceContext != null)
      aXPath.setNamespaceContext (aNamespaceContext);
    return aXPath;
  }

  /**
   * Create a new XPath expression for evaluation using the default
   * {@link XPathFactory}.
   * 
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @param aFunctionResolver
   *        Function resolver to be used. May be null.
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @param sXPath
   *        The main XPath string to be evaluated
   * @return The {@link XPathExpression} object to be used.
   * @throws IllegalArgumentException
   *         if the XPath cannot be compiled
   */
  @Nonnull
  public static XPathExpression createNewXPathExpresion (@Nullable final XPathVariableResolver aVariableResolver,
                                                         @Nullable final XPathFunctionResolver aFunctionResolver,
                                                         @Nullable final NamespaceContext aNamespaceContext,
                                                         @Nonnull @Nonempty final String sXPath)
  {
    return createNewXPathExpresion (createNewXPath (aVariableResolver, aFunctionResolver, aNamespaceContext), sXPath);
  }

  /**
   * Create a new XPath expression for evaluation using the default
   * {@link XPathFactory}.
   * 
   * @param aVariableResolver
   *        Variable resolver to be used. May be null.
   * @param sXPath
   *        The main XPath string to be evaluated
   * @return The {@link XPathExpression} object to be used.
   * @throws IllegalArgumentException
   *         if the XPath cannot be compiled
   */
  @Nonnull
  public static XPathExpression createNewXPathExpresion (@Nullable final XPathVariableResolver aVariableResolver,
                                                         @Nonnull @Nonempty final String sXPath)
  {
    return createNewXPathExpresion (createNewXPath (aVariableResolver), sXPath);
  }

  /**
   * Create a new XPath expression for evaluation using the default
   * {@link XPathFactory}.
   * 
   * @param aFunctionResolver
   *        Function resolver to be used. May be null.
   * @param sXPath
   *        The main XPath string to be evaluated
   * @return The {@link XPathExpression} object to be used.
   * @throws IllegalArgumentException
   *         if the XPath cannot be compiled
   */
  @Nonnull
  public static XPathExpression createNewXPathExpresion (@Nullable final XPathFunctionResolver aFunctionResolver,
                                                         @Nonnull @Nonempty final String sXPath)
  {
    return createNewXPathExpresion (createNewXPath (aFunctionResolver), sXPath);
  }

  /**
   * Create a new XPath expression for evaluation using the default
   * {@link XPathFactory}.
   * 
   * @param aNamespaceContext
   *        Namespace context to be used. May be null.
   * @param sXPath
   *        The main XPath string to be evaluated
   * @return The {@link XPathExpression} object to be used.
   * @throws IllegalArgumentException
   *         if the XPath cannot be compiled
   */
  @Nonnull
  public static XPathExpression createNewXPathExpresion (@Nullable final NamespaceContext aNamespaceContext,
                                                         @Nonnull @Nonempty final String sXPath)
  {
    return createNewXPathExpresion (createNewXPath (aNamespaceContext), sXPath);
  }

  /**
   * Create a new XPath expression for evaluatio using the default
   * {@link XPathFactory}n.
   * 
   * @param sXPath
   *        The main XPath string to be evaluated
   * @return The {@link XPathExpression} object to be used.
   * @throws IllegalArgumentException
   *         if the XPath cannot be compiled
   */
  @Nonnull
  public static XPathExpression createNewXPathExpresion (@Nonnull @Nonempty final String sXPath)
  {
    return createNewXPathExpresion (createNewXPath (), sXPath);
  }

  /**
   * Create a new XPath expression for evaluation.
   * 
   * @param aXPath
   *        The pre-created XPath object. May not be null.
   * @param sXPath
   *        The main XPath string to be evaluated
   * @return The {@link XPathExpression} object to be used.
   * @throws IllegalArgumentException
   *         if the XPath cannot be compiled
   */
  @Nonnull
  public static XPathExpression createNewXPathExpresion (@Nonnull final XPath aXPath,
                                                         @Nonnull @Nonempty final String sXPath)
  {
    ValueEnforcer.notNull (aXPath, "XPath");
    ValueEnforcer.notNull (sXPath, "XPathExpression");

    try
    {
      return aXPath.compile (sXPath);
    }
    catch (final XPathExpressionException ex)
    {
      throw new IllegalArgumentException ("Failed to compile XPath expression '" + sXPath + "'", ex);
    }
  }
}




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