src/main/org/apache/tools/ant/ProjectHelperRepository.java - ant - Git at Google

 /*
  *  Licensed to the Apache Software Foundation (ASF) under one or more
  *  contributor license agreements.  See the NOTICE file distributed with
  *  this work for additional information regarding copyright ownership.
  *  The ASF licenses this file to You 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
  *
  *      https://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 org.apache.tools.ant;

 import java.io.BufferedReader;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.lang.reflect.Constructor;
 import java.net.URL;
 import java.net.URLConnection;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.stream.Stream;

 import org.apache.tools.ant.helper.ProjectHelper2;
 import org.apache.tools.ant.types.Resource;
 import org.apache.tools.ant.util.LoaderUtils;
 import org.apache.tools.ant.util.StreamUtils;

 /**
  * Repository of {@link ProjectHelper} found in the classpath or via
  * some System properties.
  *
  * <p>See the ProjectHelper documentation in the manual.</p>
  *
  * @since Ant 1.8.0
  */
 public class ProjectHelperRepository {

     private static final String DEBUG_PROJECT_HELPER_REPOSITORY =
         "ant.project-helper-repo.debug";

     // The message log level is not accessible here because everything
     // is instantiated statically
     private static final boolean DEBUG =
         "true".equals(System.getProperty(DEBUG_PROJECT_HELPER_REPOSITORY));

     private static ProjectHelperRepository instance =
         new ProjectHelperRepository();

     private List<Constructor<? extends ProjectHelper>> helpers = new ArrayList<>();

     private static Constructor<ProjectHelper2> PROJECTHELPER2_CONSTRUCTOR;

     static {
         try {
             PROJECTHELPER2_CONSTRUCTOR = ProjectHelper2.class.getConstructor();
         } catch (Exception e) {
             // ProjectHelper2 must be available
             throw new BuildException(e);
         }
     }

     public static ProjectHelperRepository getInstance() {
         return instance;
     }

     private ProjectHelperRepository() {
         collectProjectHelpers();
     }

     private void collectProjectHelpers() {
         // First, try the system property
         registerProjectHelper(getProjectHelperBySystemProperty());

         // A JDK1.3 'service' (like in JAXP). That will plug a helper
         // automatically if in CLASSPATH, with the right META-INF/services.
         try {
             ClassLoader classLoader = LoaderUtils.getContextClassLoader();
             if (classLoader != null) {
                 for (URL resource : Collections.list(classLoader.getResources(MagicNames.PROJECT_HELPER_SERVICE))) {
                     URLConnection conn = resource.openConnection();
                     conn.setUseCaches(false);
                     registerProjectHelper(getProjectHelperByService(conn.getInputStream()));
                 }
             }

             InputStream systemResource =
                 ClassLoader.getSystemResourceAsStream(MagicNames.PROJECT_HELPER_SERVICE);
             if (systemResource != null) {
                 registerProjectHelper(getProjectHelperByService(systemResource));
             }
         } catch (Exception e) {
             System.err.println("Unable to load ProjectHelper from service "
                                + MagicNames.PROJECT_HELPER_SERVICE + " ("
                                + e.getClass().getName()
                                + ": " + e.getMessage() + ")");
             if (DEBUG) {
                 e.printStackTrace(System.err); //NOSONAR
             }
         }
     }

     /**
      * Register the specified project helper into the repository.
      * <p>
      * The helper will be added after all the already registered helpers, but
      * before the default one (ProjectHelper2)
      *
      * @param helperClassName
      *            the fully qualified name of the helper
      * @throws BuildException
      *             if the class cannot be loaded or if there is no constructor
      *             with no argument
      * @since Ant 1.8.2
      */
     public void registerProjectHelper(String helperClassName)
             throws BuildException {
         registerProjectHelper(getHelperConstructor(helperClassName));
     }

     /**
      * Register the specified project helper into the repository.
      * <p>
      * The helper will be added after all the already registered helpers, but
      * before the default one (ProjectHelper2)
      *
      * @param helperClass
      *            the class of the helper
      * @throws BuildException
      *             if there is no constructor with no argument
      * @since Ant 1.8.2
      */
     public void registerProjectHelper(Class<? extends ProjectHelper> helperClass) throws BuildException {
         try {
             registerProjectHelper(helperClass.getConstructor());
         } catch (NoSuchMethodException e) {
             throw new BuildException("Couldn't find no-arg constructor in "
                     + helperClass.getName());
         }
     }

     private void registerProjectHelper(Constructor<? extends ProjectHelper> helperConstructor) {
         if (helperConstructor == null) {
             return;
         }
         if (DEBUG) {
             System.out.println("ProjectHelper "
                     + helperConstructor.getClass().getName() + " registered.");
         }
         helpers.add(helperConstructor);
     }

     private Constructor<? extends ProjectHelper> getProjectHelperBySystemProperty() {
         String helperClass = System.getProperty(MagicNames.PROJECT_HELPER_CLASS);
         try {
             if (helperClass != null) {
                 return getHelperConstructor(helperClass);
             }
         } catch (SecurityException e) {
             System.err.println("Unable to load ProjectHelper class \""
                                + helperClass + " specified in system property "
                                + MagicNames.PROJECT_HELPER_CLASS + " ("
                                + e.getMessage() + ")");
             if (DEBUG) {
                 e.printStackTrace(System.err); //NOSONAR
             }
         }
         return null;
     }

     private Constructor<? extends ProjectHelper> getProjectHelperByService(InputStream is) {
         try {
             // This code is needed by EBCDIC and other strange systems.
             // It's a fix for bugs reported in xerces
             BufferedReader rd = new BufferedReader(new InputStreamReader(is,
                     StandardCharsets.UTF_8));
             String helperClassName = rd.readLine();
             rd.close();

             if (helperClassName != null && !helperClassName.isEmpty()) {
                 return getHelperConstructor(helperClassName);
             }
         } catch (Exception e) {
             System.out.println("Unable to load ProjectHelper from service "
                     + MagicNames.PROJECT_HELPER_SERVICE + " (" + e.getMessage() + ")");
             if (DEBUG) {
                 e.printStackTrace(System.err); //NOSONAR
             }
         }
         return null;
     }

     /**
      * Get the constructor with not argument of an helper from its class name.
      * It'll first try the thread class loader, then Class.forName() will load
      * from the same loader that loaded this class.
      *
      * @param helperClass
      *            The name of the class to create an instance of. Must not be
      *            <code>null</code>.
      *
      * @return the constructor of the specified class.
      *
      * @exception BuildException
      *                if the class cannot be found or if a constructor with no
      *                argument cannot be found.
      */
     private Constructor<? extends ProjectHelper> getHelperConstructor(String helperClass) throws BuildException {
         ClassLoader classLoader = LoaderUtils.getContextClassLoader();
         try {
             Class<?> clazz = null;
             if (classLoader != null) {
                 try {
                     clazz = classLoader.loadClass(helperClass);
                 } catch (ClassNotFoundException ex) {
                     // try next method
                 }
             }
             if (clazz == null) {
                 clazz = Class.forName(helperClass);
             }
             return clazz.asSubclass(ProjectHelper.class).getConstructor();
         } catch (Exception e) {
             throw new BuildException(e);
         }
     }

     /**
      * Get the helper that will be able to parse the specified build file. The helper
      * will be chosen among the ones found in the classpath
      *
      * @param buildFile Resource
      * @return the first ProjectHelper that fit the requirement (never <code>null</code>).
      */
     public ProjectHelper getProjectHelperForBuildFile(Resource buildFile) throws BuildException {
         ProjectHelper ph = StreamUtils.iteratorAsStream(getHelpers())
                 .filter(helper -> helper.canParseBuildFile(buildFile))
                 .findFirst().orElse(null);

         if (ph == null) {
             throw new BuildException("BUG: at least the ProjectHelper2 should "
                     + "have supported the file " + buildFile);
         }
         if (DEBUG) {
             System.out.println("ProjectHelper " + ph.getClass().getName()
                     + " selected for the build file " + buildFile);
         }
         return ph;
     }

     /**
      * Get the helper that will be able to parse the specified antlib. The helper
      * will be chosen among the ones found in the classpath
      *
      * @param antlib Resource
      * @return the first ProjectHelper that fit the requirement (never <code>null</code>).
      */
     public ProjectHelper getProjectHelperForAntlib(Resource antlib) throws BuildException {
         ProjectHelper ph = StreamUtils.iteratorAsStream(getHelpers())
                 .filter(helper -> helper.canParseAntlibDescriptor(antlib))
                 .findFirst().orElse(null);

         if (ph == null) {
             throw new BuildException("BUG: at least the ProjectHelper2 should "
                     + "have supported the file " + antlib);
         }
         if (DEBUG) {
             System.out.println("ProjectHelper " + ph.getClass().getName()
                     + " selected for the antlib " + antlib);
         }
         return ph;
     }

     /**
      * Get an iterator on the list of project helpers configured. The iterator
      * will always return at least one element as there will always be the
      * default project helper configured.
      *
      * @return an iterator of {@link ProjectHelper}
      */
     public Iterator<ProjectHelper> getHelpers() {
         Stream.Builder<Constructor<? extends ProjectHelper>> b = Stream.builder();
         helpers.forEach(b::add);
         return b.add(PROJECTHELPER2_CONSTRUCTOR).build().map(c -> {
             try {
                 return c.newInstance();
             } catch (Exception e) {
                 throw new BuildException("Failed to invoke no-arg constructor"
                         + " on " + c.getName());
             }
         }).map(ProjectHelper.class::cast).iterator();
     }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You 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
	*
	* https://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 org.apache.tools.ant;

	import java.io.BufferedReader;
	import java.io.InputStream;
	import java.io.InputStreamReader;
	import java.lang.reflect.Constructor;
	import java.net.URL;
	import java.net.URLConnection;
	import java.nio.charset.StandardCharsets;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Iterator;
	import java.util.List;
	import java.util.stream.Stream;

	import org.apache.tools.ant.helper.ProjectHelper2;
	import org.apache.tools.ant.types.Resource;
	import org.apache.tools.ant.util.LoaderUtils;
	import org.apache.tools.ant.util.StreamUtils;

	/**
	* Repository of {@link ProjectHelper} found in the classpath or via
	* some System properties.
	*
	* <p>See the ProjectHelper documentation in the manual.</p>
	*
	* @since Ant 1.8.0
	*/
	public class ProjectHelperRepository {

	private static final String DEBUG_PROJECT_HELPER_REPOSITORY =
	"ant.project-helper-repo.debug";

	// The message log level is not accessible here because everything
	// is instantiated statically
	private static final boolean DEBUG =
	"true".equals(System.getProperty(DEBUG_PROJECT_HELPER_REPOSITORY));

	private static ProjectHelperRepository instance =
	new ProjectHelperRepository();

	private List<Constructor<? extends ProjectHelper>> helpers = new ArrayList<>();

	private static Constructor<ProjectHelper2> PROJECTHELPER2_CONSTRUCTOR;

	static {
	try {
	PROJECTHELPER2_CONSTRUCTOR = ProjectHelper2.class.getConstructor();
	} catch (Exception e) {
	// ProjectHelper2 must be available
	throw new BuildException(e);
	}
	}

	public static ProjectHelperRepository getInstance() {
	return instance;
	}

	private ProjectHelperRepository() {
	collectProjectHelpers();
	}

	private void collectProjectHelpers() {
	// First, try the system property
	registerProjectHelper(getProjectHelperBySystemProperty());

	// A JDK1.3 'service' (like in JAXP). That will plug a helper
	// automatically if in CLASSPATH, with the right META-INF/services.
	try {
	ClassLoader classLoader = LoaderUtils.getContextClassLoader();
	if (classLoader != null) {
	for (URL resource : Collections.list(classLoader.getResources(MagicNames.PROJECT_HELPER_SERVICE))) {
	URLConnection conn = resource.openConnection();
	conn.setUseCaches(false);
	registerProjectHelper(getProjectHelperByService(conn.getInputStream()));
	}
	}

	InputStream systemResource =
	ClassLoader.getSystemResourceAsStream(MagicNames.PROJECT_HELPER_SERVICE);
	if (systemResource != null) {
	registerProjectHelper(getProjectHelperByService(systemResource));
	}
	} catch (Exception e) {
	System.err.println("Unable to load ProjectHelper from service "
	+ MagicNames.PROJECT_HELPER_SERVICE + " ("
	+ e.getClass().getName()
	+ ": " + e.getMessage() + ")");
	if (DEBUG) {
	e.printStackTrace(System.err); //NOSONAR
	}
	}
	}

	/**
	* Register the specified project helper into the repository.
	* <p>
	* The helper will be added after all the already registered helpers, but
	* before the default one (ProjectHelper2)
	*
	* @param helperClassName
	* the fully qualified name of the helper
	* @throws BuildException
	* if the class cannot be loaded or if there is no constructor
	* with no argument
	* @since Ant 1.8.2
	*/
	public void registerProjectHelper(String helperClassName)
	throws BuildException {
	registerProjectHelper(getHelperConstructor(helperClassName));
	}

	/**
	* Register the specified project helper into the repository.
	* <p>
	* The helper will be added after all the already registered helpers, but
	* before the default one (ProjectHelper2)
	*
	* @param helperClass
	* the class of the helper
	* @throws BuildException
	* if there is no constructor with no argument
	* @since Ant 1.8.2
	*/
	public void registerProjectHelper(Class<? extends ProjectHelper> helperClass) throws BuildException {
	try {
	registerProjectHelper(helperClass.getConstructor());
	} catch (NoSuchMethodException e) {
	throw new BuildException("Couldn't find no-arg constructor in "
	+ helperClass.getName());
	}
	}

	private void registerProjectHelper(Constructor<? extends ProjectHelper> helperConstructor) {
	if (helperConstructor == null) {
	return;
	}
	if (DEBUG) {
	System.out.println("ProjectHelper "
	+ helperConstructor.getClass().getName() + " registered.");
	}
	helpers.add(helperConstructor);
	}

	private Constructor<? extends ProjectHelper> getProjectHelperBySystemProperty() {
	String helperClass = System.getProperty(MagicNames.PROJECT_HELPER_CLASS);
	try {
	if (helperClass != null) {
	return getHelperConstructor(helperClass);
	}
	} catch (SecurityException e) {
	System.err.println("Unable to load ProjectHelper class \""
	+ helperClass + " specified in system property "
	+ MagicNames.PROJECT_HELPER_CLASS + " ("
	+ e.getMessage() + ")");
	if (DEBUG) {
	e.printStackTrace(System.err); //NOSONAR
	}
	}
	return null;
	}

	private Constructor<? extends ProjectHelper> getProjectHelperByService(InputStream is) {
	try {
	// This code is needed by EBCDIC and other strange systems.
	// It's a fix for bugs reported in xerces
	BufferedReader rd = new BufferedReader(new InputStreamReader(is,
	StandardCharsets.UTF_8));
	String helperClassName = rd.readLine();
	rd.close();

	if (helperClassName != null && !helperClassName.isEmpty()) {
	return getHelperConstructor(helperClassName);
	}
	} catch (Exception e) {
	System.out.println("Unable to load ProjectHelper from service "
	+ MagicNames.PROJECT_HELPER_SERVICE + " (" + e.getMessage() + ")");
	if (DEBUG) {
	e.printStackTrace(System.err); //NOSONAR
	}
	}
	return null;
	}

	/**
	* Get the constructor with not argument of an helper from its class name.
	* It'll first try the thread class loader, then Class.forName() will load
	* from the same loader that loaded this class.
	*
	* @param helperClass
	* The name of the class to create an instance of. Must not be
	* <code>null</code>.
	*
	* @return the constructor of the specified class.
	*
	* @exception BuildException
	* if the class cannot be found or if a constructor with no
	* argument cannot be found.
	*/
	private Constructor<? extends ProjectHelper> getHelperConstructor(String helperClass) throws BuildException {
	ClassLoader classLoader = LoaderUtils.getContextClassLoader();
	try {
	Class<?> clazz = null;
	if (classLoader != null) {
	try {
	clazz = classLoader.loadClass(helperClass);
	} catch (ClassNotFoundException ex) {
	// try next method
	}
	}
	if (clazz == null) {
	clazz = Class.forName(helperClass);
	}
	return clazz.asSubclass(ProjectHelper.class).getConstructor();
	} catch (Exception e) {
	throw new BuildException(e);
	}
	}

	/**
	* Get the helper that will be able to parse the specified build file. The helper
	* will be chosen among the ones found in the classpath
	*
	* @param buildFile Resource
	* @return the first ProjectHelper that fit the requirement (never <code>null</code>).
	*/
	public ProjectHelper getProjectHelperForBuildFile(Resource buildFile) throws BuildException {
	ProjectHelper ph = StreamUtils.iteratorAsStream(getHelpers())
	.filter(helper -> helper.canParseBuildFile(buildFile))
	.findFirst().orElse(null);

	if (ph == null) {
	throw new BuildException("BUG: at least the ProjectHelper2 should "
	+ "have supported the file " + buildFile);
	}
	if (DEBUG) {
	System.out.println("ProjectHelper " + ph.getClass().getName()
	+ " selected for the build file " + buildFile);
	}
	return ph;
	}

	/**
	* Get the helper that will be able to parse the specified antlib. The helper
	* will be chosen among the ones found in the classpath
	*
	* @param antlib Resource
	* @return the first ProjectHelper that fit the requirement (never <code>null</code>).
	*/
	public ProjectHelper getProjectHelperForAntlib(Resource antlib) throws BuildException {
	ProjectHelper ph = StreamUtils.iteratorAsStream(getHelpers())
	.filter(helper -> helper.canParseAntlibDescriptor(antlib))
	.findFirst().orElse(null);

	if (ph == null) {
	throw new BuildException("BUG: at least the ProjectHelper2 should "
	+ "have supported the file " + antlib);
	}
	if (DEBUG) {
	System.out.println("ProjectHelper " + ph.getClass().getName()
	+ " selected for the antlib " + antlib);
	}
	return ph;
	}

	/**
	* Get an iterator on the list of project helpers configured. The iterator
	* will always return at least one element as there will always be the
	* default project helper configured.
	*
	* @return an iterator of {@link ProjectHelper}
	*/
	public Iterator<ProjectHelper> getHelpers() {
	Stream.Builder<Constructor<? extends ProjectHelper>> b = Stream.builder();
	helpers.forEach(b::add);
	return b.add(PROJECTHELPER2_CONSTRUCTOR).build().map(c -> {
	try {
	return c.newInstance();
	} catch (Exception e) {
	throw new BuildException("Failed to invoke no-arg constructor"
	+ " on " + c.getName());
	}
	}).map(ProjectHelper.class::cast).iterator();
	}
	}