Hibernate example source code file (InjectionAction.java)

This example Hibernate source code file (InjectionAction.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Hibernate tags/keywords

arraylist, baseinjectiontarget, baseinjectiontarget, ctclass, ctclass, ctfield, ctmethod, file, injectionexception, injectionexception, io, net, network, override, throwable, unable, unable, util

The Hibernate InjectionAction.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2011, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */

package org.hibernate.build.gradle.inject;

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;

import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtField;
import javassist.CtMethod;
import javassist.LoaderClassPath;
import javassist.Modifier;
import javassist.NotFoundException;
import javassist.bytecode.ClassFile;
import javassist.bytecode.ConstantAttribute;
import javassist.bytecode.FieldInfo;
import org.gradle.api.Action;
import org.gradle.api.Project;
import org.gradle.api.Task;
import org.gradle.api.plugins.JavaPluginConvention;
import org.gradle.api.tasks.SourceSet;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Steve Ebersole
 */
public class InjectionAction implements Action<Task> {
	private static final Logger log = LoggerFactory.getLogger( InjectionAction.class );

	private final Project project;

	private List<Injection> injections = new ArrayList();

	private LoaderClassPath loaderClassPath;
	private ClassPool classPool;

	public InjectionAction(Project project) {
		this.project = project;
	}

	void addInjection(Injection injection) {
		injections.add( injection );
	}

	@Override
	public void execute(Task task) {
		final ClassLoader runtimeScopeClassLoader = buildRuntimeScopeClassLoader();

		loaderClassPath = new LoaderClassPath( runtimeScopeClassLoader );
		classPool =  new ClassPool( true );
		classPool.appendClassPath( loaderClassPath );

		try {
			performInjections();
		}
		finally {
			loaderClassPath.close();
		}
	}

	private ClassLoader buildRuntimeScopeClassLoader() {
		final ArrayList<URL> classPathUrls = new ArrayList();
		final SourceSet mainSourceSet = project
				.getConvention()
				.getPlugin( JavaPluginConvention.class )
				.getSourceSets()
				.findByName( SourceSet.MAIN_SOURCE_SET_NAME );
		for ( File file : mainSourceSet.getRuntimeClasspath() ) {
			try {
				classPathUrls.add( file.toURI().toURL() );
			}
			catch (MalformedURLException e) {
				throw new InjectionException( "Could not determine artifact URL [" + file.getPath() + "]", e );
			}
		}
		return new URLClassLoader( classPathUrls.toArray( new URL[classPathUrls.size()] ), getClass().getClassLoader() );
	}

	private void performInjections() {
		for ( Injection injection : injections ) {
			for ( TargetMember targetMember : injection.getTargetMembers() ) {
				resolveInjectionTarget( targetMember ).inject( injection.getExpression() );
			}
		}
	}

	private InjectionTarget resolveInjectionTarget(TargetMember targetMember) {
		try {
			final CtClass ctClass = classPool.get( targetMember.getClassName() );
			// see if it is a field...
			try {
				CtField field = ctClass.getField( targetMember.getMemberName() );
				return new FieldInjectionTarget( targetMember, ctClass, field );
			}
			catch( NotFoundException ignore ) {
			}

			// see if it is a method...
			for ( CtMethod method : ctClass.getMethods() ) {
				if ( method.getName().equals( targetMember.getMemberName() ) ) {
					return new MethodInjectionTarget( targetMember, ctClass, method );
				}
			}

			// finally throw an exception
			throw new InjectionException( "Unknown member [" + targetMember.getQualifiedName() + "]" );
		}
		catch ( Throwable e ) {
			throw new InjectionException( "Unable to resolve class [" + targetMember.getClassName() + "]", e );
		}
	}

	/**
	 * Strategy for performing an injection
	 */
	private static interface InjectionTarget {
		/**
		 * Inject the given value per this target's strategy.
		 *
		 * @param value The value to inject.
		 *
		 * @throws org.hibernate.build.gradle.inject.InjectionException Indicates a problem performing the injection.
		 */
		public void inject(String value);
	}

	private abstract class BaseInjectionTarget implements InjectionTarget {
		@SuppressWarnings( {"UnusedDeclaration"})
		private final TargetMember targetMember;
		private final CtClass ctClass;
		private final File classFileLocation;

		protected BaseInjectionTarget(TargetMember targetMember, CtClass ctClass) {
			this.targetMember = targetMember;
			this.ctClass = ctClass;
			try {
				classFileLocation = new File( loaderClassPath.find( targetMember.getClassName() ).toURI() );
			}
			catch ( Throwable e ) {
				throw new InjectionException( "Unable to resolve class file path", e );
			}
		}

		@Override
		public void inject(String value) {
			doInjection( value );
			writeOutChanges();
		}

		protected abstract void doInjection(String value);

		protected void writeOutChanges() {
			log.info( "writing injection changes back [" + classFileLocation.getAbsolutePath() + "]" );
			long timeStamp = classFileLocation.lastModified();
			ClassFile classFile = ctClass.getClassFile();
			classFile.compact();
			try {
				DataOutputStream out = new DataOutputStream( new BufferedOutputStream( new FileOutputStream( classFileLocation ) ) );
				try {

					classFile.write( out );
					out.flush();
					if ( ! classFileLocation.setLastModified( System.currentTimeMillis() ) ) {
						log.info( "Unable to manually update class file timestamp" );
					}
				}
				finally {
					out.close();
					classFileLocation.setLastModified( timeStamp );
				}
			}
			catch ( IOException e ) {
				throw new InjectionException( "Unable to write out modified class file", e );
			}
		}
	}

	private class FieldInjectionTarget extends BaseInjectionTarget {
		private final CtField ctField;

		private FieldInjectionTarget(TargetMember targetMember, CtClass ctClass, CtField ctField) {
			super( targetMember, ctClass );
			this.ctField = ctField;
			if ( ! Modifier.isStatic( ctField.getModifiers() ) ) {
				throw new InjectionException( "Field is not static [" + targetMember.getQualifiedName() + "]" );
			}
		}

		@Override
		protected void doInjection(String value) {
			final FieldInfo ctFieldInfo = ctField.getFieldInfo();

			ctFieldInfo.addAttribute(
					new ConstantAttribute(
							ctFieldInfo.getConstPool(),
							ctFieldInfo.getConstPool().addStringInfo( value )
					)
			);

		}
	}

	private class MethodInjectionTarget extends BaseInjectionTarget {
		private final CtMethod ctMethod;

		private MethodInjectionTarget(TargetMember targetMember, CtClass ctClass, CtMethod ctMethod) {
			super( targetMember, ctClass );
			this.ctMethod = ctMethod;
		}

		@Override
		protected void doInjection(String value) {
			try {
				ctMethod.setBody( "{return \"" + value + "\";}" );
			}
			catch ( Throwable t ) {
				throw new InjectionException( "Unable to replace method body", t );
			}
		}
	}
}