net.sf.jasperreports.eclipse.classpath.OutputFolderClassLoader.java Source code

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Here is the source code for net.sf.jasperreports.eclipse.classpath.OutputFolderClassLoader.java

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/*******************************************************************************
 * Copyright (C) 2005 - 2014 TIBCO Software Inc. All rights reserved.
 * http://www.jaspersoft.com.
 * 
 * Unless you have purchased  a commercial license agreement from Jaspersoft,
 * the following license terms  apply:
 * 
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 ******************************************************************************/
package net.sf.jasperreports.eclipse.classpath;

import java.io.File;
import java.io.IOException;

import net.sf.jasperreports.eclipse.util.FileUtils;

import org.eclipse.core.resources.IFolder;
import org.eclipse.core.resources.IWorkspaceRoot;
import org.eclipse.core.runtime.IPath;
import org.eclipse.jdt.core.IClasspathEntry;
import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.jdt.core.IPackageFragmentRoot;

/**
 * Custom class loader implementation that try to re-load the specified class
 * using the generated .class file in the output folder either of the java project 
 * or of the source folders classpath entries.
 * 
 * @author Massimo Rabbi (mrabbi@users.sourceforge.net)
 *
 */
public class OutputFolderClassLoader extends ClassLoader {

    private IJavaProject javaProject;

    public OutputFolderClassLoader(IJavaProject javaProject) {
        super();
        this.javaProject = javaProject;
    }

    public OutputFolderClassLoader(IJavaProject javaProject, ClassLoader parent) {
        super(parent);
        this.javaProject = javaProject;
    }

    /**
     * Tries to force the reload of the class looking the the output folder(s).
     * 
     * @param className the canonical name of the class to reload
     * @return the Class instance loaded, <code>null</code> if it could not be located
     */
    public Class<?> reloadClass(String className) {
        try {
            byte[] bytes = loadClassData(className);
            if (bytes != null) {
                return defineClass(className, bytes, 0, bytes.length);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /*
     * Tries to load the specified class from the output folder(s) of
     * the current involved java project and its required ones.
     * First of all it searches in the project default location, if nothing
     * is found it searches potential custom output locations for every classpath entries.
     */
    private byte[] loadClassData(String className) throws Exception {
        String[] requiredProjectNames = javaProject.getRequiredProjectNames();
        for (String reqPrjName : requiredProjectNames) {
            IJavaProject prj = javaProject.getJavaModel().getJavaProject(reqPrjName);
            if (prj.exists()) {
                byte[] classBytes = loadClassData(className, prj);
                if (classBytes != null) {
                    return classBytes;
                }
            }
        }
        return null;
    }

    private byte[] loadClassData(String className, IJavaProject javaProject) throws Exception {
        IPath defaultLocationPath = javaProject.getOutputLocation();
        IWorkspaceRoot wsRoot = javaProject.getProject().getWorkspace().getRoot();
        IFolder folder = wsRoot.getFolder(defaultLocationPath);
        String prjDefaultLocation = folder.getLocation().toOSString();
        byte[] classBytes = loadClassFile(prjDefaultLocation + "/" + className.replaceAll("\\.", "/") + ".class");
        if (classBytes == null) {
            // Iterate over the (possible) output locations of the sourcefolder classpath entries
            IClasspathEntry[] classpathEntries = javaProject.getRawClasspath();
            for (IClasspathEntry e : classpathEntries) {
                if (e.getContentKind() == IPackageFragmentRoot.K_SOURCE) {
                    IPath entryOutputLocation = e.getOutputLocation();
                    if (entryOutputLocation != null) {
                        IFolder entryOutputFolder = wsRoot.getFolder(entryOutputLocation);
                        classBytes = loadClassFile(
                                entryOutputFolder + "/" + className.replaceAll("\\.", "/") + ".class");
                        if (classBytes != null)
                            break;
                    }
                }
            }
        }
        return classBytes;
    }

    /*
     * Loads the class file bytecode.
     */
    private byte[] loadClassFile(String classFile) {
        File f = new File(classFile);
        if (f.exists()) {
            try {
                return FileUtils.getBytes(f);
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        }
        return null;
    }

}