org.immutables.generator.ExtensionLoader.java Source code

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Here is the source code for org.immutables.generator.ExtensionLoader.java

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/*
   Copyright 2016 Immutables Authors and Contributors
    
   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 org.immutables.generator;

import com.google.common.base.Splitter;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;
import com.google.common.io.Resources;
import java.io.IOException;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Enumeration;
import java.util.List;
import javax.annotation.processing.Filer;
import javax.tools.StandardLocation;

public final class ExtensionLoader {
    private ExtensionLoader() {
    }

    private static final Splitter RESOURCE_SPLITTER = Splitter.on("\n").omitEmptyStrings().trimResults();

    public static Supplier<ImmutableSet<String>> findExtensions(final String resource) {
        // Provide lazy-once supplier
        return Suppliers.memoize(new Supplier<ImmutableSet<String>>() {
            @Override
            public ImmutableSet<String> get() {
                List<String> extensions = Lists.newArrayList();

                // best effort to read it from compilation classpath
                if (StaticEnvironment.isInitialized()) {
                    try {
                        String lines = getClasspathResourceText(StaticEnvironment.processing().getFiler(),
                                resource);
                        extensions.addAll(RESOURCE_SPLITTER.splitToList(lines));
                    } catch (RuntimeException | IOException cannotReadCompilationClasspath) {
                        // we ignore this as we did or best effort
                        // and there are no plans to halt whole compilation
                    }
                }

                ClassLoader classLoader = ExtensionLoader.class.getClassLoader();
                try {
                    Enumeration<URL> resources = classLoader.getResources(resource);
                    while (resources.hasMoreElements()) {
                        URL nextElement = resources.nextElement();
                        String lines = Resources.toString(nextElement, StandardCharsets.UTF_8);
                        extensions.addAll(RESOURCE_SPLITTER.splitToList(lines));
                    }
                } catch (RuntimeException | IOException cannotReadAnnotationProcessingClasspath) {
                    // we ignore this as we did or best effort
                    // and there are no plans to halt whole compilation
                }
                return FluentIterable.from(extensions).toSet();
            }
        });
    }

    private static String getClasspathResourceText(Filer filer, String resourceName) throws IOException {
        return filer.getResource(StandardLocation.CLASS_OUTPUT, "", resourceName).getCharContent(true).toString();
    }
}