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Java example source code file (PluginChecker.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

device, element, file, integer, override, plugin, pluginchecker, require, runtimeexception, set, string, this, typeelement, util

The PluginChecker.java Java example source code

/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */
package checker;

import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.tools.Diagnostic;
import javax.xml.bind.JAXBContext;
import java.io.File;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import javax.xml.bind.JAXBException;

/**
 * Reads the device configuration from the XML file specified by -Adevice=device.xml.
 * For each class in a project, checks required modules. If the device doesn't have
 * the required module, then a compilation error will be shown.
 */
@SupportedAnnotationTypes("checker.RequireContainer")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class PluginChecker extends javax.annotation.processing.AbstractProcessor {

    /**
     * Name of the option to get the path to the xml with device configuration.
     */
    public static final String DEVICE_OPTION = "device";
    private Device device;

    /**
     * Only the device option is supported.
     *
     * {@inheritDoc}
     */
    @Override
    public Set<String> getSupportedOptions() {
        return new HashSet<>(Arrays.asList(DEVICE_OPTION));
    }

    /**
     * Initializes the processor by loading the device configuration.
     *
     * {@inheritDoc}
     */
    @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        try {
            String deviceOption = processingEnv.getOptions().get(DEVICE_OPTION);
            device = (Device) JAXBContext.newInstance(Device.class)
                    .createUnmarshaller().unmarshal(new File(deviceOption));
        } catch (JAXBException e) {
            throw new RuntimeException(
                    "Please specify device by -Adevice=device.xml\n"
                    + e.toString(), e);
        }
    }

    /**
     * Processes @Require annotations and checks that Device meets requirements.
     *
     * {@inheritDoc}
     */
    @Override
    public boolean process(Set<? extends TypeElement> annotations,
            RoundEnvironment roundEnv) {
        for (Element el : roundEnv.getElementsAnnotatedWith(RequireContainer.class)) {
            for (Require req : el.getAnnotationsByType(Require.class)) {
                //for every Require annotation checks if device has module of required version.
                Integer version = device.getSupportedModules().get(req.value());

                if (version == null
                        || version < req.minVersion()
                        || version > req.maxVersion()) {
                    //if module is optional then show only warning not error
                    if (req.optional()) {
                        processingEnv.getMessager()
                                .printMessage(Diagnostic.Kind.WARNING,
                                        "Plugin [" + el + "] requires " + req
                                        + "\n but device " + (version == null
                                        ? "doesn't have such module."
                                        + " This module is optional."
                                        + " So plugin will work but miss"
                                        + " some functionality"
                                        : "has " + version
                                        + " version of that module"));
                    } else {
                        processingEnv.getMessager()
                                .printMessage(Diagnostic.Kind.ERROR,
                                        "Plugin [" + el + "] requires " + req
                                        + "\n but device "
                                        + (version == null
                                        ? "doesn't have such module"
                                        : "has " + version
                                        + " version of that module"));
                    }
                }
            }
            return true;
        }
        return false;
    }
}

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