APLCache.java

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package br.ufrgs.inf.prosoft.aplcache.caching;

import br.ufrgs.inf.prosoft.jsonserialiser.JSONSerialiser;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 *
 * @author romulo
 */
public class APLCache {

    private static final Logger LOGGER = Logger.getLogger(APLCache.class.getName());
    private static String APLCACHE_CACHEABLE_PARAMETERS = System.getenv("APLCACHE_CACHEABLE_PARAMETERS");
    private static final Map<String, Collection<String>> APLCACHE_METHOD_HAS_CACHEABLE_PARAMETERS = new HashMap<>();
    private static final String APLCACHE_LOG = System.getenv("APLCACHE_LOG");

    private static void loadCacheableParameters() {
        if (APLCACHE_CACHEABLE_PARAMETERS == null) {
            return;
        }
        try (FileReader fileReader = new FileReader(APLCACHE_CACHEABLE_PARAMETERS)) {
            JsonParser jsonParser = new JsonParser();
            JsonObject jsonObject = jsonParser.parse(fileReader).getAsJsonObject();
            jsonObject.entrySet().forEach(entry -> {
                Collection<String> parameters = new ArrayList<>();
                entry.getValue().getAsJsonArray().forEach(parameter -> {
                    parameters.add(parameter.getAsString());
                });
                APLCACHE_METHOD_HAS_CACHEABLE_PARAMETERS.put(entry.getKey(), parameters);
            });
            LOGGER.log(Level.INFO, "cache file loaded");
        } catch (FileNotFoundException ex) {
            LOGGER.log(Level.SEVERE, "invalid cache file");
        } catch (IOException ex) {
            LOGGER.log(Level.SEVERE, "invalid cache file");
        }
        APLCACHE_CACHEABLE_PARAMETERS = null;
    }

    public static boolean isCacheable(Thread currentThread, Object... parameters) {
        StackTraceElement[] stackTrace = currentThread.getStackTrace();
        StackTraceElement stackTraceElement = null;
        try {
            stackTraceElement = stackTrace[2];
        } catch (ArrayIndexOutOfBoundsException ex) {
            stackTraceElement = stackTrace[0];
        }
        return isCacheable(stackTraceElement, parameters);
    }

    public static boolean isCacheable(StackTraceElement stackTraceElement, Object... parameters) {
        try {
            String methodName = stackTraceElement.getClassName() + "." + stackTraceElement.getMethodName();
            return isCacheable(methodName, parameters);
        } catch (Exception ex) {
            return false;
        }
    }

    public static boolean isCacheable(String method, Object... parameters) {
        loadCacheableParameters();
        if (APLCACHE_METHOD_HAS_CACHEABLE_PARAMETERS.isEmpty()) {
            LOGGER.log(Level.WARNING, "no method is cacheable");
            return false;
        }
        Collection<String> cacheableParameters = APLCACHE_METHOD_HAS_CACHEABLE_PARAMETERS.get(method);
        if (cacheableParameters == null) {
            LOGGER.log(Level.WARNING, "method not cacheable: {0}", method);
            return false;
        }
        String serialisedParameters = Stream.of(parameters).map(JSONSerialiser::serialise)
                .collect(Collectors.joining(",", "[", "]"));
        if (cacheableParameters.contains(serialisedParameters)) {
            return true;
        }
        log("uncacheable " + method + " : " + serialisedParameters);
        return false;
    }
    
        private static void log(String message) {
        if (APLCACHE_LOG == null) {
            return;
        }
        try (FileWriter fileWriter = new FileWriter(APLCACHE_LOG, true)) {
            fileWriter.write(message + "\n");
        } catch (IOException ex) {
        }
    }
}