CustomFunctionLoader.java

package com.googlecode.aviator;

import com.googlecode.aviator.runtime.type.AviatorFunction;

import java.io.BufferedReader;
import java.io.Closeable;
import java.io.InputStream;
import java.io.InputStreamReader;


public class CustomFunctionLoader {

    private static String CUSTOM_FUNCTION_LIST_FILE = System
        .getenv("com.googlecode.aviator.custom_function_config_file");
    private static int tatalCustomFunctions = 0;
    static {
        if (CUSTOM_FUNCTION_LIST_FILE == null || CUSTOM_FUNCTION_LIST_FILE.trim().length() == 0) {
            CUSTOM_FUNCTION_LIST_FILE = "aviator_functions.config";
        }
    }


    private static void info(String msg) {
        System.out.println("[Aviator INFO] " + msg);
    }


    private static void error(String msg) {
        System.out.println("[Aviator ERROR] " + msg);
    }


    /**
     * Load custom functions from config file, default is
     * "aviator_functions.config" in classpath.
     * 
     * @return
     */
    public static void load() {
        InputStream in = null;
        InputStreamReader inreader = null;
        BufferedReader reader = null;
        try {
            in = CustomFunctionLoader.class.getClassLoader().getResourceAsStream(CUSTOM_FUNCTION_LIST_FILE);
            if (in != null) {
                inreader = new InputStreamReader(in);
                reader = new BufferedReader(inreader);
                String line = null;
                while ((line = reader.readLine()) != null) {
                    line = line.trim();
                    if (line.startsWith("#")) {
                        // skip comment
                        continue;
                    }
                    if (line.length() > 0) {
                        loadClass(line);
                    }
                }
            }
        }
        catch (Throwable e) {
            error("Load aviator custom functions config from " + CUSTOM_FUNCTION_LIST_FILE + " failed.");
            e.printStackTrace();
        }
        finally {
            closeQuietly(reader);
            closeQuietly(inreader);
            closeQuietly(in);
            if (tatalCustomFunctions > 0) {
                info("Total " + tatalCustomFunctions + " custom functions loaded.");
            }
        }
    }


    public static void loadClass(String className) {
        info("Loading custom aviator function class: '" + className + "'.");
        try {
            Class<AviatorFunction> clazz = (Class<AviatorFunction>) Class.forName(className);
            AviatorFunction func = clazz.newInstance();
            if (func != null) {
                AviatorEvaluator.addFunction(func);
                tatalCustomFunctions++;
            }
        }
        catch (Throwable e) {
            error("Load custom aviator function class: " + className + "' failed with error:" + e.getMessage() + ".");
        }
    }


    private static void closeQuietly(Closeable c) {
        if (c != null) {
            try {
                c.close();
            }
            catch (Throwable e) {
                e.printStackTrace();
            }
        }
    }
}