类扫描

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.io.File;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class ClassUtil {
    private static LoadingCache<String, ArrayList<Class>> classCache;

    static {
        classCache = buildAllClassCache();
    }

    /**
     * 获取接口上的泛型T
     *
     * @param o     接口
     * @param index 泛型索引
     */
    public static Class<?> getInterfaceT(Object o, int index) {
        Type[] types = o.getClass().getGenericInterfaces();
        ParameterizedType parameterizedType = (ParameterizedType) types[0];
        Type type = parameterizedType.getActualTypeArguments()[index];
        return checkType(type, index);

    }


    /**
     * 获取类上的泛型T
     *
     * @param o     接口
     * @param index 泛型索引
     */
    public static Class<?> getClassT(Object o, int index) {
        Type type = o.getClass().getGenericSuperclass();
        if (type instanceof ParameterizedType) {
            ParameterizedType parameterizedType = (ParameterizedType) type;
            Type actType = parameterizedType.getActualTypeArguments()[index];
            return checkType(actType, index);
        } else {
            String className = type == null ? "null" : type.getClass().getName();
            throw new IllegalArgumentException("Expected a Class, ParameterizedType"
                + ", but <" + type + "> is of type " + className);
        }
    }

    private static Class<?> checkType(Type type, int index) {
        if (type instanceof Class<?>) {
            return (Class<?>) type;
        } else if (type instanceof ParameterizedType) {
            ParameterizedType pt = (ParameterizedType) type;
            Type t = pt.getActualTypeArguments()[index];
            return checkType(t, index);
        } else {
            String className = type == null ? "null" : type.getClass().getName();
            throw new IllegalArgumentException("Expected a Class, ParameterizedType"
                + ", but <" + type + "> is of type " + className);
        }
    }

    /**
     * 功能描述 获取接口的所有实现类
     *
     * @return java.util.ArrayList<java.lang.Class>
     */
    public static ArrayList<Class> getAllClassByInterface(Class clazz) {
        ArrayList<Class> list = new ArrayList<>();
        // 判断是否是一个接口
        if (clazz.isInterface()) {
            try {
                ArrayList<Class> allClass = classCache.getUnchecked(clazz.getPackage().getName());
                /**
                 * 循环判断路径下的所有类是否实现了指定的接口 并且排除接口类自己
                 */
                for (int i = 0; i < allClass.size(); i++) {
                    /**
                     * 判断是不是同一个接口
                     */
                    // isAssignableFrom:判定此 Class 对象所表示的类或接口与指定的 Class
                    // 参数所表示的类或接口是否相同，或是否是其超类或超接口
                    if (clazz.isAssignableFrom(allClass.get(i))) {
                        if (!clazz.equals(allClass.get(i))) {
                            // 自身并不加进去
                            list.add(allClass.get(i));
                        }
                    }
                }
            } catch (Exception e) {
                throw new RuntimeException("出现异常" + e.getMessage());
            }
        }
        return list;
    }

    /**
     * 从一个指定路径下查找所有的类
     *
     * @param packagename
     */
    private static ArrayList<Class> getAllClass(String packagename) {

        List<String> classNameList = getClassName(packagename);
        ArrayList<Class> list = new ArrayList<>();

        for (String className : classNameList) {
            try {
                String realClassName = className.replace("/", ".");
                list.add(Class.forName(realClassName));
            } catch (ClassNotFoundException e) {
                throw new RuntimeException("load class from name failed:" + className + e.getMessage());
            }
        }
        return list;
    }

    /**
     * 获取某包下所有类
     *
     * @param packageName 包名
     * @return 类的完整名称
     */
    public static List<String> getClassName(String packageName) {

        List<String> fileNames = null;
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        String packagePath = packageName.replace(".", "/");
        URL url = loader.getResource(packagePath);
        if (url != null) {
            String type = url.getProtocol();
            if (type.equals("file")) {
                String fileSearchPath = url.getPath();
                fileSearchPath = fileSearchPath.substring(0, fileSearchPath.indexOf("/classes"));
                fileNames = getClassNameByFile(fileSearchPath);
            } else if (type.equals("jar")) {
                try {
                    JarURLConnection
                        jarURLConnection = (JarURLConnection) url.openConnection();
                    JarFile jarFile = jarURLConnection.getJarFile();
                    fileNames = getClassNameByJar(jarFile, packagePath);
                } catch (java.io.IOException e) {
                    throw new RuntimeException("open Package URL failed：" + e.getMessage());
                }
            } else {
                throw new RuntimeException("file system not support! cannot load MsgProcessor！");
            }
        }
        return fileNames;
    }

    /**
     * 从项目文件获取某包下所有类
     *
     * @param filePath 文件路径
     * @return 类的完整名称
     */
    private static List<String> getClassNameByFile(String filePath) {
        List<String> myClassName = new ArrayList<String>();
        File file = new File(filePath);
        File[] childFiles = file.listFiles();
        for (File childFile : childFiles) {
            if (childFile.isDirectory()) {
                myClassName.addAll(getClassNameByFile(childFile.getPath()));
            } else {
                String childFilePath = childFile.getPath();
                if (childFilePath.endsWith(".class")) {
                    childFilePath = childFilePath.substring(childFilePath.indexOf("/classes") + 9, childFilePath.lastIndexOf("."));
                    childFilePath = childFilePath.replace("/", ".");
                    myClassName.add(childFilePath);
                }
            }
        }

        return myClassName;
    }

    /**
     * 从jar获取某包下所有类
     *
     * @return 类的完整名称
     */
    private static List<String> getClassNameByJar(JarFile jarFile, String packagePath) {
        List<String> myClassName = new ArrayList<String>();
        try {
            Enumeration<JarEntry>
                entrys = jarFile.entries();
            while (entrys.hasMoreElements()) {
                JarEntry jarEntry =
                    entrys.nextElement();
                String entryName
                    = jarEntry.getName();
                if (entryName.endsWith(".class")) {
                    entryName =
                        entryName.replace("/", ".").substring(0, entryName.lastIndexOf("."));
                    myClassName.add(entryName);
                }
            }
        } catch (Exception e) {
            throw new RuntimeException("发生异常:" + e.getMessage());
        }
        return myClassName;
    }

    private static LoadingCache<String, ArrayList<Class>> buildAllClassCache() {
        LoadingCache<String, ArrayList<Class>> cache = CacheBuilder.newBuilder()
            //设置并发级别为8，并发级别是指可以同时写缓存的线程数
            .concurrencyLevel(8)
            //设置缓存容器的初始容量为10
            .initialCapacity(10)
            //设置缓存最大容量为100，超过100之后就会按照LRU最近虽少使用算法来移除缓存项
            .maximumSize(100)
            //设置写缓存后n秒钟过期
            .expireAfterWrite(30, TimeUnit.DAYS)
            //build方法中可以指定CacheLoader，在缓存不存在时通过CacheLoader的实现自动加载缓存
            .build(new AllClassCacheLoader());
        return cache;
    }

    /**
     * 从diamond获取配置并加载到缓存
     */
    public static class AllClassCacheLoader extends CacheLoader<String, ArrayList<Class>> {
        @Override
        public ArrayList<Class> load(String packagename) throws Exception {
            return getAllClass(packagename);
        }
    }
}