Java Web框架 基础知识 类加载 动态加载 jar class

1、获取指定包名下的所有类。如JarURLConnection、JarFile的用法。

2、ClassUtil.java

package mvc.framework.util;

import java.io.File;
import java.io.FileFilter;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

// 类操作工具类
public final class ClassUtil {

    private static final Logger LOGGER = LoggerFactory.getLogger(ClassUtil.class);

    // 获取类加载器
    public static ClassLoader getClassLoader() {
        return Thread.currentThread().getContextClassLoader();
    }

    // 加载类
    public static Class<?> loadClass(String className, boolean isInitialized) {
        Class<?> cls;
        try {
            cls = Class.forName(className, isInitialized, getClassLoader());
        } catch (ClassNotFoundException e) {
            LOGGER.error("load class failure", e);
            throw new RuntimeException(e);
        }
        return cls;
    }

    // 加载类（默认将初始化类）
    public static Class<?> loadClass(String className) {
        return loadClass(className, true);
    }

    // 获取指定包名下的所有类
    public static Set<Class<?>> getClassSet(String packageName) {
        Set<Class<?>> classSet = new HashSet<Class<?>>();
        try {
            Enumeration<URL> urls = getClassLoader().getResources(packageName.replace(".", "/"));
            while (urls.hasMoreElements()) {
                URL url = urls.nextElement();
                if (url != null) {
                    String protocol = url.getProtocol();
                    if (protocol.equals("file")) {
                        String packagePath = url.getPath().replaceAll("%20", " ");
                        findClass(classSet, packagePath, packageName);
                    } else if (protocol.equals("jar")) {
                        JarURLConnection jarURLConnection = (JarURLConnection) url.openConnection();
                        if (jarURLConnection != null) {
                            JarFile jarFile = jarURLConnection.getJarFile();
                            if (jarFile != null) {
                                Enumeration<JarEntry> jarEntries = jarFile.entries();
                                while (jarEntries.hasMoreElements()) {
                                    JarEntry jarEntry = jarEntries.nextElement();
                                    String jarEntryName = jarEntry.getName();
                                    if (jarEntryName.endsWith(".class")) {
                                        String className = jarEntryName.substring(0, jarEntryName.lastIndexOf(".")).replaceAll("/", ".");
                                        addClass(classSet, className);
                                    }
                                }
                            }
                        }
                    }
                }
            }
        } catch (Exception e) {
            LOGGER.error("get class set failure", e);
            throw new RuntimeException(e);
        }
        return classSet;
    }

    // 查找类
    private static void findClass(Set<Class<?>> classSet, String packagePath, String packageName) {
        File[] files = new File(packagePath).listFiles(new FileFilter() {
            public boolean accept(File file) {
                return (file.isFile() && file.getName().endsWith(".class")) || file.isDirectory();
            }
        });
        for (File file : files) {
            String fileName = file.getName();
            if (file.isFile()) {
                String className = fileName.substring(0, fileName.lastIndexOf("."));
                if (StringUtil.isNotEmpty(packageName)) {
                    className = packageName + "." + className;
                }
                addClass(classSet, className);
            } else {
                String subPackagePath = fileName;
                if (StringUtil.isNotEmpty(packagePath)) {
                    subPackagePath = packagePath + "/" + subPackagePath;
                }
                String subPackageName = fileName;
                if (StringUtil.isNotEmpty(packageName)) {
                    subPackageName = packageName + "." + subPackageName;
                }
                findClass(classSet, subPackagePath, subPackageName);
            }
        }
    }

    // 把查找到的类加入集合
    private static void addClass(Set<Class<?>> classSet, String className) {
        Class<?> cls = loadClass(className, false);
        classSet.add(cls);
    }
    
    // 测试
  public static void main(String[] args) {
    // file
    Set<Class<?>> clsPackage = ClassUtil.getClassSet("mvc.web");
    for (Class clazz : clsPackage) {
      System.out.println(clazz.getName());
    }
    
    // jar
    Set<Class<?>> clsJar = ClassUtil.getClassSet("org.apache.commons.io");
    for (Class clazz : clsJar) {
      System.out.println(clazz.getName());
    }
    
    /*
    try {
      URL classes_path = ClassUtil.class.getProtectionDomain().getCodeSource().getLocation();
      String lib_path = classes_path.toString().replace("classes", "lib");
      URL url = new URL("jar:" + lib_path + "commons-io-2.4.jar!/");
      System.out.println(url.toString());
      
      JarURLConnection conn = (JarURLConnection) url.openConnection();
      JarFile jarFile = conn.getJarFile();

      if (jarFile != null) {
        Enumeration<JarEntry> jarEntries = jarFile.entries();
        while (jarEntries.hasMoreElements()) {
          JarEntry jarEntry = jarEntries.nextElement();
          String jarEntryName = jarEntry.getName();
          if (jarEntryName.endsWith(".class")) {
            String className = jarEntryName.substring(0, jarEntryName.lastIndexOf(".")).replaceAll("/",
                ".");
            System.out.println(className);
          }
        }
      }

    } catch (IOException e) {
    }
    */

  }
}