Web框架学习:类加载工具

Java的类加载机制

Java的代码都是运行在JVM虚拟机中的,使用类加载机制来完成代码的运行,具体内容还不是很了解,但是类加载机制总需要有一个线程来操作,Web框架中的类加载工具就是获取到这个线程,并把框架里的类加载进去.

类加载工具流程

1. 新建一个HashSet存放Class
2. 通过File文件目录/jar包/“.class”文件三种方式遍历取出Class
3. 获取到类加载线程进行加载

Example

package org.smart4j.framework.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.smart4j.framework.util.tool.StringUtil;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
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;


public final class ClassUtil {

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

    public static Set<Class<?>> getClassSet (String packageName) {
        //init a Classset
        Set<Class<?>> classSet = new HashSet<Class<?>>();
        //loop for find 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"," ");
                        addClass(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> jarEnties = jarFile.entries();
                                while (jarEnties.hasMoreElements()) {
                                    JarEntry jarEntry = jarEnties.nextElement();
                                    String jarEntryName = jarEntry.getName();
                                    if (jarEntryName.endsWith(".class")) {
                                        String className = jarEntryName.substring(0, jarEntryName.lastIndexOf(".")).replaceAll("/",".");
                                        doAddClass(classSet,className);
                                    }
                                }
                            }
                        }
                    }
                }

            }
        } catch (IOException e) {
            LOGGER.error("get class set failure", e);
            throw new  RuntimeException(e);
        }
        //return ClassSet
        return classSet;
    }

    private static void doAddClass(Set<Class<?>> classSet, String className) {
        Class<?> cls = loadClass(className, false);
        classSet.add(cls);
    }

    private static void addClass(Set<Class<?>> classSet, String packagePath, final String packageName) {
        final File[] files = new File(packagePath).listFiles(new FileFilter() {
            public boolean accept(File pathname) {
                return (pathname.isFile() && pathname.getName().endsWith(".class"))|| pathname.isDirectory();
            }
        });

        for (File file: files) {
            //Get File name
            String fileName = file.getName();
            //
            if (file.isFile()) {
                String className = fileName.substring(0,fileName.lastIndexOf("."));
                if (StringUtil.isNotEmpty(packageName)) {
                    className = packageName+"."+className;
                }
                doAddClass(classSet, className);
            }else {
                String subPackagePath = fileName;
                if (StringUtil.isNotEmpty(packagePath)) {
                    subPackagePath = packagePath + "/" + subPackagePath;
                }
                String subPackageName = fileName;
                if (StringUtil.isNotEmpty(packageName)) {
                    subPackageName = packageName + "." +subPackageName;
                }
                addClass(classSet, subPackagePath, subPackageName);
            }
        }
    }

    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;
    }

    public static ClassLoader getClassLoader() {
        return Thread.currentThread().getContextClassLoader();
    }

}

赏

请问老板还招人么(/ω＼)

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