Question

我想在类JarClassLoader和Menu中启用日志记录。

在Menu类中它可以工作（日志打印到文件和控制台）。但是日志记录在JarClassLoader中不起作用（日志记录在控制台或文件中都不起作用）。

为简单起见，我仅将消息添加到JarClassLoader的类构造函数，并在main(String[] args)方法的开头添加了一条消息。

log4j2.properties

name=PropertiesConfig
property.filename=classloading/menu-module/logs
appenders=console, file

appender.console.type=Console
appender.console.name=STDOUT
appender.console.layout.type=PatternLayout
appender.console.layout.pattern=[%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %c{1} - %msg%n

appender.file.type=File
appender.file.name=LOGFILE
appender.file.fileName=${filename}/propertieslogs.log
appender.file.layout.type=PatternLayout
appender.file.layout.pattern=[%-5level] %d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %c{1} - %msg%n

rootLogger.level=info
rootLogger.appenderRefs=stdout
rootLogger.appenderRef.stdout.ref=STDOUT

loggers=file
logger.file.name=com.example.classloading
logger.file.level=info
logger.file.appenderRefs=file
logger.file.appenderRef.file.ref=LOGFILE

JarClassLoader

package com.example.classloading;

import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class JarClassLoader extends ClassLoader {

    private static final Logger log = LogManager.getLogger(JarClassLoader.class);

    private HashMap<String, Class<?>> cache = new HashMap<String, Class<?>>();
    private String jarFileName;
    private String packageName;
    private static String WARNING = "Warning : No jar file found. Packet unmarshalling won't be possible. Please verify your classpath";

    public JarClassLoader(String jarFileName, String packageName) {         
        log.info(">> inside JarClassLoader");

        this.jarFileName = jarFileName;
        this.packageName = packageName;

        cacheClasses();
    }

    private void cacheClasses() {
        try {
            JarFile jarFile = new JarFile(jarFileName);
            Enumeration entries = jarFile.entries();
            while (entries.hasMoreElements()) {
                JarEntry jarEntry = (JarEntry) entries.nextElement();
                // simple class validation based on package name
                if (match(normalize(jarEntry.getName()), packageName)) {
                    byte[] classData = loadClassData(jarFile, jarEntry);
                    if (classData != null) {
                        Class<?> clazz = defineClass(stripClassName(normalize(jarEntry.getName())), classData, 0, classData.length);
                        cache.put(clazz.getName(), clazz);
                        System.out.println("== class " + clazz.getName() + " loaded in cache");
                    }
                }
            }
        }
        catch (IOException IOE) {
            System.out.println(WARNING);
        }
    }

    public synchronized Class<?> loadClass(String name) throws ClassNotFoundException {
        Class<?> result = cache.get(name);
        if (result == null)
            result = cache.get(packageName + "." + name);
        if (result == null)
            result = super.findSystemClass(name);    
        System.out.println("== loadClass(" + name + ")");    
        return result;
    }

    private String stripClassName(String className) {
        return className.substring(0, className.length() - 6);
    }

    private String normalize(String className) {
        return className.replace('/', '.');
    }

    private boolean match(String className, String packageName) {
        return className.startsWith(packageName) && className.endsWith(".class");
    }

    private byte[] loadClassData(JarFile jarFile, JarEntry jarEntry) throws IOException {
        long size = jarEntry.getSize();
        if (size == -1 || size == 0)
            return null;

        byte[] data = new byte[(int)size];
        InputStream in = jarFile.getInputStream(jarEntry);
        in.read(data);

        return data;
    }
}

Menu

package com.example.classloading;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.util.Scanner;

public class Menu {

    private static final Logger log = LogManager.getLogger();

    public static void main(String[] args) {

        int select;
        do {
            log.info(">> menu started");

            System.out.println("=== MENU ===");
            System.out.println("This is a simple multi-module project that can dynamically load modules.");
            System.out.println("1. Load and run simple-module");
            System.out.println("2. Load and run module in jar from ...");
            System.out.println("0. EXIT");

            Scanner scanner = new Scanner(System.in);
            select = scanner.nextInt();

            switch (select) {
                case 1: {
                    JarClassLoader jarClassLoader = new JarClassLoader("classloading/simple-module/target/simple-module-1.0-SNAPSHOT.jar", "com.example.classloading");
                    try {
                        Class<?> clas = jarClassLoader.loadClass("com.example.classloading.SimpleModule");
                        Module sample = (Module) clas.newInstance();
                        sample.run();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                }
                case 2: {
                    System.out.print("    Path to jar: ");
                    String jarFileName = scanner.next();
                    System.out.print("    Package name: ");
                    String packageName = scanner.next();
                    System.out.print("    Class to load and run: ");
                    String classToLoad = scanner.next();

                    JarClassLoader jarClassLoader = new JarClassLoader(jarFileName, packageName);
                    try {
                        Class<?> clas = jarClassLoader.loadClass(classToLoad);
                        Module sample = (Module) clas.newInstance();
                        sample.run();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                }
            }
        } while (select != 0);
    }

}

那么，为什么不在JarClassLoader课程中记录工作？

Answer 1

我已运行您的代码，日志记录没有问题。当我运行确切的代码时，输出如下;

[INFO ] 2017-04-09 20:07:15.208 [main] Menu - >> menu started
=== MENU ===
This is a simple multi-module project that can dynamically load modules.
1. Load and run simple-module
2. Load and run module in jar from ...
0. EXIT
1
[INFO ] 2017-04-09 20:07:20.681 [main] JarClassLoader - >> inside JarClassLoader

在您的屏幕截图中，我没有看到您已输入＆＃34; 1＆＃34;或＆＃34; 2＆＃34;在您的控制台中作为选择。只要您不从控制台输入任何内容，java程序就会等待输入，因此，它永远不会到达记录完成的行。

log4j2日志记录仅适用于一个类

1 个答案: