指定目录输出日志（根据日期和操作员信息）

package com.microjava.log;

public interface ILog {
	public void write(Object o);
}

package com.microjava.log;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;


public class LogService implements ILog {
	
	private String filename;
	private FileOutputStream fileoutputstream;
	private String encoding;
	private static Map instances = null;
	private LogService() {
		
	}
	private LogService(String today, String branchid) {
		//filename = CommonProperties.getAppPath()+"/logs/"+today+"/"+branchid+"/message.log";
		filename = "d:/logs/"+today+"/"+branchid+"/message.log";
		encoding = "gbk"; //"GB2312";
	}
	
	public synchronized static ILog getInstance() {
		String branchid = null;
		String bankid = "01";//(String)Sessions.getCurrent().getAttribute("bankid");
		String branchid_ = "002";//(String)Sessions.getCurrent().getAttribute("branchid");
		if(bankid!=null) {
			branchid = bankid;
		}
		if(branchid_!=null) {
			if(branchid==null) {
				branchid = branchid_;
			} else {
				branchid += branchid_;
			}
		}
		if(branchid==null || branchid.equals("")) {
			branchid = "undefined";
		}
		String today = new SimpleDateFormat("yyyyMMdd").format(new Date());
		if(instances==null) {
			instances = new HashMap();
			instances.put(today+branchid, new LogService(today, branchid));
		} else if(!instances.containsKey(today+branchid)) {
			instances.put(today+branchid, new LogService(today, branchid));
		}
		return (ILog)instances.get(today+branchid);
	}
	
	private synchronized void rollingFile() throws IOException {
		File file = new File(filename);
		if(!file.exists()) {
			new File(file.getParent()).mkdirs();
			file.createNewFile();
			fileoutputstream = null;
		} else if(file.length()>=5000000L) {//可以参数化
			File file_;
			do {
				String ext = String.valueOf(System.currentTimeMillis());
				file_ = new File(filename+"."+ext);
			} while(file_.exists());
			file.renameTo(file_);
			fileoutputstream = null;
			file_ = null;
		}
		fileoutputstream = new FileOutputStream(file, true);
	}
	public void write(Object o) {
		// TODO Auto-generated method stub
		try {
			rollingFile();
			fileoutputstream.write(("["+new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS").format(new Date())+"]"+o.toString()+"\n").getBytes(encoding));
			fileoutputstream.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

package com.microjava.log;

import junit.framework.TestCase;

public class ILogTest extends TestCase {
	
	private ILog log;
	
	protected void setUp() {
		log = LogService.getInstance();
	}
	
	public void testWrite() {
		log.write("Hello,microjava!");
	}
}