How Tomcat works 7: Logger日志系统

1. Logger接口

（1）Code:

		package com.cisco.tomcat.logger;
		
		import java.beans.PropertyChangeListener;
		import com.cisco.tomcat.lifecycle.Container;
		
		public interface Logger {
			public static final int FATAL = Integer.MIN_VALUE;
			public static final int ERROR = 1;
			public static final int WARNING = 2;
			public static final int INFORMATION = 3;
			public static final int DEBUG = 4;
			
			public void setVerbosity(int verbosity);
			public int getVerbosity();
			public Container getContainer();
			public void setContainer();
			public String getInfo();
			public void addPropertyChangeListener(PropertyChangeListener propertyChangeListener);
			public void removePropertyChangeListener(PropertyChangeListener propertyChangListener);
			
			public void log(String message);
			public void log(String message, Throwable throwable);
			public void log(String message, int verbosity);
			public void log(String message, Throwable throwable, int verbosity);
}

（2）接口包含五个日志层次：

FATAL>ERROR>WARNING>INFORMATION>DEBUG

（1）主要包含三个类：

FileLogger, SystemErrLogger, SystemOutLogger。它们都继承自LoggerBase.

UML图：

（2）LoggerBase抽象类：

代码：

			package com.cisco.tomcat.logger;
			
			public abstract class LoggerBase implements Logger{
				protected int verbosity = ERROR;
				
				public void setVerbosityLevel(String verbosity) {
					if("FATAL".equalsIgnoreCase(verbosity)) {
						this.verbosity = FATAL;
					}else if("ERROR".equalsIgnoreCase(verbosity)) {
						this.verbosity = ERROR;
					}else if("WARNING".equalsIgnoreCase(verbosity)) {
						this.verbosity = WARNING;
					}else if("INFORMATION".equalsIgnoreCase(verbosity)) {
						this.verbosity = INFORMATION;
					}else if("DEBUG".equalsIgnoreCase(verbosity)) {
						this.verbosity = DEBUG;
					}
				}
				
			
				public abstract void log(String message);
				
				public void log(String message, int verbosity) {
					if(this.verbosity >= verbosity) {
						log(message);
					}
				}
				
				public void log(String message, Throwable throwable, int verbosity) {
					if(this.verbosity >= verbosity) {
						log(message, throwable);
					}
				}
				
			}

（3）SystemOutLogger类：

代码：

			public class SystemOutLogger extends LoggerBase{
			
				protected static final String Info = "logger.SystemOutLogger/1.0";
			
				@Override
				public void log(String message) {
					System.out.println(message);
				}
			}

（4）SystemErrLogger类：

代码：

			public class SystemErrLogger extends LoggerBase{
			
				protected static final String Info = "logger.SystemErrLogger/1.0";
			
				@Override
				public void log(String message) {
					System.err.println(message);
				}
			}

（5）FileLogger类：

根据时间创建日志文件，写入内容

代码：

			public class FileLogger extends LoggerBase{
			
				private String date;
				
				private PrintWriter writer;
				private String directory;
				private String prefix;
				private String suffix;
				private boolean timestamp = false;
				@Override
				public void log(String message) {
					Timestamp ts = new Timestamp(new Date(), null);
					String tsString  = ts.toString().substring(0, 19);
					String tsDate = tsString.substring(0, 10);
					
					if(!date.equals(tsDate)) {
						synchronized (this) {
							if(!date.equals(tsDate)) {
								close();
								date = tsDate;
								open();
							}
						}			
					}
					
					if(writer != null) {
						if(timestamp) {
							writer.println(tsString + " " + message);
						}else {
							writer.println(message);
						}
					}
					
				}
				
				private void open() {
					File dir = new File(directory);
					if(!dir.isAbsolute()) {
						dir = new File(System.getProperty("catalina.base"), directory);
					}
					dir.mkdirs();
					
					try {
						String pathname = dir.getAbsolutePath() + File.separator + prefix + date+suffix;
						writer = new PrintWriter(new FileWriter(pathname, true), true);
					}catch(IOException e) {
						writer = null;
					}
				}
				
				private void close() {
					if(writer == null) {
						return;
					}
					writer.flush();
					writer.close();
					writer = null;
					date = "";
				}
			}