JavaSE使用log4j个性化控制日志

在JavaSE中使用log4j来个性化控制日志，需求为：

1.将Warning以上级别的log记录到error log中。

2.将正常的Info信息记录到info log中。

3.将Debug信息记录到trace log中。

4.log信息尽可能详细，并且格式简明易读，关键内容包括：包名，类名，方法名，调用参数，异常信息，出错行数等等。

每种log最多保留10个日志文件，超过10个文件时最老的log被删除，实现滚动记录日志，日志文件命名格式为：“*_0.log”，"*_1.log"..."*_9.log"。单个log文件最大容量10MB。

log4j配置文件log4j.xml如下：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false" threshold="null">
  <!--This is final xml4j that confirms xml4j.dtd-->
  <appender class="com.log4j.test.TestLoggingRollingFileAppender" name="error">
  	<param name="threshold" value="WARN"/>
    <param name="File" value="/var/opt/test/log/test_error0_0.log"/>
    <param name="Append" value="true"/>  
    <param name="maxFileSize" value="10MB"/>
    <param name="maxBackupIndex" value="10"/>
    <layout class="org.apache.log4j.PatternLayout">
    	<param name="ConversionPattern" value="%d{yyyy-MM-dd-'T'HH:mm:ss.SSSZ} | ${host} | %x | %-15t | %-5p | %c | %m%n"/>
    </layout>
    <filter class="org.apache.log4j.varia.LevelRangeFilter">
            <param name="LevelMin" value="WARN" />
            <param name="LevelMax" value="FATAL" />
    </filter>
  </appender>
  <appender class="com.log4j.test.TestLoggingRollingFileAppender" name="info">
    <param name="threshold" value="INFO"/>
    <param name="File" value="/var/opt/test/log/test_info0_0.log"/>
    <param name="Append" value="true"/>
    <param name="maxFileSize" value="10MB"/>
    <param name="maxBackupIndex" value="10"/>
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d{yyyy-MM-dd-'T'HH:mm:ss.SSSZ} | ${host} | %x | %-15t | %-5p | %c | %m%n"/>
    </layout>
    <filter class="org.apache.log4j.varia.LevelRangeFilter">
            <param name="LevelMin" value="INFO" />
            <param name="LevelMax" value="INFO" />
    </filter>
  </appender>
  <appender class="com.log4j.test.TestLoggingRollingFileAppender" name="trace">
    <param name="threshold" value="DEBUG"/>
    <param name="File" value="/var/opt/test/log/test_trace0_0.log"/>
    <param name="Append" value="true"/>
    <param name="maxFileSize" value="10MB"/>
    <param name="maxBackupIndex" value="10"/>
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d{yyyy-MM-dd-'T'HH:mm:ss.SSSZ} | ${host} | %x | %-15t | %-5p | %c | %m%n"/>
    </layout>
  </appender>
  <logger additivity="true" name="com.log4j.test">
       <level value="INFO"/>
       <appender-ref ref="error"/>
       <appender-ref ref="info"/>
       <appender-ref ref="trace"/>
  </logger>
  <root>
    <level value="INFO"/>
    <appender-ref ref="error"/>
    <appender-ref ref="info"/>
    <appender-ref ref="trace"/>
  </root>
</log4j:configuration>

由于log4j默认的RollingFileAppender滚动记录日志功能文件名格式是：”*.log1“，”*.log2“等不满足需求中“*_0.log”，"*_1.log"..."*_9.log"格式，因此自定滚动日志记录类，实现自定义的log序号格式如下：

log4j.xml配置文件中的如下配置指定了log文件的存放目录和名称格式：

<param name="File" value="/var/opt/test/log/test_error0_0.log"/>

<param name="File" value="/var/opt/test/log/test_info0_0.log"/>

<param name="File" value="/var/opt/test/log/test_trace0_0.log"/>

使用下面自定义的log文件滚动追加类，可以实现日志文件命名格式为：“*_0.log”，"*_1.log"..."*_9.log"，并且log4j在记录日志时，当前记录的文件序号总是0_0：

class TestLoggingRollingFileAppender extends RollingFileAppender {

    private static final String FILE_NAME_POSTFIX = "_0.log";

    public TestLoggingRollingFileAppender() {
        super();
    }

    public TestLoggingRollingFileAppender(Layout layout, String filename, boolean append) throws IOException {
        super(layout, filename, append);
    }

    public TestLoggingRollingFileAppender(Layout layout, String filename) throws IOException {
        super(layout, filename);
    }
	
	//重写log4j RollingFileAppender的滚动记录log方法，log文件写满时，自动写新文件，log4j默认文件名规则为：*.log0, *.log1...
	//将log文件名规则修改为：*_0.log, *_1.log...该方法在每个日志文件写满时由log4j自动调用
    public void rollOver() {
        File target;
        File file;

        if (qw != null) {
            long size = ((CountingQuietWriter) qw).getCount();
            LogLog.debug("rolling over count=" + size);
        }
        LogLog.debug("maxBackupIndex=" + maxBackupIndex);

        boolean renameSucceeded = true;
        //配置的log文件数目大于0
        if (maxBackupIndex > 0) {
            //获取最老的log文件名，序号最大的是最老的log文件
            file = new File(fileName.substring(0, fileName.length() - FILE_NAME_POSTFIX.length()) + '_' + maxBackupIndex + ".log");
            //删除最老的log文件，不一定存在最老文件，只有当log文件个数等于所配置的最大日志文件数时才删除最老日志文件
			if (file.exists()) {
                renameSucceeded = file.delete();
            }
			//将log文件名的序号加1，如*_2.log变为*_3.log，即最新的log会记录在序号最小的log文件中
            for (int i = maxBackupIndex - 1; i >= 1 && renameSucceeded; i--) {
                //获取log文件名
				file = new File(fileName.substring(0, fileName.length() - FILE_NAME_POSTFIX.length()) + '_' + i + ".log");
                if (file.exists()) {
					//将log文件名的序号加1，最小的序号是2
                    target = new File(fileName.substring(0, fileName.length() - FILE_NAME_POSTFIX.length()) + '_' + (i + 1) + ".log");
                    LogLog.debug("Renaming file " + file + " to " + target);
                    renameSucceeded = file.renameTo(target);
                }
            }
			//将最新写满的log文件命名为序号1
            if (renameSucceeded) {
                //命名*_1.log文件
                target = new File(fileName.substring(0, fileName.length() - FILE_NAME_POSTFIX.length()) + '_' + 1 + ".log");

                this.closeFile();
                file = new File(fileName);
                LogLog.debug("Renaming file " + file + " to " + target);
                renameSucceeded = file.renameTo(target);
                //log文件重命名失败，重新打开log文件继续向里面追加log
                if (!renameSucceeded) {
                    try {
                        this.setFile(fileName, true, bufferedIO, bufferSize);
                    } catch (IOException e) {
                        if (e instanceof InterruptedIOException) {
                            Thread.currentThread().interrupt();
                        }
                        LogLog.error("setFile(" + fileName + ", true) call failed.", e);
                    }
                }
            }
        }
        //所有的log文件都改名成功
        if (renameSucceeded) {
            try {
				//关闭所有滚动的log文件
                this.setFile(fileName, false, bufferedIO, bufferSize);
            } catch (IOException e) {
                if (e instanceof InterruptedIOException) {
                    Thread.currentThread().interrupt();
                }
                LogLog.error("setFile(" + fileName + ", false) call failed.", e);
            }
        }
    }
}

上述日志文件滚动改名方法中，由于当前记录的日志文件序号总是从0开始，因此要依次顺序地日志文件序号加1，以实现序号滚动。

定义自己的log记录类，读取log4j.xml配置文件，调用log4j相应log记录方法，实现自定义格式的log。

public class TestLog{
    private static final String LOGGER_NAME = "com.log4j.test";
    private static final String LOG_PATH = "/etc/opt/log4j_test/conf/"
    private static final String LOG_CONF_NAME = "log4j.xml";
    private static final String ERROR_LOG_ENTRY_SEPARATOR = ", ";
    private static final String EMPTY_STRING = new String();
    private static Logger log = null;

    //Initialize and load log configuration
    static{  
        try {
			//先从服务器上指定位置加载log4j配置文件
            File file = new File(LOG_PATH + LOG_CONF_NAME);
            if(file.exists()){
                DOMConfigurator.configure(Constants.RAC3GP_CONF_DIR + LOG_CONF_NAME);
            }
            //如果服务器上指定位置log4j配置文件不存在，加载jar包中的log4j配置文件
            else{
                InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(LOG_CONF_NAME);
                new DOMConfigurator().doConfigure(in, LogManager.getLoggerRepository());c
            }
        } catch (Exception e) {
            System.err.println("Loading log4j configuration failed, errorMsg:" + e.getMessage());
        }
        log = Logger.getLogger(LOGGER_NAME);
        log.trace("Log initializing ...");
    }

    public static void logAudit(String message) {
        log.info(message);
    }
    
    public static void logTrace(String message)
    {
        log.debug(message);
    }
    
    public static void logError(Object location, String method, String errorMessage)
    {
        logError(location, method, null, errorMessage);
    }

    public static void logError(Object location, String method, Exception exp, String errorMessage)
    {
        String className = location.getClass().getName();
        if( errorMessage == null )
        {
            errorMessage = "";
        }
        String errorMsg = className + " " + method + ": " + errorMessage;
        StringBuffer msg = new StringBuffer(errorMsg);

        if (exp != null)
        {
            msg.append(Constants.NL).append(Constants.NL).append(
                getStackTrace(exp));
        }
        else{
            msg.append(getStackTrace(new BulkCmException()));
        }
        log.error(msg);
    }

    public static void logError(Object location, String method, Exception exp, String sessionId, String errorMessage)
    {
        String msg = sessionId + ERROR_LOG_ENTRY_SEPARATOR + errorMessage;
        logError(location, method, exp, msg);
    }
    
    private static String getStackTrace(Throwable t)
    {
        if (t == null)
        {
            return EMPTY_STRING;
        }
        try
        {
            StringWriter localSw = new StringWriter();
            PrintWriter localPw = new PrintWriter(localSw);
            t.printStackTrace(localPw);
            return localSw.toString();
        }
        catch (Throwable u)
        {
            return EMPTY_STRING;
        }
    }
    
    public static void logInfo(Object location, String message)
    {
        String className = location.getClass().getName();
        String msg = className + ": " + message;
        log.info( msg );
    }

    public static void logInfo(String message)
    {
        log.info(message);
    }
}

在应用程序中，直接调用该log类的日志记录方法即可实现自定义log记录需求。