一、Logback简介

Logback是由log4j创始人设计的又一个开源日志组件。logback当前分成三个模块：logback-core,logback- classic和logback-access。logback-core是其它两个模块的基础模块。logback-classic是log4j的一个 改良版本。此外logback-classic完整实现SLF4J API使你可以很方便地更换成其它日志系统如log4j或JDK14 Logging。logback-access访问模块与Servlet容器集成提供通过Http来访问日志的功能。

二、编写背景

很不明白客户为什么要求将日志信息写入到数据库中去，还要提供个页面给系统使用人员查看相应日志。作为一个业务人员真的就能看懂系统日志上报错信息是啥意思么，个人深表怀疑。没办法，作为一枚屌丝程序猿，需求下来了只能硬着头皮去开发。

三、编写目的

只相信一句话:好记性不如烂笔头，何况我记性差到前一周写的代码到现在竟毫无印象的境地呢。

四、Java日志信息存库详细解决方案

1.开发环境说明

Eclipse+Tomcat6+JDK1.6+Oracle+logback1.1

2.Java日志存库实现方案

(1)使用logback组件默认的DBAppender类实现

最初需求下来的时候想着logback应该有自己的写数据库的解决办法，于是乎结合源码及度娘终究还是找到了。在logback-classic-1.1.3.jar的ch/qos/logback/classic/db/script/路径下找到了Oracle数据库对应的建表语句脚本oracle.sql，其建表语句如下所示:

--Logback: the reliable, generic, fast and flexible logging framework.--Copyright (C) 1999-2010, QOS.ch. All rights reserved.--

--See http://logback.qos.ch/license.html for the applicable licensing--conditions.

--This SQL script creates the required tables by ch.qos.logback.classic.db.DBAppender--

--It is intended for Oracle 9i, 10g and 11g databases. Tested on version 9.2,--10g and 11g.

--The following lines are useful in cleaning any previously existing tables

--drop TRIGGER logging_event_id_seq_trig;--drop SEQUENCE logging_event_id_seq;--drop table logging_event_property;--drop table logging_event_exception;--drop table logging_event;

CREATE SEQUENCE logging_event_id_seq MINVALUE 1 START WITH 1;CREATE TABLElogging_event

(

timestmpNUMBER(20) NOT NULL,

formatted_messageVARCHAR2(4000) NOT NULL,

logger_nameVARCHAR(254) NOT NULL,

level_stringVARCHAR(254) NOT NULL,

thread_nameVARCHAR(254),

reference_flagSMALLINT,

arg0VARCHAR(254),

arg1VARCHAR(254),

arg2VARCHAR(254),

arg3VARCHAR(254),

caller_filenameVARCHAR(254) NOT NULL,

caller_classVARCHAR(254) NOT NULL,

caller_methodVARCHAR(254) NOT NULL,

caller_lineCHAR(4) NOT NULL,

event_idNUMBER(10) PRIMARY KEY);--the / suffix may or may not be needed depending on your SQL Client--Some SQL Clients, e.g. SQuirrel SQL has trouble with the following--trigger creation command, while SQLPlus (the basic SQL Client which--ships with Oracle) has no trouble at all.

CREATE TRIGGERlogging_event_id_seq_trig

BEFOREINSERT ONlogging_eventFOREACH ROWBEGIN

SELECTlogging_event_id_seq.NEXTVALINTO:NEW.event_idFROMDUAL;END;/

CREATE TABLElogging_event_property

(

event_idNUMBER(10) NOT NULL,

mapped_keyVARCHAR2(254) NOT NULL,

mapped_valueVARCHAR2(1024),PRIMARY KEY(event_id, mapped_key),FOREIGN KEY (event_id) REFERENCESlogging_event(event_id)

);CREATE TABLElogging_event_exception

(

event_idNUMBER(10) NOT NULL,

iSMALLINT NOT NULL,

trace_lineVARCHAR2(254) NOT NULL,PRIMARY KEY(event_id, i),FOREIGN KEY (event_id) REFERENCESlogging_event(event_id)

);

该sql脚本共创建了3张表,一个序列和一个触发器。其中主要日志信息记录在logging_event中，触发器是在logging_event数据新增时，将创建的序列值赋值给logging_event表的event_id。

1)JDBC连接池方式

oracle.jdbc.driver.OracleDriver

jdbc:oracle:thin:@127.0.0.1:1521:orcl

tiger

123456

2) JNDI方式

A.Tomcat服务器安装目录/conf/server.xml配置JNDI信息

B.Spring配置文件applicationContext.xml配置JNDI信息

java:comp/env/jdbc/logging

C.logback.xml文件配置JNDI信息

?xml version="1.0" encoding="UTF-8" ?>

java:comp/env/jdbc/logging

注:对于JNDI的配置不熟悉的，可以去找度娘帮忙或参考JNDI官方文档，本文不做细究。

(2)使用自定义DBAppender类实现

当初按上述的配置轻轻松松实现了日志信息存库，但天有不测风云，完成后却被告知客户那边任务触发器不安全，禁用触发器。得知此消息后心里仿佛有千万只草泥马飞奔而过，没办法只有继续想着怎么去改造了。于是就只能去自定义个DBAppender了，既然是自定义就干脆把其他两张表直接删了，仅使用logging_event表，其表结构如下：

字段名

中文说明

类型

为空

TIMESTMP

记录时间

NUMBER(20)

N

FORMATTED_MESSAGE

格式化后的日志信息

CLOB

N

LOGGER_NAME

执行记录请求的logger

VARCHAR2(256)

N

LEVEL_STRING

日志级别

VARCHAR2(256)

N

THREAD_NAME

日志线程名

VARCHAR2(256)

Y

REFERENCE_FLAG

包含标识：1-MDC或上下文属性;2-异常;3-均包含

INTEGER

Y

ARG0

参数1

VARCHAR2(256)

Y

ARG1

参数2

VARCHAR2(256)

Y

ARG2

参数3

VARCHAR2(256)

Y

ARG3

参数4

VARCHAR2(256)

Y

CALLER_FILENAME

文件名

VARCHAR2(256)

N

CALLER_CLASS

类

VARCHAR2(256)

N

CALLER_METHOD

方法名

VARCHAR2(256)

N

CALLER_LINE

行号

VARCHAR2(256)

N

EVENT_ID

主键ID

NUMBER(10)

N

注：这个表结构与logback提供的默认表结构有细微差别，主要体现在字段类型上，由于FORMATTED_MESSAGE存储的是详细的日志信息，字段类型VARCHAR2(4000)无法存储大文本信息，所以直接改造成了CLOB类型。

1)自定义DBAppender类(ATSDBAppender.java)

packagecom.hundsun.fund.ats.core.system.loggingevent.dao;importjava.lang.reflect.Method;importjava.sql.Connection;importjava.sql.PreparedStatement;importjava.sql.SQLException;importjava.util.HashMap;importjava.util.Map;import staticch.qos.logback.core.db.DBHelper.closeStatement;import staticch.qos.logback.core.db.DBHelper.closeConnection;importch.qos.logback.classic.db.DBHelper;importch.qos.logback.classic.db.names.DBNameResolver;importch.qos.logback.classic.db.names.DefaultDBNameResolver;importch.qos.logback.classic.spi.CallerData;importch.qos.logback.classic.spi.ILoggingEvent;importch.qos.logback.core.db.DBAppenderBase;public class ATSDBAppender extends DBAppenderBase{protectedString insertSQL;protected static finalMethod GET_GENERATED_KEYS_METHOD;privateDBNameResolver dbNameResolver;static final int TIMESTMP_INDEX = 1;static final int FORMATTED_MESSAGE_INDEX = 2;static final int LOGGER_NAME_INDEX = 3;static final int LEVEL_STRING_INDEX = 4;static final int THREAD_NAME_INDEX = 5;static final int REFERENCE_FLAG_INDEX = 6;static final int ARG0_INDEX = 7;static final int ARG1_INDEX = 8;static final int ARG2_INDEX = 9;static final int ARG3_INDEX = 10;static final int CALLER_FILENAME_INDEX = 11;static final int CALLER_CLASS_INDEX = 12;static final int CALLER_METHOD_INDEX = 13;static final int CALLER_LINE_INDEX = 14;static final int EVENT_ID_INDEX = 15;static final StackTraceElement EMPTY_CALLER_DATA =CallerData.naInstance();static{

Method getGeneratedKeysMethod;try{

getGeneratedKeysMethod= PreparedStatement.class.getMethod("getGeneratedKeys", (Class[]) null);

}catch(Exception ex) {

getGeneratedKeysMethod= null;

}

GET_GENERATED_KEYS_METHOD=getGeneratedKeysMethod;

}public voidsetDbNameResolver(DBNameResolver dbNameResolver) {this.dbNameResolver =dbNameResolver;

}

@Overridepublic voidstart() {if (dbNameResolver == null)

dbNameResolver= newDefaultDBNameResolver();

insertSQL=ATSSQLBuilder.buildInsertSQL(dbNameResolver);super.start();

}public voidappend(ILoggingEvent eventObject) {

Connection connection= null;

PreparedStatement insertStatement= null;try{

connection=connectionSource.getConnection();

connection.setAutoCommit(false);

insertStatement=connection.prepareStatement(getInsertSQL());synchronized (this) {

subAppend(eventObject, connection, insertStatement);

}

connection.commit();

}catch(Throwable sqle) {

addError("problem appending event", sqle);

}finally{

closeStatement(insertStatement);

closeConnection(connection);

}

}

@Overrideprotected void subAppend(ILoggingEvent event, Connection connection,PreparedStatement insertStatement) throwsThrowable {

bindLoggingEventWithInsertStatement(insertStatement, event);

bindLoggingEventArgumentsWithPreparedStatement(insertStatement, event.getArgumentArray());

bindCallerDataWithPreparedStatement(insertStatement, event.getCallerData());int updateCount =insertStatement.executeUpdate();if (updateCount != 1) {

addWarn("Failed to insert loggingEvent");

}

}protected voidsecondarySubAppend(ILoggingEvent event,

Connection connection,long eventId) throwsThrowable {

}voidbindLoggingEventWithInsertStatement(PreparedStatement stmt,

ILoggingEvent event)throwsSQLException {stmt.setLong(TIMESTMP_INDEX, event.getTimeStamp());

stmt.setString(FORMATTED_MESSAGE_INDEX, event.getFormattedMessage());

stmt.setString(LOGGER_NAME_INDEX, event.getLoggerName());

stmt.setString(LEVEL_STRING_INDEX, event.getLevel().toString());

stmt.setString(THREAD_NAME_INDEX, event.getThreadName());

stmt.setShort(REFERENCE_FLAG_INDEX, DBHelper.computeReferenceMask(event));

}voidbindLoggingEventArgumentsWithPreparedStatement(PreparedStatement stmt,

Object[] argArray)throwsSQLException {int arrayLen = argArray != null ? argArray.length : 0;for(int i = 0; i < arrayLen && i < 4; i++) {

stmt.setString(ARG0_INDEX+i, asStringTruncatedTo254(argArray[i]));

}if(arrayLen < 4) {for(int i = arrayLen; i < 4; i++) {

stmt.setString(ARG0_INDEX+i, null);

}

}

}

String asStringTruncatedTo254(Object o) {

String s= null;if(o != null) {

s=o.toString();

}if(s == null) {return null;

}if(s.length() <= 254) {returns;

}else{return s.substring(0, 254);

}

}voidbindCallerDataWithPreparedStatement(PreparedStatement stmt,

StackTraceElement[] callerDataArray)throwsSQLException {

StackTraceElement caller=extractFirstCaller(callerDataArray);

stmt.setString(CALLER_FILENAME_INDEX, caller.getFileName());

stmt.setString(CALLER_CLASS_INDEX, caller.getClassName());

stmt.setString(CALLER_METHOD_INDEX, caller.getMethodName());

stmt.setString(CALLER_LINE_INDEX, Integer.toString(caller.getLineNumber()));

}privateStackTraceElement extractFirstCaller(StackTraceElement[] callerDataArray) {

StackTraceElement caller=EMPTY_CALLER_DATA;if(hasAtLeastOneNonNullElement(callerDataArray))

caller= callerDataArray[0];returncaller;

}private booleanhasAtLeastOneNonNullElement(StackTraceElement[] callerDataArray) {return callerDataArray != null && callerDataArray.length > 0 && callerDataArray[0] != null;

}

MapmergePropertyMaps(ILoggingEvent event) {

Map mergedMap = new HashMap();

Map loggerContextMap =event.getLoggerContextVO().getPropertyMap();

Map mdcMap =event.getMDCPropertyMap();if (loggerContextMap != null) {

mergedMap.putAll(loggerContextMap);

}if (mdcMap != null) {

mergedMap.putAll(mdcMap);

}returnmergedMap;

}

@OverrideprotectedMethod getGeneratedKeysMethod() {returnGET_GENERATED_KEYS_METHOD;

}

@OverrideprotectedString getInsertSQL() {returninsertSQL;

}

}

2)自定义SQLBuilder类(ATSSQLBuilder.java)

packagecom.hundsun.fund.ats.core.system.loggingevent.dao;importch.qos.logback.classic.db.names.ColumnName;importch.qos.logback.classic.db.names.DBNameResolver;importch.qos.logback.classic.db.names.TableName;public classATSSQLBuilder {staticString buildInsertSQL(DBNameResolver dbNameResolver) {

StringBuilder sqlBuilder= new StringBuilder("INSERT INTO ");

sqlBuilder.append(dbNameResolver.getTableName(TableName.LOGGING_EVENT)).append(" (");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.TIMESTMP)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.FORMATTED_MESSAGE)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.LOGGER_NAME)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.LEVEL_STRING)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.THREAD_NAME)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.REFERENCE_FLAG)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.ARG0)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.ARG1)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.ARG2)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.ARG3)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.CALLER_FILENAME)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.CALLER_CLASS)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.CALLER_METHOD)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.CALLER_LINE)).append(", ");

sqlBuilder.append(dbNameResolver.getColumnName(ColumnName.EVENT_ID)).append(") ");

sqlBuilder.append("VALUES (?, ?, ? ,?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?,LOGGING_EVENT_ID_SEQ.nextval)");returnsqlBuilder.toString();

}

}

注：类中LOGGING_EVENT_ID_SEQ序列需自行创建，logback默认建表语句中有该序列的创建语句，直接拿来使用即可。

3)logback.xml配置

此时JDBC与JNDI方式配置只需要将原name为DB的appender标签class属性的值指向自定义DBAppender即可,其他配置不变，下述代码为JDBC配置示例:

oracle.jdbc.driver.OracleDriver

jdbc:oracle:thin:@127.0.0.1:1521:orcl

tiger

123456

(3)测试类的编写

packagecom.hundsun.fund.ats.modules.server.test;importorg.slf4j.Logger;importorg.slf4j.LoggerFactory;public classLogbackTest {public static voidmain(String[] args) {//dblog为logback.xml中logger标签name属性的值

Logger logger= LoggerFactory.getLogger("dblog");

logger.debug("DEBUG级别信息");

logger.warn("WARN级别信息");

logger.info("INFO级别信息");

logger.error("ERROR级别信息");

}

}

五、总结

文中涉及到的Logback日志信息存库的处理只是在源代码的基础上做了点小小的改动而已，并非完整地介绍该组件的功能。想要全面学习Logback日志组件，请参考官方提供的源码和相应的API帮助文档。