我們都知道log4j是一個(gè)優(yōu)秀的開(kāi)源日志記錄項目，我們不僅可以對輸出的日志的格式自定義，還可以自己定義日志輸出的目的地，比如：屏幕，文本文件，數據庫，甚至能通過(guò)socket輸出。
現在讓我們對日志輸出到數據庫來(lái)進(jìn)行配置
配置如下：
#---JDBC ---輸出到數據庫
# JDBCAppender log4j.properties file
#log4j.rootCategory=WARN,JDBC
# APPENDER JDBC
log4j.appender.JDBC=org.apache.log4j.jdbc.JDBCAppender
log4j.appender.JDBC.driver=com.mysql.jdbc.Driver
log4j.appender.JDBC.URL=jdbc:mysql://localhost:3306/test
log4j.appender.JDBC.user=use
log4j.appender.JDBC.password=password
log4j.appender.JDBC.layout=org.apache.log4j.PatternLayout
log4j.appender.JDBC.sql=INSERT INTO LOGGING (log_date, log_level, location, message) VALUES (‘%d{ISO8601}‘, ‘%-5p‘, ‘%C,%L‘, ‘%m‘)
表結構如下：
log_date varchar2(50)
log_level varchar2(5)
location varchar2(100)
message varchar2(1000)
筆者照做，但沒(méi)有運行成功，而且此種方法是利用傳統的數據庫連接方法，對于數據庫的管理和效率嚴重不足，在現在這個(gè)連接池橫行的時(shí)代,為什么我們不能給給Log4j配上連接池，讓Log4j利用數據連接池的連接和數據庫進(jìn)行通訊?，F查看Log4j的Api,發(fā)現JDBCAppender這個(gè)類(lèi)有以下幾段話(huà)：WARNING: This version of JDBCAppender is very likely to be completely replaced in the future. Moreoever, it does not log exceptions. The JDBCAppender provides for sending log events to a database.
For use as a base class:
Override getConnection() to pass any connection you want. Typically this is used to enable application wide connection pooling.
Override closeConnection(Connection con) -- if you override getConnection make sure to implement closeConnection to handle the connection you generated. Typically this would return the connection to the pool it came from.
Override getLogStatement(LoggingEvent event) to produce specialized or dynamic statements. The default uses the sql option value.
原來(lái)log4j建議我們把其提供的JDBCAppender作為基類(lèi)來(lái)使用，然后Override三個(gè)父類(lèi)的方法：getConnection(),closeConnection(Connection con)和getLogStatement(LoggingEvent event)。
原來(lái)如此，那就寫(xiě)一個(gè)子類(lèi)JDBCPoolAppender來(lái)替代這個(gè)JDBCAppender
JDBCPoolAppender代碼和其相關(guān)代碼如下：
JDBCPoolAppender.java:
package common.log;
import java.sql.Connection;
import org.apache.log4j.spi.LoggingEvent;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Iterator;
import org.apache.log4j.spi.ErrorCode;
import org.apache.log4j.PatternLayout;
import common.sql.MyDB;
import common.sql.GeneralDb;
public class JDBCPoolAppender extends org.apache.log4j.jdbc.JDBCAppender {
private MyDB mydb = null;
protected String sqlname=""; //增加一個(gè)數據庫jndiName的屬性
protected Connection connection = null;
protected String sqlStatement = "";
/**
* size of LoggingEvent buffer before writting to the database.
* Default is 1.
*/
protected int bufferSize = 1;
public JDBCPoolAppender() {
super();
}
/**
* ArrayList holding the buffer of Logging Events.
*/
public void append(LoggingEvent event) {
buffer.add(event);
if (buffer.size() >= bufferSize)
flushBuffer();
}
/**
* By default getLogStatement sends the event to the required Layout object.
* The layout will format the given pattern into a workable SQL string.
*
* Overriding this provides direct access to the LoggingEvent
* when constructing the logging statement.
*
*/
protected String getLogStatement(LoggingEvent event) {
return getLayout().format(event);
}
/**
*
* Override this to provide an alertnate method of getting
* connections (such as caching). One method to fix this is to open
* connections at the start of flushBuffer() and close them at the
* end. I use a connection pool outside of JDBCAppender which is
* accessed in an override of this method.
* */
protected void execute(String sql) throws SQLException {
Connection con = null;
Statement stmt = null;
try {
con = getConnection();
stmt = con.createStatement();
stmt.executeUpdate(sql);
} catch (SQLException e) {
if (stmt != null)
stmt.close();
throw e;
}
stmt.close();
closeConnection(con);
//System.out.println("Execute: " + sql);
}
/**
* Override this to return the connection to a pool, or to clean up the
* resource.
*
* The default behavior holds a single connection open until the appender
* is closed (typically when garbage collected).
*/
protected void closeConnection(Connection con) {
mydb=null;
try {
if (connection != null && !connection.isClosed())
connection.close();
} catch (SQLException e) {
errorHandler.error("Error closing connection", e,
ErrorCode.GENERIC_FAILURE);
}
}
/**
* Override 此函數來(lái)利用連接池返回一個(gè)Connetion對象
*
*/
protected Connection getConnection() throws SQLException {
try {
mydb = GeneralDb.getInstance(sqlname);
connection = mydb.getConnection();
} catch (Exception e) {
errorHandler.error("Error opening connection", e, ErrorCode.GENERIC_FAILURE);
}
return connection;
}
/**
* Closes the appender, flushing the buffer first then closing the default
* connection if it is open.
*/
public void close() {
flushBuffer();
try {
if (connection != null && !connection.isClosed())
connection.close();
} catch (SQLException e) {
errorHandler.error("Error closing connection", e,
ErrorCode.GENERIC_FAILURE);
}
this.closed = true;
}
/**
* loops through the buffer of LoggingEvents, gets a
* sql string from getLogStatement() and sends it to execute().
* Errors are sent to the errorHandler.
*
* If a statement fails the LoggingEvent stays in the buffer!
*/
public void flushBuffer() {
//Do the actual logging
removes.ensureCapacity(buffer.size());
for (Iterator i = buffer.iterator(); i.hasNext(); ) {
try {
LoggingEvent logEvent = (LoggingEvent) i.next();
String sql = getLogStatement(logEvent);
execute(sql);
removes.add(logEvent);
} catch (SQLException e) {
errorHandler.error("Failed to excute sql", e,
ErrorCode.FLUSH_FAILURE);
}
}
// remove from the buffer any events that were reported
buffer.removeAll(removes);
// clear the buffer of reported events
removes.clear();
}
/** closes the appender before disposal */
public void finalize() {
close();
}
/**
* JDBCAppender requires a layout.
* */
public boolean requiresLayout() {
return true;
}
/**
*
*/
public void setSql(String s) {
sqlStatement = s;
if (getLayout() == null) {
this.setLayout(new PatternLayout(s));
} else {
((PatternLayout) getLayout()).setConversionPattern(s);
}
}
/**
* Returns pre-formated statement eg: insert into LogTable (msg) values ("%m")
*/
public String getSql() {
return sqlStatement;
}
public void setSqlname(String sqlname){
sqlname=sqlname;
}
public String getSqlname(){
return sqlname;
}
public void setBufferSize(int newBufferSize) {
bufferSize = newBufferSize;
buffer.ensureCapacity(bufferSize);
removes.ensureCapacity(bufferSize);
}
public int getBufferSize() {
return bufferSize;
}
}
MyDB.java:
package common.sql;
import java.sql.*;
import com.codestudio.sql.*; //引入開(kāi)源項目Poolman數據庫連接池的包
public class MyDB {
public static final String module = MyDB.class.getName();
private String dbName = "";
private PoolMan plmn = null;
public MyDB(String dbName) {
try {
if (plmn == null) {
plmn = (PoolMan) Class.forName("com.codestudio.sql.PoolMan").
newInstance();
}
} catch (Exception ec) {
System.out.println(ec.toString()+module);
}
this.dbName = dbName;
}
private Connection getNewConnection() {
Connection conn = null;
try {
conn = plmn.connect("jdbc:poolman://" + dbName);
conn.setAutoCommit(true);
} catch (Exception ec) {
System.out.println(ec.toString()+"First:Connect sqlsever failed"+module);
try {
Thread.sleep(1000);
conn = plmn.connect("jdbc:poolman://" + dbName);
conn.setAutoCommit(true);
} catch (Exception ecs) {
System.out.println(ecs.toString()+"Again:Connect sqlsever faile"+module);
}
}
return conn;
}
public Connection getConnection() {
return getNewConnection();
}
}
GeneralDb.java:
package common.sql;
package common.sql;
import java.util.*;
public class GeneralDb {
private static Hashtable dbPool;
public static MyDB getInstance(String dbname) {
if (dbPool == null) {
dbPool = new Hashtable();
}
MyDB db = (MyDB) dbPool.get(dbname);
if (db == null) {
db = new MyDB(dbname);
dbPool.put(dbname, db);
}
return db;
}
}
Log4j數據庫連接池的配置如下：
log4j.appender.JDBC=common.log.JDBCPoolAppender
log4j.appender.JDBC.sqlname=log
log4j.appender.JDBC.layout=org.apache.log4j.PatternLayout
log4j.appender.JDBC.sql=INSERT INTO LOGGING (log_date, log_level, location, message) VALUES (‘%d{ISO8601}‘, ‘%-5p‘, ‘%C,%L‘, ‘%m‘)
poolman.xml配置如下：
〈?xml version="1.0" encoding="UTF-8"?>
〈poolman>
〈management-mode>local〈/management-mode>
〈datasource>
〈dbname>log〈/dbname>
〈jndiName>log〈/jndiName>
〈driver>com.mysql.jdbc.Driver〈/driver>
〈url>jdbc:mysql://localhost:3306/test〈/url>
〈username>use〈/username>
〈password>password〈/password>
〈minimumSize>0〈/minimumSize>
〈maximumSize>10〈/maximumSize>
〈logFile>logs/mysql.log〈/logFile>
〈/datasource>
〈/poolman>
運行成功！對于JDBCPoolAppender的屬性（比如sqlname屬性）我們可以利用Log4j的反射機制隨便添加，只要在配置文件給其附上值即可應用，而原來(lái)的父類(lèi)里面的一些屬性（username什么的)和其get,set方法由于在連接池中不需要，所以刪除。而在JDBCPoolAppender類(lèi)中，我也只是將getConnection 方法Override ，在這個(gè)方法中我們可以根據需要生成我們的Connection對象，另外兩個(gè)方法大家可以根據需求來(lái)決定怎樣Override。：）
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