Log4j custom jdbc appender, datasource

Question

To use the data source in my log4j application, I wrote a custom appender. The application is trying to get the data source as a spring bean. However, the application cannot get a bean. I use a technology stack: mybatis, tomcat and spring.

My log4j files look like this:

#configuring the requestinterceptor  
log4j.category.com.db.wscis.core.web.interceptor=INFO, sql
log4j.appender.sql=com.db.wscis.core.util.appender.CustomJDBCAppender
log4j.appender.sql.sql=INSERT INTO LOGS VALUES ('%x', current_timestamp ,'%C','%p','%m')
log4j.appender.sql.layout=org.apache.log4j.PatternLayout

The code for the user application is as follows:

public class CustomJDBCAppender extends org.apache.log4j.jdbc.JDBCAppender {

 protected java.sql.Connection getConnection() throws java.sql.SQLException {

         if(connection == null) {
             org.springframework.jdbc.datasource.DataSourceTransactionManager dstm = (org.springframework.jdbc.datasource.DataSourceTransactionManager) ExternalBeanFactory.getBean("txManager");
             if(dstm==null) throw new java.sql.SQLException("dstm is null");
             System.out.println("here");
             connection = DataSourceUtils.getConnection(dstm.getDataSource());
             return connection;
         } else{
             return connection;
         }
     }

    /* protected void execute(String sql) throws java.sql.SQLException {

         Connection con = null;
         Statement stmt = null;

         try {
             con = getConnection();
             stmt = con.createStatement();
             stmt.executeUpdate(sql);
             con.commit();
         } catch (SQLException e) {
            if (stmt != null)
                 stmt.close();
            closeConnection(con);
            throw e;
         } 
       }
     */
     protected void closeConnection() throws java.sql.SQLException {
             if (connection != null && !connection.isClosed())
                   connection.close();
     }
}

The external Bean factory class is as follows:

/* 
 */    
package com.db.wscis.core.util;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;

public class ExternalBeanFactory implements BeanFactoryAware {

    /**
     * Bean factory instance.
     */
    private static BeanFactory beanFactory;

    /**
     * Sets beanfactory.
     * 
     * @param beanFactory
     *            BeanFactory object
     * 
     * @see org.springframework.beans.factory.BeanFactoryAware#
     *      setBeanFactory(org.springframework.beans.factory.BeanFactory)
     * @exception BeansException
     *                if failed to set factory
     */
    public final void setBeanFactory(final BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }

    /**
     * DO NOT use this method in the application classes. This is meant to be
     * used by the framework level classes ONLY!!!!
     * 
     * Finds from bean from the factory.
     * 
     * @param beanName
     *            Name of the bean
     * @return bean object
     */
    @Deprecated
    public static final Object getBean(final String beanName) {
    //  if(beanFactory==null) System.out.println("Bean factory is null");
        return beanFactory.getBean(beanName);
    }

    public final Object getBeanInstance(final String beanName) {
        return beanFactory.getBean(beanName);
    }
}

Now that the tomcat server is starting up, I assume that it is trying to initialize log4j. Thus, it calls the getConnection method in the user application. This inturn calls ExernalFactory.getBean (), however the beanfactory property in the External BeanFactory is not yet initialized. The error stack trace is as follows:

SEVERE: Error configuring application listener of class com.db.wscis.core.web.context.FWContextLoaderLis
java.lang.NullPointerException
        at com.db.wscis.core.util.ExternalBeanFactory.getBean(ExternalBeanFactory.java:64)
        at com.db.wscis.core.util.appender.CustomJDBCAppender.getConnection(CustomJDBCAppender.java:27)
        at org.apache.log4j.jdbc.JDBCAppender.execute(JDBCAppender.java:215)
        at org.apache.log4j.jdbc.JDBCAppender.flushBuffer(JDBCAppender.java:289)
        at org.apache.log4j.jdbc.JDBCAppender.append(JDBCAppender.java:186)
        at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
        at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.
        at org.apache.log4j.Category.callAppenders(Category.java:206)
        at org.apache.log4j.Category.forcedLog(Category.java:391)
        at org.apache.log4j.Category.log(Category.java:856)
        at org.apache.commons.logging.impl.Log4JLogger.info(Log4JLogger.java:176)
        at com.db.wscis.core.web.context.FWContextLoaderListener.<init>(FWContextLoaderListener.java:34)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.j
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
        at java.lang.Class.newInstance(Class.java:374)
        at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:140)
        at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4888)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5467)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:632)
        at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:1073)
        at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1857)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
        at java.util.concurrent.FutureTask.run(FutureTask.java:166)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:724)

, , , datasource Bean appender.

Answer 1

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