Java EE Servlet/JSP tutorial : Adding an error page, logging, and other forms of debugging

Revision as of 00:00, 9 May 2012

In progress....

Background on logging

Background information on logging

http://www.vogella.com/articles/Logging/article.html

http://onjava.com/onjava/2002/06/19/log.html

http://tutorials.jenkov.com/java-logging/index.html

http://docs.oracle.com/javase/7/docs/api/java/util/logging/SimpleFormatter.html

Common problem with logging

http://stackoverflow.com/questions/6315699/why-are-my-level-fine-logging-messages-not-showing

Understandng the outptut for logging

http://docs.oracle.com/javase/7/docs/technotes/guides/logging/index.html

http://docs.oracle.com/javase/7/docs/technotes/guides/logging/overview.html

http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax

http://docs.oracle.com/javase/7/docs/api/java/util/logging/SimpleFormatter.html#format(java.util.logging.LogRecord)

Resin and logging

Logging in Resin

http://www.caucho.com/resin-4.0/admin/logging.xtp

http://www.caucho.com/resin-4.0/admin/resin-admin-command-line.xtp#loglevelsettingloglevel

Changing log levels in Resin:

~/workspace/javaee/Servers/Resin 4.0 at localhost-config/resin.xml

...
  <!-- Logging configuration for the JDK logging API -->
  <log-handler name="" level="all" path="stdout:"
               timestamp="[%y-%m-%d %H:%M:%S.%s]"
               format=" {${thread}} ${log.message}"/>

...

  <!--
     - level='info' for production
     - 'fine' or 'finer' for development and troubleshooting
    -->
  <logger name="" level="${log_level?:'info'}"/>

  <logger name="com.caucho.java" level="config"/>
  <logger name="com.caucho.loader" level="config"/>

Changing log levels in Resin:

~/workspace/javaee/Servers/Resin 4.0 at localhost-config/resin.properties

# log_level : info
# app-0.log_level : finest

Using Java log API

package com.bookstore;
...
import java.util.logging.Level;
import java.util.logging.Logger;

public class Book implements Cloneable {
	
	private transient Logger log = Logger.getLogger(Book.class.getName());
...

	public Book cloneMe()  {
		try {
			return (Book) super.clone();
		} catch (CloneNotSupportedException e) {
			log.logp(Level.WARNING, 
					this.getClass().getName(), 
					"cloneMe", "Unable to clone", e);
			return null;  
		}
	}
	
...

Info about logp http://docs.oracle.com/javase/6/docs/api/java/util/logging/Logger.html#logp(java.util.logging.Level, java.lang.String, java.lang.String, java.lang.String, java.lang.Throwable)

Why you should not use static http://wiki.apache.org/commons/Logging/StaticLog

Another example:

package com.bookstore;

...
import java.util.logging.Logger;

import javax.enterprise.context.ApplicationScoped;

@ApplicationScoped @InMemory
public class BookRepositoryCollectionsImpl implements BookRepository {
    ...
	private Book book(String title, String description, String aPrice,
			String aPubDate)  {

		Date pubDate = null;
		BigDecimal price = null;
		
		try {
			price = new BigDecimal(aPrice);
		}catch (Exception ex) {
			log.throwing(this.getClass().getName(), "book", ex);
		}
		
		try {
			pubDate = dateFormat.parse(aPubDate);
		}catch (Exception ex) {
			log.throwing(this.getClass().getName(), "book", ex);
		}
		
		return new Book("" + (count++), title, description, price, pubDate);
		
	}

Info about throwing http://docs.oracle.com/javase/6/docs/api/java/util/logging/Logger.html#throwing(java.lang.String, java.lang.String, java.lang.Throwable)