Java EE Servlet/JSP tutorial : Adding an error page, logging, and other forms of debugging
From Resin 4.0 Wiki
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Contents |
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
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)
package com.bookstore;
...
import java.util.logging.Level;
import java.util.logging.Logger;
...
@ApplicationScoped @JDBC
public class BookRepositoryJDBCImpl implements BookRepository {
private transient Logger log = Logger.getLogger(Book.class.getName());
...
private <T> T withDB(JDBCRunner<T> runner) {
log.entering("BookRepositoryJDBCImpl", "withDB");
Connection connection = null;
try {
connection = dataSource.getConnection();
boolean auto = connection.getAutoCommit();
connection.setAutoCommit(false);
T result = runner.run(connection);
log.finest("about to commit");
connection.commit();
log.finest("committed");
connection.setAutoCommit(auto); //set it to what it was previously.
log.exiting("BookRepositoryJDBCImpl", "withDB");
return result;
}catch (Exception ex) {
log.log(Level.WARNING, "Transaction did not succeed", ex);
try {
log.finest("About to rollback transaction");
connection.rollback();
} catch (SQLException e) {
log.log(Level.WARNING, "Unable to rollback", ex);
}
throw new BookStoreException(ex);
} finally {
if (connection!=null) {
try {
connection.close();
} catch (Exception ex) {
log.log(Level.WARNING, "Unable to cleanup", ex);
}
}
}
}
}
http://docs.oracle.com/javase/6/docs/api/java/util/logging/Logger.html#exiting(java.lang.String, java.lang.String) http://docs.oracle.com/javase/6/docs/api/java/util/logging/Logger.html#entering(java.lang.String, java.lang.String, java.lang.Object[])
public class BookRepositoryJDBCImpl implements BookRepository {
private transient Logger log = Logger.getLogger(Book.class.getName());
...
@Override
public void updateBook(final String id, final String title, final String description,
final String price, final String pubDate) {
if (log.isLoggable(Level.FINER)) {
log.entering(this.getClass().getName(), "updateBook", new Object[]{id, title, description, price, pubDate});
}
withDB(new JDBCRunner<Book>(){
@Override
public Book run(Connection connection) throws Exception {
PreparedStatement prepareStatement = connection.prepareStatement("update book set title=?, " +
"description=?, price=?, pubdate=? where id = ?");
prepareStatement.setString(1, title);
prepareStatement.setString(2, description);
prepareStatement.setBigDecimal(3, new BigDecimal(price));
Calendar calendar = Calendar.getInstance();
calendar.setTime(dateFormat.parse(pubDate));
prepareStatement.setDate(4, new Date(calendar.getTimeInMillis()));
prepareStatement.setLong(5, Long.parseLong(id));
int rowCount = prepareStatement.executeUpdate();
if (rowCount!=1) {
throw new BookStoreException("Unable to update book into bookstore");
}
return null;
}});
if (log.isLoggable(Level.FINER)) {
log.exiting(this.getClass().getName(), "updateBook", new Object[]{id, title, description, price, pubDate});
}
}
