Class JDBCAppender

java.lang.Object
org.apache.log4j.AppenderSkeleton
org.apache.log4j.jdbc.JDBCAppender
All Implemented Interfaces:
Appender, OptionHandler

public class JDBCAppender extends AppenderSkeleton implements Appender
The JDBCAppender provides for sending log events to a database. It does not log exceptions.

JDBCAppender shipping in 1.2.18.2 produces PreparedStatement instances. Thanks to the remarkable work of Vladimir Sitnikov JDBCAppender now interprets the SQL expression on the fly and inserts new events using PreparedStartement instances. Note that the table column types are restricted to those types compatible with Java's String.

Versions 1.2.18.0 and prior are vulnerable to SQL injection attacks..

Each append call adds to an ArrayList buffer. When the buffer is filled each log event is placed in a sql statement (configurable) and executed.

BufferSize, db URL, User, & Password are configurable options in the standard log4j fashion.

The setSql(String sql) sets the SQL statement to be used for logging -- this statement is sent to a PatternLayout (either created automatically by the appender or added by the user). Therefore by default all the conversion patterns in PatternLayout can be used inside of the statement. (see the test cases for examples).

As mentioned earlier, the produced SQL is translated in an additional phase to use PreparedStatement.

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.
  • As of 1.2.18.1 getLogStatement(org.apache.log4j.spi.LoggingEvent) is no longer in use.
Author:
Kevin Steppe (ksteppe@pacbell.net)
  • Field Details

    • databaseURL

      protected String databaseURL
      URL of the DB for default connection handling
    • databaseUser

      protected String databaseUser
      User to connect as for default connection handling
    • databasePassword

      protected String databasePassword
      User to use for default connection handling
    • connection

      protected Connection connection
      Connection used by default. The connection is opened the first time it is needed and then held open until the appender is closed (usually at garbage collection). This behavior is best modified by creating a sub-class and overriding the getConnection and closeConnection methods.
    • sqlStatement

      protected String sqlStatement
      Stores the string given to the pattern layout for conversion into a SQL statement, eg: insert into LogTable (Thread, Class, Message) values ("%t", "%c", "%m"). Be careful of quotes in your messages! Also see PatternLayout.
    • bufferSize

      protected int bufferSize
      size of LoggingEvent buffer before writting to the database. Default is 1.
    • buffer

      protected ArrayList<LoggingEvent> buffer
      ArrayList holding the buffer of Logging Events.
  • Constructor Details

    • JDBCAppender

      public JDBCAppender()
  • Method Details

    • activateOptions

      public void activateOptions()
      Description copied from class: AppenderSkeleton
      Derived appenders should override this method if option structure requires it.
      Specified by:
      activateOptions in interface OptionHandler
      Overrides:
      activateOptions in class AppenderSkeleton
    • getLocationInfo

      public boolean getLocationInfo()
      Gets whether the location of the logging request call should be captured.
      Returns:
      the current value of the LocationInfo option.
      Since:
      1.2.16
    • setLocationInfo

      public void setLocationInfo(boolean flag)
      The LocationInfo option takes a boolean value. By default, it is set to false which means there will be no effort to extract the location information related to the event. As a result, the event that will be ultimately logged will likely to contain the wrong location information (if present in the log format).

      Location information extraction is comparatively very slow and should be avoided unless performance is not a concern.

      Parameters:
      flag - true if location information should be extracted.
      Since:
      1.2.16
    • append

      public void append(LoggingEvent event)
      Adds the event to the buffer. When full the buffer is flushed.
      Specified by:
      append in class AppenderSkeleton
    • getLogStatement

      protected String getLogStatement(LoggingEvent event)

      As of 1.2.18.1 getLogStatement(org.apache.log4j.spi.LoggingEvent) is no longer in use.

      Parameters:
      event -
    • execute

      protected void execute(String sql) throws SQLException
      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.
      Throws:
      SQLException
    • closeConnection

      protected void closeConnection(Connection con)
      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).
    • getConnection

      protected Connection getConnection() throws SQLException
      Override this to link with your connection pooling system. By default this creates a single connection which is held open until the object is garbage collected.
      Throws:
      SQLException
    • close

      public void close()
      Closes the appender, flushing the buffer first then closing the default connection if it is open.
      Specified by:
      close in interface Appender
    • flushBuffer

      public void flushBuffer()
      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!
    • finalize

      public void finalize()
      closes the appender before disposal
      Overrides:
      finalize in class AppenderSkeleton
    • requiresLayout

      public boolean requiresLayout()
      JDBCAppender requires a layout.
      Specified by:
      requiresLayout in interface Appender
    • setSql

      public void setSql(String s)
    • getSql

      public String getSql()
      Returns pre-formated statement eg: insert into LogTable (msg) values ("%m")
    • setUser

      public void setUser(String user)
    • setURL

      public void setURL(String url)
    • setPassword

      public void setPassword(String password)
    • setBufferSize

      public void setBufferSize(int newBufferSize)
    • getUser

      public String getUser()
    • getURL

      public String getURL()
    • getPassword

      public String getPassword()
    • getBufferSize

      public int getBufferSize()
    • setDriver

      public void setDriver(String driverClass)
      Ensures that the given driver class has been loaded for sql connection creation.