```
public abstract class Logger
extends Object
```
The FreeMarker logging facility. This is a polymorphic implementation that will use whatever logging package it can find on the system: SLF4J, Apache Commons Logging, Apache Log4J, Apache Avalon LogKit, java.util.logging (in this order). If it fails to find any of the above, logging will be suppressed and a short notice will be printed to System.err.
You can use the selectLoggerLibrary(int) static method to force use of a specific logger package, or to turn off logging.

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`LIBRARY_AUTO`	Constant used with `selectLoggerLibrary(int)` that indicates the engine should automatically lookup and use any available logger library.
`static int`	`LIBRARY_JAVA`	Constant used with `selectLoggerLibrary(int)` that indicates the engine should use the `java.util.logging` logger package.
`static int`	`LIBRARY_NONE`	Constant used with `selectLoggerLibrary(int)` that indicates the engine should use no logger package (i.e.
`static int`	`LIBRARY_SLF4J`	Constant used with `selectLoggerLibrary(int)` that indicates the engine should use the SLF4J logger adapter package.

Constructor Summary

Constructors
Constructor Description

Logger()

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`abstract void`	`debug(String message)`	Logs a debugging message.
`abstract void`	`debug(String message, Throwable t)`	Logs a debugging message with accompanying throwable.
`abstract void`	`error(String message)`	Logs an error message.
`abstract void`	`error(String message, Throwable t)`	Logs an error message with accompanying throwable.
`static Logger`	`getLogger(String category)`	Returns a logger for the specified category.
`abstract void`	`info(String message)`	Logs an informational message.
`abstract void`	`info(String message, Throwable t)`	Logs an informational message with accompanying throwable.
`abstract boolean`	`isDebugEnabled()`	Returns true if this logger will log debug messages.
`abstract boolean`	`isErrorEnabled()`	Returns true if this logger will log error messages.
`abstract boolean`	`isFatalEnabled()`	Returns true if this logger will log fatal error messages.
`abstract boolean`	`isInfoEnabled()`	Returns true if this logger will log informational messages.
`abstract boolean`	`isWarnEnabled()`	Returns true if this logger will log warning messages.
`static void`	`selectLoggerLibrary(int library)`	Selects the logger library to use.
`static void`	`setCategoryPrefix(String prefix)`	Sets a category prefix.
`abstract void`	`warn(String message)`	Logs a warning message.
`abstract void`	`warn(String message, Throwable t)`	Logs a warning message with accompanying throwable.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LIBRARY_AUTO
```
public static final int LIBRARY_AUTO
```
    Constant used with selectLoggerLibrary(int) that indicates the engine should automatically lookup and use any available logger library.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NONE
```
public static final int LIBRARY_NONE
```
    Constant used with selectLoggerLibrary(int) that indicates the engine should use no logger package (i.e. turn off logging).
    
    See Also:
    
    Constant Field Values
  - LIBRARY_JAVA
```
public static final int LIBRARY_JAVA
```
    Constant used with selectLoggerLibrary(int) that indicates the engine should use the java.util.logging logger package.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_SLF4J
```
public static final int LIBRARY_SLF4J
```
    Constant used with selectLoggerLibrary(int) that indicates the engine should use the SLF4J logger adapter package.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Logger
```
public Logger()
```
- Method Detail
  - selectLoggerLibrary
```
public static void selectLoggerLibrary(int library)
                                throws ClassNotFoundException
```
    Selects the logger library to use. If you want to change the default setting, do it early in application initialization phase, before calling any other FreeMarker API since once various parts of the FreeMarker library bind to the logging subsystem, the change in this value will have no effect on them.
    
    Parameters:
    
    library - one of LIBRARY_XXX constants. By default, LIBRARY_AUTO is used.
    
    Throws:
    
    ClassNotFoundException - if an explicit logging library is asked for (that is, neither NONE, nor AUTO), and it is not found in the classpath.
  - setCategoryPrefix
```
public static void setCategoryPrefix(String prefix)
```
    Sets a category prefix. This prefix is prepended to any logger category name. This makes it possible to have different FreeMarker logger categories on a per-application basis (better said, per-classloader basis). By default the category prefix is the empty string. If you set a non-empty category prefix, be sure to include the trailing separator dot (i.e. "MyApp.") If you want to change the default setting, do it early in application initialization phase, before calling any other FreeMarker API since once various parts of the FreeMarker library bind to the logging subsystem, the change in this value will have no effect on them.
  - debug
```
public abstract void debug(String message)
```
    Logs a debugging message.
  - debug
```
public abstract void debug(String message,
                           Throwable t)
```
    Logs a debugging message with accompanying throwable.
  - info
```
public abstract void info(String message)
```
    Logs an informational message.
  - info
```
public abstract void info(String message,
                          Throwable t)
```
    Logs an informational message with accompanying throwable.
  - warn
```
public abstract void warn(String message)
```
    Logs a warning message.
  - warn
```
public abstract void warn(String message,
                          Throwable t)
```
    Logs a warning message with accompanying throwable.
  - error
```
public abstract void error(String message)
```
    Logs an error message.
  - error
```
public abstract void error(String message,
                           Throwable t)
```
    Logs an error message with accompanying throwable.
  - isDebugEnabled
```
public abstract boolean isDebugEnabled()
```
    Returns true if this logger will log debug messages.
  - isInfoEnabled
```
public abstract boolean isInfoEnabled()
```
    Returns true if this logger will log informational messages.
  - isWarnEnabled
```
public abstract boolean isWarnEnabled()
```
    Returns true if this logger will log warning messages.
  - isErrorEnabled
```
public abstract boolean isErrorEnabled()
```
    Returns true if this logger will log error messages.
  - isFatalEnabled
```
public abstract boolean isFatalEnabled()
```
    Returns true if this logger will log fatal error messages.
  - getLogger
```
public static Logger getLogger(String category)
```
    Returns a logger for the specified category.
    
    Parameters:
    
    category - a dot separated hierarchical category name. If a category prefix is in effect, it is prepended to the category name.

Class Logger

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LIBRARY_AUTO

LIBRARY_NONE

LIBRARY_JAVA

LIBRARY_SLF4J

Constructor Detail

Logger

Method Detail

selectLoggerLibrary

setCategoryPrefix

debug

debug

info

info

warn

warn

error

error

isDebugEnabled

isInfoEnabled

isWarnEnabled

isErrorEnabled

isFatalEnabled

getLogger